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ORNITOLOGIA NEOTROPICAL _________________________________________________________________________ Volume 20 2009 No. 1 _________________________________________________________________________

ORNITOLOGIA NEOTROPICAL 20: 1–18, 2009© The Neotropical Ornithological Society

THE CURRENT STATE OF KNOWLEDGE ON MOLT AND PLUMAGE SEQUENCES IN SELECTED NEOTROPICAL BIRD

FAMILIES: A REVIEW

Thomas B. Ryder1,3 & Jared D. Wolfe2

1Department of Biology, University of Missouri-St. Louis and Whitney R. Harris Center for World Ecology, 1 University Blvd., St. Louis, Missouri, 63121, USA.

E-mail: pipridae@gmail.com2Humboldt State University, Wildlife Department, 1 Harpst St., Arcata, California, 95521, USA.

Resumen. – El estado de conocimiento actual en mudas y secuencia de plumajes en siertasfamilias tropicales: una revisión. – Las mudas anuales y sus subsecuentes plumajes se encuentranampliamente representados en la historia de vida de las aves. La investigacion relacionada a la utilidadde mudas y plumaje ha producido un marco conceptual confiable para la caracterizacion de edad en lamayoria de la avifauna de la zona temperada. En comparacion a la zona temperada; sin embargo, cono-cemos muy poco sobre las mudas y plumajes de las aves tropicales residentes. Los datos publicadoscon respecto a mudas y secuencias de plumaje son limitados en rango, cubren pocas especies, y, hastanuestro entendimiento, no estan actualmente resumidos. Aqui combinamos nueva informacion recolec-tada en trabajo de campo y en museos con una sintesis de un trabajo previo para revisar muda y plu-maje para 15 familias de paserinos y cuasi-paserinos del Nuevo Mundo. Especificamente, resumimossecuencias y extension de mudas debido a que se encuentran relazionadas con la categorizacion deedad; ademas, asignamos estrategias de muda generales basadas en patrones encontrados entre ge-neros dentro de cada familia. Dada la diversidad de la mayoria de familias de paserinos tropicales, esteresumen no incluye a todas ellas; sin embargo, lo presentamos como un marco conceptual amplio con elfin de incrementar nuestro entendimiento de la muda y secuencia de plumaje en la avifauna tropical.

Abstract. – Annual molts and the subsequent plumages they produce are a ubiquitous element of avianlife history. Research pertaining to the utility of molt and plumage has produced a robust framework ofage-categorization for the vast majority of temperate avifauna. In comparison to temperate bird species,however, we know very little about resident topical bird molt and plumage. Published data pertaining tomolt and plumage sequences are limited in scope, covering few species, and, to our knowledge, are notcurrently synthesized. Here we combine new information gathered from field and museum specimens______________ 3Current address: Smithsonian Migratory Bird Center, National Zoological Park, PO Box 37012-MRC 5503,Washington, DC, 20013, USA.

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with a synthesis of previous work to review molt and plumage for 15 families of New-World tropicalpasserines and near-passerines. More specifically, we outline plumage sequences and molt extent as itrelates to age-categorization; we also assign generalized molt strategies based on common patternsfound among genera within each family. Given the diversity of most tropical passerine families, this syn-thesis is not all-inclusive; however, it is presented in a broad framework with the goal of advancing ourknowledge of tropical avian molt and plumage sequences. Accepted 19 November 2008.

Key words: Molt, plumage, plumage-sequence, tropical, New World.

INTRODUCTION

The utilitarian value of molt and plumagesequences, as it pertains to aging birds, is wellestablished in both Europe (Jenni & Winkler1994) and North America (Mulvihill 1993).However, the applicability of these practicesis wholly reliant on available information forfamilies, genera and species of interest. Intemperate North America, molt and plumageinformation on passerines and near-passe-rines have been summarized by Pyle (1997),which facilitates the placement of capturedindividuals into accurate and repeatable ageclasses. Despite recent advances in our under-standing of molt and plumage developmentfor temperate species, relatively little is knownabout resident terrestrial bird taxa in the Neo-tropics (Pyle et al. 2004). Moreover, there is aneed for a new progressive system of age clas-sification for tropical resident birds given thepotential difficulties of applying the calendar-based age-classification system to tropicaltaxa (Wolfe et al. unpubl data).

The majority of work on molt in tropicalresident birds has focused on the timing ofmolt in relation to other activities in theannual cycle (Snow & Snow 1964, Foster1975, Poulin et al. 1992, Piratelli et al. 2000,Marini & Duraes 2001, Mallet-Rodrigues2005) rather than duration and extent ofmolts, and progression of plumages (Pyle et al.2004, Ryder & Durães 2005, Doucet et al.2007). In families for which these data areavailable, information is limited to few specieswith the assumption that related species showsimilar characteristics. This assumption may

be warranted in species where a phylogeneticanalysis of molt shows well-conserved pat-terns across closely related species (Hall &Tullberg 2004). Some related species thatoccur in different habitat types appear to havedifferent molt strategies, which may be corre-lated with different environmental attributes(e.g., amount of solar radiation in open vs.shady habitats).

Previous studies suggest that most tropi-cal residents have a single annual prebasic andpartial preformative molt (Dickey & Van Ros-sem 1938, Piratelli et al. 2000, DuVal 2005,Mallet-Rodrigues 2005, Ryder & Durães 2005,Doucet et al. 2007). The existence of a partialpreformative molt in many tropical taxamakes molt-based aging criteria (i.e., retainedjuvenile plumage, delayed plumage matura-tion and molt-limits) possible for tropical res-idents. Here, we present data compiled fromcontemporary literature, personal field obser-vations, and review of museum specimens tosummarize what is known about tropical birdmolt. We use our findings to develop conser-vative estimates of molt strategy, extent, andassociated plumage sequences (when avail-able) for 15 Neotropical avian families. Wealso include information on other relevantcharacters that vary by age (i.e., eye and billcolor).

METHODS

Field observations were made at two studysites in Central America and northern SouthAmerica. The Central American site is locatedin Tourtuguero, Costa Rica (10°33’51”N,

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83°31’7”W), in lowland Caribbean rain forest.Klamath Bird Observatory and Redwood Sci-ences Laboratory (USFS) have operated amonitoring station at five sites around Tour-tuguero since 1994 (Ralph et al. 2005). Bothauthors served as primary banders at thesestations for a total of three years, duringwhich time information on molt and plumagesequence was compiled. The South Americansite is located in eastern Ecuador at the Tipu-tini Biodiversity Station (0º38’S, 76º08’W),also in lowland rain forest. TBR conductedhis dissertation research at this site over thepast five years, during two of which JDW waspresent; both authors documented plumageand molt information.

In addition to field observations, we vis-ited museum bird collections to documentplumage sequences and the extent of molt inpreviously unstudied tropical families. We vis-ited the Field Museum of Natural History inChicago (n = 3522 specimens), CaliforniaAcademy of Sciences, Department of Orni-thology and Mammalogy, San Francisco (n =477) and the Smithsonian National Museumof Natural History, Washington, D.C. (n =589).

Here we chose to examine 14 families, 1subfamily, and 106 genera based on theirdiverse taxonomic relationships and the avail-ability of previously published molt and plum-age data. Given the astounding diversity oftropical taxa not all representative familiescould be included. All taxonomic assignmentincluded in this paper follow the recommen-dations of the AOU South American Classifi-cation Committee. The subfamily Dendrocol-aptinae was included because of its diversityand distinct molt and plumage patterns.

To limit confusion, promote molt homol-ogies across taxa, and encourage non-ambigu-ous nomenclature, we have used modifiedHumphrey-Parkes terminology (Howell et al.2003). The most relevant terminologicalchanges are the renaming of the traditional

‘prejuvenile molt’ as the ‘first prebasic molt,’and the traditional ‘first prebasic molt’ as the‘preformative molt.’ Molt and their corre-sponding cycles are named for the plumagethey produce (e.g., the preformative molt pro-duces the formative plumage). We use theterm ‘juvenile’ in place of ‘first basic’ becausethe former is more widely recognized. Also ofnote is the use of ‘definitive’ instead of themore commonly used ‘adult’ to describeplumage and molt cycles associated with laterphases of a bird’s life cycle. The term ‘defini-tive plumage’ describes attainment of plum-age maturation (e.g., a Pipra filicauda male afterthe third prebasic molt has attained definitiveplumage). The term ‘adult’ often implies sex-ual maturity, which typically has no relevancewhen considering plumage maturation ormolt (e.g., a formative plumaged Setophagaruticulla male is in a predifinitive plumage, yet,it is capable of breeding and can be consid-ered sexually an ‘adult’ or ‘mature’). FollowingHowell et al. (2003), we have assigned familiesto molt strategies: either Complex Basic Strat-egy (CBS), Complex Alternate Strategy(CAS), or both.

RESULTS

Molt and plumages of tropical families

Trogonidae (CBS and CAS). The juvenile plum-age in Trogonidae is variable, with some spe-cies in the genus Trogon having spottedplumage (Dickey & van Rossem 1938), buffy-tipped flight-feather coverts, brownish over-all plumage, barred and/or spotted underparts (Stiles & Skutch 1989).

Apparently all Trogon species retain all orsome of their rectrices during the preforma-tive molt. Formative plumage in Trogonidaegenerally resembles either female definitiveplumage, or respective definitive plumage(Dickey & van Rossem 1938). Evidence frommuseum skins suggests that all formative

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plumaged Trogonidae typically have distinctlyretained tails, and/or a differential amount ofiridescence in body and head plumage in rela-tion to definitive plumage. Some specieswithin the genus Trogon (e.g., T. elegans) haveage-specific tail patterns (see Pyle 1997). Thepreformative molt in Euptilotis neoxenus andsome Trogon species can be incomplete,including the tertials and one or more second-aries. Interestingly, in E. neoxenus, definitiveprebasic molts can retain one or more sec-

ondaries and one or more rectrices (Pyle1997). Definitive prebasic molts in most spe-cies appear to be complete. Rectrix replace-ment in Trogon sallaei and T. elegans may beunique where some individuals molt the cen-tral tail feathers first, and others the lateralones. In some instances these species mayreplace one entire side before the other(Dickey & van Rossem 1938). The prealter-nate molt can be limited to the head, upper-parts or back in T. melanocephala, T. sallaei, and

FIG. 1. Formative plumage (top) and definitive plumaged (bottom) Motmotus mexicanus can be distin-guished by the wear and coloration pattern of retained flight feathers and coverts (photo: P. Pyle).

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T. elegans. Additionally, Pyle (1997) found thatnorthern populations of T. elegans lack a pre-alternate molt. Prealternate molts in othertrogonids are undocumented.

Momotidae (CBS). Evidence from museumskins suggests that juvenile plumage in Elec-tron, Eumomota, Baryphthengus, Hylomanes, andMomotus are typically duller, sometimes lackingtail-rackets (when appropriate) and centralbreast spots (Dickey & van Rossem 1938,Stiles & Skutch 1989, Howell & Webb 1995).

Rectrices and possibly flight feathersappear to be universally retained during thepreformative molt across the family. Dickey &Van Rossem (1938) describe Momotus andEumomota as having a preformative molt,which lasts no more than two months. Flightfeathers and rectrices are retained until thesecond (definitive) prebasic molt (Fig. 1).Retained first prebasic rectrices are easily dis-tinguishable by their brown slate color andterminally tapered shape, where definitivecentral rectrices are more truncate. Retainedjuvenile flight feathers are washed brownish.Other than retained flight feathers and rec-trices, definitive plumaged and formativeplumaged birds appear similar. Protracteddefinitive prebasic molts in Momotus andEumomota conclude with the flight feathers,and finish at the same time as the rectrices(Dickey & van Rossem 1938). There appearsto be no prealternate molt in this family.

Bucconidae (CBS or CAS). Juvenile plumagesare reportedly often indistinguishable fromdefinitive plumages, although juvenile plum-ages in Bucco, Malacoptila, and Hypenelusmuseum skins are typically duller with promi-nent plumage markings greatly reduced. Incomparison, juvenile individuals of Monasa aremore readily distinguishable, with a bodyplumage being heavily veiled grayish-brown ascompared to the glossy black definitive plum-age. In addition, Monasa species show age

variation in bill coloration. Subadult individu-als are marked by an incomplete color pattern,with dull orange to yellow mandibles, whichare distinguishable from the adults more uni-form bill coloration.

Evidence for several genera suggests thatthe preformative molt in Bucconidae is eithercomplete (e.g., Notharcus, Bucco, and Malacop-tila) or sometimes uniquely incomplete (e.g.,Notharchus hyperrhynchusas; Dickey & van Ros-sem 1938). The preformative molt in Nothar-chus hyperrhynchusas is characterized byscattered replacement of secondaries and/orprimaries. In addition, this species has uniquefeather replacement patterns during defini-tive prebasic molts as well as an incompleteprealternate molt which includes all bodyplumage, irregular replacement of tertials,inner primaries, and rectrices (Dickey & vanRossem 1938). Investigation of museum skinsfor three species of Monasa (e.g., M. atra, nigri-frons, and morpheus) revealed retained greater,median, and lesser coverts in a mixed pattern.The retained coverts show extensive wear anddiscoloration and are easily differentiatedfrom fresh coverts. Despite the apparentretention of primary and secondary coverts,no retained flight feathers or rectrices havebeen documented. Lesser, median, andgreater coverts are either retained during anincomplete preformative molt or during anincomplete prealternate molt. The lack ofretained flight feathers and rectrices point to apartial or incomplete prealternate molt, whichcould create a mixed-wear pattern in thecoverts. Specimen evidence for other bucco-nids, however, suggests a single annual molt.The unique feather replacement patterns asdescribed by Dickey & van Rossem (1938)may account for mixed age and wear in thegreater coverts of bucconids.

Thamnophilidae (CBS). Juvenile plumageresembles female plumage (Zimmer & Isler2003), although subtle differences in colora-

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tion, as in Pipridae, may be detected with fur-ther study. See Howell & Webb (1995) forgenera specific details on Taraba, Thamnophi-lus, Dysithamnus, Microphias, and Cercromacra.The duration of these juvenile plumagesremain undocumented but are likely to last nomore than one to two months.

Subsequent preformative molts are partialfor many genera (e.g., Taraba, Thamnophilus,Neoctantes, Dysithamnus, Thamnomanes, Myrmo-therula, Dichrozona, Herpsilochmus, Formicivora,

Drymophila, Terenura, Cercromacra, Myrmoborus,Hypocnemis, Percnostola, Schistocichla, and Hylo-phylax) and males may not attain definitiveplumage until their second or possibly thirdprebasic molt. Some genera have eccentric orincomplete preformative molts (e.g., Cymbilia-mus, Pygptila, Microphias, and some species ofMyrmoborus, Formicivora, and Cercromacra) whileother genera appear to have complete prefor-mative molts (e.g., Gymnopithys, Rhegmatorhina,Sclateria, Pyriglena, and Phlegopsis). Formative

FIG. 2. A) Formative-plumaged male Dysithamnus mentalis showing replaced lesser coverts and retainedflight feathers and greater, primary, median coverts; B) formative plumaged Myrmotherula hauxwelli showingreplaced greater coverts with a broad white edging. Note that retained juvenile tertials and outer greatercoverts in many Myrmotherula species have a buffy orange coloration.

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plumages in thamnophilids are more easilyrecognized in males, which show a mixture ofmale and juvenile (female type) plumage (e.g.,Hylophylax, Myrmeciza, Myrmoborus, Myrmothe-rula, Thamnophilus, Thamnomanes, etc.) indicat-ing delayed plumage maturation (Zimmer &Isler 2003). However, the extent of maleplumage gained during the preformative moltvaries individually and by genera. The extentof the partial preformative molt in this familyis variable, but is most broadly characterizedby replacement of body feathers, lesser andmedian coverts, and a variable number ofinner greater coverts while outer greatercoverts, primary coverts, alula, rectrices, andflight feathers are retained (Fig. 2A). In somegenera, alula’s may be replaced (e.g., Hylophy-lax), but this pattern needs further documen-tation. Taxa with incomplete (or possiblyeccentric) preformative molts typically replaceone to three tertials, a variable number ofouter secondaries, and a variable number ofinner primaries. In all cases, the correspond-ing primary coverts are also replaced. Theretention of juvenile feathers in formative-plumaged thamnophilids is distinct, therebyfacilitating easy recognition of molt limits.Replaced coverts have distinct broad edgingin many taxa, which contrast markedly withretained juvenile coverts that differ in colorand extent of edging. For example, in Myr-motherula species with wing bars and tertial tip-ping (e.g., M. hauxwelli, and axillaris, etc.)retained juvenile tertials and coverts have abuffy orange coloration compared with whitetips and edging of adult feathers (Fig. 2B). Noprealternate molt has been documented inthis family.

The timing of molt and breeding appearto overlap greatly in this family (Snow &Snow 1964, Foster 1975). However, overlapdata may be inconclusive because individualscaptured in breeding condition while under-going a corresponding molt were not used toestimate overlap frequency. The data may

indeed suggest an overlap of annual activitiesor high asynchrony in annual activities (seeMallet-Rodrigues & de Noronha 2001).

Rhinocryptidae (probably CBS). Little is knownabout the plumage and molt patterns in tapac-ulos, which is in part due to the complexity ofspecies identification of juveniles. The juve-nile plumage in this family remains largelyunknown. Barred juvenile plumages havebeen observed in the field (e.g., Scytalopus) andare also known from museum skins (e.g.,Myornis, and Eugralla). Juvenile plumages inRhinocrypta specimens are similar to definitiveplumages, except that the breast, throat, andcrown stripes are washed buff, and smallpatches of buff are scattered on the back anduppertail coverts. Juveniles of Scelorchilus aresimilar to those of Rhinocrypta, except moreheavily scalloped in buff on the flanks anduppertail coverts and scalloped white on thecrown. Juveniles of Myornis are washedbrownish with light barring on the tertials anduppertail coverts, while the juvenile plumagein Pteroptochos tarnii is generally darker rufouson the underparts. Additionally, specimens ofthe latter have white lower mandibles, whichbecome completely black prior to the initia-tion of the preformative molt.

Several genera in this family exhibit com-plex and irregular plumage and molt patterns.Evidence from museum skins suggests thatScytalopus, Myornis, and Eugralla may have suc-cessive molts after the preformative molt,resulting in one or two predifinitive plumages,but occasionally an individual may changedirectly into a nearly definitive plumage(Krabbe & Schulenberg 2003b). Possibly, indi-viduals may undergo a two- to three-year tran-sition into a predictable definitive plumage(e.g., Scytalopus, Myornis, and Eugralla), facilitat-ing accurate age categorization. Review ofmuseum skins suggest that in other genera(e.g., Melanopareia, Rhinocrypta, and possiblyScelorchilus, and Pteroptochos) a transition to a

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nearly definitive plumage occurs immediatelyafter the preformative molt. The preforma-tive molt in Melanopareia, Rhinocrypta, Scelorchi-lus, and Pteroptocho appears not to includeflight feathers, primary coverts, and rectrices.No prealternate molt has been documentedin the family.

Formicariidae (probably CBS). Juvenile plum-ages have been documented in a number ofdifferent genera (e.g., Formicarius, Chamaeza,Grallaria, Myrmothera, Conopophaga, Pittasoma,and Grallariculla) and have been described asbeing loosely textured (Krabbe & Schulen-berg 2003a). Juvenile Formicarius in Mexicoand Peru have sooty brownish throats andolive washed chests (Howell & Webb 1995, D.Lebbin pers. com.). Field observations of thegenus Grallaria indicate a fluffy juvenile plum-age that is replaced by a barred formativeplumage (N. Krabbe pers. com., Krabbe &Schulenberg 2003a). However, the barredplumage may actually represent the juvenilestage, some of which is retained after the pre-formative molt. Juveniles may rather havevery dark breasts, throat, crown, and nape,with white to buffy shaft streaks throughoutthe plumage as documented in Grallaria guati-malensis museum specimens. In Conopophagaspecies, juvenile plumages are characterizedby barred or scalloped underparts, and at leastone species (e.g., C. lineata) shows distinctrufous edging on the median and greatercoverts. Juvenile-plumaged Myrmothera andGrallaricula have extensive buffy-tipped wingcoverts, otherwise, juvenile plumage resem-bles definitive plumage. Lastly, juvenile Pitta-soma michleri specimens exhibit a distinctochraceous wash across the throat, with lim-ited amounts of black in the throat, under-parts washed buff, and limited to no whitespotting on the wing coverts.

The extent of the preformative molt inFormicariidae is reportedly either partial or insome genera limited. Formative plumages

have been observed in Central AmericanGrallaria (see Howell & Webb 1995). The pre-formative molt in Grallaria guatimalensisappears to be partial, including several innergreater coverts and several median coverts(Dickey & van Rossem 1938). Examination ofspecimens of five other Grallaria species (e.g.,G. squamigera, quitensis, bangsi, and rufficapilla)indicate that the preformative molt is partial,with formative-plumaged individuals havingretained outer greater coverts, primarycoverts and a variable number of median andlesser coverts. In most cases, these juvenilecoverts have buffy or rufous edging and dis-tinctly contrast with the replaced coverts thatlack edging. Likewise, the preformative moltin Myrmothera and Pittasoma is partial and doesnot include primary coverts, flight feathers,and, in some cases, several outer greatercoverts (e.g., Pittasoma michleri). The extent andduration of juvenile and formative plumagesacross other taxa remains undocumented butcould prove useful in age-class differentiation.No prealternate molt has been documentedin this family.

Furnariidae (probably CBS and CAS). Manyspecies appear to have distinct juvenile plum-ages, although documentation is lacking andplumage categorization may be difficult(Remsen 2003). Some genera may lack age-related differences (e.g., Sclerurus) (Howell &Webb 1995). Juvenile plumage in some Fur-nariidae is characterized by the reduction orabsence of contrasting plumage patchesfound in definitive plumage, duskier feathermargins in the throat and breast, and anochraceous wash on the underparts (Remsen2003). The duration of the juvenile plumagelikely lasts from a few weeks to a few months(Howell & Webb 1995, Remsen 2003).

The extent of the preformative molt infurnariids is highly variable, with several gen-era (e.g., Hyloctistes, Syndactyla, Philydor, andAutomolus) showing evidence of a complete

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preformative molt, whereas other genera (e.g.,Synallaxis, and Cranioleuca) show substantialevidence of a partial preformative molt.Dickey & Van Rossem (1938) documentedretention of rectrices and flight feathers inSynallaxis during the preformative molt. Ourstudies of specimens of eight other Synallaxisspecies (e.g., S. ruficapilla, azarae, frontalis,obscura, cabanisi, spixi, hypospodia, and albescens)and seven Cranioleuca species (e.g., C. pyrrho-phia, erythrops, curtata, subcrista, vulpina, marca-patae, and albiceps) revealed a partial preforma-tive molt with retained rectrices, flightfeathers, and alula feathers, which contrastwith the replaced lesser and median coverts.The retention of greater coverts varies by gen-era, with Synallaxis species showing completereplacement and Cranioleuca species replacingzero to all greater coverts. These two generaboth probably retain all primary coverts.Dickey & Van Rossem (1938) also docu-mented an extensive definitive prealternatemolt in Synallaxis erythrothora which includessome body feathers and (usually) completeretrix replacement. Further field and museuminformation is needed for genera that appearto have complete preformative molts (seeabove). Molt timing, sequence, and overlap

with breeding remain poorly documented forthe family (Remsen 2003), although a maleSynallaxis erythrothora tending a nest in ElSalvador was collected in extensive bodymolt, suggesting breeding-molt overlap in atleast one species (Dickey & Van Rossem1938).

Subfamily Dendrocolaptinae (CBS). The existenceof a distinct juvenile plumage in most dendro-colaptids is undocumented. Many taxa mayhave a juvenile plumage that resembles aloosely textured definitive plumage, or havedistinctly barred underparts, yet further docu-mentation is required. Juvenile plumage inLepidocolaptes closely resembles definitiveplumage, although it may have darker andricher color overall and more prominent blackedging to the streaking. The bill is dark col-ored, attaining its full degree of lighter colorwhen several months old (Dickey & van Ros-sem 1938).

The extent of molt in this family is cur-rently poorly known. Some species of wood-creepers undergo a single definitive prebasicmolt which lasts four to six months (Marantzet al. 2003), while other species complete thedefinitive prebasic molt in two months (e.g.,

FIG. 3. The retention of central rectrices may be useful for age class differentiation in some species ofDendrocolaptids. Dendrocolaptes certhia is pictured here showing retained center retrices.

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Lepidocolaptes souleyetii) (Dickey & van Rossem1938). For some species, age class differentia-tion may be complicated by a complete pre-formative molt (e.g., Dendrocincla, Sittasomus,Glyphorynchus, Nasica, Dendrocolaptes; Howell &Webb 1995), although Dendrocolaptes certhia inCentral America can apparently retain two tothree central retrices (Fig. 3). Recent photo-graphic evidence of Xiphorhynchus flavigasterfrom El Salvador suggests a partial preforma-tive molt, including retained greater coverts(Pyle, per. com.). Field evidence suggests thatformative-plumaged Xiphocolaptes tend to havemore buffy coloration. This criterion, com-bined with retained flight feathers (tapered,shorter, with more extensive rufous on theinner webs) (Dickey & van Rossem 1938) andretained greater coverts (Pyle, pers. com.),may facilitate accurate age categorization.However, the above characters, except for thetapered nature of retained flight feathers,were not found in museum specimens of twoother Xiphocolaptes species (e.g., X. promeropi-rhynchus, and major). Tapered flight feathersmay be the best way to age woodcreeper spe-cies that retain flight feathers during the pre-formative molt. Unlike Xiphocolaptes flavigaster,which replaces rectrices during the preforma-tive molt, the preformative molt in Lepidoco-laptes souleyetii does not include the center pairof rectrices, although flight feathers arereplaced (Dickey & Van Rossem 1938). Thisvery unique replacement pattern is similar toDendrocolaptes certhia (see above) and mayreflect true retention of juvenile rectrices or a‘suspension limit’ derived from the retentionof retrices from a previous definitive prebasicmolt.

Apparently no prealternate molt occurs inthis family. Typically, woodcreepers molt afterthe breeding season, although the timing ofmolt and breeding season may overlap in Den-drocolaptes, Lepidocolaptes, and Xiphorhynchus(Dickey & Van Rossem 1938, Foster 1975,Marantz et al. 2003).

Tyrannidae (CBS & CAS). Juvenile plumagesare distinguishable from definitive plumagesin many genera (e.g., Colonia, Tyrannus, Platyrin-chus, Tolmomyias, Lophotriccus, Capsiempis, Elae-nia (brown above), and Leptopogon (typicallypaler below). Juvenile plumages in Myiarchusare charcterized by the presence of buffy orrufous-edged wing coverts that are distin-guishable from the yellowish white covertsof definitive plumages. In several other generathe color and width of the edging ofrufous on wing coverts can help distinguishjuveniles from adults (e.g., Legatus, Megarhyn-chus, Myiodynastes, Myiozetetes, Pitangus, andTerenotriccus).

The preformative molt is partial in manygenera (e.g., Contopus, Empidonax, Sayornis,Megarynchus, Myiozetetes, Myiodynastes, Mionectes,Myiarchus, Lophotriccus, Oncostoma, Rhynchocy-clus, Legatus, and Tyrannus) to complete in oth-ers (e.g., Todirostrum, Tolmomyias, Tyrannus, andCamptostoma) and highly variable across thefamily (Dickey & van Rossem 1938, Howell &Webb 1995, Pyle 1997, Pyle et al. 2004, Wolfe& Pyle unpubl.). The preformative moltreplaces some, none or all of the primaries,secondaries and rectrices, but most or all ofthe primary coverts are usually retained (Pyleet al. 2004). The presence, extent, and/or col-oration of wing bars on the coverts are usefulcriteria for differentiating formative fromlater plumages in many genera (e.g., Contopus,Empidonax, Sayornis, Megarynchus, Myiozetetes,Myiodynastes, Legatus, and Tyrannus) (Howell &Webb 1995)(see above).

Prealternate molts occur in many genera(e.g., Pitangus, Empidonax, Pachyramphus, Platyp-saris, and Myiarchus) yet are variable in nature,being partial in first-year birds of some spe-cies, to nearly complete in others (Dickey &van Rossem 1938, Lanyon 1975, Pyle 1997,Wolfe & Pyle unpubl.). The extent of thesemolts remains undocumented for many tropi-cal species. Generally, many genera also showdistinct and recognizable eye color variation

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(e.g., Oncostoma, Todirostrum, Tolmomyias, andAttila; see Howell & Webb 1995 for detaileddescriptions).

Pipridae (CBS). Molt in the family Pipridae isfairly well documented. The juvenile plumageis similar to female plumage in Pipra,Machaeropterus, Chiroxiphia, and Manacus,although it is likely duller in color and moreloosely textured (Ryder, pers. obs.). Docu-mentation of the juvenile plumage is stillneeded for Neopelma, Xenopipo, Corapipo, andMasius species.

The preformative molt is partial, wherebirds replace all body tracts and a variablenumber of greater coverts (Snow 2004) but

no rectrices, resulting in distinguishable moltlimits (Ryder & Durães 2005, Doucet et al.2007). Retained juvenile outer greater covertsin most manakin genera are shorter and moreloosely textured than the replaced innergreater coverts (Fig. 4A & B) (also see figuresin Ryder & Durães 2005). Consecutive moltsare complete, and males within sexuallydimorphic genera often reach definitive plum-age during their second (Manacus species andPipra mentalis), third (other Pipra species),fourth, and/or fifth (Chiroxiphia species) pre-basic molts (Foster 1987, McDonald 1993,DuVal 2005, Ryder & Durães 2005, Doucet etal. 2007). Many species in the genus Pipra alsoshow variation in eye color with age (Ryder

FIG. 4. Formative plumage in Chiroxiphia pareola (A) (photo: J. Blake) and formative plumage in C. linearis(B) with distinct molt-limits in the inner greater coverts designated with a white arrow. Note that retainedjuvenile coverts are shorter and more loosely textured than replaced feathers.

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pers. obs., Howell & Webb 1995). The singleannual molt of manakins occurs at the end ofthe breeding seasons, although non-breedingmales initiate molt before breeding femalesand adult males (Ryder unpubl.). No prealter-nate molt has been documented for this fam-ily.

Troglodytidae (CBS & rarely CAS). Some taxashow distinct juvenile plumages (e.g., Thryotho-rus, Henicorhina, Microcerculus, and Campylorhyn-chus) (Howell & Webb 1995, Kroodsma &Brewer 2005). The juvenile plumages in manyother genera resemble the definitive plumageexcept for some subtle differences in colora-tion.

Little is known about the molt patterns ofCentral and South American wren species(Kroodsma & Brewer 2005). The preforma-tive molt is typically partial (Howell & Webb1995) and rarely incomplete. The preforma-tive molt occurs within two or three monthsafter fledging, where body feathers, and insome species, only a few flight feathers arereplaced (Kroodsma & Brewer 2005). Basedon both field observations and museum skins,the preformative molt in Thryothorus nigricapil-lus includes all wing coverts, usually the ter-tials and (occasionally) the central rectrices.Variability in the Thryothorus genera is evi-denced by other species that only replace sev-eral inner greater coverts and sometimes oneor more tertials, but no flight feathers or rec-trices (Fig. 5). The replacement of flightfeathers in some species during the preforma-tive molt is often incomplete and eccentric,with southern populations of at least one spe-cies (e.g., Thryomanes bewickii) replacing morefeathers than northern populations(Kroodsma & Brewer 2005). Therefore,other species with a broad latitudinal range(e.g., Troglodytes aedon) should be tested inorder to reveal if this trend is more commonamong members of this family. Definitiveprebasic molts are complete. At least one

tropical genus, Cistothorus, undergoes a partialprealternate molt before breeding, but thisappears rare in the family (Kroodsma &Brewer 2005).

Turdidae (CBS & rarely CAS). Juvenile plum-ages of tropical Turdus, Myadestes, and Catharusare characterized by either buffy margins orspotting on the breast feathers and buffyshaft-streaking on back and covert feathers(Dickey & van Rossem 1938, Howell & Webb1995).

Juvenile plumage is replaced by the pre-formative molt one to two months afterfledging and is typically partial (Pyle et al.2004). However, some tropical species mayhave incomplete (Pyle et al. 2004) or completepreformative molts (Howell & Webb 1995,Collar 2005). Age categorization is facilitatedby retention of inner greater coverts, primarycoverts, and rectrices. The second prebasicmolt is typically complete (Pyle 1997). Muchlike temperate thrushes, most tropical specieslikely undergo one annual molt per year, but itis more protracted and may overlap with thereproductive cycle (Collar 2005). Prealternatemolts are reported to occur in Turdus infusca-tus; this prealternate molt includes body feath-ers and sometimes one or two rectrices(Dickey & van Rossem 1938). In addition,some species show variation in bill color withage (Howell & Webb 1995).

Thraupidae (CBS & CAS). Molt in tropicalthraupid varies and is insufficiently known.Most species likely have juvenile plumagesthat are similar to definitive plumages butdrabber in color and with more loosely tex-tured feathers. Juvenile plumages have beenobserved in Ramphocelus and Tangara (D. Leb-bin pers. com.), but the extent and duration ofthese plumages remains poorly documented(but see Mallet-Rodrigues et al. 1995). Manytropical tanagers attain a definitive plumageafter the preformative molt. Data taken from

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MOLT AND PLUMAGE IN THE NEOTROPICS

museums skins, however, suggest that somespecies of Euphonia have delayed plumagematuration, with males attaining a mottledappearance in second basic plumage. In addi-tion, bill coloration maybe useful for agingspecies in at least two genera (e.g., Habia, andRamphocelus).

Both field studies and evidence frommuseum specimens suggest that the prefor-mative molt in many tropical tanagers is par-tial in nature (Tangara, Dacnis, Tachyphonus,Chlorophonia, Piranga, Euphonia, and Thraupis).A few genera appear to have complete prefor-mative molts (Buthraupis, Anisognathus, andCyanerpes), and some species within severalgenera possibly exhibit an incomplete prefor-mative molts (Rhamphocelus, and Euphonia).Extent of the preformative molt in most gen-era of tropical tanagers follows temperate pat-terns in which body plumage, lesser, medianand a variable number of greater coverts arereplaced, with rectrices, flight feathers andprimary coverts retained. According toDickey & van Rossem (1938) and Howell &Webb (1995), Cyanerpes has a complete prefor-mative molt. Despite the complete nature ofthe preformative in Cyanerpes, accurate age

categorization is still possible, due to distinctpreformative plumages (Dickey & van Ros-sem 1938). Some species of Ramphocelus (e.g.,R. nigrogularis, and passerini) and Euphonia (e.g.,E. affinis) have incomplete preformative moltswhere tertials and some primaries and sec-ondaries are replaced. Nevertheless, theseincomplete preformative molts are highlyvariable. Alternatively, Ramphocelus bresilius hasbeen documented as having a complete pre-formative molt (Mallet-Rodrigues et al. 1995).Euphonia spp. show large amounts of variabil-ity both within and between species. In thegenus Piranga, incomplete prealternate moltsoccur, which include some or all greatercoverts and often the tertials and central rec-trices (Dickey & van Rossem 1938, Pyle1997). Other genera with documented partialprealternate molts are Thraupis, Habia, andCyanerpes (Dickey & van Rossem 1938), butthe existence of prealternate molts in mostgenera remains unknown. In all genera, theannual prebasic molt likely takes place afterthe breeding season.

Emberizidae (CAS & CBS). Streaky juvenileplumage is recognizable in many genera (for

FIG. 5. Formative plumaged Thryothorus rufalbus with a molt-limit in the greater coverts and replaced ter-tials contrasting with retained secondary and primary flight feathers (photo: P. Pyle). Note the more exten-sive barring on the replaced greater coverts and tertials.

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RYDER & WOLFE

Zonotrichia description see Miller 1961). Thejuvenile plumage in genera, such as Atlapetes,and Aimophila, can be characterized by havingbuffy-tipped greater coverts, a duskier andstreakier breast and throat. Sporophila juvenileplumage is typically brownish overall withbuffy-tipped greater coverts. Oryzoborus juve-nile plumage is more loosely textured, yetresembles female and formative-plumagedindividuals. Arremon typically has darker andbrowner flanks, and sooty breast and throat(Stiles & Skutch 1989).

After leaving the nest in juvenile plumageand prior to the preformative molt, at leastone genus, Passerina, has a presupplementalmolt comprised of only body plumage(Thompson & Leu 1995). Additionally, thesepresupplemental molts may also occur inAimophila spp. (Pyle pers. com.). Preformativemolts are variable, but generally partial toincomplete in extent, and in just a few genera,complete (e.g., Arremonops and Volatinia;Dickey & Van Rossem 1938, Miller 1961,Howell & Webb 1995, Wolfe & Pyle unpubl.).Although male Volatinia may have completepreformative molts, distinct delayed plumagematuration within the species is conducive toaccurate age categorization (formative plum-aged males are similar to females except fordark flight feathers and rectrices edged brownor gray; Dickey & van Rossem 1938, Howell& Webb 1995). Saltator species apparentlyretain rectrices and flight feathers during thepreformative molt (Dickey & van Rossem1938). Some Oryzoborus species have partialpreformative molts which include body andsome or all of the wing coverts, whereas thesecond prebasic molt in other members ofthis genus is incomplete or eccentric (e.g.,Oryzoborus funereus).

Prealternate molts in the Emberizidae aresometimes absent (e.g., Buarremon, Arremonops,Oryzoborus, Saltator), partial (e.g., Melozone,Aimophila, Volatinia, Guiraca, Sporophila, Zono-trichia, Junco, Saltator), or incomplete in other

genera (e.g., Spizella, Aimophila). Complexplumage sequences occur in the family; forexample, Dickey & van Rossem (1938) statedthat Sporophila minuta takes three years toreach definitive plumage. Aimophila ruficaudahas been documented to have breeding-moltoverlap (Dickey & van Rossem 1938).

Parulidae (CBS and CAS). Review of the litera-ture and study of museums skins indicate thatmany genera (e.g., Parula, Geothlypis, Myioborus,Basileuterus, Euthlypis, and Granatellus) have dis-tinct juvenile plumages (Curson et al. 1994). Inmany genera, juvenile plumages are character-ized by buff, brown or rufous edging on themedian and greater coverts forming twoindistinct wing bars (e.g., Parula, Myioborus,Euthlypis, and Basileuterus) (for species specificdetails see Curson et al. 1994). Duller bodyand head plumage in relation to definitively-plumaged individuals may be apparent as well.

Preformative molts appear to be partial inmost genera (e.g., Geothlypis, Myioborus, Parula,Euthlypis, and Basileuterus) and are partial orincomplete/complete in other genera (e.g,Granatellus). Typically, flight feathers, rectrices,primary coverts and a variable number ofouter greater coverts are retained. These pat-terns result in molt-limits typically occurringin the outer greater coverts or betweengreater and primary coverts, with the retainedjuvenile feathers often showing distinct buffyor rufous tipping (Curson et al. 1994, Pylepers. com.). Curson et al. (1994) documentunclear patterns for Granatellus, in which G.pelzelni and venustus both show a partial prefor-mative with retained flight feathers and rec-trices while, G. sallaei, replaces tertials andouter secondaries. They assume the replace-ment of flight feathers suggests a completemolt but could also represent an incompletepreformative. A commonly used aging crite-rion for north temperate parulids that can bereadily applied to their resident Neotropicalcounterparts is rectrix shape (see Pyle 1997).

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MOLT AND PLUMAGE IN THE NEOTROPICS

The retained first-basic rectrices in many taxaare considerably more tapered than adult rec-trices, which facilitates aging given experiencewith the species. Additionally, the amount ofwhite in the outer rectrices of Myioborus andthat of color in the crown of some species ofBasileuterus, and Myioborus can help facilitatetheir age and sex categorization (Wolfe & Pyleunpubl. data). The existence of prealternatemolts is not well documented in resident trop-ical parulids, but limited prealternate moltsfor certain species in Geothlypis and Basileuterushave been reported (Dickey & van Rossem1938).

DISCUSSION

Here, we have compiled general informationon molt strategy, plumage sequences, andextent of molt for 14 families and 1 subfamilyof New World tropical landbirds. Our data onmolt and plumage sequences collected forselected Neotropical avian families detail theexistence of previously undocumented juve-nile plumages and the extent of partial andincomplete preformative molts in a substan-tial number of genera. Of the 15 familiestreated, 11 showed distinct juvenile vs. adultplumages while four proved to be indistin-guishable by plumage alone. We examined theextent of the preformative molt in 106 generaand found that 67 genera (63%) had partialpreformative molt and 25 genera (24%) hadincomplete preformative molts, providing dis-tinguishable criteria useful for age categoriza-tion. The remaining 14 genera (13%) hadcomplete preformative molts making age cat-egorization difficult. Our review shows thatthe existence of prealternate molts is variable.Of the 15 families treated, ten lack a prealter-nate molt, three have a limited or partial pre-alternate molt, and two have an incompleteprealternate molt. The existence of prealter-nate molts in tropical taxa, however, requiresfurther documentation. As such, we do not

rule out the possibility that documented pre-alternate molts might actually represent pro-tracted preformative or prebasic molts.Overall, our results largely reflect patterns ofplumage progression and molt extent in tem-perate zones.

Molt and plumage criteria facilitate accu-rate age classification in the vast majority oftemperate landbird species (Jenni & Winkler1994, Pyle 1997). Yet, research pertaining tomolt of New World tropical residents has justbegun receiving interest. In contrast, otherattributes of avian life history are more oftenstudied and, as a result, better represented inthe contemporary ornithological literature.We believe this allocation to be disproportion-ate given the critical nature of molt in relationto the avian annual cycle (i.e., certain speciesmay forgo migration and breeding events butno species has been documented forgoing theannual molt cycle). Recent work has shownthat molt sequences in temperate passerinescan provide a framework for understandingvariation in patterns of feather replacementamong tropical residents (Ryder & Durães2005). Following the model presented here,further molt and plumage sequence docu-mentation will inevitably facilitate the accurateage classification of tropical resident land-birds.

Our presentation is a review and a call fortropical ornithologists to begin collecting themolt data necessary to promote more detailedresearch into avian natural history and demo-graphics. We have illustrated the potential forornithologists to accurately age the majorityof tropical residents via molt and plumage-based criteria. Complete preformative moltssometimes confound aging attempts in tem-perate latitudes in species, such as Chamaea fas-ciata and Psaltriparus minimus, and undoubtedlytropical ornithologists will face similar prob-lems (e.g., subfamily, Dendrocolaptidae).However, given our current state of knowl-edge, complete preformative molts appear

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RYDER & WOLFE

rare in New World tropical taxa. The docu-mented presence of delayed plumage matura-tion in several families (Pipridae, Rhino-cryptidae, Thamophilidae) should facilitateaccurate age classification for many specieswell into the second, third, and in some casesfourth molt cycle.

We do not claim that our data or presenta-tion are exhaustive, but they rather provide aframework for further studies in the field aswell as in museum collections. We believe thiswill facilitate and draw further interest to moltresearch at tropical latitudes. These data willultimately enable us to place individuals intoage classes, thereby enhancing our ability tomodel population demographics. Moreover,these models are essential for proactive popu-lation-level management. As tropical orni-thology advances so must research on tropicalmolt patterns to begin building a robust agecategorization framework for tropical taxa.

ACKNOWLEDGMENTS

We are grateful to the many people who pro-vided personal observations or data toimprove the manuscript: N. Krabbe, D. Leb-bin, T. Schulenberg, S. Woltmann, C. J. Ralph,F. Mallet-Rodrigues, and A. Brown. Construc-tive comments on earlier drafts of this manu-script were provided by J. Blake, P. Pyle, J. C.Eitniear and one anonymous reviewer. J.Hidalgo kindly provided assistance withabstract translation. Special thanks to themany volunteer banders at the CaribbeanConservation Corporation in Tortugero,Costa Rica. Thanks to Klamath Bird Obser-vatory, Point Reyes Bird Observatory, Red-wood Sciences Laboratory and HumboldtBay Bird Observatory. Special thanks toDavid and Consuelo Romo, Kelly Swing,Jaime Guerra and all the Tiputini BiodiversityStation staff for their tireless logistical andfield support. IACUC protocol number 5-12-20 for fieldwork at Tiputini Biodiversity Sta-

tion. This research was conducted in accor-dance with permit number 13-IC-FAUDFN,Ministerio de Ambiente, Distrito ForestalNapo, Tena, Ecuador. We thank them forallowing us to conduct our research at theTiputini Biodiversity Station. Funding wasprovided by the International Center forTropical Ecology, AFO’s Alexander Berg-strom Award, National Geographic Society(7113-01) and National Science Foundation(IBN 0235141, IOB 0508189, OISE0513341). This has been a contribution of theTortuguero Integrated Bird MonitoringProject.

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