AOS Classification Committee – North and Middle America
Proposal Set 2021-A
10 November 2020; final revision 15 April 2021
No. Page Title
01 02

Revise the classification of the Euphoniinae (Fringillidae): transfer Euphonia musica
and E. elegantissima to resurrected genus Cyanophonia or to Chlorophonia, andrevise the linear sequence of the subfamily

02 06

Split Band-rumped Storm-Petrel Hydrobates castro

03 17

Split Mew Gull Larus canus brachyrhynchus and rename as Short-billed Gull

04 22

Revise generic limits in the Phalacrocoracidae (cormorants)

05 26

Adopt split of Long-billed Gnatwren Ramphocaenus melanurus

06 29

Change the linear sequence of the gnatcatchers (Polioptila spp.)

07 31

Split Tropical Gnatcatcher Polioptila plumbea into two or more species

08 37

Split Fregata rothschildi from Magnificent Frigatebird F. magnificens

09 43

Resurrect Corthylio for Ruby-crowned Kinglet

10 47

Change the linear sequence of species in Chaetura

11 51

Reconsider the case to split Saxicola maurus and S. stejnegeri from Common
Stonechat S. torquatus

12 64

Resurrect Philodice as a separate genus from Calliphlox

13 68

Treat McKay’s Bunting Plectrophenax hyperboreus as conspecific with Snow Bunting
P. nivalis

12021-A-1

N&MA Classification Committee

p. 584

Revise the classification of the Euphoniinae (Fringillidae): transfer Euphonia musica andE. elegantissima to resurrected genus Cyanophonia or to Chlorophonia, and revise thelinear sequence of the subfamily
Note: These issues, in slightly different form, are being considered by SACC in Proposal 856.
See SACC votes and comments at https://www.museum.lsu.edu/~Remsen/SACCprop856.htm
Effect on NACC:
YES votes on part a and Option b-1 would resurrect Cyanophonia and transfer Euphonia
musica and E. elegantissima to this genus, whereas YES votes on part a and Option b-2 would
transfer these species to Chlorophonia. A YES vote on part c would revise the linear sequenceof species within the subfamily Euphoniinae to reflect new phylogenetic information.
Background and New Information:
Prior to the recent publication of a phylogenomic study of the true-finch subfamily Euphoniinae,
the most comprehensive molecular phylogeny of the group (Zuccon et al. 2012) had found that
Euphonia was paraphyletic with respect to Chlorophonia, the other genus in the subfamily.
Specifically, E. musica was found to be sister to C. cyanea. The authors noted this taxonomic
conflict but suggested that further sampling of species would be necessary to adequately
resolve this issue. More recently, Imfeld et al. (2020) used target-capture and enrichment toFigure 1. Time-scaled phylogeny of
Euphoniinae. This tree is from Imfeld et al.’s
Figure 4. The topology of this phylogeny wasinferred by maximum likelihood estimation ofa species tree from 4,944 UCE loci, and its
branch lengths were optimized and timescaled by a fossil-calibrated Bayesiananalysis of 150 completely sampled UCE lociand cytochrome-b sequences. The bluehooded euphonia species, noted by anasterisk, form a monophyletic clade sister tothe genus Chlorophonia to the exclusion of
the remaining Euphonia species. All nodes inthis tree received localized posterior
probability of 1 and bootstrap support of
100% except for nodes 19 (0.76, 87%) and21 (0.98, 90%).

2Figure 2. Maximum-likelihood phylogenies of the Euphoniinae generated fromconcatenated UCE loci. These trees are from Imfeld et al.’s Figure 1. Black nodes indicate
bootstrap support of 100%, and any node receiving <100% support has its value reported. The
topologies of these trees, especially the one inferred from all UCE loci, are largely similar to thespecies tree topology presented above. Triangles adjacent to the right tree indicate conflicting
nodes between the concatenated phylogenies.
---------------------------------------------------------------------------------------------------------------------------sequence thousands of ultraconserved elements and mitogenomes for every species of
Euphonia and Chlorophonia presently recognized by the checklist committees of the American
Ornithological Society. Every phylogenetic analysis performed in this study, whether withconcatenation or species-tree methods, maximum likelihood or Bayesian approaches, or using
nuclear or mitochondrial sequence data, found the three species of blue-hooded euphonias (E.
cyanocephala, elegantissima, and musica) to form a monophyletic clade sister to the five
Chlorophonia species to the exclusion of all other euphonias (see Figs. 1, 2). Thus, genericplacement of this blue-hooded euphonia clade requires revision.
Two blue-hooded species, E. elegantissima and E. musica, occur in the NACC area and would
be affected by this revision. Imfeld et al. (2020) discussed three possible scenarios to resolve
the paraphyly of Euphonia: lumping all species in Euphoniinae into the genus Euphonia, placing
the blue-hooded euphonias in the genus Chlorophonia, or resurrecting the genus Cyanophonia
for the blue-hooded euphonias. Euphonia has priority over Chlorophonia, being established in1806 versus 1851, respectively; however, the first option would remove a long-standing genus
for chlorophonias and was not recommended. This option also would change the names of fivespecies, three of which occur in the NACC area. The second option would require a revision of
the blue-hooded species only, but the authors argued that the name Chlorophonia would notdescribe the phenotypes of these species particularly well. Adult males, except for the Lesser
3Antillean subspecies of E. musica, lack any green plumage. Imfeld et al.’s third option, and therecommendation of this proposal, is to resurrect the genus Cyanophonia and place the 3 bluehooded species in it. Cyanophonia was established by Bonaparte (1851) for the blue-hooded
euphonias in the same volume as Chlorophonia and, thus, has equal priority to Chlorophonia.
Additionally, given that all plumages of these three species possess blue hoods, even juveniles,
the name is a better descriptor than Chlorophonia.
Recommendation:
Based on the new phylogenetic information presented in Imfeld et al. (2020), we recommend:(1) that E. elegantissima and E. musica be transferred to the genus Cyanophonia, and(2) that a new linear sequence be adopted for the subfamily Euphoniinae:
Cyanophonia (or Chlorophonia) elegantissima
Cyanophonia (or Chlorophonia) musica
Chlorophonia flavirostris
Chlorophonia occipitalis
Chlorophonia callophrys
Euphonia jamaica
Euphonia affinis
Euphonia luteicapilla
Euphonia minuta
Euphonia hirundinacea
Euphonia laniirostris
Euphonia imitans
Euphonia gouldi
Euphonia fulvicrissa
Euphonia anneae
Euphonia xanthogaster
Please vote on the following:(a) YES/NO: transfer Euphonia musica and E. elegantissima to a new genus;(b) Option 1/Option 2: transfer these species (1) to resurrected genus Cyanophonia or (2) to
Chlorophonia; and(c) YES/No: revise the linear sequence of the subfamily.
Literature Cited:
Bonaparte, C.L. 1851. Note sur les Tangaras, leurs affinités, et descriptions d’espèces
nouvelles. Revue et Magasin de Zoologie Pure et Appliquée 2(3): 129-138.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019.
https://www.birds.cornell.edu/clementschecklist/download/
4Zuccon D., Prŷs-Jones R., Rasmussen P.C., and Ericson P.G.P. 2012. The phylogenetic
relationships and generic limits of finches (Fringillidae). Molecular Phylogenetics andEvolution 62(2): 581-596.

Submitted by: Tyler S. Imfeld and Nicholas A. Mason
Date of Proposal: 5 May 2020, revised October 20205

2021-A-2

N&MA Classification Committee

p. 25

Split Band-rumped Storm-Petrel Hydrobates castro
Background:
The Band-rumped Storm-Petrel complex (Hydrobates castro sensu lato) contains seven named
taxa distributed across the Atlantic and Pacific Ocean basins. The complex has long beenthought to contain multiple cryptic species due to vocal differences between populations and thepresence of both hot-season and cool-season breeding populations present on single islands orarchipelagos. However, plumage patterns and morphometrics in the group are highly
conserved, making it extremely difficult to assign individuals to taxa under field conditions,especially away from breeding colonies.
The named taxa in the group, in order of date of description, are:castro (Harcourt, 1851) – widespread North Atlantic breeder
jabejabe (Bocage, 1875) – Cape Verde Islands
cryptoleucura (Ridgway, 1882) – Hawaii
bangsi (Nichols, 1914) – Galapagos Islands
helena (Mathews, 1934) – southern Atlantic islands
kumagai (Mathews, 1938) – Japanmonteiroi (Bolton et al., 2008) – Azores hot season breeders
Additionally, at least two breeding populations lack formal taxonomic descriptions. The firstconsists of North Atlantic cool-season breeders (Howell 2012, Taylor et al. 2019) sometimes
called “Grant’s” Storm-Petrel (hot-season North Atlantic breeders are nominate H. castro). The
second is a population breeding on islands in the Gulf of Guinea (Flood et al. 2012).
The NACC tackled this problem as recently as 2019 in proposal 2019-C-10, which resulted in
the unanimous acceptance by the committee of the split of Monteiro’s Storm-Petrel, H.
monteiroi, from all other taxa in the group. This split was based on the findings of Bolton et al.
(2008), who showed convincingly that populations of monteiroi and castro breeding on the
Azores segregated temporally, did not recognize one another vocally, and exhibited very low
levels of gene flow, thus qualifying as distinct species under the Biological Species Concept.
Hydrobates monteiroi has also been recognized by global lists (Clements et al. 2019, HBW and
BirdLife International 2019, Gill et al. 2020). Additionally, the population breeding on the Cape
Verde Islands has been recognized as a species by several authorities (Clements et al. 2019,
HBW and BirdLife International 2019, Gill et al. 2020) under the name Cape Verde StormPetrel, H. jabejabe, but this split has not yet been considered by the NACC.
A series of publications has tackled the phylogeography of the complex using mitochondrial
DNA, microsatellite markers, and small numbers of nuclear loci (Friesen et al. 2007, Sangster et
al. 2012, Silva et al. 2016, Smith et al. 2007, Smith and Friesen 2007, Wallace et al. 2017), buteach has had either a narrow geographic focus or has lacked genetic samples from some
populations or named taxa. Additionally, the complex has been the focus of vocal playback
studies (Bolton 2007), which are described in detail below.
As an aside, another recent proposal accepted by the committee (2019-B-7) transferred all
species in the genus Oceanodroma to Hydrobates, due to paraphyly in the former genus(Wallace et al. 2017; Hydrobates has priority and is embedded within Oceanodroma). The
6

decision to lump the genera in place of splitting Oceanodroma was made in part due to the factthat no name was thought to be available for one of the clades in Oceanodroma. That clade
contained samples of monteiroi and jabejabe (= the old castro), for which a name is in fact
available: Thalobates (Mathews 1943), which has castro as the type species (Mathews andHallstrom 1943). Although the current proposal contains insufficient information with which torevisit the generic-level classification of the Hydrobatidae, this is simply to note that should
Hydrobates be split in the future, the H. castro complex could be transferred to Thalobates.
New Information:
Taylor et al. (2019) provided, for the first time, a phylogenetic study of Band-rumped StormPetrels that included all named populations, both hot- and cool-season breeders, and many
thousands of nuclear loci, all of which allows for a more complete revision of the taxonomy of
the group. The only unsampled population consists of the as-yet unnamed breeders on islandsof the Gulf of Guinea. Taylor et al. (2019) sequenced 3,707 nuclear loci using ddRAD-Seq andtwo mitochondrial loci (cytochrome b and the control region). They estimated phylogenies fromthe nuclear SNPs using RAxML and SNAPP, and from the mitochondrial data in BEAST.
In both the nuclear and mitochondrial phylogenies, they recovered monteiroi as embedded
within the currently defined H. castro (Figs. 5-7). These phylogenies found with high support that
jabejabe was sister to the remainder of the group. The topology of the rest of the tree was rather
less resolved, with different analyses placing monteiroi either as sister to the remaining five taxa
(nuclear RAxML tree) or as sister to castro sensu stricto (nuclear SNAPP tree, mitochondrialtree).
Two methodological shortfalls are worth mentioning, both of which may affect the taxonomic
conclusions. The first is the selection of an outgroup taxon and the second is the model used forthe estimation of the RAxML phylogeny. None of the phylogenies estimated by Taylor et al.
(2019) used a sample outside of the Band-rumped Storm-Petrel complex as an outgroup.
Instead, they opted to root all of the trees with their samples of jabejabe, a decision that was
based on the mitochondrial cytochrome b phylogeny in Wallace et al. (2017), who foundjabejabe to be sister to the rest of castro (sensu lato) and also did use an outgroup. Althoughrooting the mitochondrial phylogeny with jabejabe in Taylor et al. (2019) is likely a safe
assumption given the similar locus-sampling of the two studies, it is certainly not the case for thetree based on the nuclear SNPs, given the many documented cases of topological discordance
between mitochondrial and nuclear phylogenies across the tree of life. Different analyses of thenuclear data in Taylor et al. (2019) show conflicting results with regard to the genetic
distinctiveness of each taxon, which would have been clarified by the use of an outgroup. Boththe STRUCTURE and PCA results of nuclear SNPs in Taylor et al. (2019) show that castro(sensu stricto) is the most genetically distinct taxon analyzed (Figure S3, Figure 3), andjabejabe doesn’t show up as genetically distinct from the rest of the group in the STRUCTURE
results until K=4 (Figure S3A). While PCA and STRUCTURE analyses do not implicitly test
phylogenetic relationships, this does suggest that the nuclear and mitochondrial genetic
patterns differ, and that rooting the nuclear phylogeny with jabejabe is not a safe assumption.
However, the SNAPP phylogeny of nuclear data (which does not require the setting of an
outgroup) did recover jabejabe as sister to the rest of complex. The second factor is the model
used to infer the RAxML phylogeny. RAxML provides a SNP-specific model that corrects for theascertainment bias of using DNA datasets that contain variable sites only, but this appears tohave not been used. This, plus the amount of missing data in SNP datasets, has been shown toaffect both topology and branch lengths of SNP-based phylogenies (Leaché et al. 2015) and---------------------------------------------------------------------------------------------------------------------------7

Figures 5, 6 (both above), and 7 (on next page) from Taylor et al., presenting phylogenetic
results from Bayesian, maximum likelihood, and SNAPP analyses. For ease of interpretation, I
provide here the taxonomic names that correspond to their sampling populations: “North
Atlantic” = castro, “Azores hot” = monteiroi, “South Atlantic” = helena, “Cape Verde” = jabejabe,“Galapagos” = bangsi, “Hawaii” = cryptoleucura, “Japan” = kumagai.
8-----------------------------------------------------------------------------------------------------------------

Figures S3A and S3B from Taylor et al. (2019). The STRUCTURE results presented in the main
paper show all populations for only K=2 (the K value with the lowest log likelihood), while K = 2
through K = 7 are presented only in the supplemental material pasted here. Population
assignments: 1 = monteiroi, 2-7 = castro, 8 = jabejabe, 9-10 = bangsi, 11 = cryptoleucura, 12 =kumagai, 13-16 = helena.
910may account for the non-monophyly of monteiroi in Figure 6. In fact, using different locus
filtering strategies, Taylor et al. (2019) recovered an identical topology to Figure 6, but with all
samples of monteiroi as monophyletic and in the same position in the tree (Figure S7A, S7B). It
is unclear why these phylogenies were presented as supplementary material and not in themain paper. For these reasons, the SNAPP phylogeny should, I think, be given greater weight
than the RAxML phylogeny.
The STRUCTURE results produced some interesting patterns, with some taxa showing
assignments from multiple populations. In particular, all individuals of monteiroi showed aproportion of genetic assignments from all other populations, perhaps due to incomplete lineage
sorting after a recent divergence or to introgression. Even at K=7 the Japanese and Hawaiian
populations do not fully segregate, a finding corroborated by the variable phylogenetic positionof kumagai. No explicit tests of gene flow were performed, however.
Based on the results of Taylor et al. (2019), the current treatment by the NACC results in aparaphyletic Hydrobates castro, although this may be expected given the recent divergencetimes between taxa in this group (see below), perhaps due to peripatric speciation and rapid
evolution of reproductive isolation, at least between some taxa (e.g. monteiroi). The threephylogenies in Taylor et al. (2019) contain discordant topologies that differ with regard to theposition of monteiroi and the three Pacific taxa, but a three-way split of H. castro would result inmonophyletic species according to each phylogenetic hypothesis. Given the strong evidence ofreproductive isolation between monteiroi and castro presented in Bolton et al. (2008) and theunanimous acceptance of monteiroi as a species by this committee, the merging of monteiroi
back into castro is not a valid option. A three-way split of castro would result in the elevation of
H. jabejabe (which has been accepted by other global bird checklists) and H. cryptoleucura(including kumagai, bangsi, and helena) to species, leaving a monophyletic H. castro. Both hotseason and cool-season North Atlantic breeders clustered together in the mitochondrial andRAxML SNP phylogenies, indicating that “Grant’s” Storm-Petrel is not genetically distinct fromcastro and should probably not be treated as a distinct taxon. Clustering the Pacific and South
Atlantic taxa under one species makes little biogeographic sense, so an argument could bemade to also elevate the South Atlantic taxon helena to species level. However, themitochondrial phylogeny did not recover monophyletic Pacific and South Atlantic groups, butinstead recovered kumagai as sister to helena (to the exclusion of cryptoleucura and bangsi),
albeit with low support. Although the two phylogenetic analyses of nuclear data did recovermonophyletic Pacific basin or South Atlantic groups, the discordant mitochondrial phylogeny
suggests incomplete lineage sorting or introgression between Pacific and South Atlantic
populations. The Pacific and South Atlantic populations also cluster together quite closely in the
mitochondrial haplotype network (Figure 4).
Based on the reciprocal monophyly of each taxon in all three phylogenies, Taylor et al. (2019)suggested a six-species solution, elevating all taxa to species level with the exception ofmaintaining kumagai as a subspecies of cryptoleucura based on the low levels of genetic
differentiation between the two taxa in their STRUCTURE analyses. Taylor et al. (2019) did notprovide an estimate for the divergence times in the group, but a date is available from Silva etal. (2016) who estimated the divergence of castro, monteiroi, kumagai, and bangsi at ~200,000
years using a strict mitochondrial molecular clock. Given how recent the entire radiation is, aswell as the lack of explicit tests of introgression between taxa, I think it best to proceed moreconservatively for the time being.
Vocal analyses have not been conducted for all taxa, but Bolton (2007) did conduct playback
experiments on Azores (monteiroi), Galapagos (bangsi), and Cape Verde (jabejabe) populations
11

by presenting each of these populations to playback of other taxa (including recordings ofcastro) and control sounds. Some of this evidence was used to support the splitting of monteiroi
from castro. Bolton’s results indicated that monteiroi and bangsi both did not respond to
playback of other populations any more than they responded to a control. Cape Verde jabejabe
did respond more to their own calls than to those of other populations, but showed slightly
elevated response to castro. Although these data are incomplete for our purposes, they dosuggest a pre-zygotic isolation for Pacific Ocean taxa and for monteiroi, but are equivocal for
jabejabe. This is interesting because the some of the phylogenies suggest that jabejabe is themost genetically differentiated taxon of the group. It does provide support for species status forcryptoleucura (which would include bangsi), but additional playback experiments that include
helenae, cryptoleucura, and kumagai are desirable. In the Figure 2 from Bolton (2007) shown
below, GD=bangsi, AH=monteiroi, AC=castro, CV=jabejabe, and CS, SL, and LS are calls fromcontrol taxa.

In summary, mitochondrial DNA data supported four clusters corresponding to castro,
cryptoleucura, monteiroi, and jabejabe, but with some shared haplotypes between castro andjapejabe. The nuclear phylogenies supported these same four groups, but may also support
helena and bangsi as distinct. The SNAPP phylogeny of nuclear data, in particular, supported
jabejabe as quite distinct from all other taxa. Branch lengths for all of these groups (except for
jabejabe) were very short, indicating very recent divergence times for most taxa. The
STRUCTURE analysis of nuclear data, however, showed extensive shared population
assignments (i.e., indicative of introgression or incomplete lineage sorting) in some cases. In
particular, monteiroi showed shared population assignments with most other taxa (which is ofnote, considering its documented reproductive isolation from castro), andcryptoleucura/kumagai show shared population assignments with bangsi, helena, and perhaps
12to a lesser degree with castro. The taxa castro, jabejabe, bangsi, and helena showed no (orminimal) shared population assignments with any other taxa at any value of K. Vocal playback
experiments suggested that monteiroi and bangsi are each distinct (no vocal recognition) fromcastro and jabejabe, but were equivocal with regards to jabejabe being distinct from castro.
Vocal playback data are lacking from the other taxa.
This is an extremely complex system, and evidence from the mitochondrial DNA, nuclear DNA,and vocal recognition data do not present a clear taxonomic solution. Despite the many studies
published on the group, much work remains to be done. Particularly relevant to taxonomic
decisions would be studies that include estimates of rates of gene flow between taxa, detailed
analyses of song structure, and vocal recognition experiments including all taxa.
Recommendation:
At least four taxonomic treatments are available given the results from Taylor et al. (2019) and
Bolton (2007), and the relative importance given to each line of evidence. These are discussed
below as options A-D:
A (the recommended option) – 3 species (castro, jabejabe, cryptoleucura)B – 2 species (castro, jabejabe)C – 4 species (castro, jabejabe, cryptoleucura, helena)
D – 5 species (castro, jabejabe, cryptoleucura, helena, bangsi).
Given the arguments outlined above, in particular the nuclear DNA evidence supporting thedistinctiveness of jabejabe and the vocal data indicating the lack of vocal recognition between
bangsi and the North Atlantic taxa, I recommend a four-species treatment for the complex,
which would divide the current Hydrobates castro into three species, H. monteiroi having
already been elevated to species status. This is option A, which would result in recognition of
the following species:
Hydrobates castro: Widely distributed in the North Atlantic. Contains both hot-season and coolseason breeding populations. The English name Madeiran Storm-Petrel is widely used,although the name is not ideal as the species occurs on other North Atlantic islands.
Hydrobates jabejabe: year-round breeder on the Cape Verde Islands. Known at sea only fromthe vicinity of the breeding islands. The English name Cape Verde Storm-Petrel is widely used.
Hydrobates cryptoleucura: widely distributed in the Pacific and South Atlantic Oceans, including
both hot-season and cool-season breeding populations. Includes the subspecies bangsi,
kumagai, and helena. No common name is in wide use for this group. Given that the distribution
does not conform to any one biogeographic region and that there are few morphologicaldifferences to separate it from other taxa, no obvious name is available. If the committee votes
to split cryptoleucura, I suggest a separate proposal be submitted to address the name for thisspecies.
Alternatively, given that vocal playback data are not available for some taxa (helena inparticular), a more conservative treatment would be to hold off on splitting cryptoleucura until
more vocal data are available. This three-species treatment would split H. jabejabe from thecurrent H. castro. This is option B:

13

Hydrobates castro: Widely distributed in the Atlantic and Pacific basins. Contains both hotseason and cool-season breeding populations of castro, and the subspecies cryptoleucura,bangsi, kumagai, and helena. The English name Madeiran Storm-Petrel is widely used,although the name is not ideal as the species occurs on many other Atlantic and Pacific islands.
In keeping with NACC policy and previous decisions, I recommend that the name Band-rumped
Storm-Petrel be retained for this widespread species, as the splitting of jabejabe would elevatea range-restricted taxon from a much more widespread form.
Hydrobates jabejabe: same as in option A.
Two alternative species treatments are available, but I believe that both would need additional
evidence from playback experiments, morphological studies, or estimates of gene flow before
the splits be considered. I have included them here for the sake of completeness. These
treatments are not recommended, given the current data available.
C) A five-species treatment, which would be the same as the four-species treatment above, withthe additional split of the southern Atlantic helena from the three Pacific taxa. Possible English
name for helena: Saint Helena Storm-Petrel.
D) A six-species treatment, following the recommendation of Taylor et al. (2019), which is thesame as C with the additional split of the Galapagos taxon bangsi from the other two Pacifictaxa. Possible English name for bangsi: Darwin’s Storm-Petrel.
Committee members should vote on the following:(a) maintain castro as currently constituted; if voting NO on (a), continue to (b)(b) split castro into three species (castro, jabejabe, cryptoleucura), as recommended in the
proposal; if voting NO on (b), continue to (c)(c) split castro into 2, 4, or 5 species; if voting YES, specify how many (and which) species to berecognized.
Status in the AOU region
Hydrobates jabejabe is known at sea only from the vicinity of the breeding islands, so is best
considered extralimital. Both H. jabejabe and H. monteiroi could occur in the AOU region, but
given the difficulty in field identification, either species would likely require DNA sequence dataor a band recovery to confirm their occurrence.
Hydrobates castro is thought to be the taxon that occurs regularly as a non-breeding visitor off
the east coast of North America and in the Gulf of Mexico. This is supported by a specimen
recovered in Alabama that had been banded as a breeding adult in the Azores in September, so
is referable to castro (Woolfenden et al. 2001).
Hydrobates cryptoleucura breeds in Hawaii. A single record from California (Singer et al. 2020)
certainly pertains to one of the Pacific breeding taxa and is thus referable to H. cryptoleucura
but remains unidentified to subspecies. The South Atlantic taxon helena is widespread at sea in
the South Atlantic but lacks documented records for our area and is unlikely to occur.

Effect on the AOS Checklist:
14

Option A would add one species to the AOS Checklist; H. cryptoleucura. Option B would add nospecies to the AOS Checklist.

Literature Cited:
Bolton, M. 2007. Playback experiments indicate absence of vocal recognition among temporally
and geographically separated populations of Madeiran Storm-petrels Oceanodroma castro.
Ibis 149: 255-263.
Bolton, M., A.L. Smith, E. Gómez-Díaz, V.L. Friesen, R. Medeiros, J. Bried, J.L. Roscales, andR.W. Furness. 2008. Monteiro’s Storm-petrel Oceanodroma monteiroi: a new species fromthe Azores. Ibis 150: 717-727.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019.
Downloaded from https://www.birds.cornell.edu/clementschecklist/download/
Flood, R. L., R.F.d. Lima, M. Melo, P. Verbelen, and W.H. Wagstaff. 2019. What is known about
the enigmatic Gulf of Guinea band-rumped storm petrels Hydrobates cf. castro? Bulletin of
the British Ornithologists’ Club 139: 173-186.
Friesen, V.L., E. Gómez-Díaz, M. Bolton, R.W. Furness, J. González-Solís, and L.R. Monteiro.
2007. Sympatric speciation by allochrony in a seabird. Proceedings of the National
Academy of Sciences USA 104: 18589-18594.
Gill, F., D. Donsker, and P. Rasmussen, eds. 2020. IOC World Bird List (v10.1).
HBW and BirdLife International. 2019. Handbook of the Birds of the World and BirdLife
International digital checklist of the birds of the world. Version 4. Available at:
http://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBWBirdLife_Checklist_v4_Dec19.zip
Howell, S.N.G. 2012. Petrels, albatrosses, & storm-petrels of North America. A photographic
guide. Princeton University Press, Princeton and Oxford.
Leaché, A.D., B.L. Banbury, J. Felsenstein, A. Nieto-Montes de Oca, and A. Stamatakis. 2015.
Short tree, long tree, right tree, wrong tree: new acquisition bias corrections for inferring
SNP phylogenies. Systematic Biology 64: 1032-1047.
Mathews, G.M. and E.J.L. Hallstrom. 1943. Notes on the order Procellariiformes. The Federal
Capital Press of Australia Limited, Canberra.
Silva, M.F., A.L. Smith, V.L. Friesen, J. Bried, O. Hasegawa, M.M. Coelho, and M.C. Silva.
2016. Mechanisms of global diversification in the marine species Madeiran Storm-petrel
Oceanodroma castro and Monteiro’s Storm-petrel O. monteiroi: insights from a multilocus
approach. Molecular Phylogenetics and Evolution 98: 314-323.
Singer, D.S., T.A. Benson, G. McCaskie, and J. Stahl. 2020. The 43 rd annual report of the
California Bird Records Committee: 2017 records. Western Birds 51: 2-26.
Smith, A.L., L. Monteiro, O. Hasegawa, and V.L. Friesen. 2007. Global phylogeography of the
band-rumped storm-petrel (Oceanodroma castro; Procellariiformes: Hydrobatidae).
Molecular Phylogenetics and Evolution 43: 755-773.
Smith, A.L. and V.L. Friesen. 2007. Differentiation of sympatric populations of the band-rumped
storm-petrel in the Galapagos Islands: an examination of genetics, morphology, andvocalizations. Molecular Ecology 16: 1593-1603.
Taylor, R.S., M. Bolton, A. Beard, T. Birt, P. Deane-Coe, A.F. Raine, J. González-Solís, S. C.
Lougheed, and V. L. Friesen. 2019. Cryptic species and independent origins of allochronic
populations within a seabird species complex (Hydrobates spp.). Molecular Phylogenetics
and Evolution 139:106552.

15

Wallace, S.J., J.A. Morris-Pocock, J. González-Solís, P. Quillfeldt, and V.L. Friesen. 2017. A
phylogenetic test of sympatric speciation in the Hydrobatinae (Aves: Procellariiformes).
Molecular Phylogenetics and Evolution 107: 39-47.
Woolfenden, G.E., L.R. Monteiro, and R.A. Duncan. 2001. Recovery from the northeastern Gulf
of Mexico of a Band-rumped Storm-Petrel banded in the Azores. Journal of Field
Ornithology 72: 62-65.

Submitted by: Oscar Johnson, Louisiana State University Museum of Natural Science
Date of proposal: 13 May 202016

2021-A-3

N&MA Classification Committee

pp. 187-188

Split Mew Gull Larus canus brachyrhynchus and rename as Short-billed Gull
Description of the problem:
The western North American form now considered a subspecies of the Mew/Common Gull,
Larus canus brachyrhynchus, was treated as a species through the third edition of the AOUchecklist, but was lumped with the widespread Palearctic L. canus in the fourth edition (AOU
1931; https://avibase.bsceoc.org/species.jsp?lang=EN&avibaseid=342F6965&sec=summary&ssver=1; Peters 1934).
The finding of a 2% mtDNA divergence between brachyrhynchus and the east Siberiankamtschatschensis (Zink et al. 1995) has encouraged the treatment of brachyrhynchus as aseparate species by some (Olsen and Larsson 2004) or treatment as three separate fieldidentifiable groups at least (Carey and Kennerley 1996, Howell and Dunn 2007). The lack ofinclusion of the nominate in the Zink et al. (1995) study (which only included one individual ofbrachyrhynchus and three kamtschatschensis), the lack of a more recent and densely sampledpublished phylogeny including these taxa, the poor state of knowledge of the characters of theeastern Palearctic forms heinei and kamtschatschensis, and the suggestion that the Americanand W Palearctic forms might form a single species-group to the exclusion of E Palearctic
kamtschatschensis (AOU 1983, Sibley and Monroe 1993) has contributed to stasis in theirtreatment as a single species (Dickinson and Remsen 2013, del Hoyo and Collar 2014,
Clements et al. 2019, Gill et al. 2020).
New information:
By far the most comprehensive molecular phylogenetic analysis of gulls of which I am aware isin a dissertation (Sternkopf 2011) as yet unpublished in a peer-reviewed journal but available infull online (https://epub.ub.unigreifswald.de/frontdoor/deliver/index/docId/770/file/Dissertation_Viviane_Sternkopf_Uni_Bib.pdf). This dissertation includes an entire section on the Larus canus clade, which also includes
Ring-billed Gull Larus delawarensis. Samples included 36 canus, 12 heinei, fivekamtschatschensis, and four brachyrhynchus. Although brachyrhynchus is not included in theseveral phylogenetic trees of the whole subfamily, the haplotype networks (e.g., Fig. 3.33,
below) support the genetic similarity of all three Palearctic forms to the exclusion ofbrachyrhynchus. An AMOVA of genetic variances showed that the best model was that in which
L. delawarensis and brachyrhynchus were treated as separate species, and the three Palearctic
taxa canus, heinei, and kamtschatschensis united (Sternkopf 2011). Based on these results andpreviously available data, Sternkopf recommended the treatment of brachyrhynchus as a
distinct species, while keeping all Palearctic taxa in L. canus.
A recent paper on the Larus canus complex (Adriaens and Gibbins 2016), published as a
special issue of Dutch Birding, provided an extremely comprehensive 63-page study focusing
on morphology and identification, but incorporating review of vocalizations as well, and it
involved field study of all taxa. A repeatable plumage scoring system with published reference
photos was used for numerous characters of large museum specimen series of all taxa (e.g.,
figs. 9-12 below from Adriaens and Gibbins 2016). Several characters (e.g., diagrams 9 and 12)
showed clear but not quite diagnostic differences between brachyrhynchus and the other taxa,
whereas other characters (e.g. diagrams 10 and 11) did not. Non-metric multi-dimensional
scaling analyses (NMDS) of wing-tip pattern showed near-complete separation between
brachyrhynchus and the Western Palearctic taxa, but a little overlap with kamtschatschensis
17

Fig. 3.33 in Sternkopf (2011): Median-joining tree for cytb, ND2 and HVR-1.

Diagrams 9-12 from Adriaens and Gibbins (2016).
18

(figs. 14 and 15 of Adriaens and Gibbins 2016), which it should be made clear is the mostdistinct from brachyrhynchus in proportions (Adriaens and Gibbins 2016: p. 7).

Figures 14-15 from Adriaens and Gibbins (2016).

Further, display vocalizations were shown to differ between the Palearctic group (withkamtschatschensis being the most different) and brachyrhynchus (as in figs. 10 and 12 from
Adriaens and Gibbins 2016, below). Qualitative vocal differences were previously noted by
Sibley (2000) and Constantine & The Sound Approach (2006).

Adriaens and Gibbins (2016) considered that the morphological diagnosability, geographic
isolation, distinctive vocalizations, and genetic divergence of brachyrhynchus is consistent with
its treatment as a separate species. They did not rule out the possibility that kamtschatschensis
may also be specifically distinct, as it has some vocal differences and is generally readily
distinguishable morphologically, but it does appear to intergrade with the central Palearctic form
heinei and groups genetically with the canus group.

19Effect on AOS-CLC area:
The American form brachyrhynchus occurs along the west coast of North America, with widelyreported vagrancy, including to the Azores (Alfrey and Ahmad 2007). Acceptance of this
proposal would require providing a separate species account for brachyrhynchus. In addition,
the European nominate has been widely reported in eastern North America at least, and there
are numerous North American records of the east Siberian kamtschatschensis, mainly from
Alaska, but also, e.g., from Hawaii and northeastern North America.
Nomenclatural issues:
Mlíkovský (2012) considered the name kamtschatschensis Bonaparte, 1857, to be both a juniorsynonym to Gavina camtschatchensis Bruch, 1855, and a nomen nudum, and Bruch’s namewas adopted by del Hoyo and Collar (2014), but was neither adopted nor commented upon by
Dickinson and Remsen (2013), nor by Gill et al. (2020). Dick Schodde kindly reviewed this case(in litt. 25 Jun 2020) and opined that, while Bonaparte’s earlier usages of kamtschatschensis all
remain nomina nuda, his 1857 usage is potentially available because it was taken up by Peters(1934) before 1961. However, because camtschatchensis Bruch, 1855, is the first available
name, Bruch is the author, but the incorrect subsequent spelling kamtschatschensis is inprevailing usage and thus protected by ICZN Article 33.3.1. Thus, on Schodde’s advice thename should be Larus canus kamtschatschensis (Bruch, 1855).
English names:
Common Gull has long been used for Palearctic birds, and Mew Gull was earlier used for North
American brachyrhynchus. However, recent extensive usage of Mew Gull for all these taxa
(e.g., Gill et al. 2020, Moskoff and Bevier 2020) and for Larus c. canus (not including
brachyrhynchus) by AOU (1886) has made its use exclusively for brachyrhynchus as a daughter
species problematic and not in keeping with our stated policy. Short-billed Gull, however, hasbeen used extensively in recent literature and is the name used in the first edition of the Checklist (AOU 1886) to refer to brachyrhynchus alone, and is apt given that its small bill is one of its
most apparent identification features. The English name Common Gull has been used for theentire complex as well, but has never become entrenched for brachyrhynchus, while being
extremely entrenched for the Palearctic taxa.
Recommendation:
In my opinion the integrative evidence favors treating brachyrhynchus as a separate species
that is best known as Short-billed Gull. The evidence for a split of kamtschatschensis is notably
weaker and would require further analyses.
Please vote separately on each of the following recommendations:
a)
b)
c)
d)
e)

Split Larus brachyrhynchus as a monotypic species from the Larus canus group.
Retain kamtschatschensis within the Larus canus group.
Change the authorship of the east Siberian form to kamtschatschensis (Bruch, 1855).
Adopt the now widely familiar English name Short-billed Gull for Larus brachyrhynchus.
Maintain Common Gull as the English name for Larus canus s.s.

Literature cited:20Adriaens, P., and C. Gibbins (2016). Identification of the Larus canus complex. Dutch Birding
38:1-64.
Alfrey, P., and M. Ahmad (2007). Short-billed Gull on Terceira, Azores, in February-March 2003
and identification of the ‘Mew Gull complex’. Dutch Birding 29:201-212.
American Ornithologists’ Union (1886). Check-list of North American Birds. First Edition.
American Ornithologists’ Union, Washington, D.C.
American Ornithologists’ Union (1931). Checklist of North American Birds, Fourth Edition.
American Ornithologists’ Union, Lancaster, PA.
American Ornithologists’ Union (1983). Check-list of North American Birds. 6th Edition. American
Ornithologists’ Union, Lawrence, KS.
Carey, G. J., and P. R. Kennerley (1996). ‘Mew’ Gull: the first record for Hong Kong and theidentification and systematics of Common Gull forms in East Asia. Hong Kong Bird Report
1995:134-149.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/
Constantine, M., and The Sound Approach (2006). The Sound Approach to birding: a guide tounderstanding bird sound. Sound Approach, Poole, Dorset, UK.
del Hoyo, J., and N. J. Collar (2014). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 1: Non-passerines. Lynx Edicions, Barcelona.
Dickinson, E. C., and J. V. Remsen, Jr. (Editors) (2013). The Howard and Moore Complete
Checklist of the Birds of the World. 4 th edition. Volume One. Non-passerines. Aves Press
Ltd., Eastbourne. UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Howell, S. N. G., and J. Dunn (2007). Gulls of the Americas. Peterson Reference Guide,
Houghton Mifflin, Boston.
Mlíkovský, J. (2012). Nomenclatural notes on the East Asian form of the Mew Gull Larus canus
Linnaeus, 1758 (Aves: Laridae). Zootaxa 3345:65-68.
Moskoff, W., and L. R. Bevier (2020). Mew Gull (Larus canus), version 1.0. In Birds of the World(S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY,
USA. https://doi.org/10.2173/bow.mewgul.01
Olsen, K. M., and H. Larsson (2003). Gulls of Europe, Asia and North America. Second edition.
A & C Black, London.
Peters, J. L. (1934). Checklist of the Birds of the World. Volume II. Harvard University Press,
Cambridge, MA.
Sibley, C. G., and B. L. Monroe, Jr. (1993). A World Checklist of Birds. Yale University Press,
New Haven, CT.
Sibley, D. (2000). The Sibley Guide to Birds. Alfred A. Knopf, New York.
Sternkopf, V. (2011). Molekulargenetische Untersuchung in der Gruppe der Möwen (Laridae)
zur Erforschung der Verwandtschaftsbeziehungen und phylogeographischer
Differenzierung. Ph.D. Dissertation. University of Greifswald.
Zink, R. M., S. Rohwer, A. V. Andreev, and D. L. Dittmann (1995). Trans-Beringia comparisonsof mitochondrial DNA differentiation in birds. Condor 97:639-649.

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 25 June 202021

2021-A-4

N&MA Classification Committee

pp. 32-34

Revise generic limits in the Phalacrocoracidae (cormorants)
Description of the problem:
For many years, all cormorants were placed in a single genus (e.g., AOU 1886, Mayr andCottrell 1979), a treatment that presumably seemed warranted due to their relative homogeneityof form and plumage. Siegel-Causey (1988), on the basis of an osteological analysis, divided
the family into two subfamilies: the Phalacrocoracinae, with four genera; and the
Leucocarboninae, with five genera, but this treatment was not widely adopted. Kennedy et al.’s(2000) early DNA phylogeny did not recover most of Siegel-Causey’s (1988) clades, including at
the subfamily level. This led Worthy (2011), who sought to determine the relationships of certain
Late Oligocene-Early Miocene (26–24 mya) Australian fossil cormorants (Nectornis andNambashag, the latter a new genus), to base his osteological analysis of modern taxa on adifferent set of newly scored characters. Worthy’s (2011) osteologically based phylogenetic tree
recovered many but by no means all of the clades in Kennedy et al. (2000, 2009). Because
many taxa were still missing from their phylogenies, Kennedy et al. (2009) recommended
continuing to retain all species in the genus Phalacrocorax, although they suggested that
ultimately two or more genera might be justified. Most world lists, however, now recognize atleast two genera, Microcarbo and Phalacrocorax (Dickinson and Remsen 2013, del Hoyo andCollar 2014, Clements et al. 2019, Gill et al. 2020); Microcarbo does not occur in the NACC
area.
More recently, Kennedy and Spencer (2014) produced a nearly complete phylogeny of
Phalacrocoracidae, which formed the basis for Remsen’s (2014) proposal #648 to SACC torecognize 7 genera in the Phalacrocoracidae (which nearly passed, failing at 6-4 to attain a 2/3
vote; see votes and comments at https://www.museum.lsu.edu/~Remsen/SACCprop648.htm),
as well as to Remsen’s recent proposal (2020-A-12) to NACC that led us to resequence the
NACC-area cormorants (Chesser et al. 2020). The latter proposal did not address generic limits
in the Phalacrocoracidae but did mention the need for such a proposal.
New information:
As NACC has not yet formally considered the issue of generic limits raised by the phylogenies(see screenshots below) of Kennedy et al. (2009, 2019), Kennedy and Spencer (2014), andWorthy (2011), the new NACC-relevant issues involved include the findings, concordant among
these studies, that:
1) Phalacrocorax carbo, the type species, forms a well-supported clade with many Old
World taxa that remain in Phalacrocorax sensu stricto;
2) Phalacrocorax auritus, P. brasilianus, and P. harrisi form a well-supported clade, with P.
harrisi (not included in Worthy 2011) sister to the other two, and with the generic nameNannopterum taking priority; and
3) The Pacific taxa P. penicillatus, P. pelagicus, and P. urile form a well-supported andhighly divergent clade, with P. penicillatus sister to the other two; the name Urile takes
priority for this clade.
The morphological phylogeny of Worthy (2011) and the molecular phylogenies of Kennedy andSpencer (2014) and Kennedy et al. (2019), despite all recovering these clades, differ in otherrespects, such as the relationships of Nannopterum (sister to Phalacrocorax s.s. in the22osteological phylogeny, but sister to Southern Hemisphere Leucocarbo in the molecularphylogenies) and of Urile (sister to Leucocarbo in the osteological phylogeny but sister toPhalacrocorax s.s. in the molecular phylogenies). Nevertheless, these clades are wellsupported and strongly divergent, and are Miocene in age (see NACC proposal 2020-A-12).

Figure 5 from Worthy (2011).

23

Figure 1 from Kennedy et al. (2019), portion relevant to NACC taxa below.

Effect on AOS-CLC area:
Acceptance of this proposal would result in two very widespread and familiar species longplaced in Phalacrocorax (auritus and brasilianus) being moved to Nannopterum, and three othermarine Pacific taxa (penicillatus, pelagicus, and urile) being moved to Urile. There would be nochange to Phalacrocorax carbo. No change is needed to English names (though some may bedesired, e.g., Pelagic Cormorant), and we have already resequenced NACC-area taxa following
Kennedy and Spencer (2014).
Recommendation:
Given the Miocene age of these divergences and the concordance between Worthy’s
osteological and Kennedy et al.’s genetic phylogenies, at least as far as defining these clades, I
recommend that we adopt Nannopterum as the genus for auritus and brasilianus and Urile forthe 3-species Pacific clade. Short of maintaining all in Phalacrocorax, which I do notrecommend considering the great age of the clades, no other treatment agrees well with bothdatasets and with basic plumage patterns and biogeography.
Please vote on both of the following:a) Recognize Nannopterum and transfer brasilianus and auritus to this genus; and24b) Recognize Urile and transfer penicillatus, pelagicus, and urile to this genus.
Literature cited:
American Ornithologists’ Union (1886). Check-list of North American Birds. First Edition,
American Ornithologists’ Union, Washington, D.C.
Chesser, R.T., S.M. Billerman, K.J. Burns, C. Cicero, J.L. Dunn, A.W. Kratter, I.J. Lovette, N.A.
Mason, P.C. Rasmussen, J.V. Remsen, Jr., D.F. Stotz, and K. Winker (2020). Sixty-first
Supplement to the American Ornithological Society’s Check-list of North American Birds.
The Auk: Ornithological Advances. https://doi.org/10.1093/auk/ukaa030.
Clements, J.F., T.S. Schulenberg, M.J. Iliff, S.M. Billerman, T.A. Fredericks, B.L. Sullivan, andC.L. Wood (2019). The eBird/Clements Checklist of Birds of the World: v2019. Downloaded
from https://www.birds.cornell.edu/clementschecklist/download/del Hoyo, J., and N.J. Collar (2014). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 1: Non-passerines. Lynx Edicions, Barcelona.
Dickinson, E.C., and J.V. Remsen, Jr. (Editors) (2013). The Howard and Moore Complete
Checklist of the Birds of the World. 4 th edition. Volume One. Non-passerines. Aves Press
Ltd., Eastbourne. UK.
Gill, F., D. Donsker, and P.C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Kennedy, M., and H.G. Spencer (2014). Classification of the cormorants of the world. MolecularPhylogenetics and Evolution 79:249–257.
Kennedy, M., R.D. Gray, and H.G. Spencer (2000). The phylogenetic relationships of the shags
and cormorants: can sequence data resolve a disagreement between behavior andmorphology? Molecular Phylogenetics and Evolution 17: 345–359.
Kennedy, M., C.A. Valle, and H.G. Spencer (2009). The phylogenetic position of the Galapagos
Cormorant. Molecular Phylogenetics and Evolution 53:94–98.
Kennedy, M., S.S. Seneviratne, N.J. Rawlence, S. Ratnayake, and H.G. Spencer (2019). The
phylogenetic placement of the enigmatic Indian Cormorant, Phalacrocorax fuscicollis(Phalacrocoracidae). Molecular Phylogenetics and Evolution 130:227–232.
Mayr, E., and G.W. Cottrell (1979). Check-list of Birds of the World. Volume 1. Second Edition.
Museum of Comparative Zoology, Cambridge, Massachusetts.
Siegel-Causey, D. (1988). Phylogeny of the Phalacrocoracidae. Condor 90:885–905.
Worthy, T.H. (2011). Descriptions and phylogenetic relationships of a new genus and two new
species of Oligo-Miocene cormorants (Aves: Phalacrocoracidae) from Australia. Zoological
Journal of the Linnean Society 163: 277–314.

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 30 June 202025

2021-A-5

N&MA Classification Committee

p. 491(A) Adopt split of Long-billed Gnatwren Ramphocaenus melanurus
Description of the problem and new information:
The Long-billed Gnatwren Ramphocaenus melanurus has long been treated as a single
widespread, highly polytypic species (Mayr and Cottrell 1964). Now, with the publication of arobust phylogeny of the Polioptilidae (Smith et al. 2018), the most divergent taxa (the sticturusgroup) of the complex have been split (Proposal 790A to SACC,
https://www.museum.lsu.edu/~Remsen/SACCprop790.htm), based on clear evidence: sympatryof vocally different but morphologically similar taxa that are also deeply diverged genetically(Harvey et al. 2014, Smith et al. 2018). I strongly recommend reading that proposal, as much in
it is not summarized here.
The second part of the proposal (790B), to split the northern rufiventris group, which includes
the subspecies in the NACC region, failed even though historically they had been considered aseparate species (see AOU 1983, Phillips 1991), but the case is far less clear and was deemedby most SACC members to require further sampling. There are typical but not absolute vocal
differences as well as plumage differences that led to the rufiventris group being considered athird potential species group by Sibley and Monroe (1990), as did del Hoyo and Collar (2016),
although Dickinson and Christidis (2014) treated the complex as being comprised of two
subspecies groups. Clements et al. (2019) and Gill et al. (2020) followed SACC in recognizing
the split of Chattering Gnatwren for the E Peruvian to SW Brazilian taxa in the sticturus group(including obscurus) from Trilling Gnatwren R. melanurus (all other races, including therufiventris group).
Effect on AOS-CLC area:
Although the split enacted in 790A involves peripheral southern taxa vs. all others and thus isextralimital to the NACC region, the English names of both daughter species have changed as aresult for the SACC area. The forms occurring in the NACC area are part of the species now
called Trilling Gnatwren by SACC. However, given that the vast preponderance of the former
range of Ramphocaenus melanurus sensu lato is occupied by Ramphocaenus melanurus sensu
stricto, it would be within our guidelines to retain the name Long-billed Gnatwren, and that would
have the advantage of stability, especially given the likelihood that the rufiventris group may bere-split in the near future. However, we generally follow SACC for groups that are largely in the
SACC area.
Other impacts would include needed revision of the Notes section and reversing the linear
sequence so that Microbates cinereiventris follows Ramphocaenus melanurus, following ourconventions.
Recommendation:
I recommend (with the above reservations) that we follow SACC and (A) adopt the split ofRamphocaenus melanurus and (B) adopt the English name Trilling Gnatwren for the taxon
group that includes those taxa occurring in the NACC area. I further recommend (C) that we
resequence the Ramphocaenini (sensu AOU 1983) so that Ramphocaenus precedes
Microbates. Please vote separately for each of these options.
26

Literature Cited:
American Ornithologists’ Union (1983). Check-list of North American Birds. Sixth Edition.
American Ornithologists’ Union, Lawrence, KS.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.
Dickinson, E. C., and L. Christidis (Editors) (2014). The Howard and Moore Complete Checklistof the Birds of the World. 4th edition. Volume Two. Passerines. Aves Press Ltd., Eastbourne.
UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Harvey, M. G., D. F. Lane, J. Hite, R. S. Terrill, S. Figueroa R., B. T. Smith, J. Klicka, and W.
Vargas C. (2014). Notes on bird species in bamboo in northern Madre de Dios, Peru
including the first Peruvian record of Acre Tody-Tyrant (Hemitriccus cohnhafti). Occasional
Papers of the Louisiana State University Museum of Natural Science 81:1–38.
Mayr, E., and G. W. Cottrell (Editors) (1964). Check-list of the Birds of the World. Volume 10.
Harvard University Press, Cambridge, MA.
Phillips, A. R. (1991). The known birds of North and Middle America, Part II: Bombycillidae;
Sylviidae to Sturnidae; Vireonidae. A. R. Phillips, Denver, CO, USA.
Sibley, C. G., and B. L. Monroe, Jr. (1990). Distribution and Taxonomy of Birds of the World.
Yale University Press, New Haven, CT.
Smith, B. T., R. W. Bryson, Jr., W. M. Mauck III, J. Chaves, M. B. Robbins, A. Aleixo, and J.
Klicka (2018). Species delimitation and biogeography of the gnatcatchers and gnatwrens(Aves: Polioptilidae). Molecular Phylogenetics and Evolution 126:45–57.

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 13 July 202027

2021-A-5

N&MA Classification Committee

p. 491(B) Retain the English name Long-billed Gnatwren for Ramphocaenus melanurus sensu stricto
SACC initially voted to replace the English name of Ramphocaenus melanurus when splitting itfrom R. sticturus, despite Dan Lane's proposal recommending that the English name beretained for melanurus sensu stricto based on this taxon occupying almost all the distributionof melanurus sensu lato (and presumably the vast majority of literature on R.
melanurus referring to this form rather than to the restricted-range sticturus). Pam noted this as
well in her proposal (2021-A-5) to follow SACC in splitting melanurus:"The forms occurring in the NACC area are part of the species now called Trilling Gnatwren by
SACC. However, given that the vast preponderance of the former range of Ramphocaenus
melanurus sensu lato is occupied by Ramphocaenus melanurus sensu stricto, it would be within
our guidelines to retain the name Long-billed Gnatwren, and that would have the advantage ofstability, especially given the likelihood that the rufiventris group may be re-split in the near
future. However, we generally follow SACC for groups that are largely in the SACC area."
Most NACC members initially agreed to go along with SACC on the English name, despite its
being at odds with our English names policy, but Van recently asked SACC to reconsider theirchange to Trilling Gnatwren and they have now agreed to retain Long-billed Gnatwren for R.
melanurus s.s. Now that SACC has changed their vote on this, we also need to vote on
retaining the English name Long-billed Gnatwren for R. melanurus s.s., a course of action that I
strongly recommend.

Submitted by: Terry Chesser
Date of Proposal: 15 April 2021

28

2021-A-6

N&MA Classification Committee

pp. 491-494

Change the linear sequence of the gnatcatchers (Polioptila spp.)
Description of the problem:
Our current sequence (Chesser et al. 2019) for gnatcatchers is:Blue-gray Gnatcatcher Polioptila caerulea
Cuban Gnatcatcher Polioptila lembeyei
California Gnatcatcher Polioptila californica
Black-tailed Gnatcatcher Polioptila melanura
Black-capped Gnatcatcher Polioptila nigriceps
White-lored Gnatcatcher Polioptila albiloris
Yucatan Gnatcatcher Polioptila albiventris
Tropical Gnatcatcher Polioptila plumbea
Slate-throated Gnatcatcher Polioptila schistaceigula
New information:
Smith et al. (2018) produced the first densely-sampled (95-98% of all subspecies) phylogeny of
the Polioptilidae using mtDNA and 6 nuclear markers (screenshot below), in which, notsurprisingly, the trees produced a very different linear sequence (see tree on next page).
Effect on AOS-CLC area:
Following our conventions for linear sequencing, this would lead to the new sequence:
Slate-throated Gnatcatcher Polioptila schistaceigula
Cuban Gnatcatcher Polioptila lembeyei
Yucatan Gnatcatcher Polioptila albiventris
Tropical Gnatcatcher Polioptila plumbea (White-browed P. bilineata if proposal passes)
Blue-gray Gnatcatcher Polioptila caerulea
Black-tailed Gnatcatcher Polioptila melanura
California Gnatcatcher Polioptila californica
Black-capped Gnatcatcher Polioptila nigriceps
White-lored Gnatcatcher Polioptila albiloris
Recommendation:
I recommend that we adopt the new sequence.
Literature Cited:
Chesser, R. T., K. J. Burns, C. Cicero, J. L. Dunn, A. W. Kratter, I. J. Lovette, P. C. Rasmussen,
J. V. Remsen, Jr., D. F. Stotz, and K. Winker (2019). Check-list of North American Birds(online). American Ornithological Society. http://checklist.americanornithology.org/taxa
Smith, B. T., R. W. Bryson, Jr., W. M. Mauck III, J. Chaves, M. B. Robbins, A. Aleixo, and J.
Klicka (2018). Species delimitation and biogeography of the gnatcatchers and gnatwrens(Aves: Polioptilidae). Molecular Phylogenetics and Evolution 126:45–57.
29

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 14 July 2020

Fig. 1D of Smith et al. (2018), showing their maximum clade credibility tree. Red dots indicate
posterior probabilities ≥ 0.95.

302021-A-7

N&MA Classification Committee

p. 493

Split Tropical Gnatcatcher Polioptila plumbea into two or more species
Note: This is a joint proposal to be considered concurrently by SACC (proposal number not yet
assigned).
Background:
The Tropical Gnatcatcher Polioptila plumbea, as with many widespread and polytypic
Neotropical species complexes, has a checkered taxonomic history (see, e.g., Mayr and Cottrell
1964; https://avibase.bsceoc.org/species.jsp?lang=EN&avibaseid=CE922FF7EFA174EE&sec=synonyms). The nature ofvariation among gnatcatchers, with the very limited suite of phenotypic characters that may varyseasonally, sexually, and geographically, has meant that plumage-based taxonomies areespecially problematic, and that has certainly been true of P. plumbea. The two main groups
recognized by Sibley and Monroe (1993), Dickinson and Christidis (2013) and del Hoyo andCollar (2016) are the bilineata group, occurring from southern Mexico through northwest Peru,
and the cis-Andean plumbea group, occurring widely in South America. To greatly simplify, theformer group has a broad white eyebrow year-round, whereas the latter group lacks this yearround. The races of the bilineata group occurring in the NACC region, as recognized by AOU(1957) and subsequent subspecies-level checklists (e.g., Dickinson and Christidis 2013, Gill et
al. 2020), are P. p. brodkorbi of southern Mexico through northern Costa Rica, P. p. superciliaris
of north-central Costa Rica to southern Panama or northern Colombia, and P. p. cinericia of
Coiba Island, Panama. Both the bilineata group and the plumbea group occur in the SACC
region, in some 8–9 races. Zimmer (1942), on the basis of a few northern South American
specimens that showed intermediacy between plumbiceps and bilineata, considered the twomain groups to be conspecific. This intermediacy mainly involved tiny, variable amounts of whitein the face of some Colombian and Venezuelan specimens, as well as a “perfect transition”
between taxa in the amount of white on the outer rectrices.
New information:
In the first densely sampled phylogeny of the Polioptilidae (Smith et al. 2018), multiple cases ofpolyphyly were uncovered, including the fact that Slate-throated Gnatcatcher P. schistaceigulaof Panama and northwestern South America was embedded within Guianan Gnatcatcher P.
guianensis, which has since been resolved with the acceptance of SACC Proposal 751.1(https://www.museum.lsu.edu/~Remsen/SACCprop751.htm) to split P. guianensis. No further
action with respect to schistaceigula is needed by NACC.
Further, and hence the subject of this proposal, P. plumbea was found to be polyphyletic, withthe taxon from northern Yucatan, then treated as P. albiloris albiventris, nested within one of two
widely diverged P. plumbea clades (see screenshot below from Smith et al. [2018] of therelevant clades) that are highly incongruent with previously recognized group boundaries as
outlined above. Instead of all cis-Andean races belonging to the plumbea clade, Smith et al.
(2018) found that those from central Colombia through the western Guianas are more closely
related to the bilineata group + albiventris. Note that Proposal NACC 2019-C-7 to treat31

Fig. 4 (part) of Smith et al. (2018). The miniature phylogenies at the top (to the left of each map)show the phylogeny of the family, whereas the larger trees with colored symbols show details of
the phylogenies of the two main clades of P. plumbea highlighted in blue on the family
phylogeny. The white-lored bilineata clade, in which all three NACC-region taxa (brodkorbi,
superciliaris, and cinericia) occur, is the clade on the upper half of the left phylogeny. SACCarea taxa occur more broadly throughout the phylogeny. Those in the lower half of the left tree
are the dark-lored northeastern SA group formerly assumed to be part of the plumbea clade;widely allopatric Marañon Valley maior (in which females have the white brow) is a rather
divergent sister to this clade.
32

Fig. 4 (part) of Smith et al. (2018). This portion of the phylogeny consists of Cuban Gnatcatcher
P. lembeyei and P. dumicola (lower half) as successive sisters to a polytomy comprised of P.
lactea + P. plumbea (the three races of the nominate group s.s.).
-----------------------------------------------------------------------------------------------------------------------------

33

albiventris as a species rather than a subspecies of P. plumbea passed, in part in recognition of
the apparent inevitability that P. plumbea comprises multiple species.
The other group, cis-Andean races from Surinam east and south, the nominate P. plumbea
group (plumbea, parvirostris, and atricapilla), instead forms a polytomy with Creamy-bellied
Gnatcatcher P. lactea. The possibility that lactea may be a distinctive form of plumbea wasrecognized by Hellmayr (1934). Sister to the plumbea s.s. + lactea group was Masked
Gnatcatcher P. dumicola of south-central South America.
Within the Middle American + trans-Andean + albiventris + northernmost South American group,
Smith et al.’s (2018) molecular phylogeny shows two fairly divergent clades, the bilineata clade(which includes the three NACC-area and the northwestern trans-Andean taxa, plus daguae of
the Cauca Valley, western Colombia) and the northeastern clade (anteocularis, plumbiceps, andinnotata) from the upper Magdalena Valley (central Colombia) through Guyana and northern
Brazil, hitherto considered part of the nominate group. The sister to the northeastern clade,maior of the Marañon Valley (Peru), was treated as a separate species by Hellmayr (1934), as a
species group by Sibley and Monroe (1993) and Dickinson and Christidis (2014), and was split
by del Hoyo and Collar (2016) based on multiple plumage differences and very different voice; itis also “decidedly larger” (Hellmayr 1934). LePage (2020) lists the bilineata group, albiventer,and maior as separate species from the plumbea group, which, however, still includes theplumbiceps group of northeastern South America, and therefore is non-congruent with thephylogeny of Smith et al. (2018). del Hoyo et al. (2020, last updated 2017) delineated multiple
monotypic groups in the plumbea s.s. clade.
Effect on AOS-NACC area:
The more complex issues involving the seemingly parapatric plumbiceps and plumbea groups
fall within the SACC area remit. NACC area taxa all belong to the bilineata group, which canhardly remain within P. plumbea because of the polyphyly in the phylogeny of Smith et al.
(2018). Because bilineata (Bonaparte, 1850) is the oldest name in the entire major clade that
includes the NACC-area species (including the plumbiceps Lawrence, 1865 group), NACC cansplit this group from the widely diverged plumbea (Gmelin, 1788) clade without concern about
having to then change the name again soon (unless the proposal to split the two main clades
fails in SACC). Nevertheless, this seems an appropriate issue for simultaneous voting by bothcommittees so that the best resolution agreeable to both will result. The fact that NACC alreadyrecognizes albiventris as specifically distinct should be taken into account in determining which
taxa (if any) beyond the Middle American and trans-Andean taxa are included in the bilineatagroup.
Acceptance of this proposal would result in change of the specific epithet of the NACC-area
taxa and almost certainly the English name, revisions to the Distribution statement, andaddition of a Notes statement in the Check-list.
Effect on SACC area:
The SACC area could gain as many as three species, or potentially suffer a net loss of one
species, depending on the outcome of this proposal.
34

Recommendations:
Please vote on the following issues (see each vote for recommendation and who should vote):(A) split the plumbea group (plumbea-parvirostris-atricapillus) from the remaining taxa
(strongly recommended due to polyphyly; all vote on this);(B) if A passes, adopt the English name White-browed Gnatcatcher for the bilineatagroup, as it is already in use in Sibley and Monroe (1993), HBW/BirdLife, Clements,and elsewhere; however, it is apt only for the Middle American and trans-Andeantaxa, if D does not pass (recommended; all vote on this);(C) if A passes, retain the English name Tropical Gnatcatcher for the plumbea group, as
it would still represent the most widely-distributed group, is already used in Sibley
and Monroe (1993), HBW/BirdLife, Clements, and elsewhere; and good names for
gnatcatchers are hard to come by; however, it is likely to cause some confusion withthe parent taxon and is apt for most gnatcatchers (recommended; SACC votes);(D) split the plumbiceps group from the bilineata group (recommended; SACC votes)*;(E) split maior from the plumbiceps group (recommended; SACC votes);(F) if E passes, adopt the English name Marañon Gnatcatcher for maior (recommended;
SACC votes). Note that Hellmayr (1934) used Greater Gnatcatcher. Either name isapt and distinctive but Marañon has gained currency recently.
(G) Retain Polioptila lactea as a species rather than treating it as conspecific with theplumbea group, pending further study (recommended; SACC votes). It seems
premature to lump this with plumbea based on present data and it would be perhaps
the most distinctive subspecies of any gnatcatcher if lumped (assuming at least A
passes).
*If D passes, a new proposal would be required for the English name of the plumbiceps group.
Hellmayr (1934) used the names Magdalena Valley Gnatcatcher, Lawrence’s Gnatcatcher, and
Rio Branco Gnatcatcher for these taxa.
Literature Cited:
American Ornithologists’ Union (1957). Checklist of North American Birds. Fifth Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1983). Check-list of North American Birds. Sixth Edition.
American Ornithologists’ Union, Lawrence, KS.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/35

del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.
del Hoyo, J., N. Collar, and G. M. Kirwan (2020). Tropical Gnatcatcher (Polioptila plumbea),
version 1.0. In Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, and T. S.
Schulenberg, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
Dickinson, E. C., and L. Christidis (Editors) (2014). The Howard and Moore Complete Checklistof the Birds of the World. 4th edition. Volume Two. Passerines. Aves Press Ltd., Eastbourne.
UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Hellmayr, C. E. (1934). Catalogue of Birds of the Americas and Adjacent Islands. Part VII.
Publication 330, Field Museum of Natural History, Chicago.
LePage, D. (2020). Avibase: the World Bird Database. https://avibase.bsceoc.org/avibase.jsp?lang=EN, accessed 14 July 2020.
Mayr, E., and G. W. Cottrell (Editors) (1964). Check-list of the Birds of the World. Volume 10.
Harvard University Press, Cambridge, MA.
Sibley, C. G., and B. L. Monroe, Jr. (1993). A World Checklist of Birds. Yale University Press,
New Haven, CT.
Smith, B. T., R. W. Bryson, Jr., W. M. Mauck III, J. Chaves, M. B. Robbins, A. Aleixo, and J.
Klicka (2018). Species delimitation and biogeography of the gnatcatchers and gnatwrens(Aves: Polioptilidae). Molecular Phylogenetics and Evolution 126:45–57.
Zimmer, J. T. (1942). Studies of Peruvian birds. No. XLII. The Genus Polioptila. American
Museum Novitates No. 1168.

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 16 July 202036

2021-A-8

N&MA Classification Committee

p. 35

Split Fregata rothschildi from Magnificent Frigatebird F. magnificens
Note: This issue is also being considered by SACC in their Proposal 872. See SACC votes andcomments at https://www.museum.lsu.edu/~Remsen/SACCprop872.htm
Background:
The frigatebirds, with their great plumage similarity among comparable ages and sexes, as wellas the very different immature stages over a period of several years, have long been thesubjects of taxonomic confusion. Few avian groups with so few species can have had so many
words, photos, and illustrations dedicated solely (and often futilely) to their identification.
Nevertheless, many early authors thought a single species inhabited pantropical oceans, andthough several taxa had by then been named, only two species were recognized in theCatalogue of the Birds in the British Museum (Ogilvie-Grant 1898). Two forms, a larger andsmaller one, were recognized to occur on the Galapagos by Ridgway (1897), but Rothschild andHartert (1899) believed they intergraded completely and therefore were not worthy even ofsubspecies status. Mathews (1914), based on study of specimens in the British Museum,recognized that two distinct frigatebird taxa breed in the Galapagos Islands. Among the several
new Fregata taxa he described from the tropics was Fregata minor magnificens Mathews, 1914,
which he considered a subspecies of Great Frigatebird F. minor (Mathews 1914, 1915).
Rothschild (1917) then reconsidered his earlier position and clarified that magnificens should betreated as a species rather than as a subspecies of minor. Since then, magnificens and minor
have been generally recognized as full species that are mostly allopatric except on the
Galapagos, and subsequent authors have generally recognized five species of frigatebird (e.g.,
Lowe 1924). Two or three subspecies are often recognized for F. magnificens, the nominate in
the Galapagos, rothschildi in most of the rest of the range, and lowei for the highly isolated
population of the Cape Verde Islands (Swarth 1933, AOU 1957, del Hoyo and Collar 2014). In
many other treatments, including most recent ones, however, magnificens is treated as
monotypic (AOU 1931, Dorst and Mougin 1979, Dickinson and Remsen 2013, Clements et al.
2019, Gill et al. 2020). The AOU (e.g., AOU 1886, 1895, 1910) long recognized just a single
regional species, what is now known as the Magnificent Frigatebird F. magnificens, but three
species are now included in the expanded NACC region (AOU 1983, Chesser et al. 2019), andfour in the SACC region (Remsen et al. 2020).
New information:
Hailer et al. (2011) found high levels of gene flow over most of the New World range of F.
magnificens, including across the Isthmus of Panama, which usually serves as a barrier toseabirds. However, despite predictions based on the extraordinary vagility of frigatebirds, theGalapagos population was found to be strongly genetically differentiated from the otherpopulations (see screenshots below of Figs. 2 and 3 from Hailer et al. 2011). The Galapagos
population therefore must have been genetically isolated for at least a few hundred thousand
years (Hailer et al. 2011).

37

Further, in a study of population structure primarily of Atlantic and Caribbean populations, Nusset al. (2016) found that, although Brazilian and Caribbean populations were genetically isolated
from one another, the geographically interposed population from French Guiana (Grand

Fig. 2 from Hailer et al. (2011). Parsimony network of mtDNA sequences, Galapagos in red.

Fig. 3 from Hailer et al. (2011). PCA of microsatellite genotypes, Galapagos in red.
----------------------------------------------------------------------------------------------------------------------Connétable) shared haplotypes with both regions. As shown by Hailer et al. (2011), theGalapagos population had highly divergent haplotypes (see screenshot of Fig. 2 from Nuss etal. 2016, below). In a study of Mexican F. magnificens populations, Rocha-Olivares and
González-Jaramillo (2014) found lower levels of gene flow between colonies and especially38between ocean basins than did Hailer et al. (2011), and offered explanations for thisdiscrepancy, including more individuals sampled, more peripheral sampling locations, andgreater geographical distances in their more recent study.

Fig. 2 from Nuss et al. (2016). Median-joining network, mtDNA haplotypes.
------------------------------------------------------------------------------------------------------------------------Despite the genetic divergence of the Galapagos F. magnificens population, the same
haemoprotean parasite, Haemoproteus iwo, occurs in F. minor as well as F. m. magnificens
from Galapagos and multiple localities within the range of F. m. rothschildi (Clade B of Fig. 1 inLevin et al. 2011, see screenshot below). This non-congruence in divergence levels between
parasite and host suggests that transfer by hippoboscid flies (e.g. Olfersia) may take place
between non-breeding frigatebirds at communal roosts, as well as at colonies. There is somemovement of non-breeding Galapagos birds to Central America, where dead and/or emaciatedbirds banded in the Galapagos have been recovered (according to a pers. comm. in Hailer et al.
2011; details not provided). The parasite’s lack of divergence may be considered confirmatoryof the mixing of frigatebird populations outside of the breeding colonies.

Fig. 1 of Levin et al. (2011). Relevant part of ML tree of haemosporidian cytb.

39

Several external measurements of Magnificent Frigatebirds (5 of each sex from the Galapagos,
11 and 16 from non-Galapagos specimens) corroborated that, in wing and inner and outer taildimensions, and culmen of females, the Galapagos population is significantly larger (Hailer et
al. 2011). My informal inspection of many eBird photos (selecting only those in nonforeshortened view) seems to confirm that the tail is relatively longer in Galapagos birds.
Otherwise, I cannot see any plumage or soft part color differences and am unaware of any thathave been reliably suggested.
The authors of the above studies are in general agreement that sex-biased dispersal (withmales exhibiting site-fidelity) and female mate choice for the complex male mating rituals of
frigatebirds is most likely to explain the patterns seen, especially the genetic distinctness of theGalapagos population. However, none presented or referenced any data on differences, forexample, in display or vocalizations. I located only one online recording from the Galapagos,
which did not prove useful, although there must be recordings in compilations and private
collections. It seems apparent that isolating mechanisms beyond simple geographical isolationmust be operating; otherwise, the Galapagos population would be experiencing gene flow withmainland birds.
The Cape Verde population named F. m. lowei has not been included in the above studies, but
as of 2012 only one bird of each sex appeared to be present at the former colony (Suarez et al.
2012), due to persecution. These authors indicated their intention to conduct genetic andmensural analyses of the distinctiveness of this virtually extinct population.
Note that Olson (2017) has recently espoused treatment of Lesser Frigatebird Fregata ariel as
two species, as the form trinitatis now restricted to Trindade Island and known from St. Helena
by fossils has different proportions (stouter wing and bill) and putative plumage differences in
immature stages. There are parallels with the case of Magnificent Frigatebird, but genetic datathat would bolster the case for specific status of trinitatis appear to be lacking. A proposal(SACC#768, https://www.museum.lsu.edu/~Remsen/SACCprop768.htm) to split trinitatis was
rejected in favor of further evidence.
Effect on AOS-NACC and SACC areas:
If split, the Galapagos population would retain the specific epithet magnificens, and thus thewidespread frigatebird of the Americas would become Fregata rothschildi. There would also
obviously be English names issues. In addition, there are evidently records of Galapagos birds
from Central America, so details would have to be located for the NACC area, and a new
species added for both.
It should be added that, even if this proposal does not pass, this species clearly should not be
considered monotypic by global checklist authorities.
Recommendations:
Although it would be ideal if there were behavioral studies and analyses of the courtship display
and vocalization repertoire that established the existence of premating isolating mechanisms
between Galapagos and mainland birds, these are not available to my knowledge. What we do
40

know is that there is little if any gene flow, despite movement of at least some non-breeding
individuals from the Galapagos to the mainland, which I take to be prima facie evidence thatspeciation has occurred. Please vote separately for each option.
a) split F. m. magnificens, with the resultant daughter species F. magnificens of theGalapagos and F. rothschildi in the remainder of the range (whether or not lowei of Cape
Verde is recognized).
If (a) passes, English name issues arise. Obviously, Magnificent Frigatebird could be retained
for the vastly more widespread rothschildi but it would no doubt cause confusion, given theretention of magnificens by the Galapagos form. (Consider though that we have all learned tolive with Great Frigatebird being Fregata minor, while Lesser is F. ariel.) Another option might
be American Frigatebird, but of course Galapagos are part of the Americas. I recommend
retention of Magnificent though as being the least disruptive option.
b) retain the English name Magnificent Frigatebird for Fregata rothschildi.
Galapagos Frigatebird would be my suggestion for F. magnificens s.s.
c) adopt the English name Galapagos Frigatebird for F. magnificens.
Literature Cited:
American Ornithologists’ Union (1886). Check-list of North American Birds. First Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1895). Check-list of North American Birds. Second Edition,
Revised. American Ornithologists’ Union.
American Ornithologists’ Union (1910). Check-list of North American Birds. Third Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1931). Check-list of North American Birds. Fourth Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1957). Check-list of North American Birds. Fifth Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1983). Check-list of North American Birds. Sixth Edition.
American Ornithologists’ Union.
Chesser, R. T., K. J. Burns, C. Cicero, J. L. Dunn, A. W. Kratter, I. J. Lovette, P. C. Rasmussen,
J. V. Remsen, Jr., D. F. Stotz, and K. Winker (2019). Check-list of North American Birds(online). American Ornithological Society. http://checklist.americanornithology.org/taxa
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.
Dorst, J., and J.-L. Mougin (1979). Order Pelecaniformes. Pp. 155–193 in: Mayr, E. and G. W.
Cottrell (Editors). Check-list of the Birds of the World. Volume 1, Ed. 2. Harvard University
Press, Cambridge, MA.

41

Dickinson, E. C., and J. V. Remsen, Jr. (Editors) (2013). The Howard and Moore Complete
Checklist of the Birds of the World. 4 th edition. Volume One. Non-passerines. Aves Press
Ltd., Eastbourne, UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Hailer, F., E. A. Schreiber, J. M. Miller, I. I. Levin, P. G. Parker, R. T. Chesser, and R. C.
Fleischer (2011). Long-term isolation of a highly mobile seabird on the Galapagos.
Proceedings of the Royal Society B 278:817–825.
Hellmayr, C. E., and B. Conover (1948). Catalogue of Birds of the Americas and AdjacentIslands. Vol. 13, Part I, No. 2. Publication 615, Field Museum of Natural History, Chicago.
Levin, I. I., G. Valkiunas, D. Santiago-Alarcon, L. L. Cruz, Tatjana A. Iezhova, S. L. O’Brien, F.
Hailer, D. Dearborn, E. A. Schreiber, R. C. Fleischer, R. E. Ricklefs, and P. G. Parker(2011). Hippoboscid-transmitted Haemoproteus parasites (Haemosporida) infect Galapagos
pelecaniform birds: evidence from molecular and morphological studies, with a descriptionof Haemoproteus iwa. International Journal for Parasitology 41:1019–1027.
Lopez-Suarez, P., C. Hazevoet, and L. Palma (2012). Has the Magnificent Frigatebird Fregata
magnificens in the Cape Verde Islands reached the end of the road? Zoologia Caboverdiana
3:82–86.
Lowe, P. R. (1924). Some notes on the Fregatidae. Novitates Zoologicae 31:299–313.
Mathews, G. M. (1914). On the species and subspecies of the genus Fregata. The Austral
Avian Record 2:117–121.
Mathews, G. M. (1915). The Birds of Australia. Volume 4. Witherby, London.
Nuss, A., C. J. Carlos, I. B. Moreno, and N. J. R. Fagundes (2016). Population genetic structureof the Magnificent Frigatebird Fregata magnificens (Aves, Suliformes) breeding colonies in
the Western Atlantic Ocean. PLoS ONE 11:e0149834.
Ogilvie-Grant, W. R. (1898). Catalogue of the Birds in the British Museum. Vol. 26. Trustees,
London.
Olson, S. L. (2017) Species rank for the critically endangered Atlantic Lesser Frigatebird(Fregata trinitatis). Wilson Journal of Ornithology 129:661–675.
Remsen, J. V., Jr., J. I. Areta, C. D. Cadena, S. Claramunt, A. Jaramillo, J. F. Pacheco, J. Perez
Emán, M. B. Robbins, F. G. Stiles D. F. Stotz, and K. J. Zimmer (Version 11 February 2020).
A Classification of the Bird Species of South America. American Ornithological Society.
http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm
Ridgway, R. (1897). Birds of the Galapagos Archipelago. No. 1116. Proceedings of the UnitedStates National Museum 19:459–670.
Rocha-Olivares, A. and M. González-Jaramillo (2014). Population genetic structure of Mexican
Magnificent Frigatebirds: an integrative analysis of the influence of reproductive behavior
and sex-biased dispersal. Revista Mexicana de Biodiversidad 85:532–545.
Rothschild, W. (1917). On the genus Fregata. Novitates Zoologicae 22:145–146.
Swarth, H. S. (1933). Frigate-birds of the west American coast. Condor 35: 148–150.

Submitted by: Pamela C. Rasmussen, Michigan State University
Date of proposal: 20 July 202042

2021-A-9

N&MA Classification Committee

p. 488Resurrect Corthylio for Ruby-crowned Kinglet
Background:
The Ruby‐crowned Kinglet (Regulus calendula) is a small, insectivorous songbird native to
North America, with a large range extending from Alaska to Mexico. It breeds in northernconiferous forests of the United States and Canada, but during migration can be encountered inalmost any habitat (Swanson et al. 2020). Regulus calendula is one of only six species in thesmall family Regulidae, which includes four representatives in the Old World and two in North
America: the Ruby‐crowned Kinglet and the Golden-crowned Kinglet (R. satrapa, Winkler et al.
2020). All species of the Regulidae are currently placed in a single genus, Regulus (Winkler et
al. 2020).
It has long been known that the Ruby-crowned Kinglet is markedly divergent from the otherregulids in plumage and other aspects of external anatomy, reflected by the fact that the genus
Corthylio Cabanis, 1853, was erected for this species. It was, however, treated within Regulus
in AOU (1886, 1895, 1910). Miller (1915) noted that a well-known defining character of all
species of Regulus except calendula is a single flat feather covering the nares, whereas R.
calendula has multiple small bristly feathers overlying the nostrils. Further, Miller (1915)
documented an additional differentiating character, the shape and reticulation of the pad of thehallux, which is much less distinctive in R. calendula than in other species of Regulus. This led
to the recognition of Corthylio in AOU (1931).
Several other authors have since indicated that R. calendula is quite distinct from the otherspecies of Regulus. Clark (1974) found differences in foot scutes between the two North
American kinglets: Golden-crowned Kinglet has three scutes near the distal end of toe IV
instead of two as in the Ruby-crowned Kinglet. These differences were hypothesized to relate toincreased hanging behavior and greater foot mobility in R. satrapa (Clark 1974). Mayr and Short(1970) suggested that the Golden-crowned Kinglet could be more closely related to the
Goldcrest (R. regulus), and that the Ruby-crowned Kinglet is not closely related to any of theother species of kinglet. Ingold et al. (1988) obtained the first molecular evidence in support ofthis idea, using protein electrophoresis to show that the genetic distance between the two North
American species was similar to distances previously reported between very closely related bird
families or between highly divergent genera within the same family. The authors proposed thatthese two species arose from separate invasions from the Old World (Ingold et al. 1988).
In vocalizations, R. calendula is also an outlier within Regulus (Becker 1978, Löhrl and Thaler
1980). Using mtDNA, Sturmbauer et al. (1998) and Päckert et al. (2003) found R. calendula tobe the rather deeply diverged sister to all other regulids. Päckert et al. (2003) mapped song
variation on the phylogeny, again showing the divergence of R. calendula. Nevertheless,despite Miller’s (1915) evidence and the recognition of Corthylio in AOU (1931), all kinglets havelong been placed in Regulus (e.g., AOU 1957, 1983; Mayr and Cottrell 1986, Dickinson andChristidis 2014, Gill et al. 2020), sometimes with Corthylio recognized as a subgenus (AOU
1998, Swanson et al. 2020).

43New information:
Päckert et al. (2009) produced a slightly more densely sampled mtDNA phylogeny based onsequences of cytb and 16S rRNA, which confirmed R. calendula as sister to the other species ofRegulus (see screenshot of their Figure 3 below).

Given that the divergence of R. calendula dates back to about 15 myr, and that it ischaracterized by well-defined morphological and vocal differences, the reinstatement ofCorthylio should be considered. This issue has been mentioned but not enacted by any recent
major global checklist (Dickinson and Christidis 2014, del Hoyo and Collar 2016, Clements et al.
2019, Gill et al. 2020).
Independent of whether Corthylio is again recognized, the linear sequence of the two NACC
species should be reversed, such that calendula precedes satrapa.
On a side note, the Guadalupe race R. c. obscurus has been considered a species by some(Miller 1915, AOU 1895) due to its differing coloration, bill, wing, and tarsal proportions, and44

wing formula. It is now considered presumably extinct, as recent targeted searches failed to findit (Quintana-Barrios et al. 2006; https://deadasthedodo.wordpress.com/tag/corthylio-calendulassp-obscurus-ridgway/).
Effect on AOS-CLC area:
Acceptance of this proposal would reinstate the genus Corthylio and would reverse the linear
sequence of the two species of kinglet. It would have no effect on English names. A separate
proposal may be needed to evaluate the specific distinctness of R. c. obscurus.
Recommendation:
Arguing against the change are the facts that the Regulidae are a monophyletic group andtherefore it is not strictly necessary to treat calendula in a different genus, and that such achange would disrupt stability (Brandon and Natalia therefore recommend retaining calendula inRegulus). Arguing for the change are the facts that the split is relatively ancient andunambiguous, and that calendula has multiple morphological and vocal differences from allother regulids (Pam therefore recommends making the change). Please vote separately oneach option.
a) reinstate Corthylio for the Ruby-crowned Kinglet, as Corthylio calendula.
b) change the linear sequence of the kinglets, with calendula preceding satrapa.
Literature Cited:
American Ornithologists’ Union (1886). Check-list of North American Birds. First Edition.
American Ornithologists’ Union, Washington, D.C.
American Ornithologists’ Union (1895). Check-list of North American Birds. Second Edition.
American Ornithologists’ Union, New York, NY.
American Ornithologists’ Union (1910). Check-list of North American Birds. Third Edition.
American Ornithologists’ Union. American Ornithologists’ Union (1931). Checklist of North
American Birds. Fourth Edition. American Ornithologists’ Union, Lancaster, PA.
American Ornithologists’ Union (1957). Checklist of North American Birds. Fifth Edition.
American Ornithologists’ Union.
American Ornithologists’ Union (1983). Check-list of North American Birds. Sixth Edition.
American Ornithologists’ Union, Lawrence, KS.
American Ornithologists’ Union (1998). Check-list of North American Birds. Seventh Edition.
American Ornithologists’ Union, Lawrence, KS.
Becker, P. H. (1978). Vergleich von Lautäußerungen der Gattung Regulus (Goldhähnchen) als
Beitrag zur Systematik. Bonner Zoologische Beiträge 29:101–121.
Clark Jr., G. A. (1974). Foot-scute differences among certain North American oscines. The
Wilson Bulletin 86: 104–109
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.

45

Dickinson, E. C., and L. Christidis (Editors) (2014). The Howard and Moore Complete Checklistof the Birds of the World. 4th edition. Volume Two. Passerines. Aves Press Ltd.,
Eastbourne. UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v 10.2). DOI
10.14344/IOC.ML.10.2. http://www.worldbirdnames.org/
Ingold, J. L., L. A. Weigt, and S. I. Guttman (1988). Genetic differentiation between North
American kinglets and comparisons with three allied passerines. The Auk 105:386–390.
Löhrl, H., and E. Thaler (1980). Das Teneriffa-Goldhähnchen Regulus regulus teneriffae—Zur
Biologie, Ethologie und Systematik. Bonner Zoologische Beiträge 31:78–96.
Mayr, E., and G. W. Cottrell (1986). Check-list of the Birds of the World. Volume 11. Harvard
University Press, Cambridge, MA.
Mayr, E., and I. L. Short (1970). Species taxa of North American birds. Cambridge,
Massachusetts, Publ. Nuttall Ornithological Club No. 9
Miller, W. DeW. (1915). Corthylio: a valid genus for the Ruby-crowned Kinglet. The Auk 32: 234236.
Päckert, M., J. Martens, J. Kosuch, A. A. Nazarenko, and M. Veith (2003). Phylogenetic signal
in the song of crests and kinglets (Aves: Regulus). Evolution 57:616–629.
Päckert, M., J. Martens, and L. L. Severinghaus (2009). The Taiwan Firecrest (Regulus
goodfellowi) belongs to the Goldcrest assemblage (Regulus regulus s. l.): evidence frommitochondrial DNA and the territorial song of the Regulidae. Journal of Ornithology
150:205–220.
Quintana-Barrios, L., G. Ruiz-Campos, P. Unitt, and R. A. Erickson (2006). Update on the birdsof Isla Guadalupe, Baja California. Western Birds 37: 23–36.
Sturmbauer, C., B. Berger, R. Dallinger, and M. Föger (1998). Mitochondrial phylogeny of thegenus Regulus and implications on the evolution of breeding behavior in sylvioid songbirds.
Molecular Phylogenetics and Evolution 10:144–149.
Swanson, D. L., J. L. Ingold, and G. E. Wallace (2020). Ruby-crowned Kinglet (Regulus
calendula), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab ofOrnithology, Ithaca, NY, USA.
Thaler, E. (1990). ‘‘Die Goldhähnchen. Winter- und Sommergoldhähnchen Regulus regulus,
Regulus ignicapillus.’’ Ziemsen, Wittenberg Lutherstadt.
Winkler, D. W., S. M. Billerman, and I.J. Lovette (2020). Kinglets (Regulidae), version 1.0. In
Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg,
Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.reguli1.01
Submitted by: Brandon Woo and Natalia C. García, Cornell University, and Pamela C.
Rasmussen, Michigan State University
Date of Proposal: 21 July 202046

2021-A-10

N&MA Classification Committee

pp. 277-279

Change linear sequence of species in Chaetura
Note: This issue is also being considered by SACC in their Proposal 880. See SACC votes andcomments at https://www.museum.lsu.edu/~Remsen/SACCprop880.htm
Effect on NACC/SACC:
This proposal would alter the current linear sequence of species in Chaetura based on new
phylogenetic information.
Background:
SACC’s current linear sequence for the genus Chaetura is as follows (Remsen et al. 2020):
Chaetura spinicaudus
Chaetura cinereiventris
Chaetura egregia
Chaetura vauxi
Chaetura pelagica
Chaetura chapmani
Chaetura meridionalis
Chaetura andrei
Chaetura brachyura
NACC’s current linear sequence of Chaetura is (Chesser et al. 2020):
Chaetura pelagica
Chaetura vauxi
Chaetura chapmani
Chaetura brachyura
Chaetura meridionalis
Chaetura spinicaudus
Chaetura fumosa
Chaetura cinereiventris
Chaetura martinica
New Information:
Chesser et al. (2018) published a robust phylogeny (below) of the genus Chaetura based on
combined nuclear and mitochondrial data from all eleven species and 21 of 30 taxa recognizedin the genus by Dickinson and Remsen (2013). Their analysis confirmed that the genus iscomposed of two nearly equally sized subclades that correspond to recognized subgenera(Marin 2000): Acanthylis (the gray/pale rumped clade) and Chaetura (the brown-rumped clade).

47

Two species-level revisions of the taxonomy of the genus were mandated by this phylogenetic
study, both of which were adopted with the passage of SACC 841(https://www.museum.lsu.edu/~Remsen/SACCprop841.htm). Within the subgenus Chaetura, C.
(v.) andrei was shown to be unrelated to and morphologically distinct from other forms grouped
within C. vauxi, which led to the recognition of the former as a distinct species, and C.
viridipennis, formerly treated as a distinct species, was reclassified as a subspecies of C.
chapmani due to minimal morphological and genetic differentiation.
Resolution of the taxa within the subgenus Acanthylis was generally poor, especially forspinicaudus, martinica, fumosa and egregia.

48Analysis:(a) Following linear sequencing conventions, the phylogeny of Chesser et al. (2018) can best be
represented as follows for the NACC species:
Chaetura cinereiventris
Chaetura spinicaudus
Chaetura fumosa
Chaetura martinica
Chaetura pelagica
Chaetura vauxi
Chaetura chapmani
Chaetura meridionalis
Chaetura brachyura(b) The phylogeny would be best reflected by a linear sequence of the SACC species asfollows:
Chaetura cinereiventris
Chaetura spinicaudus
Chaetura egregia
Chaetura pelagica
Chaetura vauxi
Chaetura chapmani
Chaetura andrei
Chaetura meridionalis
Chaetura brachyura
Recommendation:
We recommend a YES vote by NACC members on (a) and a YES vote by SACC members on(b). The new sequences better reflect the phylogeny of Chesser et al. (2018) and would bring
the two lists into agreement.
Literature Cited:
Chesser, R. T., H. Vaseghi, P. A. Hosner, L. M. Bergner, M. N. Cortes-Rodriguez, A. J. Welch,& C. T. Collins (2018). Molecular systematics of swifts of the genus Chaetura (Aves:
Apodiformes: Apodidae). Molecular Phylogenetics and Evolution 128:162–171.
Chesser, R. T., S. M. Billerman, K. J. Burns, C. Cicero, J.L. Dunn, A.W. Kratter, I.J. Lovette,
N.A. Mason, P.C. Rasmussen, J.V. Remsen, Jr., D.F. Stotz, and K. Winker (2020). Sixty-first
Supplement to the American Ornithological Society’s Check-list of North American Birds.
The Auk: Ornithological Advances. https://doi.org/10.1093/auk/ukaa030.
Dickinson, E.C. & Remsen, J.V. Jr (Eds). 2013. The Howard & Moore Complete Checklist of the
Birds of the World. 4th Edition, Volume 1 Non-passerines. Aves Press, Eastbourne, U.K.
Marín, M. 2000. Species limits, distribution, and biogeography of some New World gray-rumped
spinetailed swifts (Chaetura, Apodidae). Ornitología Neotropical 11: 93-107.
49

Remsen, J. V., Jr., J. I. Areta, C. D. Cadena, S. Claramunt, A. Jaramillo, J. F. Pacheco, J. Perez
Emán, M. B. Robbins, F. G. Stiles, D. F. Stotz, and K. J. Zimmer (Version 11 February2020). A classification of the bird species of South America. American OrnithologicalSociety. http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm

Submitted by: David B. Donsker and Pamela C. Rasmussen
Date of Proposal: 11 August 202050

2021-A-11

N&MA Classification Committee

p. 498Reconsider the case to split Saxicola maurus and S. stejnegeri from Common Stonechat
S. torquatus
Note: This is an updated and revised version of Proposal 2014-B-11, which was rejected 5-4 infavor of the status quo (no split) vs. a three-way split. We need to reconsider this case becauseof new evidence indicating sympatry between two of the species groups in the Western
Palearctic (Shirihai and Svensson 2018, Loskot and Bakhtadze 2020) and differences in bothsong and calls (Opaev et al. 2018). Three of four major world lists (Dickinson and Christidis
2014, Clements et al. 2019, and Gill et al. 2020) have now adopted a three- (or more) way splitof this extralimital species complex.
Description of the problem:
The Common Stonechat Saxicola torquatus (s.l.) is highly polytypic over most of the
Paleotropics (except Australasia) from the British Isles and Africa through East Asia. Althoughtreated as a single species for many years, this has been a contentious issue for decades, andmuch has been written on the subject of their taxonomy and identification, especially because of
the frequent appearance of vagrant “Siberian” Stonechats of the maurus group in western
Europe. Vaurie (1959) stated that two very different populations are in contact in the Caucasus
without evidence of interbreeding, but he nevertheless treated all as a single species. Sibley
and Monroe (1990) briefly split maurus from torquatus (including the western European taxa),
but soon thereafter retracted this treatment (Sibley and Monroe 1993), and many authors havecontinued to treat all taxa as conspecific (e.g. Shirihai 1996, Clement and Rose 2016, del Hoyo
and Collar 2016).
Although most taxa traditionally included in torquatus are allopatric or parapatric in breeding
distribution as far as is known (see New Information 2020 for the exception), in South Asia themarsh specialist White-tailed Stonechat S. leucurus occurs sympatrically with the very similar S.
torquatus indicus throughout its much narrower range in the Indus-Ganges-BrahmaputraIrrawaddy valleys from Pakistan to Myanmar, segregated largely by habitat. Both occur in thesame sites, where they choose different microhabitats, and they do not appear to hybridize(Rasmussen and Anderton 2012). The fact that leucurus (which looks very like indicus except
for its tail) is undeniably a valid biological species is one very good reason to doubt that all otherstonechats (which show a lot of morphological variation; HBW illustrated 8 taxa) are best
considered conspecific.
New information (as of 2014):
Several mtDNA analyses of the stonechat complex have been published in recent years (Illera
et al. 2008, Woog et al. 2008, Zink et al. 2009, van Doren et al. 2017), to add to the lesscomplete earlier ones (Wittmann et al. 1995, Wink et al. 2002a,b). Each of these focused on aparticular section of the huge range of the species complex: for example, Illera et al. (2008)
were especially concerned with the Iberian population, whereas Woog et al. (2008) focused on
the Malagasy, Reunion (Indian Ocean), and African populations. Zink et al. (2009) had several
samples from East Asian stejnegeri (Parrot, 1908) but none from the South Asian taxa indicus
51

(Blyth, 1847) or Sino-Tibetan przewalskii (Pleske, 1889); the latter has not yet been included inany study [and a Nepal “indicus” specimen (see below for circumstances) in Illera et al. (2008)
oddly enough clustered with some Iberian birds, which were distantly related to most otherIberian birds].
Illera et al. (2008) obtained 958 bp sequences of cytb from 11 of the 12 recognized species of
Saxicola and 15 of the 45 described subspecies, of which “14 morphologically diverse and/or
geographically disjunct populations (nine subspecies) were analysed” within torquata. Woog etal. (2008) obtained 915 and 1041 bp sequences of cytb and ND2 of 9 taxa of Saxicola, five ofthem normally treated within S. torquata. Both Illera et al. (2008) and Woog et al. (2008)
evidently used mostly blood samples, although exactly how many seems unclear. Zink et al.
(2009) sequenced ND2 from 171 specimens of the S. torquata complex, 27 from Eurasian and 3
from African sites. I did not find a statement of sequence length in Zink et al. (2009).
The only one of these studies to include the White-tailed Stonechat S. leucurus was Illera et al.
(2008), and that was a blood sample of a single individual taken by “Bird Conservation Nepal”,
according to the Acknowledgments. The same source is responsible for the only (blood) sample
of putative indicus in any of the studies. Given that no indication is provided as to how they wereidentified, or what sex/age they were (relevant because female leucurus are not especially
distinctive), and that the leucurus and indicus cluster close together on the tree in Illera et al.
(2008), further corroboration using better documented samples is needed. However, what theirtree putatively shows is that leucurus is very closely related to some taxa of torquatus (notsurprisingly, given their morphological and vocal similarity).
All of the most recent studies included the insular Reunion Stonechat S. tectes andFuerteventura Stonechat S. dacotiae, and it is clear that the former (not surprisingly based on
geography) is sister to the African clade(s), whereas the latter is sister to the Western Palearctic
clade (again, geographically not surprisingly). Although this could be taken to show that tectes
and dacotiae should be lumped within an inclusive torquatus, the same cannot be said for the
sympatric leucurus.
Table 1 (see below) from Zink et al. (2009) summarizes influential recent treatments of Saxicola
torquatus. This table does not mention Woog et al. (2008), which focuses on Afro-Malagasy
taxa, although no explanation is given in Zink et al. (2009) as to why, and the paper is citedtherein.
Taken together, these studies (see figs. below) show that S. torquatus (s.l.) is paraphyletic withrespect to the distinctive-appearing taxa long considered to be separate species, the CanaryIslands or Fuerteventura Stonechat S. dacotiae, the Reunion Stonechat S. tectes, and thesympatric White-tailed Stonechat S. leucurus. They also confirm the existence of the following
distinct clades: the West European rubicola group, the mainly Central Asian maurus group, theAfrican torquatus group, the Malagasy sibilla group, and the NE Asian stejnegeri, which isespecially genetically distinct and sister to the others (according to Zink et al. 2009, the only
study to sample stejnegeri). However, this latter finding is difficult to interpret without knowledgeof where przewalskii fits in.

52

53

Fig. 2. Woog et al. (2008).

54

Fig. 1. Illera et al. (2008).

55

Fig. 2. Zink et al. (2009)
Subsequent treatments:
HBW (Collar 2005, and http://www.hbw.com/species/common-stonechat-saxicola-torquatus)
and BirdLife International (http://www.birdlife.org/datazone/speciesfactsheet.php?id=6682; delHoyo and Collar 2016) have refrained thus far from adopting any split of torquatus (s.l.).
In Sangster et al. (2011), maurus was split from the nominate and rubicola, but stejnegeri wasmaintained under maurus despite the deep divergence in Zink et al. (2009), because that paper
did not include the key taxon przewalskii, which is morphologically quite distinct from bothindicus and stejnegeri (which have a moderate level of morphological divergence between
them; Rasmussen and Anderton 2012). Hence, splitting stejnegeri without knowing theplacement of przewalskii is risky because przewalskii would have priority over stejnegeri, if they
are united, and indicus over both. Rasmussen and Anderton (2012) followed the BOU on thismatter.
IOC 4.1 (http://www.worldbirdnames.org/chats-revised/) basically followed Zink et al. (2009) byrecognizing rubicola, torquatus, maurus, and stejnegeri as full species, and in addition followed
Woog et al. (2008) in treating Malagasy birds as a full species. They also adopted thetaxonomic recommendations of Svensson et al. (2012) concerning nomenclature of central
Asian maurus, which was disputed by Opaev et al. (2018) and Loskot and Bakhtadze (2020).
New information (as of 2020):
56

Although no additional densely sampled phylogenies have been published in the years since weevaluated the 2014 proposal, major strides have been made in understanding the biology andphenotypes of the stonechat complex. Unfortunately these studies did not include subHimalayan indicus or Tibetan przewalskii.
rubicola/maurus groups.―Shirihai and Svensson (2018), on the basis of study of extensive
museum series, over 3000 photographs, and field studies of almost all Western Palearctic taxa
stated that “it eventually became clear that two morphologically diagnosable taxa coexist in NE
Turkey, S Caucasus and Transcaucasia (possibly also in extreme W Iran), rubicola andvariegatus, with no intermediates evident, separated also by ecological preferences…”. Opaev
et al. (2018; see map below) mentioned a zone of sympatry between rubicola and variegatus in
Rostov Oblast, Russia, where “these two taxa bred in different although overlapping habitats
without any signs of intergradations (Kazakov & Bakhtadze, 1999; Bakhtadze, 2002).” Loskot
and Bakhtadze (2020) presented results of extensive morphological and field studies ofstonechats in the Caucasus, and showed that where rubicola and variegatus occur in sympatry,rubicola is found mostly in drier habitats over a wide elevational range including in themountains, while variegatus preferred more mesic and almost exclusively lowland habitats.

From Opaev et al. (2018).
maurus/stejnegeri groups.―Vaurie (1959) and Stepanyan (1990, not seen, as cited inHellström and Norevik 2014) considered that there was a zone of intergradation between
nominate maurus and stejnegeri from the lower Yenesei to the Irkutsk area, but neither author
provided details. In fieldwork in parts of this area, Hellström did not find any apparent
intermediate birds, and thus Hellström and Norevik (2014) suggested that the “transition from57

maurus to stejnegeri in southern Siberia may perhaps be more abrupt (and with a lower
frequency of hybridization) than implied in the literature.”rubicola/maurus/stejnegeri groups.―In a study comparing morphology and vocalizations ofrubicola, maurus, and stejnegeri, Opaev et al. (2018) showed that both songs and calls werequite different between stejnegeri and the other two groups, and calls also differed between
rubicola and maurus. They noted the strong congruence between the mtDNA phylogenetic
results of previous authors and the results of their vocalization analyses and considered this
supportive of specific status of stejnegeri, which they called a cryptic species.

Fig. 2b of Opaev et al. (2018), a PCA of song characteristics.

58

Fig. 5 of Opaev et al. (2018), showing alarm call types of the three Palearctic groups.

From Opaev et al. (2018).

59Effect on AOU-CLC area:
Stonechats of any taxon are very rare vagrants in the NACC area. The first North American
record documented photographically was of a female in New Brunswick on 1 Oct 1983 (Wilson
1986). One slightly fuzzy photograph was published(http://sora.unm.edu/sites/default/files/journals/nab/v040n01/p00016-p00017.pdf) and, as notedin the original article, it fits the eastern taxon stejnegeri, although it could also be the Central
Asian maurus s.s. (Wilson 1986). Because maurus is a frequent vagrant to western Europe(believed to be much more so than stejnegeri; Hellström and Norevik 2014), it seems perhaps
more likely to be that rather than a Siberian stejnegeri having made its way all across Alaska
and Canada, but it may never be possible to determine this. The Western European rubicola
group is not highly migratory so is less likely to occur in North America.
The first North American specimen record of a stonechat (UAM 5301, a frozen bird found in
spring in a Bank Swallow burrow in Galena, Alaska) was identified as stejnegeri, the taxon
breeding in northeastern Asia (Osborne and Osborne 1987). As this form is highly migratory, it
is not surprising that it turns up occasionally in Alaska, with several records from St. Lawrence I.
and a few others in Alaska, and one from San Clemente I., California(http://www.wfopublications.org/Rare_Birds/Stonechat/Stonechat.html).
As far as I’ve been able to determine, all North American stonechat records have been identified
as, or at least assumed to be, stejnegeri or maurus. Thus, splitting stonechats will lead to aname change in the Check-list and a revised account. If we vote to split deeper, removing
stejnegeri from maurus, at least the New Brunswick and perhaps other records will likely beindeterminable (not that this should influence anyone’s decision in the slightest).
Recommendation:
The options below represent possible treatments of this taxonomic group. I recommend optionc. Please vote YES/NO on each option separately and on English names if voting YES on
option b or c.
a) Make no change, leaving all taxa as part of Saxicola torquatus (emendation to specificepithet already accepted in a Supplement on the basis of David and Gosselin 2002).
This is untenable, given that sympatry is now clearly established to occur over aconsiderable area from Russia through Turkey.
b) Adopt a three-way split between the maurus group (including all Central Asian races,indicus, przewalskii, and stejnegeri), the W European rubicola group, and the African
torquatus group. This would be a conservative approach given the issue with przewalskii
not being included in any molecular analysis thus far and having priority over stejnegeri if
lumped. It would also mean that all North American records fit within this single species.
It would also follow the interim approach taken by BOU (Sangster et al. 2011). However,it has the disadvantage of not reflecting the deep divergence between stejnegeri and allother stonechat taxa as recovered in Zink et al. (2009), and the newly documented vocal
differences that include the distinctly different alarm calls of stejnegeri.

60

If option b passes, adopt English names European Stonechat S. rubicola, Siberian
Stonechat S. maurus, and African Stonechat S. torquatus, as used in numerous othersources.
c) Adopt a four-way split between the maurus group (Central and South Asian races only),
stejnegeri, the rubicola group, and the torquatus group. This, as noted above, ignores
przewalskii and may lead to further revision when that taxon is included in a future study.
It also means that some past NACC-area vagrant records will be unidentifiable.
Nevertheless, given the deep divergence between stejnegeri and other taxa
demonstrated in Zink et al. (2009), the vocal differences documented by Opaev et al.
(2018), and the field data by Hellström and Norevik (2014) in which intermediates were
not detected in the putative zone of intergradation, this seems the best-supported courseof action, and on the basis of these new data I change my recommendation from the2014 proposal, in which I recommended option b).
If option c passes, adopt English names European Stonechat S. rubicola, Siberian
Stonechat S. maurus, Japanese Stonechat S. stejnegeri, and African Stonechat S.
torquatus, as used in numerous other sources. Note that the English name “Siberian
Stonechat” has become widely associated with maurus, whether in the restricted senseof Option 3 or the broader sense of Option 2. If Option 3 is adopted, this name is a bit
unfortunate since much of Siberia is occupied by what is called in IOC Stejneger’s
Stonechat S. stejnegeri, although Siberian Stonechat S. maurus is widespread inwestern Siberia. Some other sources (e.g. del Hoyo and Collar 2016) use Japanese
Stonechat for stejnegeri; I suggest avoiding the creation of newish eponyms.
PS: There is a typo in the Check-list on p. 498: it should say “Winters: [torquata] group” rather
than “torguata”. This may be irrelevant if we accept Option 2 or 3, however, as I assume thattext would disappear.
Literature Cited:
Clement, P., and C. Rose (2016). Robins and Chats. Christopher Helm, London.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan,
and C. L. Wood (2019). The eBird/Clements Checklist of Birds of the World:v2019. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/
Collar, N. (2005). Family Turdidae (Thrushes). Pp. 514-807 in: del Hoyo, J., A. Elliot, and D. A.
Christie (Eds.), Handbook of the Birds of the World, vol. 10, Cuckoo-shrikes to Thrushes.
Lynx Edicions, Barcelona.
David, N., and M. Gosselin (2002). The grammatical gender of avian genera. Bulletin of the
British Ornithologists’ Club 122(4):257–282.
del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the
Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona.
Dickinson, E. C., and L. Christidis (Editors) (2014). The Howard and Moore Complete Checklistof the Birds of the World. 4th edition. Volume Two. Passerines. Aves Press Ltd., Eastbourne,UK.
Gill, F., D. Donsker, and P. C. Rasmussen (Editors) (2020). IOC World Bird List (v10.1). doi:
10.14344/IOC.ML.10.1.
61

Hellström, M., and G. Norevik (2014). The uppertail-covert pattern of ‘Stejneger’s Stonechat’.
British Birds 107:692–700.
Illera, J. C., D. S. Richardson, B. Helm, J. C. Atienza, and B. C. Emerson (2008). Phylogenetic
relationships, biogeography and speciation in the avian genus Saxicola. MolecularPhylogenetics and Evolution 48:1145–1154.
Loskot, V. M., and G. B. Bakhtadze (2020). Distribution, systematics and nomenclature of thethree taxa of Common Stonechats (Aves, Passeriformes, Muscicapidae, Saxicola) thatbreed in the Caucasian region. Zoosystematica Rossica 29:33–57.
Opaev, A., Y. Red’kin, E. Kalinin, and M. Golovina (2018). Species limits in northern Eurasiantaxa of the common stonechats, Saxicola torquatus complex (Aves: Passeriformes,
Muscicapidae). Vertebrate Zoology 68(3):199–211.
Osborne, T. O., and G. K. Osborne (1987). First specimen of Stonechat (Saxicola torquata) forNorth America. Auk 104:542–543.
Rasmussen, P. C., and J. C. Anderton (2012). Birds of South Asia: the Ripley Guide. Second
edition. Lynx Edicions, Barcelona.
Sangster, G., J. M. Collinson, P.-A. Crochet, A. Knox, D. T. Parkin, L. Svensson, and S.C.
Votier (2011). Taxonomic recommendations for British birds: seventh report. Ibis 153:883–
892.
Shirihai, H. (1996). The Birds of Israel. Academic Press.
Shirihai, H., and L. Svensson (2018). Handbook of Western Palearctic Birds, Volume 1:
Passerines: Larks to Warblers. Bloomsbury Publishing, London.
Sibley, C. G., and B. L. Monroe, Jr. (1990). Distribution and Taxonomy of Birds of the World.
Yale University Press, New Haven, CT.
Sibley, C. G., and B. L. Monroe, Jr. (1993). A Supplement to the Distribution and Taxonomy ofBirds of the World. Yale University Press, New Haven, CT.
Svensson, L., H. Shirihai, S. Frahnert, and E. C. Dickinson (2012). Taxonomy and nomenclatureof the Stonechat complex Saxicola torquatus sensu lato in the Caspian region. Bulletin of
the British Ornithologists’ Club 132:260–269.
Van Doren, B. M., L. Campagna, B. Helm, J. C. Illera, I. J. Lovette, and M. Liedvogel (2017).
Correlated patterns of genetic diversity and differentiation across an avian family. Molecular
Ecology 26(15):3982-3997.
Vaurie, C. (1959). The Birds of the Palearctic Fauna. A Systematic Reference, Order
Passeriformes. Witherby.
Wilson, J. G. (1986). Stonechat (Saxicola torquata) in New Brunswick—first record for North
America. American Birds 40:16–17.
Wink, M., H. Sauer-Gürth, P. Heidrich, H.-H. Witt, and E. Gwinner (2002a). A molecularphylogeny of stonechats and related turdids. Pp. 22–30 in: Urquhart, E. (Ed.), Stonechats.
Christopher Helm, London.
Wink, M., H. Sauer-Gürth, and E. Gwinner (2002b). Evolutionary relationships of stonechats andrelated species inferred from mitochondrial-DNA sequences and genomic fingerprinting.
British Birds 95:349–355.
Wittmann, U., P. Heidrich, M. Wink, and E. Gwinner (1995). Speciation in the Stonechat(Saxicola torquata) inferred from nucleotide sequences of the cytochrome-b gene. Journal of
Zoological Systematics and Evolution Research 33:116–122.
Woog, F., M. Wink, E. Rastegar-Pouyani, J. Gonzalez, and B. Helm (2008). Distinct taxonomic
position of the Madagascar stonechat (Saxicola torquatus sibilla) revealed by nucleotide
sequences of mitochondrial DNA. Journal of Ornithology 149:423–430.
62

Zink, R. M., A. Pavlova, S. Drovetski, M. Wink, and S. Rohwer (2009). Taxonomic status andevolutionary history of the Saxicola torquata complex. Molecular Phylogenetics andEvolution 52:769–773.

Submitted by: Pamela C. Rasmussen, Michigan State University (with thanks to David
Donsker and his library)
Date of proposal: 22 August 202063

2021-A-12

N&MA Classification Committee

p. 307

Resurrect Philodice as a separate genus from Calliphlox
Note: This issue is also being considered by SACC in their Proposal 886. See SACC votes andcomments at https://www.museum.lsu.edu/~Remsen/SACCprop886.htm
Effect on the AOS Checklist:
This proposal would transfer Magenta-throated Woodstar (Calliphlox bryantae) and Purplethroated Woodstar (C. mitchellii) to the resurrected genus Philodice.
Background:This proposal is submitted as a complement to NACC proposal 2019-D-14, submitted by Van
Remsen, which reinstated Nesophlox as the genus for C. evelynae and C. lyrura. In this
proposal we suggest that the revision of Calliphlox be extended to resurrect Philodice as thegenus for C. bryantae and C. mitchellii.
Remsen’s proposal outlined the taxonomic history of Calliphlox, Nesophlox and Philodice, which
will not be repeated in detail here. Suffice it to say that Nesophlox and Philodice were frequently
subsumed into Calliphlox because it was thought that there were insufficient morphologicaldifferences between Nesophlox, Philodice and Calliphlox to support generic separation (seealso https://www.museum.lsu.edu/~Remsen/SACCprop164.htm, which did not pass). Magentathroated Woodstar and Purple-throated Woodstar have consistently been treated as belonging
to Calliphlox by the AOU/AOS since Middle American taxa were first included in the sixth editionof the AOU Checklist (1983).
New Information:
In recent years the family Trochilidae has been the subject of several robust phylogenetic
studies. Two of these are specifically relevant to this proposal. As discussed in NACC proposal
2019-D-14, McGuire et al. (2014) examined the entire family and produced a time-calibrated
phylogram based on a sampling of 284 hummingbird species representing 101 of the 105 thenrecognized genera, using four nuclear and two mitochondrial genes. This resulted in moredetailed information on the eight major clades within the family, one of which was composed of
the woodstars, sheartails, Selasphorus, and relatives and which corresponds to the tribe
Mellisugini (or the “bees”) (McGuire et al. 2007).
Not discussed in NACC proposal 2019-D-14, however, Licona-Vera & Ornelas (2017) produced
a dated multilocus phylogeny restricted to Mellisugini based on a dense sampling of 116
individuals from all 16 recognized genera within the tribe and 32 of the 36 extant species using
two mitochondrial and four nuclear genes. Their phylogeny of Mellisugini had a similar topology
to that of McGuire et al. (2014) and corroborated the findings of that earlier paper.
The significant portions of both phylogenies are shown below:

64

McGuire et al. 201465

Licona-Vera & Ornelas (2017)

Both phylogenies demonstrate that Calliphlox, as recently treated by the NACC (and the
SACC), is polyphyletic. Of its five species, the two Bahama endemics, C. evelynae and C.
lyrura, belong to a completely different subclade (“Caribbean sheartails”) from the other three,which are in the traditional “woodstar” clade. As noted, the NACC recently dealt with this issue
by resurrecting the genus Nesophlox Ridgway, 1910 for the two Bahamian taxa (NACC 2019-D14).
To date, both committees have retained the three other species in Calliphlox. However,
although these three species belong to the same subclade, Amethyst Woodstar C. amethystina,
the type species for Calliphlox, is sister to the remaining taxa within the entire “woodstar” clade
and is deeply paraphyletic with respect to the Magenta-throated Woodstar C. bryantae and66

Purple-throated Woodstar C. mitchellii, which are sister species. These latter two species form a
distantly related subclade, phylogenetically closer to members of three other genera (Eulidia,
Microstilbon, Chaetocercus) than it is to C. amethystina. Given their deep phylogenetic
divergence, it would seem unlikely that future treatments would consider merging Magentathroated Woodstar C. bryantae and Purple-throated Woodstar C. mitchellii with any of thoseother three genera.
Despite what may have been considered only minor morphological differences in the initial
SACC proposal, these phylogenetic findings require that C. bryantae and C. mitchellii be treatedin a separate genus from C. amethystina, which as noted is the type species of Calliphlox. The
genus Philodice Mulsant, Verreaux, J & Verreaux, E, 1866 (type Trochilus mitchellii Bourcier) is
the appropriate available name.
Recommendation:
We strongly recommend a YES vote to this proposal. Note that this treatment has already been
adopted by Clements et al. (2019).
Should the proposal pass, we also strongly recommend continuing to use the group name“woodstar” for all. Most members of this clade, which is comprised of several genera, have long
been called woodstars, so this would not affect stability.
References:
Clements, J., T. Schulenberg, M. Iliff, S. Billerman, T. Fredericks, B. Sullivan, and C. Wood(2019). The eBird/Clements Checklist of Birds of the World: v2019. Cornell Lab ofOrnithology.
Licona-Vera, Y. & J.F. Ornelas. 2017. The conquering of North America: dated phylogenetic andbiogeographic inference of migratory behavior in bee hummingbirds. BMC Evolutionary
Biology 17:126.
McGuire, J.A., C.C. Witt, D.L. Altshuler & J.V. Remsen. 2007. Phylogenetic systematics andbiogeography of hummingbirds: Bayesian and maximum likelihood analyses of partitioned
data and selection of an appropriate partitioning strategy. Syst. Biol. 56(5):837–856.
McGuire, J.A., C.C. Witt, J.V. Remsen, A. Corl, D.L. Rabosky, D.L. Altshuler & R. Dudley. 2014.
Molecular phylogenetics and the diversification of hummingbirds. Current Biology 24(8):910–916.
Remsen, J.V. 2019. NACC Proposal 2019-D-14. “Reinstate Nesophlox for Calliphlox evelynae
and C. lyrura”. In: American Ornithological Society. Checklist of North and Middle American
Birds. http://checklist.americanornithology.org/nacc/proposals/2019.html
Stiles, G. 2005. SACC Proposal 164. “Recognize Philodice as a separate genus from
Calliphlox” In: Remsen, J.V. et al. A classification of the bird species of South America.
American Ornithological Society. http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm

Submitted by: David B. Donsker, Pamela C. Rasmussen, and Nicholas A. Mason
Date of Proposal: 8 September 202067

2021-A-13

N&MA Classification Committee

p. 630

Lump McKay’s Bunting Plectrophenax hyperboreus with Snow Bunting P. nivalis
Effect on the North American Checklist:
This proposal would shift the taxonomic rank of hyperboreus from species to subspecies,
resulting in the loss of one species from the Checklist.
Background:
McKay’s Bunting has been treated as a species since the first edition of the AOU checklist(1886), a mere two years after Robert Ridgway (1884) first described it. Ridgway’s own doubts
about the rank of this taxon are evident from the ambiguous title of his description (“Descriptionof a new Snow Bunting from Alaska”), the fact that he begins it with “subsp. ch.” (= subspecies
characters), and the designation “Plectrophanes nivalis hyperboreus Ridgw.” written in his own
hand on each of the original labels of the four syntypes at the U. S. National Museum (C.
Milensky, in litt. 2019). Similarly, most authorities that made explicit study of plumage variationin Holarctic Plectrophenax have concluded that hyperboreus is merely a subspecies of nivalis(Salomonsen 1931, Hellmayr 1938, Vaurie 1959, Portenko 1989). Many other authorities
treated it as a subspecies as well (Paynter 1970, Mayr and Short 1970, Cramp et al. 1994),
influenced by evidence of extralimital pairings of male McKay’s with reported female Snow
Buntings at St. Lawrence Island (Sealy 1967, 1969). Its stable taxonomic status within the AOUchecklists belies a more skeptical undercurrent, evidenced by statements such as “may beconspecific” (AOU 1998:630) and “recognized plumage differences are no more pronounced
than among many passerine subspecies” (Maley and Winker 2007:909), although both AOU(1998) and Maley and Winker (2007) ultimately treated them as separate species.
Snow and McKay’s buntings do not display any known prezygotic reproductive isolating
mechanisms in behavior or ecology; in fact, there are few if any know differences between thetwo in these attributes at all (see Lyon and Montgomerie 1995). Their songs are usuallydescribed as similar, but Plectrophenax song is relatively complex and at least in Snow
Buntings subject to regional, individual, and even annual variation (Espmark 1994, Baldo et al.
2014). A rigorous quantification of song between the two has not been conducted, but it would
remain to be demonstrated that a detectable difference (if any) would affect mate choice andlevels of introgression (i.e., was potentially meaningful evolutionarily and taxonomically).
Differences in timing of migration and habitat saturation (Winker et al. 2002, Matsuoka andJohnson 2008) may be acting as isolating mechanisms, but these are likely too porous or too
recent to allow or to have resulted in speciation (see below regarding gene flow levels andextralimital breeding). “It is unlikely that effective postzygotic reproductive isolating mechanisms
have evolved, and fertile hybrids would be expected” (Maley and Winker 2010:10), and see
below regarding intermediate phenotypes that may very well represent intergrades.
Differences in juvenal plumage have been adduced as evidence for species rank (Maley andWinker 2007), but, like the adult plumage, the juvenal plumage is variable, and some individuals
are borderline cases (see Figure 2a in Maley and Winker 2007; visual examination of 50+
68

juvenal plumaged specimens of Plectrophenax at UAM). Furthermore, recognition that the Snow
Buntings and longspurs constitute their own family (Calcariidae; Chesser et al. 2010) frees themfrom an expectation that they have a distinctive juvenal plumage as is typical in the family
Emberizidae (sensu lato) in which they were previously classified. Some evidence suggests
those plumages are evolutionarily conserved, a situation that informed the conclusions of thatstudy (Maley and Winker 2007). Graber (1955), in his review of the juvenal plumages of the
Emberizidae (as previously constituted), had already pointed out that Plectrophenax does notfollow those patterns. In the closely related longspurs (Calcarius, Rhynchophanes), the juvenal
plumage is reminiscent of the adult female plumage, as in Plectrophenax, and there is no
reason to assume the minor differences reflect a deep evolutionary divide.
Snow Buntings are uncommon (at best) during spring migration at St. Matthew Island (Winker et
al. 2002), but they are scarce there at other times (see Robinson et al. 2020). For example, inJune of 2003, during transect counts of 2,400 McKay’s Buntings, zero Snow Buntings wereidentified and only five (all males) were seen off transect, the latest on 5 June (Matsuoka andJohnson 2008), suggesting that the two forms are nearly allopatric during the breeding season.
A gap in regular breeding distribution of at least 264 km, reinforced by a process of heteropatry(migration timing) and philopatry, may be why intergrades are not more common. Snow
Buntings have never been documented breeding on St. Matthew Island (Winker et al. 2002,
Robinson et al. 2020). The limited evidence for extralimital breeding by McKay’s has rarely beenaccompanied by detailed documentation of the phenotypes involved, but phenotypic McKay’s,
usually males, are seen in very small numbers, less than annually, during the summer in the
Pribilof Islands and on St. Lawrence Island (see Kenyon and Phillips 1965, Sealy 1967, 1969,
Kessel and Gibson 1978, Lehman 2019, S. Schuette in litt. 2019, UAM unpublished data). The
male McKay’s Buntings collected by Spencer Sealy on St. Lawrence Island (University of British
Columbia 13274, 13327, and 13328) are typical McKay’s.
New information:
The distinctive appearance of male McKay’s Buntings has been the driving factor in its
taxonomic rank. Recently acquired series of buntings (both P. hyperboreus and P. nivalis
townsendi) from the Bering Sea islands have made clear that plumage variation in both taxa is
significant, not related to age, varies continuously between the extremes within a taxon, and thatthe extremes of one closely approach that of the other (Withrow 2020; Figures 1 and 2
reproduced here, see paper for more photos of intergrades and/or extremes of variation).
Intergrades, or birds that appear to be intergrades, appear more frequently than expected
between reproductively isolated populations. As a parallel to this situation, in the North Atlantic
P. n. insulae from Iceland occurs in winter on the British Isles and mainland Europe (see Bankset al. 1991, Winters 2013), but occasionally breeds on Jan Mayen, the Faroe and Shetlandislands, and northern Scotland, where some birds are intermediate with nominate nivalis(Nethersole-Thompson 1966, Smith 1996, Shirihai and Svensson 2018). Subspecies insulae isdistinguished from nominate nivalis by being darker in nearly all the same respects that
hyperboreus is paler and offers an instructive yardstick to which McKay’s Bunting may becompared (to my knowledge insulae has never been suggested to be of species rank).

69

Figure 1. Examples of male McKay’s Buntings from St. Matthew Island (four at left) and male
Snow Buntings from St. Paul Island (four at right), collected in early June and late May
respectively. The middle two McKay’s are typical; the topmost and bottommost birds represent
the pale and dark extremes within birds collected on St. Matthew Island. Similarly, the Snow
Buntings represent the breadth of phenotypes collected on St. Paul Island in the Pribilofs.

Figure 2. Examples of female McKay’s Buntings from St. Matthew Island (four on left) andfemale Snow Buntings from St. Paul Island (four on right) collected in early June and late May
respectively. The middle two McKay’s are typical; the topmost and bottommost birds represent
the pale and dark extremes within McKay’s.

70Initial mtDNA and AFLP-based work on McKay’s Bunting (Maley and Winker 2010) detected
only small genetic differences. Recent genomic work on the buntings (Winker et al. 2018) foundno fixed differences between the species across 3,431 UCE loci, few loci with large allele
frequency differences between species, and an overall F ST = 0.034, casting serious doubt on the
reproductive isolation of McKay’s Bunting. Most importantly, this work suggests that levels of
long-term gene flow between McKay’s and Snow buntings are higher than expected between
species (3-5 individuals per generation in each direction), but low overall, probably because of
the isolation of McKay’s breeding grounds.
Multiple lines of evidence, including plumage patterns, genomic data, and nearly identical life
histories all point to McKay’s Bunting being a subspecies of Snow Bunting. Its entire breeding
range, St. Matthew Island, is fully protected by inclusion in the Alaska Maritime National Wildlife
Refuge and it would be protected equivalently under U.S. law as an endemic subspecies.
Recommendation:
I recommend that NACC lump McKay’s Bunting with Snow Bunting, treating it as a subspeciesof the latter.
Literature Cited:
American Ornithologists’ Union (AOU). 1886. The Code of Nomenclature and Check-list of
North American Birds. Am. Ornithol. Union, New York.
AOU. 1998. Check-list of North American Birds, 7th ed. Am. Ornithol. Union, Washington, DC.
Baldo, S., Mennill, D. J., Guindre-Parker, S., Gilchrist, H. G., and Love, O. P. 2014. Snow
Buntings sing individually distinctive songs and show inter-annual variation in song
structure. Wilson J. Ornithol. 126:333–338; doi.org/10.1676/13-157.1.
Banks, K. W., Clark, H., Mackay, I. R. K., Mackay, S. G., and Sellers, R. M. 1991. Origins,
population structure and movements of Snow Buntings Plectrophenax nivalis wintering in
Highland Region, Scotland. Bird Study 38:10–19; doi.org/10.1080/00063659109477062.
Chesser, R. T., Banks, R. C., Barker, F. K., Cicero, C., Dunn, J. L., Kratter, A. W., Lovette, I. J.,
Rasmussen, P. C., Remsen, J. V. Jr., Rising, J. D., Stotz, D. F., and Winker, K. 2010. Fiftyfirst supplement to the American Ornithologists’ Union Check-list of North American Birds.
Auk 127:726–744; doi.org/10.1525/auk.2010.127.3.726.
Cramp, S., and Perrins, C. M. (eds.). 1994. Birds of the Western Palearctic, vol. IX. Oxford Univ.
Press, Oxford, England.
Espmark, Y. 1994. Individual and local variations in the song of the Snow Bunting(Plectrophenax nivalis) on Spitsbergen. Bioacoustics 6:117–133;
doi.org/10.1080/09524622.1995.9753279
Graber, R. R. 1995. Taxonomic and adaptive features of the juvenal plumage in North American
sparrows. Ph. D. dissertation, Univ. Okla., Norman.
Hellmayr, C. E. 1938. Catalogue of birds of the Americas. Zool. Ser. Field Mus. 13, part XI.
Kenyon, K. W., and Phillips, R. E. 1965. Birds from the Pribilof Islands and vicinity. Auk 82:624–
635; doi.org/10.2307/4083224.
Kessel, B., and Gibson, D. D. 1978. Status and distribution of Alaska birds. Studies Avian Biol.
1.

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Klicka, J. T., Zink, R. M., and Winker, K. 2003. Longspurs and snow buntings: Phylogeny andbiogeography of a high-latitude clade (Calcarius). Molec. Phylogen. Evol. 26:165–175;
doi.org/10.1016/S1055-7903(02)00360-3.
Lehman, P. 2019. The Birds of Gambell and St. Lawrence Island, Alaska. Studies Western
Birds 4.
Lyon, B., and Montgomerie, R. 1995. Snow Bunting (Plectrophenax nivalis) and McKay’s
Bunting (Plectrophenax hyperboreus) in The Birds of North America (A. Poole, F. Gill, eds.),
no. 198–199. Acad. Nat. Sci., Philadelphia.
Maley, J. M., and Winker, K. 2007. Use of juvenal plumage in diagnosing species limits: An
example using buntings in the genus Plectrophenax. Auk 124:907–915;
doi.org/10.1093/auk/124.3.907.
Maley, J. M., and Winker, K. 2010. Diversification at high latitudes: Speciation of buntings in thegenus Plectrophenax inferred from mitochondrial and nuclear markers. Molec. Ecol. 19:785–
797; doi.org/10.1111/j.1365-294X.2009.04513.x.
Matsuoka, S. M., and Johnson, J. A. 2008. Using a multimodel approach to estimate thepopulation size of McKay’s Buntings. Condor 110:371–376;
doi.org/10.1525/cond.2008.8492.
Mayr, E., and Short, L. L. 1970. Species taxa of North American birds. Publ. Nuttall Ornithol.
Club 9.
Nethersole-Thompson, D. 1966. The Snow Bunting. Oliver and Boyd, Edinburgh.
Paynter, R. A. Jr. 1970. Subfamily Emberizinae in Check-List of Birds of the World (R. A.
Paynter Jr. and R. W. Storer, eds.), vol, 13, pp. 3–214. Mus. Comp. Zool., Cambridge, MA.
Portenko, L. A. 1989. Birds of the Chukchi Peninsula and Wrangel Island, vol. 2. Smithsonian
Inst. Libraries and Natl. Sci. Foundation, Washington, DC.
Ridgway, R. 1884. Description of a new Snow Bunting from Alaska. Proc. U. S. Natl. Mus. 7:69–
70; doi.org/10.5479/si.00963801.412.68.
Robinson, B. W., Withrow, J. J., Richardson, R. M., Matsuoka, S. M., Gill, R. E. Jr., Johnson, A.
S., Lovette, I. J., Johnson, J. A., DeGange, A. R., and Romano, M. D. 2020. Further
information on the avifauna of St. Matthew and Hall islands, Bering Sea, Alaska. W. Birds
51:78–91; doi.org/10.21199/WB51.2.1.
Salomonsen, F. 1931. On the geographical variation of the Snow-Bunting (Plectrophenax
nivalis). Ibis 73:57–70; doi.org/10.1111/j.1474-919X.1931.tb01504.x.
Sealy, S. G. 1967. The occurrence and possible breeding of McKay's Bunting on St. Lawrence
Island, Alaska. Condor 69:531–532; doi.org/10.2307/1366160.
Sealy, S. G. 1969. Apparent hybridization between Snow Bunting and McKay's Bunting on St.
Lawrence Island, Alaska. Auk 86:350–351; doi.org/10.2307/4083511.
Shirihai, H., and Svensson, L. 2018. Handbook of Western Palearctic Birds, vol. 2. Helm,
London.
Smith, R. D. 1996. Racial composition of breeding and wintering Snow Buntings Plectrophenax
nivalis in the north‐east Scottish uplands. Ringing and Migration 17:123–136;
doi:10.1080/03078698.1996.9674128.
Vaurie, C. 1959. The Birds of the Palearctic Fauna. Passeriformes. H. F. and G. Witherby,
London.
Winker, K., Gibson, D. D., Sowls, A. L., Lawhead, B. E., Martin, P. D., Hoberg, E. P., andCausey, D. 2002. The birds of St. Matthew Island, Bering Sea. Wilson Bull. 114:491–509;
doi.org/10.1676/0043-5643(2002)114[0491:TBOSMI]2.0.CO;2.

72

Winker, K., Glenn, T. C., and Faircloth, B. C. 2018. Ultraconserved elements (UCEs) illuminate
the population genomics of a recent, high-latitude avian speciation event. PeerJ 6:e5735;
doi.org/10.7717/peerj.5735.
Winters, R. 2013. Snow Bunting: Sexing, ageing and subspecies. Dutch Birding 35:7–14.
Withrow, J. J. 2020. Plumage variation in Bering Sea Plectrophenax buntings and the specificstatus of McKay's Bunting. Western Birds 51:174-189.

Submitted by: Jack Withrow
Date of Proposal: 28 Oct 202073