Plumages, Molts, and Structure

Bachman's Warblers have 9 functional primaries, 9 secondaries (including 3 tertials), and 12 rectrices. No geographic or sex-specific variation in molt strategies reported or to be expected in a monotypic species with relatively restricted historical range.

Following based primarily on detailed plumage descriptions of Brewster (1891, Brewster 1905 Brewster, W. (1905). Notes on the breeding of Bachman's Warbler, Helminthophila bachmanii (Aud.), near Charleston, South Carolina, with a description of the first plumage of the species. Auk 22:392-394. Close ), Ridgway (1902), Bent (1953), Hamel and Gauthreaux (Hamel and Gauthreaux 1982 Hamel, P. B. and Jr. Gauthreaux, S. A. (1982). The field identification of Bachman's Warbler (Vermivora bachmanii Audubon). American Birds 36 (3):235-240. Close ), Curson et al. (1994), and Dunn and Garrett (1997), as well as examination of 76 specimens by PBH; Hamel and Gauthreaux (Hamel and Gauthreaux 1982 Hamel, P. B. and Jr. Gauthreaux, S. A. (1982). The field identification of Bachman's Warbler (Vermivora bachmanii Audubon). American Birds 36 (3):235-240. Close ) analyzed published descriptions and illustrations of the plumage. See also Robbins (1964) and Pyle (1997a) for specific age- and sex-related criteria. Sexes show similar appearances in Juvenile Plumaged but specific plumages thereafter. Definitive Basic Plumage acquired usually by Second Prebasic molt, rarley(?) by Third Prebasic molt, and rarely by Preformative Molt. This based on speculation on the variation in extent of black patches on crown and breast of fall male specimens with and without fully pneumatized skulls examined by PBH.

Natal Down

Not described.

Juvenile (First Basic) Plumage

Present Apr-Jul and probably was not kept for long, so poorly known. See Brewster (Brewster 1905 Brewster, W. (1905). Notes on the breeding of Bachman's Warbler, Helminthophila bachmanii (Aud.), near Charleston, South Carolina, with a description of the first plumage of the species. Auk 22:392-394. Close ) and Curson et al. (1994) for descriptions and illustration, although parts of these descriptions may represent developing Formative Plumage. Juvenile Plumage overall buffy or dusky, darker above, lighter below, and darker on the wings. Crown, head and upperparts faded hair brown; middle of crown perhaps tinged ashy and lower upperparts perhaps tinged olive in some birds (if not incoming formative feathers); greater and middle wing coverts brownish, broadly tipped with light brown, forming two well-marked wing-bars; chin and throat brownish white; sides of throat smoke gray; remainder of underparts ashy white. Yellow may have occurred to variable extent on underparts of Juvenile Plumage or descriptions of this may have been based on incoming formative feathers. Remainder of wing and tail retained during preformative molt and described under Formative Plumage. Except for amount of white in rectrices (see Formative Plumage) juvenile male and female probably alike, although Brewster (Brewster 1905 Brewster, W. (1905). Notes on the breeding of Bachman's Warbler, Helminthophila bachmanii (Aud.), near Charleston, South Carolina, with a description of the first plumage of the species. Auk 22:392-394. Close : 393) quotes Wayne that on the young female “the yellow on the sides of the breast is very much paler and more restricted and the back is not greenish, but brownish.” Wayne's description may or may not have been influenced by incoming Formative Plumage.

Formative Plumage

"First Basic" or "Basic I" plumage of Pyle (1997a) and previous authors. Present Sep-Aug. Differed from Definitive Basic Plumage as follows: Male had fewer black feathers on crown, smaller black patch on throat, less yellow in upper secondary coverts, and smaller white patches on outer rectrices. Plumage pattern became sharper, less veiled by spring, apparently resulting from wearing off of light tips to the black feathers of breast and crown and yellow feathers of breast. Some spring males appear to have had more black feathers on crown and larger black throat patches than fall males, leading to speculation that a First Prealternate Molt may have occurred (see Prealternate Molts, above), but this also might result from protracted and suspended Preformative Molt on the winter grounds (see also Definitive Basic Plumage, below). Females much more faintly marked than Definitive Basic females; forehead with small amount of dull yellow; crown and nape olive-gray; eye-ring whitish; throat faint yellow or light drab; upperparts yellowish olive-green; underparts light drab; wings and tail dark brownish olive, hair brown, or dark drab; rectrices with little or usually no white.

In both sexes Formative Plumage can be further distinguished from Definitive Basic Plumage by having duller and browner retained juvenile primary coverts, contrasting with newer formative greater coverts, and thinner and more pointed (juvenile) outer primaries and rectrices (Pyle 1997a).

Definitive Basic Plumage

Present Sep-Aug. Male forehead, eye-line, malar region, chin, and eye-ring spectrum yellow; crown black grading to olive-gray on nape; auriculars dusky, drab, or olive-gray; upperparts olive-green, brighter yellowish on rump; underparts spectrum yellow grading to lighter on undertail coverts, with a black patch of variable size on throat and upper breast; flanks light drab or drab gray; background color if wings and tail dark brownish olive, hair brown, or dark drab; bend of wing and upper secondary coverts variably washed spectrum yellow; inner webs r2-r6 with white patches that vary in shape and extent, typically outer pair (r6) having largest patch, extending over approximately half of the inner web of the feather but not to the tip of the rectrix, and pairs r2-r5 having successively smaller patches which occupied more central areas of the feather (sometimes lacking on r2); central rectrices (r1) lacked white patches. Females generally paler than males; forehead light spectrum yellow and chin light spectrum yellow or light drab; eye-ring whitish; crown and nape olive-gray, grading to drab or drab gray on neck; upperparts yellowish olive-green, brighter on rump; underparts light spectrum yellow or light drab grading to grayish on flanks and whitish crissum, the throat with darker drab gray patch and with or without a few black feathers; wings and tail as in male but bend of wing and upper secondary coverts with much duller and more olive-tinged yellow than in male ,and rectrices with smaller and less-distinct white patches on respective feathers, sometimes very indistinct or lacking.

Males and females in Definitive Basic Plumage further separated from those in Formative Plumage by having duskier and olive-edged primary coverts, not contrasting in feather quality with greater coverts, and broader, more truncate and duskier outer primaries and rectrices, the latter averaging larger white patches per feather and by sex (Curson et al. 1994, Pyle 1997a).

Definitive Prealternate Molt not observed and probably does not exist (see above). Black feathers on crown, throat, and breast tipped with dusky and yellow feathers of underparts were paler-tipped in fresh fall plumage; these tips apparently wore off to produce brighter appearance in spring. This change more distinct and apparent in males but also occurred in females.

Molt and plumage terminology follows Humphrey and Parkes (1959) as modified by Howell et al. (2003, 2004). Bachman's Warbler probably exhibited a Complex Basic Strategy (cf. Howell et al. 2003, Howell 2010), including complete prebasic molts and partial preformative molt but no prealternate molts (Bent 1953; Curson et al. 1994; Dunn and Garrett 1997; Pyle 1997a, 1997b; Fig. 5). Existence of limited prealternate molts (feathers replaced twice during a molt cycle) reported by Bent (1953), Pyle (1997a) and others but this molt probably does not occur (see below). Definitive molt cycle commenced with Second Prebasic Molt.

Prejuvenile (First Prebasic) Molt

Presumably complete (Apr-Jul) and occurred in the nest, as in other altritious birds. No information on timing or sequence of pennaceous feather irruption and development.

Preformative Molt

"First prebasic" or "Prebasic I" molt of Pyle (1997a) and previous authors. Partial, May-Aug, on breeding grounds. Less than 6 specimens in Juvenile Plumage examined by PBH and all showed some evidence of Preformative Molt, indicating this molt occurs shortly after leaving nest, as in other wood-warblers (Curson et al. 1994). Of 76 specimens examined by PBH, 17 were undergoing molt; specimens in Preformative Molt collected from 1 May (1907, Charleston Co., SC; Museum of Comparative Zoology [MCZ] #306637) to Aug (1892, King William Co., VA; U.S. National Museum [USNM] 135001 also 28 Aug 1890, Monroe Co., FL; California Academy of Science [CAS] #14494). Preformative Molt includes most or all body plumage and secondary coverts but no primary coverts, primaries, secondaries, or rectrices. Three of nine specimens in Formative Plumage had 1-2 outer juvenile greater coverts retained (Pyle 1997b).

First And Definitive Prealternate Molts

Prealternate Molts probably did not exist. Reportedly limited to some feathers of head and throat (Jan-Apr, on non-breeding grounds) but acquisition of breeding appearance more likely resulted from wearing of buff feather veiling (see Definitive Basic Plumage, below), as in other warblers and birds originally presumed but not confirmed to have prealternate molts. If feather replacement existed on winter grounds it may also have represented protracted Preformative or Prebasic molts.

Definitive Prebasic Molt

Complete, Jun-Sep, reportedly on or near breeding grounds although small proportion of specimens taken in Cuba in Sep have molt on head and neck (e.g., USNM #454255, Oriente Prov., 25 Sep 1907), suggesting it could have completed after migration in at least some birds. Sequence very likely as in other wood-warblers: primaries replaced distally (p1 to p9), secondaries replaced proximally from s1 and proximally and distally from the central tertial (s8), and rectrices probably replaced distally (r1 to r6) on each side of tail, with some variation in sequence of rectrix replacement possible.

Most collectors failed to note colors of bare parts on specimen labels. Following notes from specimen labels (PBH examination):

Bill And Gape

Raw umber or brownish horn, paler at base in younger birds, apparently becoming darker in older birds.

Iris

Color not noted.

Legs And Feet

Brown, dark brown, bluish horn (1 bird), greenish horn (1 bird). Soles of feet brown, dark brown, yellowish, or bluish horn (1 bird).

Linear Measurements

Data shown as mean (SD). Sample size for males: 191; females: 60. Bill length (exposed culmen, mm): males 11.7 (0.62); females 11.5 (0.59). Wing chord (mm): males 60.2 (1.67); females 57.4 (1.45). Tail length (mm): males 42.3 (2.12); females 40.7 (1.62). Tarsus length: males 16.2 (0.62); females 16.1 (0.76).

Mass

No live individual has ever been weighed.