THEAUK

A QUARTERLY JOURNAL OF
ORNITHOLOGY
VoL. 76AN

JANV0AR¾,
1959

APPROACH
BY

TO
PHILIPTHE

STUDY

S. HUMPHREY

1.

NO. 1

OF MOLTSANDKENNETHANDC.

PLUMAGES

PARKESINTRODUCTION

During the courseof studiesof the moltsand plumagesof certain
waterfowland other birds,it hasbecomeapparentto us, as it has toa number of other workers,that the descriptionof plumagesuccessionshasoften beenhamperedby the lack of a uniform and practicalterminology.It wasour originalintent to introducea new terminology
applicable,as far as possible,to all birds,in order to eliminatesomeof the semanticdifficultiesof the past. As this projectprogressed,itbecameobvious that knowledgeof the plumage stagesof many
speciesis sadly incompleteor poorly understood;further study revealed the need of a reexaminationof many long-heldconceptsof
plumage succession
and of more precisedefinitionsof widely but
ambiguously
usedterms. The subjectis too large to be coveredin asingle paper. We proposehere to discussplumage succession
beginningat the time of lossof the juvenalplumage,i.e., the bird'sfirstcoveringof true (in somecases
modified)contourfeathers. We hopein a later paperto analyzethe developmentof the plumagesfrom theembryothroughthe completedjuvenal plumage. We have adopted
thisreversed
chronologicalsequence
becauseof the complexityof thequestionof the "natal downs"and their origin, which we intend toinvestigateat somelength.
We hopein this paperto thrownew light on conceptsof plumage
and molt, and we presenta frameworkwithin which descriptive
andcomparative
studiesmaybe made. In spiteof the vastprogress
madeby many workersin recent decadesin understandingsomeof thefactorswhichaffectthe physiology
of molt (geneticcontrol,hormonalbalance,photoperiod,temperature,diet, etc.),it mustbe rememberedthat such information

is available for but a small fraction of thespeciesof birdsof theworld. We believeit is greatlydesirable
to have
1

2

HUMPHREYANDPARKE•,
MoltsandPlumages[ Auk

kVol.76a systemavailable whereby variations in the patterns of plumage
succession
may be described,compared,and contrastedamong different groupsof birds,whetheror not the physiologicalmechanisms
have

beenworkedout for the groupsin question.
In reviewingthe recentliterature in which intrinsic and extrinsic
factorsaffectingmolt have beendiscussed,
it hasbecomeapparent thatsuchfactorsmay vary widely in relative importanceamongdifferent
groupsof birds. In striking contrastto this heterogeneityis what
appearsto be a fundamentalpatternof plumagesuccession
whichcanbe tracedalmostthroughoutthe classAves. Such a pattern has been
notedand utilized by studentsof this subjectfor overa century. The
prevalenceof this apparently consistentpattern leads us to believethat a broad conceptof homology,suchas that advocatedby Hubbs(1944), may usefully be applied to plumagesand molts, and that
descriptiveand comparativeplumagestudieswill proceedin a moreorderlyfashionif they are conductedin the light of sucha homolofty
concept. It is, of course,impossibleto be certain that plumage
sequenceswhichappearto be exactlyequivalentin variousgroupsof
birds are truly homologousin the phylogeneticsense;however,webelieveit is not onlyusefulbut evennecessary
to treatsuchequivalence
provisionallyas homologyin studiesof the type we have mentioned.
A few groupsof birds presentexceptionallydifficult problemsof interpretation
when attemptsare made to fit them into the systemof homologieshere proposed.
Further study of some of thesedifficult groups,which will be mentionedlater,
may ultimately prove them to be real exceptionsto the general pattern, withsequencesof plumagesuccession
which have evolvedindependently.On the other

hand, their apparentnonconformity
may somedaybe resolvedand their sequenceof plumage succession
shown to be merely extreme modificationsof the general
pattern.

Various drafts of the manuscripthave been read entirely or inpart by many of our colleagues;
we are grateful for their comments
and helpful suggestions.We wish particularly to acknowledgethe
constructive
criticismgivenus by Ralph S. Palmer,ThomasR. Howell,Finn Salomonsen,
EugeneEisemnann,and CharlesH. Blake.
2.

DEFINITIONS

Any descriptionof the plumagesuccessionof a speciesdepends
ultimately on the way in which the terms"plumage"and "molt" aredefined. Ambiguoususeof suchwordsmakesit difficult to arrive at
straightforwardinterpretationsfor any one species,and virtually
impossibleto tracehomologies.
(1) Cycle. In most birds of temperateregions,which are the best
known, there are severalcyclicphenomenawhich coincidewith the•959aHUMPHREYAND
PARKES,
MoltsandPlumages

3

calendaryear:reproduction,
migration,molting,etc. It is convenient,
for suchbirds,to speakof "numberof plumagesper year." But there
is increasingevidencethat someequatorial,antarctic,and oceanic
species
may havereproductivecyclesof lessor more than a calendar
year,viz., the 9.6-monthnestingcycleof Ascension
Island SootyTerns(Sterna[uscata) (Chapin, 1954), and the 14- to 18-monthbreeding
cycle of South Georgia.King Penguins(Aptenodytespatagonica)(Stonehouse,1956). Althoughlittle is yet knownon this point, thecyclesof plumagesuccession
in suchspecies
may alsobe of more or
lessthan a year. Sinceour aim in this paperis to suggest
homologiesof plumages(and a resultantnomenclature)applicableto birdsof any
part of the world, we will be, for the mostpart, usingthe expression"per cycle"rather than "per year." "Cycle"in this senseis to beunderstoodas a shortenedversionof "plumage cycle;" a "cycle" (inan adult bird) runs from a givenplumageor molt to the next occurrenceof the sameplumageor molt.
(2) Plumage. This is much more difficult to define than it would
first appear. Dwight (1900) differentiatedbetween "winter" and"nuptial" plumages,evenwhenno molt intervenes,in orderto describe
thosebirds which changetheir appearancemarkedly through wear.
But he even extendedthis two-plumageconceptto birds which do
not changetheir appearance
at all (c[. the two "plumages"of Progne
subis, Dwight, 1900: 225). This concept of individually-named
plumagesattained by either molt or wear is probably not widely
acceptedat present. If followedto its logicalconclusion,it would benecessaryto statethat the adultmaleBobolink(Dolichonyxoryzivorus)
has three plumages:the "winter," which is lost by a completemolt,the "spring,"and the "summer,"attainedthroughwear.
Another type of plumagedefinition basedon the over-all appearanceof thebird involvesthosespeciesin which a molt may be greatly protractedor eventemporarilysuspended;that is, virtually dividedinto two stagesby a pausein theprocessof feather replacement.The temptationis then to give separateplumage
names basedon the appearanceof the two stagesof the molting bird. As Mrs.

Stresemann(1948:190) puts it, "The resumptionof feathergrowthafter a period
of interruptedmoult doesnot mean at all that a new plumageis assumed....
Many of the Palaearcticmigrants,for example,divide their principal moult into
twoperiods.They moultpart of their plumage(usuallythe entirebodyplumage)before migration,while the remainderof the plumage (usually wing and tailfeathers)is not moulteduntil severalweekslater in the winter quarters (as in
Hitundo, Delichon,and Riparia)." This is alsotrue of certainNearericmigrants,
for examplemany Tyrannidae.

For purposesof hornologywe feel that it is necessaryto confine
the word "plumage,"as used in studiesof plumagesuccession,toHUMPHREY^•D P^mZES,
MoltsandPlumages[- AukI.Vol.76

a singlegenerationo[ leathers. Sucha generationmay include lessthan the entire feathercoveringof a bird; thus the feathersattainedby a partial molt constitutein themselvesa plumageby this definition.
Perhaps the most important point to stresshere is that by ourdefinition the number of plumagesis equal to the number of molts
in a given cycle. Salomonsen(1941, 1949) describedand named noless than four "plumages"for the Oldsquaw (Clangula), although
admitting that no feather is renewedmore than three timesper cycle,
and mostfeathersonly onceor twice. Accordingto our concept,theplumagesof the Oldsquaware homologous
with thoseof other ducks,
exceptfor the fact that an additionalgenerationof feathers,including
only the scapularsand parts of the head, occursduring each cycle.
These few feathersconstitutethe only additional "plumage"of theOldsquaw,all othersbeinghomologous
not only with the plumagesof other ducksbut of other birds in general.
The traditional concept by which a bird can wear only one"plumage"at any given time, the "plumage"beingdescribedin termsof the bird's appearancerather than of the particular generationsof
feathers producing this appearance,makes the determinationof
plumagehomologiesdifficultif not impossible. In birds with greatly
protractedmolts the appearancemay be changingcontinually,and
subdivisioninto "plumages"on the appearancebasismust be, to say
the least,arbitrary.
Several authors, including Dwight and Meylan (1932) have used
the term "compoundplumage." By their definition, a bird wearsa"simple plumage" following a complete molt, and a "compound
plumage"after a partial molt. By our definition, this is impossible;
after a partial molt the bird wearsthe newly assumedplumageplus
parts of one or more previousplumagesrather than a single "compound" plumage.
The various semantic difficulties outlined above arise, we feel, outof a real needfor additionalterms. If a bird at a given time may,accordingto our usage,be wearingfeathersbelongingto two or more
plumages,how may the bird bestbe describedat that moment? To
aid in resolvingthesedifficulties,two additionaltermsappear to benecessary,
asfollows:(3) Aspect.This word may be usedin descriptionsof the total
appearanceof a bird at anygiventime,no matterhowmanygenerations of featherscombineto producethat appearance.Aspectalso
takesinto accountchangesin appearancebroughtabout by adventitious factorssuchas fading, staining,and abrasion (wear). In field
guidesor othersimplifieddescriptions,
it will be possibleto describe•OSO-•HUMPHREYANnPARKES,
MoltsandPlumages

5and portraythe "springaspect"or "winter aspect"of a givenspecies,
without referenceto plumagenamesor to actual stageof molt. Thus,a frequentlyseenlate summeraspectof young Starlings(Sturnus
vulgaris)consistsof a grayish-brown
head,white-spangled
black body,and blackishwingsand tail. A given aspectmay be analyzedin asmuch detailas seems desirable.

It is thus apparent that Salomonsen(1941, 1949) has divided
variousstagesof the threeplumagesof the Oldsquawinto four aspects,
which he has designatedas "plumages."(4) Feather coat. This term may convenientlybe usedwhen it isdesirableto describethe aggregateof featherswornby a bird regardlessof the relative time of assumptionof the componentsof that aggregate. The feather coat may, at any given moment,consistof feathersof one, two, or more plumages,i.e., generationsof feathers.Descriptionsof the feathercoatmay be madewhetheror not a molt is under
way at the time. Thus, the feathercoatof youngStarlingsduring afrequently observectstageof molt in late summer comprisesheadfeathersof the juvenal plumageand body and flight feathersof thenext succeedingplumage.
Enumerationof the componentsof the feather coat actuallyrepresentsan analysis,in part, of the elementswhich producea given
aspect (although adventitiousfactorsare irrelevant in describinga feathercoat). It shouldbe pointedout that the aspectof an individual living bird or specimencan be describedeven though theplumagesequenceof its speciesis not well enoughunderstoodto
permit analysisof the components
of its feathercoat.
When, later in the present paper, it is necessaryto refer to"plumage"in Dwight's sense (a combinationof our conceptsoffeather coat, aspect,and plumage), the word will be enclosedin
quotationmarks to distinguishit from the term as we use it in a
restrictedsense.

A few of our colleagues,
on reading this paper in manuscript,have felt that
we have givenan unduly restricteddefinitionto the word plumageby limiting
its use in technicaldiscussionsof plumagesequenceto a single generationoffeathers.As hasbeenshown,the word "plumage"as formerlyusedis a vaguelydefined combinationof three different concepts. We feel that it is desirable tocontinueto use the word plumagefor one of thesethree conceptsrather thanto abandon the word and introduce three new terms; a technical discussionof themolts of a bird without any use at all of the word plumage is almost unthinkable.

Even thongh, as used in such expressions
as "juvenal plumage","first winterplumage",etc.,in the past,the word "plumage"doesnot alwaysconformto ourrestricted
definition,we feel that this wordcarriesan establishedimplicationof a
stagein a sequence.It seemslogical,therefore,to choosea restricteddefinitionof plumageas we havedone in order to be able to continueusingthe word in6

HUMPHREYANDPARKES,
MoltsandPlumages

1- Auk

LVol.76

technicaldiscussionsof the sequentialphenomenonof featherreplacements.
As soused,therecanhardlybe confusion
with the broadlydescriptive
useof the word
plumage as in such expressions
as "brightly-plumagedbirds," "lax plumage,""worn plumage," etc.

(5) Molt. A molt may be definedas the normal sheddingof
feathersand thereplacementof mostor all of theseby a newgeneration of feathers. This definition holds no matter how few feathers

areinvolvedandregardlessof the timerequiredfor thisprocess.
Thefeatherswhichare shedduringa givenmolt may belongto a single
generationor may includefeathers,belongingto earlier generations,whichhavesurvivedoneor morepreviousmolts.
The definitionof molt given aboveincludestwo distinctphe--.
nomena:The sheddingof feathersand the growth of new feathers.
The loss of feathers during normal molting has relatively little
physiologicalimpacton the organism. The developmentof a generation of newfeathers,on theotherhand,is profoundlyinterrelatedwith
other physiologicalprocesses,
affectingsome and being affectedby
others.

Some authorshave sought to restrict the term "molt" to the loss
alone, using an additional term for the subsequentgrowth of newfeathers. This is an unnecessaryand erroneousrestriction; the word
"molt" is derived from the Latin mutare, "change",implying thesubstitutionof the new for the old.

There is evidence (Staebler, 1941) that some birds of northernlatitudeshave evolveda mechanismwherebymore individual bodyfeathersare worn in winter than in summer,presumablyby losing
feathersfrom certain folliclesin the springand not replacingthese
until the autumn. There are severalwaysin which this adaptation
may havedeveloped.Elaborationon this topic would be peripheral
to the presentpaper, but it shouldbe statedthat suchadaptations
can be interpretedwithin the frameworkof the conceptshere presented.

In birds which renew all their feathersonly once per cycle, theprocessof featherreplacementmay occur (1) throughall or mostof

the year as a protractedmolt, (2) during a relativelybrief period
at a particulartime of year, suchas just after nesting,or (8) inseveral,temporallyisolatedperiods;thus, part of the molt mightoccurduring a brief period in the summerand another part after
the bird had reached the wintering ground. In other words, asinglemolt may be temporallyextendedor compressed,
continuousor discontinuous.In addition,the temporalpositionof a particularmolt maybe shiftedsothat it may commence
immediatelyupon the19/59HUMPHREYAND
PARKES,
MoltsandPlumages

7completionof the prior molt, or, in certain groups, even before
completionof the prior molt. The bestknown exampleof suchoverlapping molts occursin certain ducks. The molting of the remiges
in theseduckshas been widely acceptedas the last portion of themolt into the "eclipseplumage." Before the growth of the remiges
is completed,the next molt is initiated; seedescriptionof a specimenof Velvet Scoter(Melanitta fusca) in Witherby et al. (1943, vol.
3: 355).
We use "partial" and "complete"in their traditional senses;thelatter for the assumptionof a generationof feathersby the renewalof all tracts,the former for the assumption'of a generationinvolving
only specificportionsof the bird's coveringof feathers.Most adultbirdshaveat leastone completemolt per cycle;many haveone complete and one partial molt. Someadult birds acquire two different
plumagesby two completemolts per cycle. Adults of a very small
numberof species
haveone completeand two or threepartial molts
per cycle. Thus, any given feather follicle may be activatedonce,
twice,or rarelythreeor four timesper cycle.
An additionalpoint on usagemay be mentionedhere. For reasonsof clarity, we prefer in general to confine the noun "molt" to theentire changebetweenplumages,and when dealingwith an individualfeatheror group of feathers (but lessthan an entire generation),to
use the presentparticiple,thus: (a) this species
undergoesa partial
molt; (b) the molting (not "molt") of the rectricesis centrifugal.
In summary,it may be said
1) A molt consistsof the normalsheddingof feathersand the replacement of most or all of these by a new generation of feathers, a
process
whichoccursperiodicallyin more or lessdefiniterelationshipto othereventsin the life historyof an individual bird. This excludes
accidentallossand replacementof feathers.
2) Within a single cycleof plumagesuccession,feathersof various
tractsmay be renewedonce,twice,or (rarely) three or four times.
3) A bird canhaveno more moltsin a singlecycleof plumagesuccession than the maximum number of times any feather follicle isactivated.

4) Within a cycle,a molt maybe protractedor compressedin time.
5) A molt maybe continuous,
limitedin time,or interruptedin time.
6) The temporalpositionof a homologous
molt in the cyclesof
plumagesuccession
may vary amongdifferentgroupsof birds oramongindividualsof a species.
7) A molt may commence
immediately
upon (or in certaingroups
evenbefore)completionof the prior molt.

8

HUMPHREYANDPARKES,
Molts and Plumages[ Auk

LVol.768) The characteristics
of a molt may vary with the age, sex, or
geographic
originof an individual,andmaybc influenced
by environmental

factors.

3. CURRENTLY ACCEPTED CONCEPTS OF PLUMAGE SUCCESSION

Althoughseveralauthors,includingMayaud,A. H. Miller, Pitclka,
Portmann,Salomonsen,
Schi½lcr,Strcscmann,Sutton, Withcrby, andothers,have publishedpaperson specificproblemsinvolvingmolts
and plumages,therehasbccnno recentgeneralpaperon the subject.
Currentpracticeswith regardto namingmoltsand plumages,and theworksof Dwight and Mcylan,indicaterather clearlythe nature of theassumptions
underlyingcurrentlyacceptedconceptsof plumagesuccession.

The so-called"nuptial plumage,"accordingto presentlyaccepted
views,is commonto all "adult" birds, as is the "postnuptial"molt.
Plumage equivalencesof the sort to which we have applied thehornologyconcepthave been establishedlargely in relation to thepostnuptialmolt. In the wordsof Dwight (1900: 130): "The only
invariable moult is the postnuptial,which, except in a very rare
few cases,
is absolutelycompleteand takesplacein all speciesat thecloseof or soonafter the breedingseasonpeculiar to each." Since
the postnuptialmolt takesits name from the "plumage"preceding
it, it is obviousthat either the molt or the "plumage"or both may
be usedas landmarksof homology.
A fundamental assumption,with which we concur, is that mostnormal adult birds have at least one completemolt per cycle;themolting of any feather which is normally renewedonly once per
cycleis thus part of this molt no matter when it occurs. This molt
(usually called the "post-nuptial"or "completeannual") and the"plumage"precedingit havebeengenerallyassumed
to be equivalent
in most birds.

Correlation with the reproductivecycle has also been used inattemptingto determineequivalenceof plumages,as implied by thelastportionof the passage
quotedfrom Dwight,above. Birdswith but
a singleplumageand one molt per year must obviouslybe wearing
their "nuptial plumage" the year round. Many birds have, in one
or both sexes,two plumagesper year, one of which is a bright"nuptialplumage"usuallycorrelatedwith reproductive
behaviorand
lostby a completemolt, and the othera dull "non-nuptialplumage"whichis partially lostduring the partial "prenuptial"molt.
The "reproductiveplumages"worn by adult birds, whetherthey
have an additional "non-nuptial plumage" or not, have been con-•9õ9aHUMPHREYANDPARKES,
MoltsandPlumages

9sideredequivalent,particularlyin view of the fact that these"reproductiveplumages"are almostalwayslost by a completemolt. This
relationship constitutesthe fundamental basis of what might becalledcurrent conceptsof plumagehomologies. The variousso-called"immature plumages"are interpreted by working backwardsfrom
the first postnuptial (complete)molt as a landmark and countingthe"plumages"(usuallytwo or three)betweenit and the "natal plumage."On the basis,then, of current conceptsof plumagehomologiesas
outlined above,the plumagesof an adult bird with one plumageper
cycle (example,the Starling)and an adult bird with two "plumages"
per cycle (example, the Scarlet Tanager, Piranga olivacea)may bediagrammedas in Figure I.
CYCLE

CYCLE

2

plumagefeef hers

PARTIALPARTIALPRENUPTIAL

MOLTPRENUPTIAL

MOLT

F•ight•eathers

FlcuP.
E 1. Schematicpresentationof traditional conceptof sequenceof molts
and plumages in mature individuals of (a) Starling (Sturnus vulgaris) and (b)Scarlet Tanager (Piranga olivacea). In these two speciesone cycle corresponds
to one year; two cycles (two years in this case) are illustrated. Stippled areas

signify"bright" plumage;white areassignify"dull" plumage. In this and Figures
3-7, molts are shown symbolically;the diagrams merely indicate the sequenceof
molts and plumagescharacteristicof each of the species. The diagramsare notintended to show temporal position or duration o[ any o[ the molts, or extent o[partial molts.
4.

A NEW APPROACH TO PLUMAGE AND MOLT HOMOLOGIE$

There are severalweaknesses
in the currently acceptedconcepts
outlined in the previoussection. One of the mostimportantof these
involvesthe use of the postnuptial molt as the critical landmark of

10

HUMPHREYANDPARKES,
MoltsandPlumages[- Auk

LVol.76homology;the "plumages"precedingthe postnuptialmolt of different
birds have been consideredequivalent. The idea that it is the"nuptial plumage" that is followed by the complete molt in all
birds was expressedby Dwight (1902: 249) as follows: "From time
immemorial, the adult plumage of the breeding seasonhas been
acceptedas the one most typical of the species,and the moult by
which it is entirely sweptaway formsa fixed point in everyplumage
cycle. The plumagemay well be called the nuptial and the moult
the postnuptial." Thus the criterionfor the hornologyof the "nuptial
plumage" is the molt by which the nuptial feathersare lost. Fromthe physiologicalstandpoint this appears unjustified. The energy
expenditureand other physiologicalchangesconnectedwith growth
are significantin relation to the incomingfeathersand have nothing
to do with the feathers that have been shed.

Determinationof feather

color, pattern, and shapeoccursduring the molt responsiblefor thedevelopmentof the feather.
It seemsillogical to establishthe hornologyof a plumageby meansof the molt which is responsiblefor the lossof that plumageand forthe developmentof the next succeedingplumage. Yet this is precisely
what is done when the postnuptial molt is used as a landmark to
identify (asthe "nuptial plumage")the "plumage"which precedesit.
The idea that the complete molt is homologousin most birds
makesmore senseif we associatethis completemolt with the incoming
generation of feathers. If we assume the complete molt to behomologousin mostbirds, then the plumagewhich resultsfrom (notprecedes)this molt may more properly be deemedhomologousin
these birds.

Associatingthe completemolt with the feathersassumedthereby
will also clarify the problem of the so-called"compoundplumages."
In most birds with two "plumages"per cycle,accordingto Dwight's
concept,all feathers (body and remiges)are shed at the complete
postnuptialmolt and are replacedby a completeset of non-nuptialfeathers. A partial prenuptial molt, involvingbody feathersbut not
remiges,then renews the "nuptial plumage." Therefore, when thebird is in "nuptial plumage,"it is carryingnon-nuptialremiges;i.e.,remigesassumedat the postnuptialmolt. However, in a bird with
only a singleplumageper cycle(whichwe haveseenmust,by definition, be the "nuptial plumage" in the traditional sequence),theremigesmustconsistof nuptial feathersand thus cannotbe equivalent
to the remigesof birdswith two plumagesper cycle. In other words,
to usethe sametwo speciesfor illustration, the wing featherslost by
the Starlingat its completemolt are nuptial feathers;thoselost by

•959
J

HUMPHREYAND
PARKES,
MoltsandPlumagesll

the Scarlet Tanager, having been attained with the "non-nuptial
plumage," are non-nuptial feathers, and therefore not homologous
with thoselostby the Starling--ifthe traditionalreasoningbe pursued
down

the line.

Thesediscrepancies
may be resolved,first,by namingall moltson
a "pre-" basis. All featherswhich are renewedonly once per cycle
will then belong to homologousplumagesregardlessof the numberof molts per cycleundergoneby other featherson the bird. Since
the plumageattained by the completemolt of differentbirds is tobe consideredhomologous,it follows that the plumage assumedat
this molt by the Starlingis homologous
not with the "nuptial" butwith the "non-nuptial" plumage of the Scarlet Tanager. The"nuptial" plumageof the latter is an "added" plumageassumedby
an incompletemolt without counterpartin the Starling.
5.

A PROPOSEDPRACTICAL TERMINOLOGY OF MOLTS AND PLUMAGESOf the various early efforts to arrive at a uniformly applicableterminologyof molts and plumages,the systemproposedby Dwight(1900, 1902, 1905) has been the foundation of most, if not all, subsequent work. Palmer (1955) and others have modified Dwight's
original terminologyin an effort to achievea more truly universal
applicability. Someauthors(notablySalomonsen,
1939, 1941, 1949)
who havestudiedintensivelythe moltsof groupsof birds presenting
specialdifficultiesof interpretation (e.g., Lagopus, Clangula) havefound Dwight'sterminologymisleadingor inadequateand have, fordescriptivepurposes,erecteda specialterminologyfor their subject
species.The terminologyhasbeen further complicatedby useof thesame word "plumage" for the conceptsfor which we employ theseparateterms"plumage,""aspect,"and "feathercoat."
All proposedsystemsof nomenclaturefor molts and plumages
known to us have in common the fault that they derive all or partof their terminologyfrom seasonal,reproductive,developmental,orother phenomena.Ideally, the plumagecycleshouldhave an independentterminologyso that moltsand plumagesmay be considered
in relationto other cyclicphenomenarather than namedin termso[
such phenomena. Such an independentterminologywill permit
clearexpressionof thedifferencesin the relationshipof plumagecycles
to other cyclesamongvariousbirds.

Dwight'soriginal nomenclature(1900)was basedpartly on theseasons("winter plumage")and partly on the reproductivecycle("nuptialplumage").There are obviousdisadvantages
to naminga
plumagesequenceby referenceto seasons.Homologousplumages

]2HUM•'HgE¾•,NDPAgKES,
MoltsandPlumages[ Auk

LVol.76

may be worn by differentbirds at differentseasons,even within asingle species. Northern Hemispheremigrantsare wearing their"winter plumage" in the Southern Hemisphereduring the local
summer. The termsare quite meaninglessin the equatorialregions
where many cyclic phenomenaare correlatedwith dry and rainy
periodsrather than "summer"and "winter" (c[. A. H. Miller, 1954).
We have already mentionedthe likelihood that the plumage cycles
of somebirds may be lessor more than a calendaryear. This isalsoa reasonto abandonthe widely usedterm "annual molt."
Another difficultywith seasonalterms involvesthe relationship ofplumage-names
and molt-names.The nomenclature
should,in someway,relate the moltsand the plumages,but this hasnot usuallybeen
done when seasonal terms were used. When similar names are used

for bothplumages
andmolts,e.g.,"summerplumage,""summermolt,"
it becomesnecessary
for the author to explain carefullywhether (a)the molt is being named in relation to the plumage or merely on
the basisof seasono[ actualmolt, and (b) if the former,whetherthe"summermolt" is that by which the "summerplumage"is acquiredor lost.

Dwight (1902),Palmer(1955),andothers,havingeliminatedthese
undesirableseasonalterms, rely principally on terms relating theplumagecycleto the reproductivecycle. Thus the plumagesare
callednuptial and non-nuptial,breedingand non-breeding,nesting
and non-nesting,etc. Suchterminologies
are morenearlyuniversally
applicablethan are the seasonaltype, and have thus had wide
acceptance.However,terminologies
dependenton stagesof the
reproductive
cyclehaveimportantundesirable
featuresof their own.
The relativelylittle that is known about the actual relationships
betweenthesetwo physiologicalcyclesin mostbirds indicatesthat
theserelationships
are highly variable (see,for example,Wolfson,
1954;Marshalland Disney,1957;Miller, 1954). It thereforeappears

unjustified
to link themin a fixedsystem
of nomenclature.
Relationshipsmaybetterbe definedand studiedif the terminology
carriesno
preconceived
implicationsof dependency.
In addition,the useof plumagenamesbasedon the reproductive
cycleresultsin misnomers
whenappliedto the manyspeciesof birds
which do not breed until after their first year. If followed unswerv-

ingly,sucha terminology
resultsin suchawkwardand self-contradictory circumlocutions
as "lst Nuptial (Non-Breeding)plumage" (Palmer,1955). In this sameconnection,a truly uniform
terminology
shouldmakeallowances
for a species
whichmaycarryon
its courtshipdisplays
in a plumagenot homologous
with the so-•9•9-s

HUMi'lt•¾^soP^RKES,
MoltsandPlumages

13

called "nuptial" plumageof most birds. Salomonsen(1939: 397)
pointsout that the displayof the male Rock Ptarmigan(Lagopus
mutus) "takes place in full S[ummer]-plumagein Scotland,in aparticoloured,pattimoulteddressin Scandinaviaand in the purewhite W[inter]-dressin NortheastGreenland." Obviouslyin thisspeciesno one plumagemay correctlybe calleda "nuptial" plumage
in the functional

sense.

Perhapsin an effortto avoidsomeof the pitfallslistedabove,someauthorshaveresortedto purely descriptivenamesfor plumages,such
as bright vs. dull, ornate vs. plain, etc. The one descriptiveterm
which has found widespreadacceptanceis "eclipse";althoughused
almostuniversallyfor ducks,it has also been applied to the "dull"or "winter" plumage of other groups,particularly the sunbirds(Nectariniidae). The word "eclipse"implies a dull plumageworn
for a short time by an otherwisebrightly coloredbird, such as themale Mallard (Anasplatyrhynchos.)The word becomesmeaninglesswhen an attempt is made to apply it to birds in which both stagesof the plumage cycle are dull in color, such as the female Mallard
or both sexesof the Black Duck (Anas rubripes). Further, the "dull"
plumage assumedby males of the brightly colored ducks at an ageof 12 or 14 monthsis universallycalledthe "first eclipse"in spiteof
the fact that many (perhapsmost) duckshavea homologous
plumage
immediatelysucceedingthe juvenal plumage; the so-called"firsteclipse"is thereforeactuallythe secondeclipsewhen viewedin thelight of developmental
homologyl
Some authors, for example Witherby et al. (1943-1944), havepartially circumventedthe terminologyproblem by using definite
namesfor certain plumagesonly, particularlythoseof youngbirds;
nestling,juvenile,etc. For adults,the aspectrather than the plumage
is described.This procedureis of useprincipallyfrom the viewpointof the field observer and is of little

value in a detailed

discussion ofmolt and plumagecyclesin variousgroupsof birds.
The termsusedby Witherby et al. for the plumagesof youngbirds(seeabove) introducethe problemsof a terminologybasedon age,or developmental
stageof the bird. Rather than namingthe plumage
itself,thismethodactuallydescribes
the ageo)• the bird whichhappens
to be wearing a particular plumage. Such a terminologyconcerns
itself with such chronologicaleventsas the young bird's attainmentof independenceof its parents,or flight, or sexualmaturity--thatis,
whetheror not the bird breedsor is able to breed in the particular
plumage. In practice,regardlessof what terminologyis used, it isalwaysdesirableto statechronologicalageat which a plumageor molt

14

HUMPHREYANDPARKES,
MoltsandPlumages[- Auk

LVol.•6

occurs,a bird first breeds,etc. A hybrid terminology,combining
developmentaland plumage-stage
characteristics,
was proposedfor
use by bird-banders (Michener and Farner, 1948).
Someof the objectionsto an age-based
terminologyare similar
to thosecitedabovein connectionwith plumagenamesbasedon thebreedingcycle. There are enough casesof speciesknown to courtor actuallybreed in plumagesother than the so-called"adult" forthe disadvantagesof namingplumagesin termsoœsupposed
sexualmaturity to be obvious. An ideal nomenclaturewould not permit
us to speakof sexuallymaturebirdsbreedingin "subadult"or "immature" plumages,as we so often do now. Different speciesobviously
may be wearing different plumages (from the developmentalstandpoint) when they firstbecomesexuallymature.
It is thus our contentionthat currently used terminologiesfor
molts and plumageshave a sufficientnumber of seriousdrawbacks
to warrant a thorough revision. We have no argument with thefindings of modern workers regarding the nature and pattern of
plumagesuccessionof birds as it may be related to seasonalrhythms,
reproductivecycle,ontogeny,and various other environmentalandendocrinalphenomena. We do contend,however,that thesephenomenamay be relatedin differentwaysin differentgroupsof birds,
and that these relationshipscan only be obscuredby making thenomenclatureof plumagesand molts contingent on stagesof any
other cycleor developmentalprocess.There is clearly a need for asemantically"clean,"independent,uniform,and practicalterminology
applicableto plumagesandmoltsof all birds. The desirableattributesof sucha terminologymay be listed as follows:
1) The nomenclaturemust consistof termswhich are independentof other terminologies
applied to birds.
2) It mustbe capableof expressing
homologies,and thereforemust
be basedon somereasonableassumptions
upon which to fix thehomologies.

3) The nomenclature
mustbe flexible;i.e., adaptableto all known(andreasonable,
yetsofar undiscovered)modificationsof the patternsof plumagesuccession.
4) The nomenclature
mustbe consistentand assimpleas possible.
We are fully aware of the vast amount of work yet to be done,
particularly on the more aberrant groupsof birds, before anything
like a full understandingof the biologyof moltsand plumagescan
be achieved.Our aim is to presentwhat we believeto be an improvedmeansof communication
for presentingthe resultsof suchstudies.

•959
a

HIJMPHREY
ANDPARKES,
MoltsandPlumages]5

We endeavoralsoto introduce
a terminology
of moltsandplumages
whichwill assistin clarifyinghomologies.

We advocate
retentionof the familiartermjuvenalplumagefor
the firstcoveringof true feathers.As mentionedin the introduction,
the juvenal plumageitself doesnot comewithin the scopeof thepresentpaper, but is mentioned here becausewe begin with thereplacementof the juvenal feathers. This has traditionally been
knownas the "postjuvenal
molt," and describedas either "complete"or "incomplete"by Dwight and other authors. However,sinceall of
the juvenal feathersare eventuallylost and replaced,it is misleadingßto speakof an "incompletepostjuvenalmolt." Sinceseveralmolts
maybe involvedin the replacementof all of the juvenal feathers,thecollectiveterm "postjuvenalfeatherreplacement"may be usedwhen
this phaseof plumagesuccession
is being studied,but it shouldnot
be used as a formal molt name. As mentioned earlier, we believe thatmolts shouldbe named in terms of the incominggenerationoffeathers;thus, insteadof "postjuvenalmolt," we conceiveof thetotal postjuvenalfeatherreplacementas being accomplishedin oneor more "pre-" molts.
In birds which have, as "adults," one plumage per cycle (viz.

the Starling),thisplumageis almostinvariablylostand renewedby acompletemolt. We have selectedthe term basicfor this plumage.
The molt by which the basicplumageof "adults"is renewedis thus
the prebasic
molt. Althoughcompletein "adults,"thismolt maybe

eithercompleteor partial in youngbirdsundergoing
postjuvenal
featherreplacement.

In birds whichhave,as "adults,"two plumagesper cycle (viz.
ScarletTanager),the completemolt is againthe prebasicmolt, followedby the basicplumage. The basicplumagein suchbirds isfollowedby anotherplumage,i.e., generationof feathers(usuallycomprisingfeathersotherthan the remigesand rectrices),
whichweproposeto call the alternateplumage. The interveningmolt is thus

theprealternate
molt,usuallypartial,but complete
in somespecies(viz.theBobolink).In mostbirdswith twoplumages
percycle,thebasicplumage
iscompletely
renewedeverycycle,whilefor partof thecyclethefeathercoatisa composite
of retained
basicfeathers(usuallyremiges
andrectrices)
plusbodyfeathersof alternate
plumageattainedat the partial prealternatemolt.
A few specieshave evolveda cyclein which, as "adults,"morethan two moltsoccur. The plumageresultingfrom suchan addi-

tionalor supplementarymolt is calledthe supplemental
plumage.

16

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HUMPHREY
ANI•P^gKES,
MoltsandPlumages

LVol.
76

Sucha plumagemay be insertedin the typicaltwo-plumage
cycle
eitherbeforeor after the alternateplumage;its positionwill dependon the functionalbasisfor the evolutionof suchan additionalplumage. Much additionalwork is neededon the plumagehomologies
ofthosespecies
in whicha supplemental
plumagehasdeveloped.
For thosespecies(suchas the Herring Gull, Larus argentatus)in whichageclasses
are identifiablefor the firstyearor morethroughplumagecharacteristics,
the namesof the plumagestagesmay bear
numericalprefixessuchas first prebasicmolt, first basicplumage,firstprealternatemolt, etc.,as needed. Traditionally,the plumage
which, once attained, does not changefurther with age has beencalled "adult;" thus, "adult nuptial plumage,""adult non-nuptial
plumage,"etc. But, as mentionedearlier, the word adult when usedin this connection,has an implicationof sexualmaturity which is
misleading,sincemany speciesof birds may breed before attaining"adult" plumages. Therefore, we suggestthe term definitive forthose plumageswhich do not change further with age; thus it

might be said of a given speciesthat its secondalternateplumage
is followedby its definitivebasicplumage. All plumagesmay notreach the definitiveconditionduring the sameyear of a bird's life;
thus, the often bright and ornamentalalternate plumagemay notreach the definitive

condition

in some birds until

the thirdor fourthyear,while the more conservative
basicplumagemay not undergoany
further detectablechangeafter the secondyear.
After the juvenal plumagehas been lost, the plumagesof a bird
are ordinarily acquiredand lost in cyclicalfashion. For example,
the male ScarletTanager, a bird with two plumagesper cycle,and
first-yearindividualsrecognizableas such,has a cyclewhich may bediagrammedas in Figure 2.

IJUVENAL
PLUMAGEI> IstPrebasicmolt(partial)
JlstALTERNATEPLUMAGEJ:)nd (and subsequent) Prebasm molt•
FIGURE 9.

'>list
BASIC
PLUMA
)
tst
PreaJternate
molt(partial)

ß JDEFINITIVEBASICPLUMAGE,I(complete)

2nd (and subsequent)PreaJternate

PLUMAGE

molt(partial)

Pattern of plumagesuccessionof ScarletTanager (Piranga olivacea).

•059.s

HUMPHREYANDPARKES,
MoltsandPlumages

17

To clarifyfurtherour interpretationof the homologies
of molts
and plumages,
we presentbelowa comparative
list of our proposed
nomenclature(whichreflectsour interpretationof homologies)
andthe nomenclatureof Palmer (1955), which is modifiedfrom that of
Dwight (1902). The list showsthe nomenclaturefor a bird with two

plumages
per cycle;the namesof thosemoltsandplumages
missinginbirdswith but a singleplumageper cycleare enclosed
in squarebrackets[ ]. The fewspecialcases
involvingsupplemental
plumagesare not shownhere. Plumagenamesare in bold face, molt namesin

italics. It shouldbe notedthat the starred(*) termsin the left-handcolumnare usuallynot plumagesas we havedefinedthe word, but
are in mostcasesapplied to feathercoatsconsistingof more than one
plumage.
OLD

juvenalpostjuvenal* [first non-nuptial][firstprenuptial]*first nuptial
first postnuptial[secondnon-nuptial][secondprenuptial]*secondnuptial
etc.

NEW

juvenalfirst prebasic
first basic[first prealternate][first alternate]secondprebasic
second basic[secondprealternate][secondalternate]etc.

The old andnewconceptsof plumagehomology
and nomenclatureare compareddiagrammaticallyin Figure 3.
We are well aware that difficultieswill be encounteredin applying thisterminology
to certaingroupsof birds. In somecasesthis will proveto be due
to incompleteknowledgeof the moltsand plumagesof that group,and further
studywill showthat suchbirds conformto the pattern of hornologyoutlined
above,with, of course,
their ownspecialized
modificationsof the pattern. Othercasesmay well showthat parts of our fundamentalthesisneed to be altered or

broadened.We feel, however,that an understandingof the mostprevalentpatternsof plumageand molt and their homologies
is a necessary
prerequisite
tothe studyof groupswhichmayseemto departfromthosepatterns,and we believe
the systemoutlinedabovewill aid materiallyin gainingsuchan understanding.
Examplesof the problemswhich will eventuallyneed to be studied from theviewpointof hornology
may be foundamongthe loons(Gavia),the leaf-warblers(Phylloscopus),and the sunbirds(Nectariniidae).

Thereis muchcontroversy
and confusionin the literaturewith respect
to thewing-moltof loons;
theremiges
havebeenstatedto be shed(1) at theprebasic
molt in the fall; (2) at the prealternate
molt in the spring(thusmakingthe
prebasicmolt partial and the prealternatecomplete,a reversalof the normal

18

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HUMPHREY^NO
P^•tKES,
Molts
andPlumages

OLD

LVol.
76

NOMENCLATURE
CYCLE

I

CYCLE Z

No. of&--.

plumages"• per cycle
ONE

PRENUPTIAL
MOLT(PARTI_AL)

POSTNUPTIAL

MOLT(COMPLETE)NONUILPLUMAGENEWTWONOMENCLATURE

CYCLEI
•

"•

%

/'•

CYCLE2No of•plumages• percycleo•oø?•p
REA
LTE
RNAT
E PREBASIC
MOLT(COMPLETE).bo•'/MOLT(PARTIAL)b ::•/i•/•:lC:O::l•:•:•iiii]
I PLUMAGE::::::::::::::::::::: :::::::::::::::::::::::::::::::::::::::::TWO•iGu• 3. Compatiso.
o[olda.d .ew.ome.c]atut•
a.d co.cep•o[equiva]•ce.

Stippledplumages
ate co.sldetedequi•a]e.t•. ea• c•e.

situatio.);ot (3) twice,bothi. spti.ga.d Jail. Theremaybe•adatio.o[ thewi.g-mo]t
withi. •e ge.usG• ot e•e. withi. a si.g]especie.
••h•o•co•there appeatsto be a. u.usua] amou.t o[ vatiatio. i. theexte.t o[ themoltot molts.Amo.gthespec1•d•ibed by Withetbye• •.
(]•3, vol 2: ]-2?),the [o]]ow1.g
pattet.so[ leathertep]aceme.
t ate Hsted:
completeptebasic,.o ptea]te•ate(P. •ch•rzJ);complete
pteb•ic,ptea]te•ate(•. •rochJ•o•de•,•Jb•rJ•, bore•J•);complete
pteb•ic,completeptea]te•ate(•. •rochJ•u•).
A detailed
stud?

1959

HUMPHREy
ANDPARKES,
MoltsandPlumages

19

would obviouslybe rewarding, sinceat least three speciesare said to reversethe
normal pattern of completeprebasicand partial prealternatemolts.
It is possiblethat in certain speciesof sunbirds(Nectariniidae) the dull basic
plumagemay be completelysuppressed,
sincemalesof somespeciesmolt directlyfrom a bright to a bright plumage,while in other, closelyrelated species,the males
wear a dull "eclipse"plumagefor part of the cycle (Mackworth-Praed
and Grant,1945). The matter is further complicatedby the variation among closelyrelated
speciesin presenceor absenceof a dull plumage between the juvenal and firstbright plumages. This family thus presentsone of the most challengingproblems
in the study of plumage succession.The theory that the basicplumagemay havebeen completelysuppressedin somesunbirdsis buttressedby the situation in many
ducks,in which the first basicplumageis rudimentary (SchiOler,1921 and 1925),
and the later basic plumagesare held for but a few weeks and may even be
partly or completelylost in some individual birds (Hochbaum, 1944: 112). As
emphasizedabove, the more thoroughly the typical patterns are understood,themore conspicuous
will be theseand other apparentexceptionswhich need further
study.

6.

PATTERNSOF POSTJUVENALFEATHERR.EPLACEMENTAs mentionedearlier,postjuvenal
featherreplacement
is invariably
completein the sensethat all juvenalfeathersare eventuallyreplaced
duringthe courseof one (theso-called"postjuvenal")
or moremolts.
There are many variationsin the programof postjuvenalfeather
replacement.Suchvariationsinvolvenot only the numberof molts
undergonein total replacementof the juvenalfeathers,but alsothe
extent,temporalposition,and duration of the molt or molts.
The followingvariationsmay occurin the numberof moltstaking
placebeforepostjuvenalfeatherreplacementis completed:
1. Onemolt, thefirstprebasic(seeFigure4a). Williamsoh'S(1956)
studyof plumagesuccessionin Anna'sHummingbird(Calypteanna)
illustratesthe occurrenceof completepostjuvenal
featherreplacement
in a singleprebasicmolt. Compareour figures4a and 8.
2. Two molts,the first and secondprebasics(seeFigure 4b). Stellet's Jays(Cyanocittastelleri) completelyreplaceall juvenal feathersin two molts, the first and secondprebasicmolts, as Pitelka's (1958)
excellentstudyshows. CompareFigures4b and 9.
3. Three molts, the first prebasic,first prealternate, and second
prebasic (seeFigures4c and 4d). In most speciesknown to us inwhich three molts occur before the juvenal plumage is completely
replaced,only twoof thesemolts (the firstand secondprebasicmolts)
actuallyinvolve sheddingand replacementof juvenal feathers. The
first prealternatemolt in thesespeciesreplacesfirst basicfeathers--notjuvenal feathers. This pattern of postjuvenalfeather replacementis
describedby Miller (1928 and 1931) for the Loggerhead Shrike([•aniusludovicianus;seeFigures4c and 10).

20

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HUMPHRœyANO
PA•X•,
Molts
andPlumages

LVol.
76

/,.-IstPREBASIC
MOLT

•,_
(PARTIAL lsl(COM
PREBASIC
MOLT
PLETE)

2nd PREBASIC

MOLT (COMPLETE)

t'"IstPREBASIC
MOLT(PARTIAL)(COMPLETE).lstPREBASIC
MOLT(PARTIAL)• IstPREALTERNATE
MOLT(PARTIAL)•"

plumage

•

ß

'•k.•
9•PREBASICp•FRAcar•'MOLT--feathers
2nd(COMPLETE)FmuPa•
4. Fourpatternsof postjuvenal
featherreplacement.
The moltsare
indicated
symbolically;no indication
hasbeenmadeof theirextent(otherthan
partialor complete),
temporalposition,or duration.Thejuvenal
plumagemaybelostin onemolt(a), twomolts(b andc), or threemolts(d). Stippledareas
signifyjuvenalplumage.

Phillips(1951)hasshownthat in the Rufous-winged
Sparrow(Aimophila
carpalis)certainof thejuvenalwingandtail feathers
arereplacedat the first prealternatemolt. Thus, in at least this one
species,somejuvenalfeathers
are replacedin eachof threesuccessive
molts.

7.

PATTERNSOF SUCCESSION
OF DEFINITIVE PLUMAGES

Onemoltandoneplumage
percycle.--In
thisandthefollowing
discussions
ofpatterns
ofplumagesuccession
wewillbedealing
only
withplumage
andmoltcycles
occurringafterplumages
havebecome
definitive.It is not practicablefor us to treat here all of the tremendous
numberof patternsof plumagesuccession
whichoccurin
natureasa resultof combinationsof variations
in patternof juvenal

featherreplacement,
replacementof undefinitive
plumages,andreplacementof definitiveplumages.

Birdswithonemolt (prebasic)
andoneplumage(basic)percyclemayor maynot exhibitsexualdimorphismof plumagecolor. The

HUMPHREY^SO
p^a•gs,
Molts
andPlumages

21

completeprebasicmolt may vary in temporalposition,duration, andin order within the molt. The completecycle may be less thana year (this needsdocumentation),more commonlya year, or insomecases(somecranes?cf. Mayaud, 1950) greater than a year inlength.
There are three commonvariations in "brightness"or "dullness"of the basicplumagein the two sexes. Males and femalesof many
birds (e.g. Thryothorus,Troglodytes)wear dull basicplumages(oneusefulbut

notinvariable

criterionofthe"dullness"ofa basic

plumageis generalsimilarity to the juvenal plumage). In an Icterid,
the Red-wingedBlackbird(Agelaiusphoeniceus),
and many harriers(Circus) the male wears a bright definitive basic plumage and thefemale a dull one rather like that of the juvenal. In somespecies,
suchasthe EmperorGoose(Ansercanagica)and the EuropeanRobin(Erithacusrubecula),both sexeswear a bright basic plumage quite
differentin appearancefrom that of the juvenile.
It is clear that "dullness"and "brightness"are more or lesssubjective termswhen usedto describethe appearanceof a bird's plumage. Also,the appearanceof the juvenal plumagemaybe affectedby
a wide varietyof selectiveagencies
and hencecannotbe usedcomparatively as an invariably trustworthycriterion of the "dullness"of adefinitiveplumage. The important thing we wish to stresshere isthat sexualdimorphismof plumagecolor has developedin various
groupsof birds having only one plumageand one molt per cycle.
Male with two molts and plumagesper cycle,female with one.-Witschi (1935, 1936) statesthat malesof certain weaverbirds(Pyromelana, Euplectes,Quelea) have two plumagesand molts per cycle,
while the femaleshavebut one. This needsmore study.
The occurrenceof a "bright" alternate plumage in males of a
speciesin which the femalesare alleged to have only a single molt
per cycle,wearingthe dull basicplumagethroughout,is of particularinterestsince it further supportsour contentionthat the alternate
plumageis an "added"plumage. It alsosuppliesus with a conditionintermediatebetween1) that in which both sexeswear only a basic
plumage throughoutthe cycle,and 2) that in which both sexeshave
an added alternate plumage as well. This suggeststhat there are atleasttwo evolutionarypathsby which sexualdimorphismof plumage
pattern and colorationmay be attained: 1) by the "brightening"of
the basic plumage in one sex, or 2) by the addition of a "bright"
alternateplumagein one sex.
One completeand one partial molt per cyclein both sexes.--Agreat
many speciesof birds have two molts per cycle,one complete (the

22

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HUMeH•E¾
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PA•.•,Molts
andPlumages

LVol.
76

prebasic)and one partial (the prealternate). Numerousdifferent
variationsin thispatternof plumagesuccession
are possible.The
completeprebasicmolt variesin temporalpositionand duration;thepartialprealternate
molt variesin extentas well as in temporal
positionand duration.

The partialprealternate
molt mayinvolveonlya veryfew feathers(e.g.Laniusludovicianus;
Miller, 1928) or nearlyall of the feathers
on a bird. The definitionof a partial molt might includeboth thereplacementof a singlefeatherandthereplacementof all but a single
feather. It is impracticableto try to make use of such a refined
definition. In mostcasespartial molts involve the body feathers. If
CYCLE

I

CYCLE

2

CYCLE

I

CYCLE

2

.l

o

CYCLE

I

CYCLE

2

CYCLE

I

CYCLE

2

C

FmVR•5. Variationsin "brightness"and "dullness"of plumagein birdswhich
havetwoplumages
and two molts(oneof thempartial) per cycle. Shadedareas
indicate"bright"plumage;unshaded
areasindicate"dull" plumage.B = basic;A =alternate.

any feathersat all are retained,someof the remiges
usuallyare
amongthem. A partial molt will seldominvolveall of the remiges
but not the feathers from some other tracts.

Alternateplumagesof manybirdsare sexuallydimorphic(e.g.
manyAnatinae). In species
with a sexuallydimorphicalternate
plumage,the femalesmay changerelativelylittle in aspectat theprealternatemolt (e.g. Anas platyrhynchos). In other cases,thefemale,althoughdecidedly"duller"thanthe malein alternateplumage,is nonetheless"brighter"thanis eithersexin the basicplumage(e.g.,somespeciesof Dendroica). The lattersituationprevailsin the
Phalaropes(Phalaropodidae),
exceptthat in thisfamilythe femaleisthe "bright" sex.
A greatmanyspeciesof birdsexhibit seasonal
dimorphismin that•959.j

HUMPHREYAND
PARKES,
MoltsandPlumages

23

they have a non-sexuallydimorphic alternate plumagewhich differs
more or lessstrikinglyfrom the basicplumage (e.g., Podicipedidae,
Alcidae, etc.) (see Figure 5b). Such specialized,non-sexuallydimorphic alternate plumagespresumablyhave some importance inrelation to the reproductivecycle,servingperhapsin mutual displays,
or to facilitatespecies
recognition,or perhapsasa response
to differing
environmentalconditionson summeringand wintering areas.
The alternate and basic plumagesin both sexesare "dull" andpracticallyidentical in many speciesof birds. In somecases(e.g.,somewaterfowl)this suggests
secondarylossof sexualdimorphismof
plumagecolorationwithout lossof the "added"alternateplumage. At
sometime in the historyof suchspeciesthe male alternate plumage
was presumablybright in contrastto the dull alternate plumageof
the female. This appearsto be illustratedwell by the Mallard andits insular relatives,A. wyvilliana •tnd A. laysanensis.
Abrasion of the plumage may have been the selectiveinfluence
in somespecies(e.g.,SavannahSparrow,Passerculus
sandwichensis)
bringing about the evolution of an alternate plumage to replacebadly worn basic feathers. In such casesthe alternate plumage
appearsto be practicallyidentical with the basicplumage (Figures
5c and 5d).
Two completemoltsper cycle.--Veryfew speciesare known to have
two completemolts per cycle. One suchspeciesis the Sharp-tailed
Sparrow(Ammospizacaudacuta),which showslittle sexualor seasonal
dimorphism. In the Bobolink,which also has two completemolts
per cycle,the malewearsa bright alternateplumagewhichis replaced
by a basicplumagelike that of the female. The basicand alternate
plumagesof the female are practicallyidentical.
There may be speciesin which the male has two completemolts
per cycleand the female either 1) only one completemolt per cycle,or 2) a completeand a partial molt per cycle. We are not aware ofsuchspecies,but this is a possibleintermediatestagein the evolutionof patternsof plumage succession.
Supplemental
plumages.--Afew speciesof birds have three molts
and plumagesper cycle,the third or supplementalplumagebeingan "added",usuallyspecialized,
plumagein addition to the basic
and alternateplumages.Males of the Ruff (Philomachus
pugnax)
have a supplemental
plumage,accordingto Kozlova (1957), whilefemalesdo not. The Oldsquawhas a supplementalplumage (c[.
Salomonsen,1941 and 1949; Stresemann,1948; and Sutton, 1932).
Males and femalesof three of the four speciesof ptarmigan havesupplemental
plumages(c[. Salomonsen,
1939). Salomonsen(pers.

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MoltsandPlumages

LVol.
76

comm.)saysthat Johnsen(1929)hasshownthat somepopulationsof Willow Grouse(Lagopuslagopus)
havefour generations
per cycleof certainfeathers. This is the only species,
thus far, to which two
supplementalplumageshave been attributed; thesemay be distinguishednomenclatoriallyby the letters"A" and "B".

For illustrations
showingpossible
patternsof plumagesuccession
involvingthreemoltsand plumages,
seeFigure6.
CYCLE ICYCLE 2•CYCLE I

CYCLE

b

Fxcvm•6. Possiblepatterns of plumage successionin which some feathers are
replaced three times during a cycle. Shaded areas indicate alternate plumage;
black areas indicate supplementalplumage; white areas indicate basic plumage.

Summaryof patternsof plumagesuccession.--The
variouspatternsof successionof plumagesmay be outlinedas follows:

I. One completemolt and oneplumageper cycle.
II. Two moltsand two plumagesper cycle.
A. Prealternatemolt partial
B. Prealternatemolt complete
III. Three moltsand three plumagesper cycle.
A. Presupplemental
molt followsbasicplumage
B. Presupplemental
molt followsalternateplumage.
Upon thesepatternsof plumagesuccession
may be superimposedtheseveralvariationsin postjuvenalfeather replacementand in sexual
and/or seasonaldimorphismdescribedearlier.
Phylogenyof "bright" plumages.--Webelievethat the plumagesof
most birds probably were not originally sexually,seasonally,ordevelopmentallydimorphic (or polymorphic)but were dull or subduedin colorand pattern;these"primitive" or "ancestral"plumages
were mostlikely renewedperiodicallyand completelyby protracted
molts.

Theseassumptions
seemto us reasonablebecause:1) Dull juvenal
and female-likeplumagesof many sexuallydimorphicgroupsaretaxonomicallyconservativein contrastto the bright sexualplumagesof males (Trochilidae,Anatidae,etc.). 2) In sexuallydimorphic
birdswith an "added"sexual (alternate) plumagein males,the nonsexual(basic)plumagein mostcases
resembles
the femaleand juvenal
plumages. 3) The bright male sexual (alternate) plumageof two-1959]HUMPHREYAND
PARKES,
Molts
andPlumages

25

plumaged,sexuallydimorphicspecies,is undoubtedlyan "added"
plumagesinceit is acquired(with rare exceptions)by a partial molt,
and is presentasa "special"secondplumagein malesof somegroupsof birdsin whichfemalesare said to havebut a single,dull plumage
per year (some Ploceidae). 4) In some groups of birds (viz.
Anatidae), somemembersof which have two molts per year and abright sexualplumagein males (Anatinae), the specieswhich areconsidered"primitive" (Anserinae) have but one molt and one
plumage per year. 5) Since the plumage comprisesapproximately
ten per centof the total weightof a bird, replacementof the plumage
requiresa considerable
expenditureoœenergy. It seemsreasonable
CYCLE

I

CYCLE

2

CYCLE

I

CYCLE

2

F•GuPa•7. Comparisonof patternsof plumagesuccession
indieatingways inwhich increasein complexitymay have occurred. Stippledareas indicate basic
plumage.

to supposethat primitivelythis energyexpensewasbudgetedover afairlylongperiodoœtime. In viewof thetotalexpenditureof energy
requiredfor the developmentof a wholenewgenerationof feathers,
temporal compressionof molt would be disadvantageousunlesscounterbalancedby otherrequirements(c[. Lesherand Kendeigh,1941). Suchactivitiesasmigration,reproduction,
temperature
regulation,or developmentmaymakeit necessarythat manyfeathersbe
replacedin a shortperiodoœtime (wingmoltingin ducks,etc.).
The great existingvariabilityof feathermorphology,
color, andpattern,and of timingand durationof molts,indicatesthe presenceoœmany typesoœselectivepressure. It seemsreasonableto us toassumethat suchselection
may accountfor mostof the presently
knowndeviationsfrom the generalized"ancestral"or "primitive"
conditionhypothesized
above.
We havenot attemptedto outlineall possible
variationsin pattern

26

HuM?•IP.•¾
ANI)PARKES,
Molt•andPlumagesr Auk

LVol.76of plumagesuccession
and their possiblederivations;there is too
little informationfor thissortof speculation.However,rememberingthat the numberof moltsper cycleand the extentof eachmay haveresultedfrom any numberof selectiveinfluences,it is possibletoconstructa simple diagram which illustratesthe severalgeneral
patternsof successionof definitiveplumages,and suggests
waysbywhichthesemighthavebeenderived (seeFigure7).
8.

EXAMPLES

To illustrate in detail the application of our terminology to the three major
patterns of postjuvenal feather replacement and the two most common molt
sequences,
we have selectedthree species,the molts and plumagesof which havebeen thoroughlydescribedin recent papers. In each of the following discussions,and in the accompanyingdiagrams,wc have paid particular attention to extent,
temporal position, and duration of molts; diagramsof molt sequenceprior to
Figures 8, 9, and 10, have not taken these factors into considerationand haveillustratedmoltssymbolicallywithout relation to time or extent.
In Figures8, 9, and 10, the period during which the juvenal plumage is wornis stippled,the period of basicplumagewhite, and the period of alternateplumage
shaded. The black areas represent periods of molt. Variation within thespeciesin the onsetand completionof a molt is indicatedby the spreadalong
the horizontalaxisof the blackarea (exceptin Figure 10, for which this information is not available). The durationof molt for a singleindividualis approximated by the diagonalsforming the lateral bordersof the black areas. Thus, inAnna's Hummingbird (see Figure 8), the onsetof the first prebasicmolt may
occurat any time from late May to mid-September.An individual which began
this molt in late May wouldcompleteit earlyin October.
The diagramshavebccndividedhorizontallyby a dashedline to showseparately
the molting periodsof body plumageand flight feathers. Further refinementof
the diagramscould be achieved,if desired,by separateplotting of any givenfeather tract, if sufficient information were available. Thus, for some speciesit
would be desirableto divide the diagraminto three parts rather than two, breaking"flightfeathers"into remigesand rectrices.

Moltsand plumagesof the male.4nna'sHummlngbird.--Williamson(1956)has
described
the moltsand plumagesof Anna'sHummingbirdin sufficientdetail toallowa diagrammaticpresentationof the moltsof that species(seeFigure8).

Body
plumagefhght
fecJfher*s...

./
It! PREBASICMOLT(COMPLETE)

2rid PREBA$1CMOLT(COMPLETE)

F[cv•.• 8. Plumagesuccessionin Anna's Hummingbird(Calypteanna). See
text for discussion.Comparewith Figure4a.

•959J

HUMPHREYAND
PARKES,
MoltsandPlumages

27

All postjuvenalfeather replacementin Anna's Hummingbird occursduring
the completefirst prebasicmolt. This "molt may begin as early as late May,and birds in the earliest stage of molt may be found as late as September. Molt
in some birds continues into January and as some of these birds are in a
middle or late-middle stage of molt, feather replacementundoubtedly occursin

someinstancesinto February. Thus, on a population basis,molt occursover a
period of eight to nine months.... The postjuvenalmolt [= first prebasicmolt]
in the individual is estimated to take approximately four and one-half months.
In certain individuals there may be a retardation of molt in winter to the extent
that it may require about six months" (Williamson, 1956: 346). "Such retardation . . . may be related to changesin food, qualitative or quantitative, in thecourseof the fall and early winter. It has been observedin the field that thebirds congregateat this time about favorable food sourcesand the juvenal males
are lesssuccessful
than adults in maintaining feeding territories" (op. cit.: 355).

Secondand subsequentprebasicmolts are completeand take place as follows:"molt may begin as early as the first weekin June and . . . even earlier. Refeathering of the head, the last stage in the molt, may occur as late as January. The

period of time over which molt may be underway in at least some membersof
the populationis eight months....
The total period of molt in the individualis three to three and one-half months." (op. cit.: 351).
"The molt of adults is similar in most respectsto that of the juveniles. The
molt of adults is briefer ....

It

commences in the alar tract, whereas in thejuvenile it commencesin the ventral tract" (op. cit.: 355).

Molt in Steller'sJay.-The molts of a populationof Steller'sJay from Graham
Island (northernmostof the Queen Charlotte Islands, British Columbia) havebeenstudiedin great detail by Pitelka (1958). Figure 9 is basedentirely on data
drawn from Pitelka's excellentstudy.

plumage

FIGURE
9. Plumagesuccessionin Steller'sJay (Cyanocittastelleri). See text for
discussion.Comparewith Figure 4b.

Postjuvenalfeatherreplacementin Steller'sJay is completedin two molts,e.g.,
the partial first prebasicmolt and the completesecondprebasicmolt. Thereafter,
Steller'sJayswear basicplumageand replaceit once a year during a complete
prebasicmolt.

The first prebasicmolt "beginsin the interval from June 10 to July 20, andjuvenilesindividuallytake70 to 80 daysto molt" (Pitelka,1958:49). "The flight

28

HUMPHREYAND
PARKES,
MoltsandPlumagesr Auk

I.Vol.76

feathers,alula, greater primary coverts,and a variable number of the greater
secondarycovertsare retained" (op. cit.: 40). The onset of the first prebasic
molt occursshortly before the juvenal rectriceshave completedtheir growth.
In Steller'sJa)•sfrom "lower latitudesthere is typicallya time gap betweenthe
end of growth of juvenal rectricesand the onset of the postjuvenal[• firstprebasic]molt" (op. cit.: 41).
The second prebasic molt [• Pitelka's "first complete molt"] begins in theinterval from May 9 to June 4. Pitelka (op. cit.: 42) had insufficientmaterial todetermine the ending of this molt or its duration in an individual: he states that"the period of molt in the individual" is "presumably[the] same as other complete molts."

The third and subsequentprebasicmolts begin "in the interval from May 12
to July 10, and adultsindividuallytake 60 to 70 daysto molt" (op. cit.: 49). The
flight feathersare replacedduring approximatelythe same period as the bodyplumage.
Molts of the LoggerheadShrike.--Post-juvenalfeather replacementoccursduring
the first and secondprebasicmolts in the LoggerheadShrike; the first prealternate

molt as far as known replacesonly first basic feathers. The plumagesequenceof adults involvestwo molts: a complete prebasicand a partial prealternate molt.

FICURE10. Plumage succession
on LoggerheadShrike (Lanius ludovicianus). See
text for discussion.Comparewith Figures4c and 5b.
A. H. Miller's (1928 and 1931) studies of plumage successionin shrikes
illustrate the extensive individual and regional variation that may occur inextent, temporal position, and duration of molt. Figure 10 is a diagrammaticpresentationof the sequenceof molts in one race (gambeli) of the Loggerhead
Shrike basedon Miller's data. We have not indicated the possiblevariations inextent, temporal position, or duration of molt. Nor have we attempted to do
more than indicate that in the population a given molt occursduring a given
period of time.
The first prebasicmolt is a partial molt which showsconsiderable
variation inextent. In gambeli,approximately30 to 40 per cent of the populationdoesnot
renew any juvenal primariesduring the first prebasicmolt; 95 to 100 per centof the populationreplacesall greatersecondaryupper coverts;and between70
and 90 per cent of the populationreplacesall rectrices(Miller, 1931: 133-139).

"The time occupiedin molting is betweenthree and four monthsfor any

1959-•HUMPHREYAND
PARKES,
Molts
andPlumages29

one individual, usuallythree and one-half months. For a population taken as awhole the total length of the period in which molt may be encountereddepends
on the length of the breeding seasonand of the summer seasonwhich follows"(op. cit.: 130). The first prebasicmolt occursin gambeli from the latter partof April to the latter part of November;molting of the body plumage occurs
from the middle of July to the beginningof October (op. cit.: 131).
The first prealternatemolt occurs"from February to April, or rarely May....
The peak of activityoccursin the latter part of Februaryand during March....
Whether all birds undergo this molt and whether all individuals molt feathers

other than thoseof the throat, could not be ascertained.At best, the prenuptial[= prealternate] molts are little more than sporadicfeather replacements,andthe resulting fresheningof the no•'mallywhite throat produceslittle or no change
in appearance"(Miller, 1928: 409).
The secondand subsequentprebasicmolts are complete. The flight feathers
are shed and replacedduring the period from the first of July into the firstweek of October;the body plumage is completelyrenewedfrom the last weekof July to the middle of October(Miller, 1928:411). "The period of July,
August,and September,during which adult annual [= prebasic]moltshave beenfound to occuris probablya longerperiod than that requiredby any one average
individual. The previouslyestablishedmean period of three and one-halfmonths
for the incomplete[= first prebasic]molt of fix•t fall birds seemsto be at least
fifteenor twentydayslongerthan the probablemeanperiodfor adults.... adults
show more rapid replacementwithin the different feather groups--adultmolts[= prebasic]may be characterized
as more vigorous,precise,and rapid than thefirst fall [= first prebasic]molt" (op. cit.: 413).

"Adult annual[= prebasic]moltsreplaceall feathersof the body. But, in
first fall birds,only certainfeathersbeingreplaced,it would seemlogicalto
supposethat thesereplacements
constitutean adaptationfor the purposeof
reinforcing
the mostvulnerableparts of the plumage. Suchplumageparts,
althoughnot seriouslyworn at the time of the first fall [= first prebasic]molt,

might,if not replaced,reacha dangerous
stageof disintegrationby the following
summer" (op. cit.: 414).

The second
andsubsequentprealternate
moltsare in all respects
similarto thefirst prealternatemolt (op. cit.: 409).
SUMMARY

A re-evaluationof thecurrently
accepted
terminologyof plumages
andmoltsis presented.
The significanceof the complete"postnuptial"moltasa landmarkof plumage
equivalenceis supported,but the importanceof the plumagegainedat this molt shouldbe
stressedratherthan that of the "plumage"lost. The plumage
attainedat thecomplete
moltmaybeconsideredhomologous
in mostbirds;otherplumages
haveevolved
asadditions
in response
to various
typesof selection.

A practicalterminologyis suggested
for the descriptionof molts
andplumages
andfor indicatinghomologies
betweendifferentgroupsof birds with respectto patternsof featherreplacement. The new

30

HUMPHREY
ANO
PARKgS,
MoltsandPlumages[- AukLVol.
76

terminologyis neededto replaceolder oneswhich were semanticallydependenton other phenomena.
Existing patternsof feather replacementare enumerated,in orderof increasingcomplexity,from a hypotheticalancestralcondition.
Applicationof the terminologyand its use in graphicrepresentation are illustrated,usingpreviouslypublisheddata on ½alypteanna,
Cyanocittastelleri,and Lanius ludovicianus.
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SEVENTY-SEVENTH

STATEDMEETINGOF

A.O.U.

The Seventy-seventhStated Meeting of the American Ornithologists'Union willtake place August 25 to 28, 1959, at Regina, Saskatchewan.Robert W. Nero is
Chairman of the General Committee on Arrangements. Chairmen of the sub-committeesare: Miss JoyceDew, Exhibits; Elmer Fox, Finance; Frank H. Brazier,
Accommodations
and Transportation;BruceKnox, Meals;Fred G. Bard,Field Trips;
RichardW. Fyfe, Publicity;Mrs. John Hodges,Registration;MissGertrudeMurray,
Wives; and JamesMillington, Visual Aids.