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Molts and of () Author(s): Peter Pyle Source: Waterbirds, 28(2):208-219. 2005. Published By: The Waterbird Society DOI: http://dx.doi.org/10.1675/1524-4695(2005)028[0208:MAPODA]2.0.CO;2 URL: http://www.bioone.org/doi/ full/10.1675/1524-4695%282005%29028%5B0208%3AMAPODA%5D2.0.CO %3B2

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Molts and Plumages of Ducks (Anatinae)

PETER PYLE

The Institute for Populations, P.O. Box 1436, Point Reyes Station, CA 94956, USA Internet: [email protected]

Abstract.—Ducks are unusual in that males of many acquire brightly pigmented plumages in autumn rather than in spring. This has led to confusion in defining molts and plumages, using both traditional European terminology and that proposed by Humphrey and Parkes (1959). To investigate molt patterns in waterfowl relative to molt and nomenclature, 2,227 specimens of ducks and geese were examined. Both the “first prebasic” (“post-juvenile” using traditional European terminology) and the “definitive prebasic” (“adult post-breeding”) body molts in most ducks, the latter producing the cryptic spring (female) and summer (male) plumages preceding the wing molt, are considerably more variable and less extensive than reported. By contrast, the “definitive prealter- nate” (“adult pre-breeding”) body molt of most ducks, which follows the wing molt and produces the brightly col- ored plumages of males, is complete or virtually so. Based upon presumed homologies with the molts of geese, the wing molt and ensuing complete body molt of ducks are better considered the prebasic rather than the prealternate molt and, thus, the bright feathering of male ducks should be considered the basic plumage. The incomplete and ephemeral cryptic plumages, attained by some ducks in spring and summer, may have evolved more recently in spe- cies that benefit from camouflage at this time, and should be considered alternate plumages. The molts and plum- ages of the adult Ruddy (Oxyura jamaicensis) appear to be homologous with those of other Anatine ducks, with a slight temporal shift in the hormonal cycles that control pigment deposition (as opposed to differences in molt patterns) explaining the differences in plumage-coloration patterns in males. Because pigment-deposition patterns are controlled by various factors related to seasonal and reproductive phenomena, which differ consider- ably both among and within taxa, plumage color should not be a critical factor in attempts to define homologous molts and plumages. Received 25 July 2004, accepted 12 January 2005. Key words.—, , duck, molt terminology, Melanitta, Oxyura jamaicensis, plumage, Ruddy Duck, . Waterbirds 28(2): 208-219, 2005

Among , many ducks (Subfamily “summer plumage,” which occurs primarily Anatinae) are unusual in that brightly pig- in winter. Variations of this interpretation mented plumages of males are acquired in have persisted in the literature (Schiøler autumn rather than spring. In boreal spe- 1921; Witherby et al. 1939; Dement’ev and cies, of the wing tracts (including Gladkov 1952; Oberholser 1974; Cramp and the primaries, secondaries, and wing co- Simmons 1977; Marchant and Higgins 1990; verts) are replaced synchronously in the late but see Sutton 1932; Stresemann 1948). summer or early autumn, in between two Consequently, the bright plumages acquired separate molts of body-feather tracts (Cramp in autumn have been referred to as “nuptial” and Simmons 1977; Hohman et al. 1992; or “breeding,” and the cryptic summer Bellrose and Holm 1994). In Anas, Aythya, plumages acquired in spring and summer as and Somateria, the body molt prior to the “eclipsed” or “non-breeding,” despite confu- wing molt occurs in the early spring in fe- sion resulting from the fact that females of males and in the summer in males, often these genera nest in “non-breeding” plum- producing a cryptic plumage that provides age (cf. Cramp and Simmons 1977). camouflage for females during nesting and Humphrey and Parkes (1959) cited such for both sexes during the flightless period confusion in support of their revised molt and accompanying wing molt (Hohman et al. plumage nomenclature, which excluded 1992). Jackson (1915) first suggested that terms correlated with “seasonal, reproductive, this summer body molt in males be aligned developmental, or other phenomena” within with the wing molt to form the complete an- the annual cycle. The “Humphrey-Parkes” (H- nual molt. Because the body feathering pro- P) system attempts to recognize homologous duced by this molt was cryptic, Jackson molts across taxa by defining a “molt cycle” considered it the “winter plumage,” followed (usually a year in boreal species) during which by a partial molt into the brightly pigmented a single complete or near-complete molt oc-

208

MOLTS AND PLUMAGES OF DUCKS 209 curs and is termed the “prebasic molt.” Addi- Despite an extensive literature, gaps re- tional, less-complete inserted molts, defined main in our understanding of the precise tim- by the shedding of feathers more than once ing and extent of molts in ducks (Hohman et within the molt cycle, are termed “prealter- al. 1992). Palmer (1976) described the first nate molts,” and if more than one inserted prebasic (post-juvenile) molt as involving molt occurs, the second inserted molt (de- most or all body feathers; however, the few fined by the replacement of feathers three studies that have critically examined this molt times within the molt cycle) is termed the either have involved captive ducks subjected “presupplemental molt.” Regarding molts in to non-natural feeding and lighting regimes adult ducks, Humphrey and Parkes con- that likely affected molts (Weller 1957, 1970), curred with previous opinion that the spring/ or have found it at most to include only a few summer body molt should be aligned with the feathers of the head or underparts (Mendall wing molt, terming this the complete prebasic 1958; Oring 1968; Bellrose and Holm 1994). (“post-breeding” of traditional European ter- Furthermore, studies such as that of Hoch- minology) molt resulting in “basic plumage,” baum (1944) have suggested that the sum- followed by the partial prealternate (“pre- mer body molt in certain adult ducks, breeding”) molt in autumn resulting in “alter- defined as part of the prebasic or post-breed- nate plumage.” Humphrey and Parkes rea- ing molt, might be limited to a small propor- soned that the bright plumage stage in males tion of feathers or be lacking altogether, such has evolved more recently, and should be con- that males molted directly from one bright sidered the alternate plumage to conform to plumage to the next, without a more cryptic nomenclature in other birds that have bright summer plumage. Humphrey and Parkes seasonal plumages. (1959) and Palmer (1976) acknowledged Palmer (1972) further elaborated upon Hochbaum’s (and other similar) findings, H-P molt and plumage terminology in ducks but did not discuss the discrepancy in H-P ter- and subsequently (Palmer 1976) applied it to minology that results from the replacement the molts and plumages of all North Ameri- of alternate with alternate feathering without can species. Palmer defined duck molts in an intervening basic plumage. the first cycle as consisting of a partial “first To investigate molt phenology in ducks prebasic” (“post-juvenile”) molt of all or relative to molt and plumage terminology, most body feathers in late summer, followed 2,227 specimens of North American ducks rapidly by another partial “first prealternate” and geese (), the latter widely con- (“first pre-breeding”) molt of all body feath- sidered ancestral to ducks (Delacour and ers in autumn and winter, resulting in bright Mayr 1945; Palmer 1976), were examined. first-winter plumages in males. The Ruddy The objectives were: (1) to confirm the tim- Duck (Oxyura jamaicensis) differs from other ing and determine the extent of each molt in North American species in that adult males ducks; and (2) to attempt tracing the evolu- acquire bright plumage during a prealter- tion of homologous molts from Anserinae nate molt in spring rather than in autumn, (which lack additional inserted molts) to and the complete prebasic molt consists of Anatinae in to properly apply molt ter- the wings followed by the body molt in early minology to ducks. autumn (Palmer 1976). The H-P molt and plumage terminology for ducks described by METHODS Palmer (1972, 1976) has been widely accept- Specimens of geese and ducks were examined at the ed in (Hohman et al. 1992; California Academy of Sciences (CAS), San Francisco; Poole and Gill 1992-2003), and this sequence the Museum of Vertebrate Zoology (MVZ), University and extent of molts and plumages (albeit of California at Berkeley; the Museum of Wildlife and Fisheries Biology (MWFB), University of California at with different terminologies) has been ac- Davis; the Provincial Museum of Alberta (PMA), Ed- cepted throughout the world (Dement’ev monton; and the National Museum of Natural History and Gladkov 1952; Cramp and Simmons (USNM), Washington, D.C. Specimens examined were collected throughout the year (sample range 119-230 per 1977; Marchant and Higgins 1990). month) and throughout North and Central America.

210 WATERBIRDS

Age when collected and sex were determined for each For each specimen, the timing of rectrix and tertial specimen, as based primarily on plumage of the wing replacement as well as the number of feathers replaced (cf. Palmer 1976; Carney 1992) combined with informa- (symmetrically on both sides of the tail or both wings) tion noted on the specimen label. Juveniles could be during the preceding molt was recorded. Over 1,400 recognized by their more rounded feathers, contrasting specimens of 18 other species of North American ducks with the larger and squarer feathers of adults (Palmer were also examined for general evaluation of molt and 1972, 1976; Cramp and Simmons 1977; Marchant and plumage patterns in comparison with taxa examined Higgins 1990). Based on specimen availability (especial- more critically. ly in summer) and divergent molt and plumage pat- Throughout the results section I follow the “tradi- , six species of Anserine geese (Anser albifrons, Chen tional” molt and plumage terminology of Humphrey canagica, C. caerulescens, C. rossi, canadensis, and B. and Parkes (1959), as detailed by Palmer (1972, 1976). bernicula), 11 species of Anas ducks (strepera, , Traditional European terms for each molt in ducks are americana, rubripes, platyrhyncos, fulvigula, discors, cyan- also indicated. A “revised” H-P terminology, presented optera, clypeata, acuta, and crecca), three species of Melan- in Figure 1 and the discussion, includes modifications itta (perspicillata, fusca, and nigra), and one based on the results of this study and those proposed by species of Oxyura (Ruddy Duck) were selected for de- Howell et al. (2003) for first-cycle molts. tailed examinations of molt and plumage phenology. For each of these four groups, at least 20 specimens col- lected during each month of the year were examined. RESULTS For each , temporal periods of molt resulting in each plumage stage were determined, and extent of Within each taxonomic grouping, few the molt resulting in the plumage was estimated. Speci- significant differences were found in the tim- mens (N = 575) were considered to be undergoing “ac- tive molt” if >10% of contour feathers within any of six ing or extent of molt between species. With- body regions (defined by Billard and Humphrey 1972) in Anas, the traditional “prealternate” (“pre- were found to be missing or growing. Contour feathers breeding”) molts of A. discors, A. cyanoptera, throughout these regions were lifted and examined (cf. Pyle and Howell 2004), and the proportion of pins or and A. clypeata (Blue-winged Teal, Cinnamon developing feathers was estimated. Within this group, Teal, and Northern ), pooled, oc- specimens on which the primaries and secondaries were curred significantly later than in other spe- missing or growing (N = 79) were considered in “wing molt”. Temporal ranges for body-feather molts and wing cies (see below). Thus, except in these cases, molts were calculated based on mean Julian date of species within each taxon were pooled to de- specimens in active molt ±2 S.D., to encompass an esti- rive summary statistics on molt timing and mated 96% of the molting periods. In specimens not showing active feather replace- extents. Likewise, little geographic variation ment (N = 1,652), extent of the previous molt was esti- (based on collection locality) appeared to be mated by critically examining body feathers for evident. contrasts in size, shape, quality, wear, and coloration, as compared to those of corresponding feather tracts in specimens collected in the plumage or molt antecedent to the plumage in question. For males of most North Molt in Anserinae American Anatinae, the proportion of feathers re- placed within each tract (to the nearest 10%) was esti- The temporal period for the traditional mated by changes in color between succeeding feather first prebasic (post-juvenile) molt in geese, generations in most tracts. The assumption was not based on 124 specimens in active molt, was made, however, that change in feather color equated to change in feather generation. Therefore, qualitative as- 22 September to 6 March (Fig. 1A), com- sessments of feather color were performed on each mencing on the summering grounds and feather generation in male ducks (excluding three taxa, concluding on the wintering grounds. This Anas fulvigula, Black Duck A. rubripes, and “” A. platyrhynchos diazi, that lack bright molt included approximately half of the plumages in males), in consideration of relative feather body feathers, on average (Table 1): most or wear. In juveniles of both sexes, replacement of feathers all of the head and neck, and much of the could be assessed by contrasts in shape and wear be- tween the smaller and rounder juvenal feathers and the upper back (including the scapulo-humer- replaced, larger and squarer feathers. The term “cryp- als), breast, and sides, but little of the belly, tic” is used to indicate duller or browner feathers typical lower back or rump (Table 2). At least one of juvenal plumage, females, and many males in sum- mer, and the term “brightly colored” is used to indicate tertial was replaced on 29% of individuals pigmented display feathers acquired by males for court- and rectrices had been replaced on 81% of ing. For female ducks, assessment of molt extent in the specimens (mean 7.1 ± 7.8 [S.D.] of 16 adults was more difficult due to greater similarities in plumage pigmentation patterns between successive rectrices). The sequence of body molt in generations; thus, data from females were interpreted both geese and ducks, as based on propor- with more caution. In Anserinae, feathers in both sexes tions of feathers in active molt, generally were large and more readily assessed for comparative feather-replacement patterns. proceeded anterior-ventrally, commencing

MOLTS AND PLUMAGES OF DUCKS 211

Figure 1. Graphic representation of the timing of molts in North American waterfowl and a comparison of molt terminologies; see text for methods used to determine commencement and termination dates. Extents of molts are represented by line style and thickness: dotted lines represent molts of body tracts that are very limited, or absent in some to most individuals; dashed lines represent body molts that are partial and occur in most or all individuals; thinner solid lines represent body molts that are complete or nearly complete in all individuals; and thicker solid lines represent wing molts. Abbreviations for traditional molts are as follows: PB1—first prebasic (post-juvenile) molt; DPB—definitive prebasic (adult post-breeding) molt; PA1—first prealternate (first pre-breeding) molt; and DPA—definitive prealternate (adult pre-breeding) molt. The temporal periods for males and females were separat- ed only when the sex-specific difference in timing was significant (ANOVA, P < 0.05). with the head, neck, upper back, breast, and igula; CAS 31159-31166, MVZ 60844-60845) flanks, and concluding with lower scapulars and (Branta bernicula; CAS 31168 and and vent. Typically, the tertials and rectrices 31170-31176) from Nunivak Island, Alaska, were the last feathers to be replaced during collected in August and September 1927: this molt, often in winter or early spring, fol- specimens that were completing growth of lowing replacement of body feathers. the primaries (e.g., CAS 31159-60, MVZ During the definitive prebasic (adult 60844-45, and CAS 31170-31172) had just post-breeding) molt in adult geese, wing begun molt of the body feather tracts. The molt occurred from 30 June to 22 August (N longest scapulars and rectrices were the last = 22; Fig. 1A). In individuals, replacement of feathers replaced during this molt. The de- wing feathers preceded molt of body feath- finitive prebasic molt of geese was complete ers, tertials, and rectrices, which occurred or nearly so (Table 1), a small proportion of from 11 August to 15 October (N = 16; Fig. upper wing coverts, rectrices, and/or feath- 1A). This sequence of molt was exemplified ers of other tracts (Table 2) occasionally be- by series of adult Emperor Geese (Chen can- ing retained.

212 WATERBIRDS

First-cycle Molts in Anas and Melanitta

Among all Anatinae genera examined, apparent active molt during June through mid-August, involving the replacement of cryptic with cryptic feathering in males, was found solely in , Anas, and Aythya. Deter- ix body tracts (see Table mination of the timing and extent of this tra- (adult pre-breeding) Definitive prealternate

100 0ditional 65 “first prebasic” (“post-juvenile”) molt, especially in females, was difficult due

< 0.001). to apparent overlap with the traditional “first P prealternate” (“first pre-breeding”) body molt. Assuming that the acquisition of cryptic les (F) due to sex-specific differences in molt les (F) due to sex-specific differences feathers in males was part of the first prebasic ional H-P terminology ter- (traditional European

< 0.01, *** molt and that the brightly colored feathers P 311 were acquired during the first prealternate molt, as conventionally defined, the range of

Definitive prebasic 19 specimens of Anas in active molt (with in- < 0.05, ** (adult post-breeding) P

100100coming 0 0 35feathers 25 50cryptic 40 10 in 14 males) 42** 32 was 7 July- 22 August (Fig. 1B). Twenty-two other speci-

Molts mens of juvenile Anas collected during this time period did not show evidence of active 0 29* 3 7 12 100 2 84

128 54molt, 28 fully 54 retaining 100 small 1 and 90 rounded juve- nile feathers. Likewise, no juvenile Melanitta collected in July to mid October (N = 32) 4 5 01 were in active molt (Table 1, Fig. 1C). Juve- niles (N = 77) of other genera (Somateria, First prealternate

(first pre-breeding) Clangula, Bucephala, and ) collected in July to mid-October, also showed no evidence of molt. In male Anas, the first prebasic molt was limited to 8-19% of the head, neck, upper

00 back, breast, and sides (Table 2) and did not include any tertials or rectrices (see below). The first prealternate molt of body feath- ers was variable in both timing and extent. In 02 200 7 6220 10 17 72 14 162*** 33 20 99*** 99 3 148 S.D. N % S.D.Anas N, this molt % occurred S.D. Nfrom 2 September % S.D. to N 16 November in most (eight) species (N = 38; First prebasic (post-juvenile) Fig. 1B) but significantly later (ANOVA, F1,63 = 02 % 83.8, P < 0.001), 16 October to 18 January, in A. discors, A. cyanoptera, and A. clypeata (N = 26; see above). In Melanitta, the first prealternate molt occurred from 15 October to 31 March (N = 43; Fig. 1C). Replacement of juvenile ter- F00133811291 M7 M0019471 M3 F1249592 F321 See Figure 1 for the seasonal timing of these molts. Extent of molt is quantified as mean percentage of feathers replaced from s 1 for the seasonal timing of these molts. Extent molt is quantifiedSee Figure of feathers replaced from as mean percentage tials and rectrices occurred in late autumn, winter, or early spring, concurrent with the termination of the first prealternate molt, rather than with the first prebasic molt. Re- placement of these feathers is thus consid- ered part of the first prealternate molt. The extent of the first prealternate molt Anas Melanitta Oxyura able 1. Variation in overall extent of body molts North American geese (Anserinae) and ducks (Anatinae) according to tradit able 1. Variation axon Sex in these two genera ranged from 38% of AnserinaeAnatinae 49 18 56 98 5 340 T T 2), as determined specimen examination (see text). Samples of Anatinae are for each molt from separated into males (M) and fema * in extent (ANOVA; and plumage strategies. Asterisks following male N-values represent sex-specific differences minology in parentheses).

MOLTS AND PLUMAGES OF DUCKS 213 Extent of molt is quantified as

(0%) was recorded during the traditional first (0%) was recorded ogy (see Table 1). ogy (see Table for any of the six tracts (Table 1). for any of the six tracts (Table Oxyura S.D. % S.D. % S.D. % S.D. % S.D. % S.D. % Head and neck Upper back/breast Scapulo-humerals Mid-back and rump Sides and flanks Lower breast/belly or the traditional first prealternate molt of (first pre-breeding) Melanitta First prebasicDefinitive prebasicFirst prebasicFirst prealternate 340Definitive prebasic 156Definitive prealternateFirst prealternate 99Definitive prebasic 81 290 238Definitive prealternate 153 26 4 26First prebasic 100Definitive prebasic 97 46 149Definitive prealternate 12 58 99 23 67 2 6 29 19 6 32 100 73 74 5 60 99 92 52 44 19 1 99 66 22 12 31 4 19 9 100 81 28 4 99 46 66 100 16 5 43 0 92 0 11 30 25 4 97 12 33 3 10 100 75 0 10 9 100 45 66 100 14 11 0 0 37 31 18 0 99 63 0 13 6 29 100 85 0 27 54 4 99 0 6 100 15 40 0 84 36 0 10 5 98 6 9 23 2 17 100 5 0 9 100 1 8 22 68 99 0 33 5 5 2 3 21 7 0 32 100 5 8 54 16 99 35 0 0 0 18 25 4 0 0 100 0 0 0 0 0 0 able 2. Variation in extent of body molts geese (Anserinae) and male ducks (Anatinae) according to traditional H-P terminol able 2. Variation axon/Molt N the mean percentage of feathers replaced from each of six body tracts as defined and Humphrey (1972). No replacement by Billard of feathers replaced from the mean percentage (post-juvenile) molt of prebasic T T Anserinae Anatinae Anas Melanitta Oxyura 214 WATERBIRDS

feathers in female Melanitta to 72% of feath- ers, five inner secondaries (including ter- ers in male Anas (Table 1). In both genera, tials) on each wing, all 16 rectrices, and all this molt was more extensive in males than in but the distal 20% of the greater, median, females (Table 1), and in males it included a and lesser secondary coverts; whereas anoth- greater proportion of head, neck, upper er adult female collected at the back, breast, and side feathers than belly, same location on 10 August 1908 (CAS lower back, or rump feathers (Table 2). Re- 12464) had replaced only 27% of its body placement of at least one tertial occurred in feathers and no tertials, rectrices, or wing co- 36% of Anas and 21% of Melanitta, and re- verts. Other adult females in this series (CAS placement of rectrices occurred in 89% of 11998, 12277, 12585, and 12464) had inter- Anas (mean 9.1 ± 9.2 feathers of 16 total) mediate spring molt extents. The definitive and 66% of Melanitta (mean 6.5 ± 7.3 of 14 prebasic body molts of Aix and Somateria gen- total). Because patterns of feather pigmenta- erally resembled those of Anas in the timing tion were used to define this molt (see and extent of each sex. above) the proportions indicated in Tables 1 There was little evidence for a definitive and 2 reflect the proportion of bright plum- prebasic body molt in Melanitta (Table 1). Of age encountered in first-alternate (first-win- 29 specimens examined during or just prior ter) males of these genera. The timing and to wing molt, only two adult Surf Scoters extent of the first prealternate molts of Aix (M. perspicillata), a female (CAS 73173) col- and Aythya generally resembled those of lected 8 July and a male (MVZ 115902), col- Anas, being confined to autumn and early lected 25 August, showed evidence of this winter, whereas in other duck genera (Soma- molt, in each case having replaced feathers of teria, Clangula, Bucephala, and Mergus) they the nape and a small proportion of feathers resembled those of Melanitta, being protract- within tracts of the upper back, upper breast, ed through winter and early spring. sides, and flanks (Table 2). Other adult Surf Scoters collected in late July and August (e.g., Definitive Molts in Anas and Melanitta MVZ 31654 and 135919) showed no evidence of this molt (all feathers of males being worn Replacement of body feathers during the and bright), and neither did a series of first- traditional “definitive prebasic” (“adult post- summer White-winged Scoters (M. fusca) col- breeding”) molt was not complete in any in- lected at Monterey Bay, California, on 29 Au- dividual of Anas and Melanitta (Tables 1 and gust during wing molt (MVZ 18827-18831). In 2). In Anas this partial body molt was highly this series, the body tracts consisted of a mix- sex-specific, occurring from 5 February to 19 ture of very worn juvenal and moderately April in females, and from 13 May to 1 July in worn first-alternate (mean 44%) feathers males (Fig. 1B), and included a higher pro- (brightly colored in males), but no feathers portion of feathers in females than in males that could be attributed to the traditional “sec- (Table 1). Among males, bright upperpart ond prebasic” (“first post-breeding”) molt. and breast feathers were replaced by cryptic The wing molt of Anas occurred from 6 feathers (Table 2), and females also replaced July to 4 September and that of Melanitta feathers predominantly among these tracts. from 16 August to 23 September (Fig. 1B-C). Among both sexes of Anas, one or more ter- The traditional “definitive prealternate” tials was replaced in 64% of birds, and one or (“adult pre-breeding”) body molts succeed- more rectrices was replaced in 70% of birds ed the wing molts, occurring from 26 August (mean 6.8 ± 11.4 of 16 feathers). to 6 November in most Anas (N = 198; Fig. This molt also showed a high degree of 1B); 7 October-4 February in A. discors, A. cy- individual variation, especially among fe- anoptera, and A. clypeata (N = 60; later than in males (Table 1). For example, an adult fe- other Anas, ANOVA F1,237 = 95.7, P < 0.001); male Gadwall (Anas strepera) collected at Los and 29 September to 16 November in Melan- Banos, California, on 8 May 1908 (CAS itta (Fig. 1C). This body molt was essentially 11997) had replaced 90% of its body feath- complete in both sexes and all species of MOLTS AND PLUMAGES OF DUCKS 215 both genera (Tables 1 and 2), and included ing wing molt concurrent with complete the acquisition of bright plumage in males. rectrix molt, and eight other specimens of Rectrices, and ornamental tertials and scap- both sexes collected between 11 May (CAS ulars in A. discors, A. cyanoptera, and A. clypea- 66554) and 29 September (USNM 197847) ta, were the last feathers to develop during had new wing feathers and were undergoing a this molt, as late as January or later on the complete body molt, or had plumage and winter grounds. All other genera of Anati- wear patterns consistent with a recent com- nae, examined less critically, also appeared plete wing and body molt in first-year birds. to have complete or near-complete defini- Five of six males in this group showed a vari- tive prealternate body molts. able proportion of rufous coloration to the tips of the upper-back and upper-breast feath- Molts in Oxyura ers. Thus, a complete second prebasic (first post-breeding) molt appears to occur between The first prebasic (post-juvenile) molt of April and August in the Oxyura (Fig. 1D). the Ruddy Duck (Oxyura) differed from The definitive prealternate (adult pre- those of Anas and Melanitta in occurring dur- breeding) molt in the Oxyura, as traditionally ing the late autumn and winter, from 19 Oc- defined, occurred from 12 February to 18 tober to 18 February (N = 19; Fig. 1D), and May (N = 35; Fig. 1D), and was partial (Table in being more extensive, including 30-33% 1), replacing cryptic with bright feathers in of the body feathering (Table 1). Critical ex- appropriate body areas of males (Table 2). amination of 71 first-year Ruddy Ducks col- Most (85%) birds had replaced most to all lected between 13 July and 12 April rectrices (mean 11.0 of 14 feathers) during indicated that most or all of the juvenile the prealternate molt. The extent of the pre- plumage was retained through the first win- alternate molt was significantly greater in ter and early spring in many birds. Some males than in females (Table 1). birds had begun a body-feather molt with Thirteen adult Ruddy Ducks collected feathers of the face being replaced as early as during the definitive prebasic (adult post- 27 October (CAS 73241), whereas others col- breeding) molt indicated that the wing molt lected as late as 22 February (CAS 22028) occurred from 24 July to 9 September and remained in complete or near-complete that body molt occurred following the wing juvenile feathering. In males, this molt was molt, from 17 September to 23 November primarily confined to the head, neck, upper (Fig. 1D). Eight males undergoing this molt back, breast, and sides (Table 2). Feathers were replacing worn bright feathering with replaced during the earlier portions of this fresh cryptic feathering. The prebasic body molt (October-December) were cryptic in molt following the wing molt was complete coloration whereas those replaced during in all 48 specimens examined (Table 1). Ten later portions of this molt (January-March) of 29 adult males in basic plumage showed were intermediate in color between cryptic bright rufous bases to some of the larger and bright feathering. No tertials or rectrices scapulars and/or feathers of the hind flanks. were replaced during this molt. The body molt described above spanned DISCUSSION the periods of the traditional “first prebasic” (“post-juvenile”) and “first prealternate” Molt Timing, Extent, and Sequence (“first pre-breeding”) molts, but appeared to involve only a single replacement of feathers. The timing of molts in all four waterfowl Thus, 17 first-year birds collected between 25 taxa and the extent of molts in geese and the February and 12 April showed no evidence of Ruddy Duck (Oxyura) documented here, a separate first prealternate molt (Table 1). correspond closely to those reported in the Subsequently, a first-year male collected on 7 literature (Humphrey and Clarke 1964; May (CAS 13877) and a first-year female col- Palmer 1976; Cramp and Simmons 1977; Ho- lected on 21 May (CAS 12058) were undergo- hman et al. 1992). The apparent temporal 216 WATERBIRDS

shift in the second prebasic (first post-breed- Anatinae, and is rudimentary at best in oth- ing) molt of Ruddy Ducks, from the second ers. Similar results were reported by others autumn to the first spring, may help explain who critically examined this molt (Mendall the supposed “double-wing molt” in this spe- 1958; Oring 1968; Bellrose and Holm 1994). cies (see Jehl and Johnson 2004). The extent In Anas, Melanitta, and other Anatine gen- of both the traditional first prebasic (post-ju- era the traditional “first prealternate” (“first venile) and the traditional definitive preba- pre-breeding”) and “definitive prealternate” sic (adult post-breeding) body molts in (“adult pre-breeding”) molts closely resem- Anatine ducks, however, are considerably ble, respectively, the first prebasic (post-juve- less extensive than previously reported. nile) and definitive prebasic (adult post- The traditional “first prebasic molt” of breeding) molts in Anserinae and the Ruddy Palmer (1976) does not appear to exist in Duck (Fig. 1, Tables 1 and 2). These two sets most genera of Anatinae, and likewise may of molts show parallels in timing, extent by not exist in most or all species of Anas, Aix, body region, and sequence, with replacement or Aythya. Dwight (1914) concluded as much of body-feathers succeeding that of the wings, for scoters, but Palmer describes an exten- and the tertials, longer scapulars, and rec- sive molt during this period. During pro- trices being among the last feathers replaced. tracted molts of several months or more, The traditional definitive prealternate body pigment deposition can vary as a function of molts in most ducks are essentially complete, hormonal change, irrespective of the timing as is typical of prebasic molts in geese, Ruddy of feather replacement (Schiøler 1921; Voit- Ducks, and other birds. By contrast, the tradi- kevich 1966; Oring 1968; Cramp and Sim- tional definitive prebasic body molts in ducks mons 1977; see below). In young male ducks, are highly variable both intra- and inter-spe- feathers renewed earlier during the juvenile cifically, apparently being absent in some in- period (July-August) appear to be cryptic, dividuals within most genera, and thus are whereas those renewed later (September- more typical of prealternate molts in most December) are brightly colored; yet all birds. The molts of the Ruddy Duck differ might be part of the same molt. Thus, clinal from those of other ducks primarily (if not variation in pigment deposition within a sin- solely) in the sequence in which bright pig- gle molt may have resulted in the conclusion ment-deposition occurs in males. Thus, apart that two molts occur when, in fact, each folli- from feather color, the traditional “definitive cle may have been activated only once dur- prealternate” (“adult pre-breeding”) body ing a single protracted molt. Cryptic feathers molts of most Anatinae appear homologous have been noted among the brightly colored with the definitive prebasic (adult post-breed- feathers of first-year male ducks throughout ing) body molts of the Ruddy Duck, and vice the winter and spring (Oring 1968; Palmer versa (Fig. 1). 1976; this study), and these could represent feathers replaced earlier during the tradi- Molt Cycles versus Color-deposition Cycles tional first prealternate molt, before hormon- al changes controlling pigment saturation Humphrey and Parkes (1959) regarded had occurred (see below). Alternatively, plumage brightness as a determinant factor young ducks continue to develop in size in assigning plumage nomenclature in throughout their first autumn (Weller 1957; ducks; however, the mechanisms that con- Oring 1968) and feathers developed during trol season-specific pigment deposition in the juvenile period may represent follicles feathers are complex and differ among vari- that have matured and been activated for the ous taxa of birds (Endler et al. 1988; Owens first time as part of a protracted pre-juvenile and Short 1995; Kimball and Ligon 1999). molt, rather than consisting of a separate Seasonal variation in plumage brightness has molt. In either case, the traditional first pre- been correlated with inter-related fluctua- basic or post-juvenile molt appears to be ab- tions in sex hormones, thyroid secretions, sent in many individuals and species of and pituitary gland activity, each of which is MOLTS AND PLUMAGES OF DUCKS 217 variably influenced by genetic control (Voit- period for attainment of bright rufous feath- kevich 1966; Payne 1972). In Anatinae, the ering in male Ruddy Ducks thus may begin as bright male plumage has been considered early as November, representing a deferred the “neutral” plumage state (Stresemann shift of only 1-2 months from these seasonal- 1948), being masked by more cryptic feath- specific pigment-deposition cycles in other ering in females and summer males by ele- Anatine ducks. Likewise, it appears that the vated levels of estrogen irrespective of second prebasic molt of body feathers can testosterone levels (Voitkevich 1966; Oring begin before this hormonal period subsides, 1968; Greij 1973; Endler et al. 1988), a pat- perhaps as early as April or May, assuming that appears to be unique to Anseri- that the wing molt can complete by this time. formes and among North Variation in these patterns, as related to indi- American orders (Kimball and Ligon 1999). vidual variation in both hormonal activity Thus, if feather pigmentation is to be consid- and molt timing, underscores: (1) that molt ered in defining homologous plumages, the and pigment-deposition cycles are indepen- “neutral” (brightly pigmented) plumage of dent of each other (Voitkevich 1966); (2) the ducks might appropriately be considered need to divorce pigment deposition patterns the basic plumage. Alternatively, because from factors used to determine molt homol- feather-pigment deposition seems to be un- ogies (Howell et al. 2004); and (3) that the der the control of various factors including prebasic molt of the Ruddy Duck correspond the sex hormones, it could be considered to the prealternate molts of Anatinae, with part of “seasonal, reproductive, developmen- plumage differences explained primarily by tal, or other phenomena” (Humphrey and a slight shift in the hormonal cycles that con- Parkes 1959), and therefore should not be a trol pigment deposition. critical factor in determining homologous molts and plumages (see also Howell et al. Molt and Plumage Terminology in Anatinae 2004). The repeated acquisition and loss of brightly pigmented male coloration among Under traditional European terminolo- taxa of the “ (Anas platyrhynchos) gy, the “post-breeding” spring and summer group” in North America and the Hawaiian body molts in adult ducks have been as- Islands, perhaps as determined by no more sumed to be complete and are linked with than two gene pairs (Johnsgard 1961), might the ensuing wing molt (Cramp and Sim- support this conclusion. mons 1977). In addition, this molt occurs be- In the Ruddy Duck, 10 of 25 definitive- fore breeding in females of some ducks (Fig. basic males showed rufous on the bases of 1), resulting in females breeding in “non- some of the longer scapulars and feathers of breeding” plumage. The nomenclature pro- the hind flanks. These are among the last posed by Humphrey and Parkes (1959) feathers replaced during the prebasic molt avoids this latter problem by divorcing molt in ducks (Billard and Humphrey 1972); thus, and plumage terminology from that of the it appears that the hormonal changes result- breeding cycle. However, based upon appar- ing in bright rufous plumage in males were ent homologies with the molts of Anserinae occurring as the prebasic molt was complet- and the Ruddy Duck, it appears that the pre- ing in November, accounting for the deposi- basic and prealternate molts of most Anati- tion of rufous pigment to the bases of these nae have been transposed under the feathers. By contrast, five of six birds collect- conventional H-P system. By re-defining the ed in second-basic plumage showed rufous- molts and plumages of male Anatine ducks tipped feathers to the upper back and upper such that the body molt producing the breast, areas of the body where molt com- bright male (and female) plumages in au- mences, indicating that these birds had be- tumn is considered part of the prebasic molt gun the second prebasic body-feather molt rather than the prealternate molt, an appar- before hormonal changes producing rufous ent homology presents itself that was previ- pigment deposition had subsided. The time ously absent (Fig. 1). 218 WATERBIRDS

Under such a re-interpretation, the puta- Anderson 1983). Thus, the bright plumages tive “first prebasic” molt (Palmer 1976) of of adult male ducks (other than Ruddy Aix, Anas, and Aythya, if it occurs, could be Duck) in late autumn and winter should be considered a presupplemental molt accord- considered basic plumages, which are com- ing to traditional H-P terminology (Thomp- pletely renewed annually as in other birds. son and Leu 1994), or an “auxiliary The ephemeral and highly variable cryptic preformative” molt according to the modifi- plumages found in spring and summer pre- cations of Howell et al. (2003). If present, sumably have evolved more recently, primari- this first autumn molt could be a novel molt ly in those species benefiting from an to replace the smaller and poorer-quality ju- ensuing camouflaged plumage, and thus venal feathers of the face and throat (which should be considered the alternate plumages may become abraded during feeding), and according to H-P terminology. of the breast and flanks (perhaps to improve water repellency and flotation), rather than ACKNOWLEDGMENTS being a more extensive and protracted molt homologous to the traditional first prebasic I thank the following specimen collection curators molt of geese and the Ruddy Duck. Follow- for assistance: Douglas J. Long and Maureen Flannery (MVZ), Carla Cicero (MVZ), Andy Engilis, Jr. (MWFB), ing Howell et al. (2003), the traditional “first Gary Erickson and Jocelyn Hudon (PMA), and James prealternate” molt of Palmer (1976) should Dean and Christina Gebhart (USNM). My understand- be considered the “preformative molt” in ing of molt and plumage strategies and terminology has been greatly enhanced by discussions with Steve N. G. most Anatine ducks, homologous to the pre- Howell, Danny I. Rogers, and Chris Corben. The manu- formative (traditional first prebasic) molts of script benefited from comments by Edward H. Burtt, Jr., geese and Ruddy Ducks (Fig. 1). If only a sin- David F. DeSante, Steve N. G. Howell, Danny I. Rogers, and an anonymous reviewer. Funding for the study of gle first-cycle molt occurs in Ruddy Duck, as molts and plumages was provided to Pyle by the Neotro- suggested by this study, it could be consid- pical Migratory Act (grant #2601) ad- ered the first prealternate molt according to ministered by the U.S. Fish and Wildlife Service. This is Contribution # 207 of the Institute for Bird Populations. the modifications of Howell et al. (2003). It is possible, as experimental studies LITERATURE CITED have suggested (Voitkevich 1966), that molt- ing is a continuous process interrupted by Bellrose, F. C. and D. J. Holm. 1994. Ecology and man- inhibitors accompanying other energy-de- agement of the . Stackpole Books, Me- chanicsburg, Pennsylvania. manding processes such as breeding and mi- Billard, R. S. and P. S. Humphrey. 1972. Molts and plum- gration and, thus, it cannot be categorized ages in the . Journal of Wildlife Man- into evolutionarily meaningful units. It is also agement 36: 765-774. Carney, S. M. 1992. Species, age and sex identification possible that, in response to environmental of ducks using wing plumage. U.S. Fish and Wildlife constraints, molts could shift, change in ex- Service, Washington D.C. tent, and become “offset” (Palmer 1972). For Cramp, S. and K. E. L. Simmons (Eds.). 1977. The birds of the western Palearctic, Vol. I. Oxford University example, relative to ancestral geese, the pre- Press, Oxford, United Kingdom. basic body molts of most Anatine ducks Delacour, J. and E. Mayr. 1945. The . could have evolved to precede the wing molt, Wilson Bulletin 57: 3-55. Dement’ev, G. P. and N. A. Gladkov (Eds.). 1952. Birds become much less complete, and become of the Soviet Union, Vol. IV. Gosudarstvennoe Izda- sexually divergent, while a novel, complete tel’stvo “Sovetskaya Nauka”, Moscow. body-feather replacement following the wing Dwight, J. 1914. The moults and plumages of the sco- ters, Oidemia. Auk 31: 293-308. molt has evolved and remained fairly static in Endler, B., B. Rahmig and E. Rutschke. 1988. On the both sexes and all genera of Anatinae. It hormonal regulation of the sexual and seasonal di- seems considerably more likely, however, morphism of the Mallard (Anas platyrhynchos). Pro- ceedings of the International Ornithological that prebasic molts have remained relatively Congress 2: 2234-2239. static while the hormonal and other mecha- Greij, E. D. 1973. Effects of sex hormones on plumages nisms for brightly pigmented plumage have of the Blue-winged Teal. Auk 90: 533-551. Hochbaum, H. A. 1944. The Canvasback in a prairie evolved according to the constraints of marsh. Monumental Printing Company, Baltimore, breeding and courting regimes (Rohwer and Maryland. MOLTS AND PLUMAGES OF DUCKS 219

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