bluuebunny/crossref_metadata_2025 huggingface dataset:
Age and Reproduction in Lesser Spotted Woodpeckers (Dendrocopos Minor)
Authors: Wiktander Ulf , Olsson Ola , Nilsson Sven G.
Published: September 2019

We examined the influence of female age, male age, and pair-bond duration on start of egg-laying, clutch size, and number of young fledged in the Lesser Spotted Woodpecker (Dendrocopos minor). We also attempted to disentangle the relative influence of individual age and pair-bond duration on reproduction, because the effect of those factors may be confounded. Breeding performance improved with age in that old females started egg-laying earlier and old males raised more young than yearlings, and old pairs both started egg-laying earlier and raised more young than new pairs. Clutch size was not affected by age, but showed a strong negative relation with laying date. Late-laying yearling females experienced a lower survival, and the survival of yearling males showed a positive relation with fledgling production. That differential survival was a likely mechanism explaining the differences in reproductive performance between yearling and old birds. Several analyses suggested that pair-bond duration had independent positive effects on reproduction. Benefit of long-term pair-bonds appeared to depend upon repeated breeding with a particular partner. The mechanisms behind the benefit of remating with a particular partner remain unclear, however. We postulate that much of the patterns of age effects on reproduction in the Lesser Spotted Woodpecker may be caused by constraints posed by the territorial system and effects of territory quality, although effects of individual quality can not be excluded.
Comparative Fuel use of Migrating Passerines: Effects of Fat Stores, Migration Distance, and Diet
Authors: Gannes Leonard Z.
Published: September 2019

Lipids are the dominant fuel source during migratory flight, but the factors controlling the relative importance of lipid, protein, and carbohydrate to flight metabolism remain unclear. I tested the nonexclusive hypotheses that diet, migration distance, or endogenous lipid reserves mediate variation in the fuels birds catabolize during migration. Blood plasma metabolite concentrations were significantly different among species, and indicated clear differences in protein and lipid utilization among three turdid chat and five sylviid warbler species caught during spring migration in the Negev Desert, Israel. Fruit-eating species (omnivores) catabolized less protein and more lipid during migration than insectivores. Metabolite concentrations of omnivorous Blackcaps (Sylvia atricapilla), Garden Warblers (S. borin), and Lesser Whitethroats (S. curruca) were consistent with low rates of proteolysis (low uric acid), and high rates of lipolysis (high free-fatty acid and β-hydroxybutyrate). On the other hand, metabolite concentrations of insectivorous Redstarts (Phoenicurus phoenicurus), Nightingales (Luscinia megarhynchos), Thrush Nightingales (L. luscinia), Barred Warblers (S. nisoria), and Orphean Warblers (S. hortensis) indicated increased proteolysis and decreased lipolysis. Blood metabolite concentrations, however, were not correlated with migration distance, and the results do not support the hypothesis that long-distance migrants use fuel differently than short-distance migrants. Triacylglycerol mobilization was positively correlated with the amount of visible subcutaneous fat, but blood metabolite composition was more strongly affected by diet. Omnivores and insectivores exhibit different fuel-use strategies to overcome the physiological challenges of migration.
Composition of Eggs and Neonates of Canada Geese and Lesser Snow Geese
Authors: Badzinski Shannon S. , Ankney C. Davison , Leafloor James O. , Abraham Kenneth F.
Published: September 2019

We collected eggs, neonates, and adults of Canada Geese (Branta canadensis interior) and Lesser Snow Geese (Chen caerulescens caerulescens) from Akimiski Island, Nunavut, during the 1996 breeding season. This was done to assess interspecific differences in egg composition, egg-nutrient catabolism, developmental maturity, tissue maturity, and body reserves, and to relate observed differences in those variables to ecological conditions historically experienced by Canada Geese and Lesser Snow Geese. Eggs of both species had identical proportional compositions, but Canada Goose embryos catabolized 13% more of their egg protein, whereas Lesser Snow Goose embryos catabolized 9% more of their egg lipid. Neonate Canada Geese and Lesser Snow Geese had similar protein reserves, relative to body size, but Lesser Snow Geese had relatively smaller lipid reserves than did Canada Geese. Relative to conspecific adults, Lesser Snow Goose goslings generally were structurally larger at hatch than were Canada Goose goslings. Neonate Lesser Snow Geese had more developmentally mature keels, wings, and breast muscles, and larger gizzards and caeca for their body size, than did neonate Canada Geese. Despite hatching from smaller eggs and having a shorter period of embryonic growth, skeletal muscles and gizzard tissues of Lesser Snow Geese were more functionally mature than those of Canada Geese. Increased lipid use during embryonic development could account for how Lesser Snow Geese hatched in a more developmentally and functionally mature state. In turn, differences in developmental and functional maturity of Lesser Snow Geese, as compared to Canada Geese, likely are adaptations that offset metabolic costs associated with their small body size, or to selection pressures associated with high arctic environmental conditions and colonial nesting and brood rearing.
Low Initial Refueling Rate at Stopover Sites: A Methodological Effect?
Authors: Schwilch Regine , Jenni Lukas
Published: September 2019

For various reasons, migrating birds may not refuel and gain mass immediately after they have arrived at a stopover site. That led to the concept of a search-settling time after arrival with a low or negative initial refueling rate, but its existence has not been clearly demonstrated in field studies. Body-mass changes resulting from capture–recapture data can be misleading if used for the estimation of a natural low initial refueling rate because (1) it is usually unknown whether the day of first capture is also the first day of stopover, and (2) handling at first capture may have an adverse effect on subsequent body-mass development. To circumvent those problems we increased probability of catching birds shortly after arrival by inducing landfall by tape-luring, and we estimated body-mass change without previous handling effects from concentration of two metabolites in blood plasma. In the Eurasian Reed-Warbler (Acrocephalus scirpaceus) studied at a stopover site in Switzerland, there was no difference in plasma-metabolite concentrations between a group of mostly newly arrived individuals and a group with few newly arrived birds. Similarly, there was no difference in those parameters between birds that had been handled before and birds at first capture. However, the analysis of capture–recapture data from two other Swiss stopover sites with longer handling times indicated that mean body mass of Eurasian Reed-Warblers and European Robins (Erithacus rubecula) dropped after capture and reached initial values only after one to several days. We concluded that mass loss after capture depended mainly on lost foraging time and that natural low initial refueling rate after arrival at a stopover site is not detectable under the conditions of this study.
Effect of Conspecific Brood Parasitism on Host Fitness for Tufted Duck and Common Pochard
Authors: Dugger Bruce D. , Blums Peter
Published: September 2019

Brood parasitism occurs disproportionately in birds with precocial young and is particularly common in Anseriformes. In part, that pattern may result because precocial hosts, relative to altricial species, incur relatively few costs when caring for precocial eggs. Empirical data do not consistently support that hypothesis, and some parameters have not been adequately compared between parasitized and nonparasitized nests or females. We used a combination of experimentation (egg and duckling additions) and analysis of a larger observational data set to compare reproductive parameters, recruitment, and adult survival between parasitized and nonparasitized female Common Pochard (Aythya ferina) and Tufted Ducks (A. fuligula). Addition of three eggs to nests during the host's laying cycle had no effect on host clutch size, host egg hatch success, or nest success for either species. Nest success was not affected by parasitism intensity for pochards, but we did detect a small drop in nest success for Tufted Duck nests parasitized with >6 eggs. Recruitment probability did not differ between parasitized and nonparasitized nests for either species, and parasitism had no negative effect on adult survival. Between-year nest initiation dates were later for parasitized Tufted Ducks, although the biological consequences of that difference (3.8 days) seem negligible. Moderate levels of parasitism do not negatively affect hosts for these two species.
Territory and Nest-Site Selection of Cerulean Warblers in Eastern Ontario
Authors: Jones Jason , Robertson Raleigh J.
Published: September 2019

We examined habitat selection by breeding Cerulean Warblers (Dendroica cerulea) at three spatial scales in eastern Ontario over three years (1997–1999). Territories were characterized by well-spaced large trees, with high canopies and dense foliage cover at heights between 12–18 m. Nesting habitat additionally was characterized by dense foliage cover above 18 m. The results of our nest-patch (0.04 ha circle around nest) and nest-site (0.01 ha circle) analyses indicate that male Cerulean Warblers may take active roles in nest-site selection when selecting territories. We conclude from our nest-patch and nest-site selection analyses that territories likely contain multiple nest patches and sites and that male Cerulean Warblers may defend areas with multiple nest patches or sites, which may attract females to settle with them. Whether or not Cerulean Warbler females use nest-site availability as a mate- or territory-choice cue remains unknown. We also tested the validity of a commonly made assumption that a random sampling of habitat by researchers is representative of the habitat actually available to birds and found that, in our study area, the assumption was invalid. Taken together, our results point toward the need to maintain sizeable stands of mature, deciduous forest to ensure the persistence of Cerulean Warblers in eastern Ontario. Population characteristics such as lower minimum area requirements and a resilience to habitat disturbance may make that an easier job in eastern Ontario than elsewhere in this species' breeding range.
Within-season Nest-site Fidelity in Eastern Bluebirds: Disentangling Effects of Nest Success and Parasite Avoidance
Authors: Stanback Mark T. , Dervan Anne A.
Published: September 2019

We manipulated nestbox choices in Eastern Bluebirds (Sialia sialis) to assess (1) whether the presence of a previously used (and presumably parasite-ridden) nest cavity increases or decreases the likelihood of within-season nestbox reuse and (2) whether birds prefer previously successful cavities. Initially, birds were presented with two clean identical nestboxes erected 1 m apart. After the first nesting, we removed nest material from half of the successful box pairs and recorded subsequent nesting choices. Given a choice between a used and an unused box, bluebirds chose the unused but parasite-free cavity significantly more often. Presented with a cleaned successful box and an identical unused one, bluebirds opted to reuse the former significantly more often. Those results suggest that (1) bluebirds recognize a cost of within-season nest reuse and are willing to switch nest sites to minimize parasitism, (2) bluebirds prefer successful cavities, but only if they are clean, and (3) in our population, in which cost of nest switching was minimized, the aversion to parasites was stronger than the preference for successful cavities.
Female Hematozoan Infection Reduces Hatching Success but not Fledging Success in Pied Flycatchers Ficedula hypoleuca
Authors: Sanz Juan J. , Arriero Elena , Moreno Juan , Merino Santiago
Published: September 2019

We report association between female blood parasite prevalence (percentage of infected birds) just after egg laying and reproductive success in two successive breeding seasons, in a breeding population of Pied Flycatcher Ficedula hypoleuca in central Spain. Females infected with Trypanosoma spp. had a higher probability of deserting their clutches during the incubation period than noninfected females. Females infected with Haemoproteus balmorali hatched proportionally fewer eggs than noninfected females. Female infected with H. balmorali during the incubation period may have a decreased ability to thermoregulate which may affect their incubation capacity. Fledging success, breeding success, fledgling mass, and tarsus length were not associated with infection of the mother by blood parasites during the incubation period, suggesting that females and their mates may compensate during the nestling period for the negative effect of blood parasites during the incubation period.
Diving Depths of Shearwaters
Authors: Burger Alan E.
Published: September 2019

Maximum diving depths were measured for shearwaters breeding on Cousin Island, Seychelles. Eighty-three percent of 23 Wedge-tailed Shearwaters (Puffinus pacificus) dived, and their mean maximum depth was 14 m (SD = 23 m, range 1–66 m, N = 19). All Audubon's Shearwaters (P. lherminieri) dived, and their mean maximum depth was 15 m (SD = 12 m, range 6–35 m, N = 7). These data contradict the hypothesis that tropical shearwaters should not specialize in underwater foraging. They are capable of exploiting deep prey unavailable to most other tropical seabirds. Five Puffinus species (temperate and tropical) attained allometrically scaled maximum depths comparable to those of penguins and alcids.
Visual Signals for Individual Identification: The Silent “Song” of Ruffs
Authors: Lank David B. , Dale James
Published: September 2019

Breeding male Ruffs (Philomachus pugnax) appear to communicate individual identity through extreme variation in coloration and pattern of their plumages. If plumage variation evolved to provide sufficient information to signal individual identity, we might expect different plumage components to vary independently. We find that variation in four plumage characteristics is largely independent. Previous studies produced conflicting answers about plumage-component independence, perhaps because they failed to separate two genetically distinct behavioral categories of males, which differ in plumage types, in their analysis. We propose that using plumage variation to signal individual identity, rather than voice (used by most other bird species) was favored by lengthy daytime male display in open habitats in close proximity to receivers. However, signaling associated with the unique dimorphism in this species' male mating behavior might also have influenced the evolution of extraordinary plumage diversity in this species.
Frequency of Egg and Nestling Destruction by Female Brown-headed Cowbirds at Grassland Nests
Authors: Granfors Diane A. , Pietz Pamela J. , Joyal Lisa A.
Published: September 2019

Researchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and documented partial or complete destruction of eggs or nestlings by cowbirds at 7 of 132 nests monitored with cameras. At least three of the seven cases appeared to be attempts to totally destroy the nest contents; those cowbirds did not appear to be motivated by food or an intent to parasitize the nest. Three cases probably were associated with parasitism, but two involved egg removal late in incubation and the third was unusually destructive. Cowbirds were responsible for 24% of egg losses and 5% of nestling losses caused by predators. The importance of cowbirds as an agent of egg and nestling loss undoubtedly varies among sites and years, but it should not be overlooked.
Nest Desertion by Field Sparrows and its Possible Influence on the Evolution of Cowbird Behavior
Authors: Strausberger Bill M. , Burhans Dirk E.
Published: September 2019

In this study, Field Sparrows (Spizella pusilla) deserted 46% of nests, parasitized by Brown-headed Cowbirds (Molothrus ater) and only 1% of unparasitized nests suggesting that desertion functions primarily as an antiparasite defense. Sparrows did not desert nests following various clutch manipulations that are often associated with parasitism, indicating that desertion was not in response to the presence of cowbird eggs. Sparrows often deserted nests following encounters with real or mounted cowbirds, suggesting that nest desertion is a response to adult cowbirds. Sparrows deserted nests only in stages most vulnerable to the effects of parasitism. That finding is consistent with the possibility that desertion is a parasite-specific response. Sparrows arrived at nests earlier in the day at our Illinois site, where parasitism was greater, than in Missouri. Our findings confirm that host vigilance can prevent successful parasitism, and we provide the first direct evidence that encounters with cowbirds may cause hosts to desert nests. Our findings may help explain why cowbirds parasitize nests extremely early in the morning and lay rapidly. We suggest that consideration be given to host response following interactions with adult brood parasites because those interactions may have implications for both the ecology and evolution of both the parasite and host.
Regional Variation in Response of Field Sparrows to the Threat of Brown-headed Cowbird Parasitism
Authors: Burhans Dirk E. , Strausberger Bill M. , Carey Michael D.
Published: September 2019

We conducted aggression experiments using model cowbirds on nesting Field Sparrows (Spizella pusilla) in heavily, moderately, and rarely parasitized populations. We also documented Field Sparrow morning nest arrival times during the laying period, because Field Sparrows appear to desert nests in response to encounters with laying female cowbirds. Field Sparrows responded most aggressively to cowbird models and arrived the earliest in Illinois, where they were most heavily parasitized. Field Sparrows responded the least to models in Pennsylvania, where they are almost never parasitized. Our results suggest that those host behaviors result from some aspect of host–cowbird interactions, but the extent to which such behaviors are genetic or learned needs further study.
Standard and Comparative Energetics of a Small Avian Herbivore (Phytotoma rara)
Authors: Rezende Enrico L. , López-Calleja M. Victoria , Bozinovic Francisco
Published: September 2019

We studied the standard and comparative energetics of the Rufous-tailed Plancutter (Phytotoma rara), one of the smallest avian herbivores. The Rufous-tailed Plancutter had basal metabolic rate (BMR) values that so far are the highest mass-independent values observed in avian herbivores. Probably the BMR values attained by P. rara reflect its geographic distribution in temperate environments. Using a comparative analysis, we observed that herbivorous birds from temperate geographic areas tend to have higher BMR than tropical ones.
Intraspecific Variation in Commuting Distance of Marbled Murrelets (Brachyramphus marmoratus): Ecological and Energetic Consequences of Nesting Further Inland
Authors: Hull Cindy L. , Kaiser Gary W. , Lougheed Cecilia , Lougheed Lynn , Boyd Sean , Cooke Fred , Danchin E.
Published: September 2019

Radio transmitters were deployed on Marbled Murrelets (Brachyramphus marmoratus) at Desolation Sound, British Columbia, Canada, during the 1998 breeding season to assess individual variation in distance birds nested from foraging areas, and potential energetic and ecological consequences of commuting those distances. Radio-tracking from a helicopter was used to locate nests, and tracking from the air and boats was used to locate murrelets on the water. Twenty-three nests were found, with active incubation at 16, and active chick-rearing at 12. A minimum of 3 nests fledged chicks, 9 were failures, and 11 were unknown. Nests were at an elevation of 806 ± 377 m and a distance of 39.2 ± 23.2 km (range 12–102 km) from locations on the water. Birds spent an estimated 1.2 ± 0.7 h per day commuting to and from nests (range 0.3–3.5 h per day). It was estimated that birds expended 3,883 ± 2,296 kJ (range 1,200–10,144 kJ) over the breeding season when commuting to those nests, which was 5–41% of their estimated field metabolic-rate during the breeding season. There was no relationship between distance to nests and breeding success. Either Marbled Murrelets can accommodate that additional energy expenditure, or reduce commuting costs by modifying their foraging behavior. They may forage closer to nest sites when provisioning chicks, thereby reducing commuting costs with a payload, or alter nest visitation rates in relation to distance they nest from foraging areas. Nests further inland may also confer advantages that compensate for the added commuting, or birds might replenish body reserves at the end of the breeding season.
Timing of Mineral Sequestration in Leg Bones of White-tailed Ptarmigan
Authors: Larison James R. , Crock J. G. , Snow Christine M. , Blem C.
Published: September 2019

Birds are unique among vertebrates in that they protect their eggs with rigid, calcium-rich shells. Thus, for a short period of time during the annual reproductive cycle, birds experience extraordinarily high demands for calcium. Two strategies appear to exist for meeting those temporally high demands. Some birds apparently seek out calcium-rich foods immediately prior to and during egg laying whereas others may store calcium in their skeletons over a much longer period of time, mobilizing those reserves only when they are needed for production of eggshells. In this study, we used dual energy, X-ray absorptiometry and inductively coupled plasma mass spectroscopy to monitor annual shifts in bone mineral content in the legs of White-tailed Ptarmigans (Lagopus leucurus). The study organisms were known to live on calcium-poor soils. Despite an apparent shortage of calcium in their diets, the test subjects stored substantial amounts of calcium in their leg bones in months prior to reproduction. Those stores were subsequently depleted during the egg-laying period. We suggest ability to store calcium in the skeleton may afford this species more flexibility in selecting suitable breeding habitats than would be possible otherwise.
Nest-attenders in the Pied Flycatcher (Ficedula hypoleuca) During Nestling Rearing: A Possible Case of Prospective Resource Exploration
Authors: Ottosson Ulf , Bäckman Johan , Smith Henrik G. , Dickinson J. L.
Published: September 2019

Visits to nest holes by birds other than their owners is a familiar phenomenon for students of breeding biology. In this study, we evaluate that behavior using a transponder reading system. Eighty-five males and females were fitted with transponders at the end of the incubation period or just after hatching. Nest boxes were fitted with transponder readers from just after hatching until all nestlings fledged. That system revealed 123 visits by birds to nest boxes other than their own, a visit being defined as at least one visit to a separate nest box on a separate day. Males were more often detected at other nests than females (53% of males vs. 29% of females visited) and males on average made more visits than females did (4.8 vs. 2.5 visits). However, both males and females devoted time to visiting other nests while still feeding nestlings. That behavior is more common than previously suspected and is consistent with birds prospecting for future nest sites or investigating patch reproductive success.
Copulatory Behavior of American Avocets and Black-necked Stilts
Authors: Sordahl Tex A. , Murphy M.
Published: September 2019

I recorded details of 231 copulations of American Avocets (Recurvirostra americana) and 39 copulations of Black-necked Stilts (Himantopus mexicanus) in northern Utah. Those data are presented as quantitative descriptions of the copulatory behavior of each species, complementing and clarifying qualitative descriptions in the literature. I observed no qualitative differences between copulatory behavior of avocets and stilts. Small quantitative differences may be related to differences in morphology and habitat preference. Across the family Recurvirostridae, the distinctive copulatory displays of avocets (Recurvirostra spp.) and stilts (Himantopus spp.) seem relatively uniform, but the behavior of the monotypic Banded Stilt (Cladorhynchus leucocephalus) of Australia appears to differ somewhat from typical recurvirostrid copulatory behavior. Attempted copulation with inanimate objects has been reported for at least 6 of the 10 recurvirostrid species.
Large-Scale Variation in Growth of Black Brant Goslings Related to Food Availability
Authors: Sedinger James S. , Herzog Mark P. , Person Brian T. , Kirk Morgan T. , Obritchkewitch Tim , Martin Philip P. , Stickney Alice A. , Bosque C.
Published: September 2019

We examined variation in growth of Black Brant (Branta bernicla nigricans) goslings among two colonies on the Yukon-Kuskokwim Delta in southwestern Alaska and the Colville River Delta on Alaska's Arctic coast. We simultaneously measured abundance and quality of a key food plant, Carex subspathacea, and grazing pressure on that plant at the three colonies. Our goal was to measure variation in gosling growth in relation to variation in grazing pressure and food abundance because growth of goslings is directly linked to first-year survival, and consequently is the principal mechanism for density-dependent population regulation. Goslings grew substantially faster on the arctic coast and were nearly 30% larger than those on the Yukon-Kuskokwim Delta at four to five weeks old. Faster growth on the arctic coast was associated with 2× greater standing crop of C. subspathacea during brood rearing than on the Yukon-Kuskokwim Delta. Dispersal rates are high enough (Lindberg et al. 1998) to rule out local adaptation and genetic variation as explanations for observed variation in growth. Our results are consistent with lower survival of goslings from the Yukon-Kuskokwim Delta during their first fall migration and stronger density-dependent regulation on the Yukon-Kuskokwim Delta than on the Arctic coast.
Reproductive Success of Forest-Dependent Songbirds Near an Agricultural Corridor in South-Central Indiana
Authors: Ford Thomas B. , Winslow Donald E. , Whitehead Donald R. , Koukol Matthew A. , du Plessis M.
Published: September 2019

Potential source populations of forest-breeding Neotropical migrant birds may be threatened by anthropogenic changes that increase brood parasitism by Brown-headed Cowbirds (Molothrus ater) and nest predation in heavily forested breeding areas. In south-central Indiana, corridors of agriculture and rural development, ranging from <50 m to several thousand meters in width, penetrate interior portions of the heavily forested landscape. These corridors provide habitat for cowbirds and nest predators. We monitored breeding success of six species of Neotropical migrants and one resident species near an agricultural corridor and in interior forest. We found that nest survival was lower near the agricultural corridor for most of the species in the nestling stage, but no consistent difference in nest survival was detected during the egg stage. Levels of cowbird parasitism were generally elevated near the agricultural corridor. Estimates of the number of fledglings per nesting attempt indicated that seasonal productivity was lower near the agricultural corridor for six of the seven species. Status of populations of birds in south-central Indiana as sources in the Midwest may be compromised by extensive intrusion of agricultural corridors within the contiguous, heavily forested landscape.
Annual Survival Rates of Wintering Sparrows: Assessing Demographic Consequences of Migration
Authors: Sandercock Brett K. , Jaramillo Alvaro
Published: September 2019

The demographic consequences of migration have important implications for both evolutionary ecology and conservation biology. We investigated local survival rates for six populations of sparrows at a wintering site. Recent developments in mark–recapture statistics were applied to a 13 year dataset with large numbers of marked individuals (n = 1,632 to 4,394). The study taxa were closely related, and included one resident species (Song Sparrow [Melospiza melodia gouldii]), one short-distance migrant (“Puget Sound” White-crowned Sparrow [Zonotrichia leucophrys pugetensis]), two moderate-distance migrants (Lincoln's [Melospiza lincolnii] and Fox [Passerella iliaca] sparrow), and two long-distance migrants (“Gambel's” White-crowned [Zonotrichia leucophrys gambelii] and Golden-crowned [Zonotrichia atricapilla] sparrow). A literature review demonstrated a cline in fecundity among these sparrows: resident and short-distance migrants laid multiple clutches of few eggs, whereas long-distance migrants tended to produce one large clutch. Annual rates of local survival were low in the interval after first capture (<0.35), possibly because of variation in true survival, site-fidelity, presence of transients and heterogeneity of capture. Estimates of local survival among birds that returned at least once were more robust and were comparable among Song (0.558 ± 0.054 SE), Puget Sound White-crowned (0.461 ± 0.026), Lincoln's (0.456 ± 0.066), Fox (0.352 ± 0.0), Golden-crowned (0.422 ± 0.023) and Gambel's White-crowned (0.432 ± 0.0) sparrows. Estimates of survivorship for Lincoln's and Fox sparrows are among the first values available for those species. Local survival was not higher among resident than migratory taxa, nor did it covary with migration distance among migratory species. These results did not support the time-allocation hypothesis of Greenberg (1980), but are consistent with aspects of bet-hedging theory. While these analyses have potential implications for conservation of migratory birds, further work is required to establish whether these patterns are applicable to Neotropical migrants.
Scales of Food Availability for an Endangered Insectivore, The Hawaii Akepa
Authors: Fretz J. Scott
Published: September 2019

The Hawaii Akepa (Loxops coccineus coccineus) is an endangered bird that has declined dramatically in the last 100 years, and is now rare or absent from many areas that appear to support suitable habitat. Food availability may play a role in these distribution patterns, but differences in food between sites may arise from different sources. I compared prey availability between a site supporting a large, stable Hawaii Akepa population, and a site from which Hawaii Akepa have declined in the last 100 years for unknown reasons. I used three spatial scales to compare food between sites to explore the basis of differences in food between sites. At a scale appropriate for comparing prey population dynamics (scale 1), I found that prey population densities are similar between sites, suggesting that introduced (or native) predators or parasitoids have not affected prey populations differently between sites. At two larger scales incorporating habitat structure, I found that food availability is much lower at the site of Hawaii Akepa declines. Differences in canopy density per square meter (scale 2), and in canopy cover per square kilometer (scale 3), result in lower food availability that may have effects on individual foraging birds as well as on potential Hawaii Akepa population density. These findings illustrate the importance of explicitly incorporating spatial scale into inquiries about food for Hawaii Akepa, and suggest that the site of population declines may not be suitable habitat with respect to food for this species.
Plasma Amino Acid Concentrations as an Indicator of Protein Availability to Breeding Herring Gulls (Larus Argentatus)
Authors: Hebert Craig E. , Shutt J. Laird , Ball Ron O.
Published: September 2019

In a captive-feeding study using Herring Gulls (Larus argentatus), plasma amino-acid concentrations increased in response to an increase in dietary protein. Plasma amino-acid concentrations were also measured in wild Herring Gulls captured during incubation at eight Laurentian Great Lakes colonies. Those concentrations were used as an indicator of protein availability at those locations. Significant differences in amino acid concentrations were observed among colonies. Lower amino acid levels, particularly of the essential amino acids, were measured in gulls nesting on Lake Superior, whereas values in gulls captured on Lake Ontario and Lake Erie were greater. Those geographic differences in protein availability likely reflected spatial differences in availability of high quality prey (e.g. fish). Geographic differences in prey availability probably affected diet composition. Comparison of amino-acid levels in wild birds to reference values obtained through the captive feeding study indicated that gulls nesting on Lake Superior may have been protein limited. Colony-wide estimates of adult female body condition, intraclutch variation in egg size, and productivity were correlated with an index of plasma amino-acid concentrations.
Effects of Feather Lice on Flight Behavior of Male Barn Swallows (Hirundo Rustica)
Authors: Barbosa A. , Merino S. , Lope Fde , Møller A. P.
Published: September 2019

Parasites may affect host behavior in a number of ways, including their locomotory performance. We investigated whether the number of holes produced by the feather louse (Myrsidea rustica) affected flight behavior in adult male Barn Swallows (Hirundo rustica) by video-taping flight performance of individuals during escape and level flight. Percentage of time spent flapping during foraging flight was positively related to number of holes, but not to other flight parameters such as wingbeat frequency. These results suggest indirect effects of feather lice on host performance that must be considered together with effects of thermoregulation and feather breakage. This is the first report of an effect of parasite load on flight behavior.
Genetic Parentage and Mate Guarding in the Arctic-Breeding Western Sandpiper
Authors: Blomqvist Donald , Kempenaers Bart , Lanctot Richard B. , Sandercock Brett K.
Published: September 2019

Extrapair copulations and fertilizations are common among birds, especially in passerines. So far, however, few studies have examined genetic mating systems in socially monogamous shorebirds. Here, we examine parentage in the Western Sandpiper (Calidris mauri). Given that Western Sandpipers nest at high densities on the Arctic tundra, have separate nesting and feeding areas, and show high divorce rates between years, we expected extrapair paternity to be more common in this species compared to other monogamous shorebirds. However, DNA fingerprinting of 98 chicks from 40 families revealed that only 8% of broods contained young sired by extrapair males, and that 5% of all chicks were extrapair. All chicks were the genetic offspring of their social mothers. We found that males followed females more often than the reverse. Also, cuckolded males were separated from their mates for longer than those that did not lose paternity. Although these results suggest a role for male mate guarding, we propose that high potential costs in terms of reduced paternal care likely constrain female Western Sandpipers from seeking extrapair copulations.
Habitat use and Breeding Distribution of Magellanic Penguins in Northern San Jorge Gulf, Patagonia, Argentina
Authors: Borboroglu Pablo García , Yorio Pablo , Boersma P. Dee , Valle Héctor Del , Bertellotti Marcelo
Published: September 2019

We evaluated distribution and size of Magellanic Penguin (Spheniscus magellanicus) colonies in northern San Jorge Gulf, Argentina, characterizing nesting habitat at 14 islands with colonies (IC) and 28 islands without nesting penguins (INC). Digital analysis of a Landsat TM satellite image and field measurements were used to assess vegetation and substrate. The 14 breeding colonies ranged in size from 13 to 96,300 nests, and number of breeding pairs was estimated at 218,460. Colonies were only located on islands. Digital analysis of the satellite image showed that the proportion of area with shrub–steppe vegetation was significantly higher at IC than at INC (38.6 vs. 4.9%), whereas percentage of rocky substrate was lower at IC (33.6 vs. 64.8%). Percentage of vegetation cover was positively correlated with island area and with number of breeding pairs. Most nests (98.6%) were located under bushes, whereas the rest were burrows dug into the substrate. Mean size of bushes used for nesting was higher at IC (4.47 vs. 0.99 m2) as was the percentage of silt–clay substrate (47.31 vs. 1.98%). Coast minimum slopes at INC were steeper than the slopes of entrance routes at IC (27.6 vs. 5.7°). Probability of occupation of islands increased with amount of shrub-type vegetation cover and silt–clay substrate, and decreased with increasing slopes and amount of sandy substrate. Magellanic Penguins selected islands with shrub-type vegetation and soil that allow building nests with adequate cover. These results are consistent with other studies showing vegetation cover is an important nesting requirement for Magellanic Penguins.
Effects of Hardwood Reduction on Winter Birds in Northwest Florida Longleaf Pine Sandhill Forests
Authors: Provencher Louis , Gobris Nancy M. , Brennan Leonard A.
Published: September 2019

Reversing decades of fire exclusion by hardwood midstory reduction is now used to recover populations of the federally endangered Red-cockaded Woodpecker (Picoides borealis) in longleaf pine (Pinus palustris) forest ecosystems. The effects of Red-cockaded Woodpecker management on winter birds in longleaf pine sandhill forests are largely unknown. Examining habitat use of winter migrants, some of which are declining, may influence the selection of habitat management techniques used for Red-cockaded Woodpeckers to benefit overwintering migrants. During the winters (December–February) of 1997–1998 and 1998–1999, we tested experimentally the effects of hardwood reduction treatments applied in 1995 on winter birds at Eglin Air Force Base in fire-excluded northwest Florida longleaf pine sandhills. Treatments were (1) prescribed spring burning, (2) herbicide application, (3) mechanical felling and girdling, and (4) a control where decades of fire exclusion was maintained. We also sampled winter bird flocks in frequently burned, nonexperimental reference plots to measure management success. Hardwood reduction techniques had no effect on flock species richness, which averaged 7.9 and 7.2, respectively, during 1997–1998 and 1998–1999. Larger flocks in felling and girdling and in herbicide plots were primarily due to significantly higher numbers of overwintering Chipping Sparrows (Spizella passerina), as well as resident Red-cockaded Woodpeckers and an influx of temperate migrant Pine Warblers (Dendroica pinus). In contrast, flocks in control plots were smaller (flock size and species composition in spring burn plots were intermediate) and composed of hardwood-associated species, such as Tufted Titmouse (Baeolophus bicolor) and Carolina Chickadee (Poecile carolinensis). The relative uses of longleaf pines and hardwoods by Red-cockaded Woodpeckers, Pine Warblers, and Brown-headed Nuthatches (Sitta pusilla) during both winters best explained that winter birds present in herbicide, felling and girdling, and reference plots were more likely to forage on the same tree species and substrates than birds in spring-burned plots, and least likely to forage on the same species and substrates as birds in the control plots. Those differences corresponded to the following increasing order of hardwood stem mortality among treatments: control, spring burn (41%), felling and girdling (62%), and herbicide (92%). Repeated burning is recommended to restore the reference foraging condition because it was eight times less expensive than other techniques, which favored mostly Chipping Sparrows.
Mexican Spotted Owl (Strix Occidentalis) Population Dynamics: Influence of Climatic Variation on Survival and Reproduction
Authors: Seamans Mark E. , Gutiérrez R. J. , May Christopher A.
Published: September 2019

Understanding the mechanisms causing temporal variability in demographic parameters is essential to understanding fluctuations in populations. As part of a long-term demographic study, we evaluated influence of climate on Mexican Spotted Owl (Strix occidentalis lucida) annual survival and reproduction in two study areas, one in Arizona and one in New Mexico. Spotted Owl survival in New Mexico and reproductive output in both study areas were positively related to total amounts of precipitation from the previous year, previous winter, or monsoon season. For both study areas, temporal process variation in reproductive output (CV[R] = 51.2 and 75.2% for Arizona and New Mexico, respectively) was greater than that for survival (CV[ϕ] = 12.9 and 7.1% for Arizona and New Mexico, respectively). Precipitation from the previous year explained 73% of σ̂2temporal reproductive output for Arizona owls and precipitation from the previous monsoon explained 42% of σ̂2temporal in reproductive output for New Mexico owls. Precipitation from the previous monsoon season explained 53% of σ̂2temporal in Arizona owl survival and precipitation from the previous winter explained 56% of σ̂2temporal in New Mexico owl survival. The two populations of Spotted Owls we studied appeared to have the same life-history strategy hypothesized for a population of Northern Spotted Owls (S. o. caurina), although the Mexican subspecies apparently responded quite differently to climatic variation.
Intromittent Organ Morphology and Testis Size in Relation to Mating System in Waterfowl
Authors: Coker Christopher R. , McKinney Frank , Hays Helen , Briggs Susan V. , Cheng Kimberly M.
Published: September 2019

The waterfowl family Anatidae is one of very few avian taxa that possesses an intromittent organ. This paper examines the adaptive significance of the intromittent organ in waterfowl by determining the relationships between intromittent organ morphology and the intensity of sperm competition (as reflected by frequency of forced extrapair copulations [FEPCs]). Intromittent organ morphological characteristics, including length and circumference (adjusted for body size), number of ridges and knobs (per unit area), ridge or knob height, ridge or knob span, and area covered by ridges and knobs, were measured from scaled drawings of museum specimens of 54 waterfowl species (33 genera), 27 of which were ranked by frequency of FEPC (1 = monogamous, 2 = rare FEPC, 3 = frequent FEPC, and 4 = polygynous or promiscuous). Testes sizes were also investigated in relation to FEPCs, where testes mass (adjusted for body size) from 44 species (24 genera) were obtained (29 species with mating strategies). The size of the testes, the length of the intromittent organ, the height of the intromittent organ ridges and knobs, and the area covered by ridges and knobs increased significantly with the frequency of FEPC, and those relationships exist after correcting for common ancestry constraints. These results are consistent with the hypothesis that waterfowl intromittent organs are involved in sperm competition. Further research into the actual mechanism by which the intromittent organ is involved would be worthwhile.
A Removal Model for Estimating Detection Probabilities From Point-Count Surveys
Authors: Farnsworth George L. , Pollock Kenneth H. , Nichols James D. , Simons Theodore R. , Hines James E. , Sauer John R.
Published: September 2019

Use of point-count surveys is a popular method for collecting data on abundance and distribution of birds. However, analyses of such data often ignore potential differences in detection probability. We adapted a removal model to directly estimate detection probability during point-count surveys. The model assumes that singing frequency is a major factor influencing probability of detection when birds are surveyed using point counts. This may be appropriate for surveys in which most detections are by sound. The model requires counts to be divided into several time intervals. Point counts are often conducted for 10 min, where the number of birds recorded is divided into those first observed in the first 3 min, the subsequent 2 min, and the last 5 min. We developed a maximum-likelihood estimator for the detectability of birds recorded during counts divided into those intervals. This technique can easily be adapted to point counts divided into intervals of any length. We applied this method to unlimited-radius counts conducted in Great Smoky Mountains National Park. We used model selection criteria to identify whether detection probabilities varied among species, throughout the morning, throughout the season, and among different observers. We found differences in detection probability among species. Species that sing frequently such as Winter Wren (Troglodytes troglodytes) and Acadian Flycatcher (Empidonax virescens) had high detection probabilities (∼90%) and species that call infrequently such as Pileated Woodpecker (Dryocopus pileatus) had low detection probability (36%). We also found detection probabilities varied with the time of day for some species (e.g. thrushes) and between observers for other species. We used the same approach to estimate detection probability and density for a subset of the observations with limited-radius point counts.
Extrinsic and Intrinsic Sources of Variation in Plasma Lipid Metabolites of Free-Living Western Sandpipers (Calidris Mauri)
Authors: Guglielmo Christopher G. , O'Hara Patrick D. , Williams Tony D.
Published: September 2019

Plasma lipid metabolites may be useful indicators of mass changes in migratory birds. To test utility of plasma metabolites in field studies, we examined effects of several extrinsic (bleed time, time of day, location) and intrinsic (body mass, sex, age, migratory state) factors on plasma concentrations of triglycerides (TRIG), glycerol (GLYC), and B-OH-butyrate (BUTY) in free-living Western Sandpipers (Calidris mauri). TRIG and GLYC decreased rapidly following capture (2–20 min), whereas BUTY did not change. GLYC and BUTY were negatively correlated to body mass. TRIG was positively correlated to body mass in migrant females, but not consistently in migrant males, or in females captured on the wintering grounds. Taking into account other sources of variation, the two measures of lipid utilization (GLYC and BUTY) varied little through the year. TRIG showed the greatest potential for use in field studies. TRIG was lowest during winter, when birds were leanest, and highest during spring and fall migration, when sandpipers were gaining mass rapidly at stopovers. TRIG differed between sandpipers refuelling a two stopover sites separated by 35 km, demonstrating that populations of birds can have characteristic lipid metabolite profiles that may reflect local differences in fattening rate.