The Wilson Journal of Ornithology 121(3):556–567, 2009

BREEDING SEASONS, MOLT PATTERNS, AND GENDER AND AGE CRITERIA FOR SELECTED NORTHEASTERN COSTA RICAN RESIDENT LANDBIRDS

JARED D. WOLFE,1,2,4 PETER PYLE,3 AND C. JOHN RALPH2

ABSTRACT.—Detailed accounts of molt and breeding cycles remain elusive for the majority of resident tropical bird species. We used data derived from a museum review and 12 years of banding data to infer breeding seasonality, molt patterns, and age and gender criteria for 27 common landbird species in northeastern Costa Rica. Prealternate molts appear to be rare, only occurring in one species (Sporophila corvina), while presupplemental molts were not detected. Most of our study species (70%) symmetrically replace flight feathers during the absence of migrant birds; molting during this period may limit resource competition during an energetically taxing phase of the avian life-cycle. Received 30 August 2008. Accepted 19 February 2009.

Temporal patterns of molt and breeding sea- of the avian life cycle, but other factors including sonality are largely unknown for many resident climate and resource availability may also affect tropical species (Dickey and van Rossem 1938, timing of molt (Aidley and Wilkinson 1987, Snow and Snow 1964, Snow 1976) in contrast to Bensch et al. 1991, Jones 1995). Little has been Nearctic-Neotropic migrants (hereafter ‘mi- published concerning temporal patterns of molt grants’). One might assume differential molt among resident tropical species in relation to sequences and extent between latitudes given competition from overwintering migrants despite different natural histories of resident tropical birds continued interest in factors influencing timing of in relation to their migrant counterparts. However, molt (Snow and Snow 1964). Given the energet- preliminary studies indicate that most neotropical ically taxing nature of molt, we believe temporal residents exhibit molt strategies similar to those in patterns of molt among resident species may be temperate latitudes (Dickey and van Rossem influenced by resource competition associated 1938, Diamond 1974, Foster 1975, Prys-Jones with presence or absence of migrant birds. Molt is 1982, Pyle et al. 2004, Ryder and Wolfe 2009, a critical facet of avian natural history and molt Wolfe et al. 2009). These strategies include partial ecology has utilitarian characteristics which aid in to incomplete preformative molts and complete understanding population structure and demo- prebasic molts that often occur in June–Septem- graphic trends. ber, following breeding. Capture-recapture, capture-telemetry, and cap- Molt and breeding events are energetically ture-observational data are often used to quantify demanding and, for the most part, independent demographic trends of resident neotropical land- phases of the avian life cycle (Snow and Snow birds (Greenberg and Gradwohl 1997, Sandercock 1964, Payne 1972, Avery 1985, Pyle 1997). et al. 2000, Cohen and Lindell 2004). Accurately However, overlap between molt and breeding modeling population structure requires methodol- has been documented in a few temperate landbirds ogy pertaining to identification of age and gender (Bancroft and Woolfenden 1982, Thompson and classes. Thus, understanding the extent and Slack 1983, Zaias and Breitwisch 1989, Hemborg sequence of molt for a given species is critical 1999) and some resident tropical landbirds for accurate age classification and subsequent (Dickey and van Rossem 1938, Snow and Snow demographic analyses. 1964, Foster 1975, Avery 1985). Breeding and The Tortuguero Integrated Bird Monitoring molt seasonality influence the temporal dynamics Project (TIBMP) was established in 1994 on the northern Caribbean coast of Costa Rica, near the 1 Humboldt State University, Wildlife Department, 1 village of Tortuguero, to monitor migrants as well Harpst Street, Arcata, CA 95521, USA. as resident bird populations through constant- 2 USDA Forest Service, Pacific Southwest Research effort mist-netting (Ralph et al. 2005). We used Station, Redwood Sciences Laboratory, 1700 Bayview 12 years of banding data from TIBMP coupled Drive, Arcata, CA 95521, USA. 3 Institute for Bird Populations, P. O. Box 1346, Point with a review of museum specimens to provide Reyes Station, CA 94956, USA. information on molt and breeding seasonality, and 4 Corresponding author; e-mail: [email protected] useful criteria for identification of age and gender 556 Wolfe et al. N MOLT AND BREEDING CYCLES OF COSTA RICAN BIRDS 557 for 27 resident bird species of northeastern Costa Formative-plumaged individuals are often identi- Rica. fiable by retained primary coverts which typically lack distinctive edging, luster, and are typically METHODS more worn in relation to definitive primary Nine monitoring sites were near the village of coverts and contrast in wear with replaced greater Tortuguero on the northeast coast of Costa Rica in coverts. Definitive flight feathers are typically Limon Province (83u 319 70 W, 10u 339 510 N; more truncate in relation to retained juvenile elevation 0–20 m). One ‘central’ station was flight feathers. We specifically looked for each of operated at least five times every 10 days while these criteria for banded birds (using standardized the remaining ‘satellite’ stations were operated at data forms) and museum specimens. least once every 10 days. Between 10 and 15 12- Molt and age terminology, including standard m mist nets were operated at each site by JDW abbreviations, follow those of Pyle (1997) as and others from August to May, 1994–2006 modified by Howell et al. (2003). The first basic (Ralph et al. 2005). Species studied were selected plumage is referred to as juvenile plumage (Juv), based on high capture rates during preliminary followed by the preformative molt (PF), first banding efforts (1994–2000). Protocols pertaining prealternate molt (PA1; if existing in the species), to captured birds follow Ralph et al. (1996). second prebasic molt (PB2), and definitive Banding efforts were not sustained during June prealternate (DPA; if existing) and definitive and July. Breeding seasonality during these prebasic (DPB) molts. Primaries and primary months was inferred based on brood patch and coverts are numbered from the innermost (prima- cloacal protuberance data obtained during May ry 1) to the outermost (primary 9 or 10), and August, juxtaposition of the prebasic molt, secondaries and the greater coverts are numbered and presence of juveniles. Recaptured individuals from the outermost (secondary 1) to the innermost in many cases were used to verify age; our sample tertial, and rectrices are numbered from the sizes include recaptured individuals as well. central pair (rectrix 1) to the outermost pair Findings based on banded birds at Tortuguero (rectrix 5 or 6). ‘‘Partial’’ for molt extent, were augmented by those from specimens exam- indicates that no flight feathers (primaries, ined at the National Museum of Natural History primary coverts, secondaries, or rectrices) were (USNM) by Pyle in early August 2001. All replaced (except the tertials or central rectrices in specimens from selected species collected in some individuals) and ‘‘incomplete’’ indicates southern Mexico through northern Panama were that some but not all flight feathers were replaced. examined and, in a few cases, specimens collected An ‘‘eccentric molt pattern’’ refers to an incom- in South America were also examined. Ages of plete molt in which molt of primaries begins at a birds were inferred when collected and, in many central feather (other than primary 1) and cases, there were no specimens collected while in proceeds distally, and molt of secondaries begins active molt. Plumage succession and molt timing with a central feather (other than secondary 1) and could often be assumed based on molt limits and proceeds proximally to the tertials (Pyle 1997, extent of feather wear (Pyle 1997). Criteria Pyle et al. 2004). The ‘‘typical molt sequence’’, developed with specimens in 2001 were con- which can be incomplete during preformative firmed or re-examined with analysis of banding molts, refers to a molt proceeding distally from data from 1994 to 2006. Banding/specimen data primary 1 and proximally from secondary 1, as is were augmented with information provided by typical of definitive prebasic molts. Stiles and Skutch (1989). Age classification follows the calendar-based The partial to incomplete nature of the system described by Pyle (1997). Age codes preformative molt in most neotropical resident include HY (hatching year), indicating a bird in landbird species can be used to facilitate accurate the calendar year of its hatching; SY (second age-class categorization of captured birds (Pyle year), indicating a bird in its second calendar year 1997). Feather characteristics, regarding molt (HY/SY indicates a bird in its first plumage cycle, limits and retained juvenile (HY) plumage among being HY until 31 Dec and SY after 1 Jan); TY tropical residents, appears to be similar to those of (third year), indicating a bird in its third calendar temperate species. For example, retained juvenile year; AHY (after-hatching year), indicating a bird retrices are often duller in coloration, more worn in at least its second calendar year; ASY (after- (in relation to definitive retrices) and tapered. second year), indicating a bird in at least its third 558 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 121, No. 3, September 2009 calendar year; ATY (after-third year), indicating a nape, and buff or whitish tipping to back feathers, bird in at least its fourth calendar year; and U tertials, and most wing coverts, absent in definitive (unknown), indicating a bird that may or may not plumage. More pointed rectrices with a deeper be in the calendar year of birth. Month ranges in white triangle at the tip (.5 mm along shaft) and parentheses indicate the timing for which ages can brownish along outer webs not extending toward be identified; e.g., ‘‘HY/SY (Oct–Sep)’’ indicates the shaft may represent HY/SYs; more study a bird with indicative criteria, usually based on an needed. Bill corrugations present in HY/SYs aspect of juvenal or formative plumage and the year-round. Gender is similar in all plumages. timing of prebasic molts, can be classified to HY Wing: F 5 48–58 mm, M 5 50–61 mm. from September to December and SY from Threnetes ruckeri (Band-tailed Barbthroat; n 5 January to October (Pyle 1997, Pyle et al. 29 specimens, 136 captures). Breeds: January– 2004). Age-classification can be complicated August (?). Molt: PF complete (Sep–Nov), DPB due to breeding seasonality overlap with 1 (Sep–Nov) complete. Juveniles (Feb–Sep) have January; a phenomenon more commonly encoun- cinnamon tipping to head and nape feathers, tered in tropical latitudes. Generally, juveniles are upper-breast mostly blackish with small amounts in the bottom 2/3’s of wing chord ranges. Wing of tawny (in relation to uniform tawny in older chord samples represent actual ranges (mm) birds) and more pointed rectrices. AHY females recorded from field and museum specimens. average slightly less and paler tawny on breast Color descriptions within species accounts follow (although there is much overlap); this criteria recommendations by Smithe (1975). Question coupled with wing-chord length can aid in marks indicate data uncertainty expressed by the identification of gender for some individuals. Bill authors. corrugations present in HY/SYs in January– October. Wing: F 5 51–59 mm, M 5 54–62 mm. SPECIES ACCOUNTS Phaethornis longirostris (Long-billed Hermit; n Leptotila cassini (Grey-chested Dove; n 5 32 5 22 specimens, 342 captures). Breeds: Novem- specimens, 90 captures). Breeds: January–Sep- ber–July (?). Molt: PF complete (?) (Mar–Nov), tember. Molt: PF incomplete-complete (year DPB complete (Mar–Nov). Juveniles (Dec–Aug) round?), DPB incomplete-complete (year round have buff-yellow tipping to crown feathers. Bill with strong peaks in Mar–Oct). Molt of primaries corrugation present in HY/SYs, January–Septem- during PF proceeds in typical sequence in ber and November–January. Gender similar in all September–May; both PF and DPB may be plumages. Wing: F 5 54–66 mm, M 5 56– suspended during winter. During both PF and 66 mm. DPB, 1–7 secondaries can be retained (25% of Phaethornis striigularis (Stripe-throated Her- museum specimens had uniform secondaries); PF mit; n 5 35 specimens, 19 captures). Breeds: may be incomplete but confirmation is needed. year-round with a major peak in March–July (?) Juvenile primary 10 is often blunt-tipped (tip 5– and a smaller peak in November–December (?). 6 mm wide), the formative primary 10 tends to Molt: PF complete (year round), DPB complete have a moderately narrow tip (4–5 mm wide), and (year-round). Juveniles (Mar–Oct) have dusky the definitive primary 10 is thinner (tip ,4mm backs (greenish in older birds) and cinnamon wide) and distinctly tipped cinnamon. HY/SYs tippingtobodyfeathers,wingcoverts,and (Aug–Jul) and AHY/ASYs (Aug–Jul) best sepa- secondaries. HY/SYs (Sep–Aug) appear to have rated by shape and color of primaries and duskier-based central rectrices and duskier and secondaries, combined with placement of retained cinnamon-tipped inner secondaries, whereas feathers, as in L. verreauxi (Pyle 1997). Gender AHY/ASYs (Sep–Aug) tend to have darker-based similar in all plumages, although AHY/ASYs with (more distinct) central rectrices and greenish- bright purplish napes are invariably male and tipped inner secondaries (cinnamon-tipped sec- wing chord enables identification of most indi- ondaries occasionally documented). Bill corruga- viduals: F 5 128–135 mm, M 5 134–140 mm. tion criteria useful year-round. AHY/ASY (at Glaucis aeneus (Bronzy Hermit; n 5 22 least) females average stronger contrast between specimens, 235 captures). Breeds: October–Au- duller cinnamon breast and brighter cinnamon gust. Molt: PF complete (?) (May–Nov), DPB belly while males show richer cinnamon breast complete (May–Dec). Juveniles (year-round?) and belly; however, overlap occurs between often have buff in the supercillium, crown, and genders. Wing: F 5 35–39 mm, M 5 35–41 mm. Wolfe et al. N MOLT AND BREEDING CYCLES OF COSTA RICAN BIRDS 559

Anthracothorax prevostii (Green-breasted Man- dark-blue spotting and gray edges to feathers go; n 5 17 specimens, 156 captures). Breeds: creating scaly appearance, and outer rectrices March–November. Molt: PF complete (Mar– without cinnamon tips. U/AHY male (Jun–May) Dec), DPB complete (Mar–Dec). Juveniles has culmen with bright red coloration on basal (Feb–Dec) have sides of underparts extensively 75% contrasting distinctly with black bill, throat white with rufous extending from malar to flanks, with extensive amount of large, dark blue spots and relatively narrow outer rectrices with indis- and feathers without gray edges, and outer tinct white tips. U/AHY females (Sep–Aug) are rectrices lacking cinnamon tips. Bill corrugations similar except for absence of cinnamon-rufous present in HY/SYs December–August. Wing: F 5 feathering (or restricted amounts) in malar region 43–52 mm, M 5 45–54 mm. and broader outer rectrices with more distinct Amazilia tzacatl (Rufous-tailed Hummingbird; patterning. U/AHY males (Sep–Aug) have dark n 5 40 specimens, 211 captures). Breeds: green flanks and purplish rectrices with little or no February–November. Molt: PF complete (year- white. No apparent differences between juvenile round), DPB complete (year-round); molt peaks in males and females. Bill corrugations present in April–November. Juv-HY/SY female (year- HY/SYs April–November and appear to become round) has upper mandible black, upperpart smooth shortly after completion of PF. Wing: F 5 feathers with cinnamon tipping, green throat 57–70 mm, F 5 57–71 mm. feathers broadly edged whitish creating scaled Thalurania colombica (Violet-crowned Wood- appearance, and belly and vent washed buff nymph; n 5 17 specimens, 73 captures). Breeds: yellow. AHY/U female (Oct–Sep) is similar February–October. Molt: PF complete (Apr–Dec) except that upperpart feathers lack cinnamon DPB complete (Apr–Dec). Juvenile female (Feb– tipping. HY/SY male (Feb–Dec) has upper Dec) has green crown, upperparts uniformly dull mandible black gradually turning to red at basal green, throat and underparts with light gray, outer 75%, bright green throat feathers with little or no rectrices with white tips, and tail fork (longest whitish edging creating uniform appearance, and rectrix 1) ,4.5 mm. U/AHY female (Aug–Jul) belly and vent dark gray, often tinged mauve. similar except wing coverts and upper lateral U/AHY male (Oct–Sep) is similar to HY/SY male scapulars bright green or turquoise green, brighter except bill bright-red (basal 75%) with black tip. than rest of the upperparts, tail fork .4.5 mm. Juvenile rectrices less often show brownish Juv/HY male (Feb–Dec) has crown, throat, and edging extending to feather tips (Stiles and Skutch underparts dusky with 25 or fewer iridescent 1989); variation occurs for at least some rectrices purple feathers, outer rectrices blackish, tinged within both age groups as some juveniles have purple without white tips, and tail fork (longest complete brown tips and some AHY/ASYs have rectrix 1) ,12 mm. U/AHY male (Aug–Jul) has rufous extending to the tip. Bill corrugations can crown and upperparts purple, breast glittering- potentially occur year-round. Wing: F 5 48– green, rectrices dark blue, and tail deeply forked. 64 mm, M 5 48–64 mm. Bill corrugations present in HY/SYs March– Amazilia amabilis (Blue-chested Hummingbird; November. Wing: F 5 44–54 mm, M 5 50– n 5 34 specimens, 57 captures). Breeds: Febru- 59 mm. ary–July (?). Molt: PF complete (Feb–Aug), DPB Hylocharis eliciae (Blue-throated Sapphire; n complete (year-round?); AHYs may molt earlier 5 27 specimens, 22 captures). Breeds: Decem- than HYs. Juv/HY female (Feb–Jul) has pale gray ber–July (?). Molt: PF complete (Mar–Aug), DPB chin with green spots, throat with 0–2 turquoise complete (Mar–Aug). Juv/HY female (Jan–Jun) blue feathers, crown dull green, and outer has culmen blackish, throat with moderate rectrices with gray tipping. U/AHY female (Jul– greenish-blue spotting, and outer rectrices usually Jun) is similar but throat with 5–15 bluish feathers with cinnamon tips. U/AHY female (Jun–May) and crown with bright green coloration. Juv/HY has culmen dusky with red wash to basal 50%, not male (Feb–Jul) has dark green chin, throat with contrasting distinctly with bill tip, throat with 15–30 bluish feathers, glittering green feathering more extensive dark-blue spotting, and outer of crown limited (often 3–4 feathers down center rectrices with or without cinnamon tips. Juv/HY of crown) and outer rectrices with little or no gray male (Jan–Jun) has culmen dusky with dull to tipping. U/AHY male (Jul–Jun) has dark-green bright red coloration on basal 75% contrasting chin, glittering-green crown, and outer rectrices distinctly with black bill tip, throat with extensive without gray tips. Bill corrugations recorded in 560 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 121, No. 3, September 2009

HY/SYs in May. Wing: F 5 47–54 mm, M 5 50– plumage but most separated by wing-chord length: 57 mm. F 5 84–94 mm, M 5 92–99 mm. Chloroceryle aenea (American Pygmy King- Thamnophilus doliatus (Barred Antshrike; n 5 fisher; n 5 91 specimens, 156 captures). Breeds: 212 specimens, 85 captures). Breeds: March– March–June (?). Molt: PF incomplete-complete October. Molts: PF incomplete-complete (Mar– (May–Feb), DPB complete (Apr–Jan). Up to four Jan), DPB complete (Mar–Jan). The PF can be juvenile middle secondaries and possibly some eccentric with 4–8 inner primaries and outer primary coverts retained during PF; occasional secondaries, and most or all primary coverts secondary retained during DPB. Juv/HYs (May– retained. Some can retain all remiges (except Sep) have paler underparts and an incomplete tertials) and primary coverts while others may breast band (female) or streaks to belly (male). have a complete molt; rectrices are usually Some HY/SYs (Sep–Aug) can be classified to age replaced. Juv/HY/SY female (Sep–Aug) has by having retained, juvenile, dusky secondaries cinnamon plumage and flight feathers with and primary coverts, contrasting distinctly in wear eccentric molt limits, the retained inner primaries with greener back and replaced formative sec- and outer secondaries with barring. U/AHY ondaries and primary coverts. U/AHYs (Aug– female (Sep–Aug) similar except remiges uni- Jul) have uniformly green secondaries and formly cinnamon and lacking bars. Juvenile/HY/ primary coverts. Some AHY/ASYs (Sep–Aug) SY male (Jul–Sep) has black and white body might be identified with retained definitive plumage with cinnamon or buff wash to lower secondaries and primary coverts, dull greenish, underparts, and molt limit criteria as in HY/SY contrasting only slightly in wear with replaced female (except replaced remiges barred black and feathers. Gender distinguished in all plumages: white). U/AHY males (Oct–Sep) have black and females have distinct green chest-band whereas white body plumage without cinnamon or buff males lack this band. Wing: F 5 52–59 mm, M 5 wash and uniformly black and white remiges. 52–59 mm. Males still molting flight feathers in September– Dendrocolaptes sanctithomae (Northern Barred January can be classified as AHY/ASY if retained Woodcreeper; n 5 145 specimens, 32 captures). outer primaries and middle secondaries are black Breeds: February–November (?). Molt: PF com- and white. Wing: F 5 63–71 mm, M 5 65– plete (?) (Mar–Dec), DPB complete (?) (Mar– 71 mm. Dec). Juveniles (Jun–Aug?) have slightly looser Thamnophilus atrinucha (Western Slaty Ant- plumage; otherwise, age classes similar and not shrike; n 5 213 specimens, 198 captures). Breeds: distinguishable. Stiles and Skutch (1989) de- February–November (?). Molts: PF partial (Mar– scribed juveniles as having crown more ochrac- Dec), DPB compete (Mar–Dec). The PF occa- eous and throat and belly with reduced, finer, and sionally can include 1–2 tertials and central less distinct barring but differences subtle if rectrices; possibly all rectrices in some individu- consistent. Gender similar in plumage; many als. Juveniles have loose textured plumage and separated by wing-chord length: F 5 117– lack white patch; plumage resembles AHYs of 127 mm, M 5 124–133 mm. each gender but upperparts of female washed Lepidocolaptes souleyetii (Streak-headed Wood- chestnut and duller, male with chestnut feathering creeper; n 5 170 specimens, 22 captures). Breeds: present on back. HY/SY female (Jul–Jun) has February–September. Molts: PF incomplete-com- brownish olive body plumage, dusky primary plete (?) (May–Oct), DPB incomplete-complete (?) coverts with cinnamon edges, replaced greater (May–Oct). Dickey and van Rossem (1938) report coverts contrasting with retained primary coverts retention of central retrices during the PF, but and secondaries, several tertials and rectrices more-worn rectrices may represent molt suspen- occasionally replaced, fresher, and underparts sion (assuming central rectrices are last replaced, as tinged chestnut. AHY/ASY female (Jul–Jun) is in woodpeckers) or wear; further study needed. similar but primary coverts with pale tips, greater Juveniles (Mar–Oct) have slightly looser plumage; coverts uniform in quality with primary coverts otherwise, age classes similar and not distinguish- and secondaries, rectrices without molt limits, and able. Stiles and Skutch (1989) describe Juveniles as underparts brownish olive without chestnut tinge. having denser yet less-distinct streaking, duller HY/SY male (Aug–Jul) has black and gray body throats with sooty fringes, and darker bills but plumage, dusky primary coverts and remiges with differences subtle if consistent. Gender similar in cinnamon edges, contrasting distinctly with re- Wolfe et al. N MOLT AND BREEDING CYCLES OF COSTA RICAN BIRDS 561 placed, black-and-white greater coverts and (at emargination), primary coverts dusky with broad times) several tertials; underparts often tinged green edging, and rectrices broad, truncate, dusky, brownish. AHY/ASY male (Aug–Jul) has black and relatively fresh. AHY/ASY male (Sep–Aug) and gray body plumage, black primary coverts similar except for thinner and more-pointed with white tips, and uniformly black remiges with primaries 10, 9, and 8 emarginated. Wing: F 5 whitish edging, not contrasting in wear with 57–64 mm, M 5 61–69 mm. greater coverts; underparts gray without brownish Manacus candei (White-collared Manakin; n 5 tinge. Wing: F 5 63–70 mm, M 5 61–71 mm. 26 specimens, 1,525 captures). Breeds: March– Myrmeciza exsul (Chestnut-backed Antbird; n November. Molts: PF partial (Aug–Jan), DPB 5 30 specimens, 98 captures). Breeds: March– complete (Jul–Jan). The PF includes a variable October (?). Molts: PF partial (Mar–Dec), DPB number of greater coverts but no flight feathers. complete (Mar–Dec). The PF includes body and Age and gender criteria similar to Pipra mentalis most or all greater coverts but usually not the regarding plumage of HY/SYs of both genders tertials and no other flight feathers; the alula may (Aug–Jul), green body plumage, molt limits rarely be replaced. Juveniles are entirely blackish- among wing coverts, and shape and color of outer brown without contrast between breast and throat; primaries and rectrices with differences. Some gender similar until PF commences. HY/SY HY/SY males (Sep–Aug) have gray to light-gray female (Oct–Sep) has grayish head and throat, throat and AHY/ASY female (Sep–Aug) can lack upperparts tawny, primary coverts brownish, alula or have a grayish throat. Leg color may also be brownish with thin or no tawny olive edging brighter orange in AHY/ASY females than in HY/ (occasionally blackish with distinct pale edge), SYs females; more study needed. AHY/ASY male and primaries and rectrices relatively worn; (Sep–Aug) has black cap, lower back, wings, and individuals with replaced alula may best be tail; white throat and upper back, green rump and classified U/AHY. AHY/ASY female (Oct–Sep) yellow belly. Males molting in September can be is similar but primary coverts dusky with tawny classified to ASY if outer primary is blackish and olive edging, alula dusky with distinct whitish narrow, measuring ,2.5 mm wide at the distal 8– edge, and primaries and rectrices relatively fresh; 10 mm end of the feather. SY/TY males may have by April–July the edging on adult alula often less white in greater coverts than ASY/ATY wears off, however, primary covert condition can males; the second-to-outermost greater covert still be used for age classification. HY/SY male should be checked for smaller and more triangular (Oct–Sep) has blackish head, throat, chest, and white patches, at times washed yellowish in SY/ belly, alula, and flight feathers as in HY/SY TYs. Wing: F 5 49–59 mm, M 5 49–59 mm. female. AHY/ASY male (Oct–Sep) similar but Pipra mentalis (Red-capped Manakin; n 5 31 primary coverts black with tawny edging, alula specimens, 293 captures). Breeds: March–Septem- black with distinct white edge, and primaries and ber. Molts: PF partial (Mar–Oct), DPB complete rectrices relatively fresh. Wing: F 5 62–68 mm, (Mar–Oct). The PF includes a variable number of M 5 61–72 mm. greater coverts but no remiges or rectrices. Juvenile Mionectes oleagineus (Ochre-bellied Flycatch- (Apr–Sep) is green with a brown or olive wash over er; n 5 32 specimens, 123 captures). Breeds: loosely textured body plumage. HY/SY of both March–July. Molts: PF partial (Aug–Feb), DPB genders (Aug–Jul) has body and tertials entirely complete (Aug–Feb). The PF includes a variable green, primary coverts brownish-gray with little or amount of wing coverts but not the alula, primary no dull green edging. Molt limits occur within coverts, tertials, rectrices or remiges. Juveniles greater coverts. Retained wing coverts and remiges (May–Aug) have throat washed gray and belly are duller and outer primaries dull-brownish, washed tawny olive. HY/SY males and females narrow, and relatively worn. Retained rectrices (Aug–Jul) have broad-tipped and more worn are narrow, pointed, brownish, and relatively worn. primaries 8, 9, and 10, primary coverts brownish Some to many HY/SY males (Aug–2 Sep) can be with thin, dull, green edging; and rectrices narrow, assigned to gender by dusky or blackish wash to pointed, brownish, and relatively worn. The outer web of one or more tertials (usually primary covert and rectrix criteria can be subtle. secondary 9), one or more body feathers blackish, AHY/ASY females (Aug–Jul) have moderately and/or one or more head feathers red. AHY/ASY tapered and fresher primaries 8, 9, and 10 with female (Aug–Jul) has entire body plumage green, primary 8 not emarginated (possibly with slight one or more tertials with or without dusky or 562 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 121, No. 3, September 2009 blackish wash, primary coverts dusky with distinct Arremonops conirostris (Black-striped Spar- bright green edging, back, wing coverts, and row; n 5 37 specimens, 143 captures). Breeds: remiges uniformly bright green, outer primaries March–September. Molts: PF complete (Sep– dusky green, broad, and relatively fresh. Rectrices Dec), DPB complete (Sep–Dec). The PF may at broad, truncate, dusky green, and relatively times be partial (more study needed), and the PF fresh. AHY/ASY male (Oct–Sep) has red head, and DPB apparently can be suspended. Juv/HYs black body (including wings and tail). SY/TY age (Apr–Sep) have underparts washed yellow with criteria unknown. Wing: F 5 51–63 mm, M 5 51– dusky streaks, head pattern indistinct and streaky, 63 mm. and outer primaries and rectrices narrow and Hylophilus decurtatus (Lesser Greenlet; n 5 29 tapered. U/AHYs (Oct–Sep) have underparts specimens, 343 captures). Breeds: March–Sep- without yellowish or dusky streaks, head pattern tember. Molts: PF partial (May–Dec), DPB distinct, and outer primary and rectrices broad. complete (May–Dec). PF includes most or all Some HY/SYs or AHY/ASYs may be classified to wing coverts but no remiges. Juveniles (Apr–Sep) age in November–October by condition of have loosely textured body plumage, pale brown retained feathers during partial or incomplete crown, and brownish suffusion to back. HY/SY molts; more study needed. Genders similar in all (Aug–Jul) has brownish-gray primary coverts plumages, although some can be identified by with little or no dull green edging, crown dull- wing chord: F 5 68–77 mm, M 5 74–81 mm. gray, sometimes washed brown and/or with green- Ramphocelus passerinii (Passerini’s Tanager; n tinged feathers, and contrasting indistinctly with 5 57 specimens, 69 captures). Breeds: March– back at nape (yellow-green); rectrices narrow, November. Molts: PF partial-complete (Mar– pointed, brownish, and relatively worn. AHY/ Dec), DPB complete (Mar–Dec). The PF is ASY (Aug–Jul) has pearly gray primary coverts variable, ranging from partial (as few as 2 greater with distinct green edging; crown pearly gray coverts replaced) to incomplete in eccentric without brown or green wash and contrasting sequence (up to primary 1–4 and secondary 1–3 crisply with back at nape (yellow-green); rectrices retained) to complete. All rectrices are often broad, truncate, dusky, and relatively fresh. replaced and primary coverts can be retained or Gender similar in all plumages. Wing: F 5 41– replaced with associated primaries. Juveniles 57 mm, M 5 48–57 mm. (Apr–Jul) have grayer head, paler throat, and Thryothorus nigricapillus (Bay Wren; n 5 34 tawny washed upperparts and underparts. HY/SYs specimens, 201 captures). Breeds: March–Octo- of both genders (Jul–Jun) have primarily olive ber. Molts: PF partial (Mar–Dec), DPB complete brown body plumage lacking dusky or black (Mar–Dec). The PF appears to include all greater feathers, molt limits present among wing coverts coverts and, at times, the tertials and central and/or flight feathers, breast and rump usually rectrices but no other flight feathers. Juveniles with pale orange yellow, lacking red feathers. (Feb–Jul) average paler cinnamon with thin chest Duller and browner-winged HY/SYs probably barring, lacking spotting on lower-underparts. female, but more study is needed. Gender of some HY/SY (Aug–Jul) has brownish-gray primary HY/SY males (Jul–Jun) can be assigned by having coverts with irregular, thin, dull-cinnamon patch- one or more black feathers on body and/or es on edge, contrasting in quality with fresher contrastingly red feathers in rump, later-molted greater coverts and, at times, tertials. Outer flight feathers (especially primary 10, secondaries primaries relatively worn and brownish; rectrices 4–6, or several rectrices), if replaced, washed relatively worn, at times with fresher central sooty or blackish. U/AHY female (Sep–Aug) feathers. AHY/ASY (Aug–Jul) has dusky primary primarily olive without dusky or black feathers, coverts with regular and more square cinnamon- wing coverts, remiges and rectrices uniformly patches extending almost to the shaft, not dark-brown, rectrices broad and truncate, and contrasting in quality with greater coverts or breast and rump rich reddish-orange, sometimes tertials, relatively fresh and dusky outer primaries, washed red. Occasional older females may have and uniformly fresh rectrices. Genders are similar one or more black feathers. AHY/ASY male (Jul– in all plumages, although females average slightly Jun) has mostly black body plumage and flight duller and wing chord useful for classifying feathers, and red rump. Some SY/TYs may be gender of some individuals: F 5 60–67 mm, M identified by having retained brownish juvenal or 5 64–70 mm. formative flight feathers (e.g., secondary 6) or Wolfe et al. N MOLT AND BREEDING CYCLES OF COSTA RICAN BIRDS 563 body plumage, slightly-dusky remiges (males), primary coverts, brown greater coverts with thin and/or yellowish to the sides of the rump and buffy tips, and rectrices narrow and brownish. HY/ undertail region; more study needed. Wing: F 5 SY female (Apr–Aug) similar except body plumage 69–78 mm, M 5 72–83 mm. mixed olive and brown, molt limits occur among Thraupis episcopus (Blue-grey Tanager; n 5 32 wing coverts or flight feathers. HY/SY male (Feb– specimens, 219 captures). Breeds: February– Nov) similar to HY/SY female except incoming September. Molts: PF partial (May–Oct), DPB body plumage and flight feathers black or dusky- complete (May–Oct). The PF includes most or all black. U/AHY female (Sep–Aug) has entirely lesser coverts, none to all median coverts, and 0–9 brownish olive body plumage, dusky primary greater coverts; some replace all greater coverts as coverts with distinct brownish olive edging, well as several tertials, and several central uniformly brownish olive wing coverts and dusky rectrices. Juveniles of both genders (Apr–Sep) flight feathers, and rectrices broad, truncate, and have body plumage washed grayish. HY/SY dusky. U/AHY male (Sep–Aug) has entirely black female (Sep–Aug) has brownish primary coverts body plumage and flight feathers. Wing: F 5 47– with little or no greenish or brownish edging, molt 57 mm, M 5 47–57 mm. limits present in the wing coverts, replaced Oryzoborus funereus (Thick-billed Seed Finch; feathers contrastingly brighter and greenish-tur- n 5 38 specimens, 149 captures). Breeds: April– quoise, and rectrices fresher, narrow, brownish, September. Molts: PF partial (Aug–Nov), DPB and washed dull greenish; outer primaries dull incomplete-complete (Aug–Nov). The PF in- brownish, narrow, and relatively worn. HY/SY cludes body and most, or all wing coverts male (Sep–Aug) is similar to HY/SY female (occasionally up to 5 juvenile greater coverts except that replaced formative greater coverts can be retained) but no flight feathers. The DPB average more blue and brighter. AHY/ASY appears to be complete (most commonly), al- female (Sep–Aug) has blackish primary coverts though, it apparently can also be eccentric (more with distinct turquoise green edging; wing coverts commonly during the PB2?) with up to four inner uniform in color and wear, rectrices broad, primaries and primary coverts, and four outer truncate, dusky, and washed bright greenish, and secondaries retained; more study needed. Juve- outer primaries dusky, truncate, and relatively niles (Jun–Sep) have pale grayish brown body fresh. AHY/ASY male (Sep–Aug) similar except plumage and loosely textured feathers; genders wing coverts distinctly more blue and brighter. are similar, however, some juvenile males may Wing coverts in all age/gender groups show a have slightly duskier flight feathers. HY/SYs of cline from brighter and more blue lesser coverts, both genders (Aug–Sep) have entirely tawny body to duller and more green median coverts, to duller plumage lacking dusky centers to feathers, molt and more green secondary coverts. Wing: F 5 81– limits among greater coverts or between these and 88 mm, M 5 80–92 mm. brown primary coverts, and rectrices relatively Sporophila corvina (Variable Seedeater; n 5 40 thin and worn. Some HY/SY males (Aug–Nov) specimens, 962 captures). Breeds: April–August can be identified by plumage averaging richer and November–February. Molts: PF incomplete- tawny and/or with one or more dusky to blackish complete (year round?), DPB complete (year feathers; crown feathers often with dusky centers, round), PA possible. Molts and plumages confusing and remiges and rectrices often washed dusky. and perhaps unique; fledglings from April–August AHY/ASY female (Sep–Aug) has entirely tawny breeding season have an incomplete PF (outer body plumage, crown without dusky-centered primaries, some rectrices, secondaries 3–6 and/or feathers, wing coverts uniform in wear, primary scattered body feathers retained) whereas fledglings coverts dusky, and rectrices relatively broad and from November–February breeding season appear fresh. AHY/ASY male (Oct–Sep) has entirely to retain most or all juvenile plumage until May, black body plumage and flight feathers. Some SY/ when a complete (PF or PB2?) molt likely occurs TY males (Sep–Aug) may be identified by having through the summer. Males (at least) may have a black plumage except tawny wash on belly and PA1 and DPA (Nov–Feb) including some body vent. AHY/ASYs showing eccentric patterns may plumage and at times one to several tertials and be identifiable as TYs (with retained dusky- central rectrices; confirmation needed. Juv/HYs washed juvenile feathers) or ATYs (with black (Nov–Sep) or SYs (Jan–Sep) of both genders have retained feathers); more study needed. Wing: F 5 entirely gray-brown body plumage, brownish 49–56 mm, M 5 49–59 mm. 564 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 121, No. 3, September 2009

FIG. 1. Breeding seasonality for 27 resident bird species captured in Tortuguero, Costa Rica from 1994 to 2006. Breeding seasonality was inferred based on presence of brood patch, cloacal protuberance, juxtaposition of the prebasic molt, and presence of juveniles coupled with a specimen review.

Habia fuscicauda (Red-throated Ant Tanager; n upperparts; throat bright-red and molt limit and 5 39 specimens, 76 captures). Breeds: April– rectrix criteria as in AHY/ASY female. Some October. Molts: PF partial (Aug–Dec), DPB older females can resemble AHY/ASY males complete (Aug–Dec). The PF includes most or except for pinkish throat and light-red back, while all lesser and median coverts, and a variable some AHY/ASY males can have interspersed number of greater coverts but few or no flight greenish feathers. Wing: F 5 83–94 mm and M 5 feathers; look for several tertials and several 85–104 mm. central rectrices at times to be replaced. Juveniles of both genders (Feb–Oct) have body plumage DISCUSSION washed tawny, brownish olive upperparts, and We provide molt patterns, breeding seasonality, brownish olive on sides and chest. HY/SY and age and gender criteria using 12 years of females (Aug–Jul) have upperparts olive, throat banding data and a museum review for 27 resident yellow, molt limits among greater coverts, and birds in northeastern Costa Rica. Three potential rectrices tapered, worn, and greenish (at times factors may confound our data: (1) data presented reddish), the central feathers occasionally re- were collected by hundreds of volunteers promot- placed. AHY/ASY female (Aug–Jul) has upper- ing observer bias and data-quality heterogeneity; parts brown, throat yellow to orange, uniform (2) the specimen review is largely-based on greater coverts, and rectrices truncate, fresh, and specimens collected outside the study area; and washed olive, tawny or greenish. HY/SY males (3) banding operations were not sustained during (Aug–Jul) have upperparts brown, throat bright- June and July. Continuing data collection will red, and molt limit and rectrix criteria as in HY/ further increase the precision of our molt and SY female. AHY/ASY male has dark red breeding accounts. Potential complications asso- Wolfe et al. N MOLT AND BREEDING CYCLES OF COSTA RICAN BIRDS 565

FIG. 2. Timing of the prebasic molt for 27 resident bird species captured in Tortuguero, Costa Rica from 1994 to 2006. Darker portions of the figure indicate symmetrical flight-feather replacement of captured birds at Totuguero. Banding activities were suspended during June and July; molt criteria for June and July were based on the juxtaposition of molt patterns during May and August, and specimen review. Symmetrical flight-feather replacement during June and July was based on juxtaposition of molt patterns of captured birds during May and August. ciated with data collection exist; however, our For example, the breeding activity of avian study provides novel information associated with communities in Minas Gerais, Brazil peaked in basic phases of the avian life cycle and utilitarian November while breeding activity in Costa Rica data pertaining to age and gender classification. peaks in April and May (Skutch 1950, Marini and Plumage and molt-based criteria can be readily Dura˜es 2001; Fig. 1). The asynchronous nature of used to classify age in 59% of our study species breeding among closely related taxa presents a (in-hand). Molt-based aging criteria remain elu- problem for neotropical field ornithologists. sive for hummingbirds and (apparently) wood- Breeding season variability throughout the tropics creepers due to complete preformative molts. becomes more dramatic in systems influenced by Plumage-based gender criteria can be used for stochastic precipitation regimes or lowland sys- 70% of our study species in post-juvenile tems near the equator where birds may breed year- plumages. Ultimately, molt and plumage-based round or immediately following precipitation criteria can be used to place the majority of events (Snow and Snow 1964, Poulin et al. captured study species into discreet age and 1992). The apparent variation in breeding seasons gender categories. across the Neotropics complicates classifying age Breeding seasons (derived from TIBMP band- of tropical landbirds; for example, 19% of our ing data) differ in duration and, in some cases, study species are believed to breed across 1 seasonality from other published accounts of January, the definitive date used to categorize age temperate and neotropical birds (Skutch 1950, class. Applying temperate models, such as the Snow and Snow 1964, Snow 1976, Sinclair 1978, calendar-year age-classification system, may not Stiles and Skutch 1989, Marini and Dura˜es 2001). be appropriate in tropical latitudes due to 566 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 121, No. 3, September 2009 asynchronous breeding seasons represented by DICKEY,D.R.AND A. J. VAN ROSSEM. 1938. The birds of El certain taxa. Bimodal breeding seasons are Salvador. 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