Appearance

Molts And Plumages

Descriptions based on Eastern Goldfinch, C. t. tristis. Individuals vary in “brightness” and wear of plumages within and between age classes (Yunick 1983, Pyle et al. 1987). Molt sequences and schedules, as described below, and structural differences in feather generations described by Middleton (1977b, 1978, 1986). Colors from Smithe (1975-81).

Hatchlings

Body and head covered with light grayish natal down, 5 to 6 mm long on frontal and occipital regions of head in a horseshow shape from the frontal to the occipital region, then back to the frontal region. Down of the mid-dorsal, scapular, femoral and humeral regions about 5 mm long and that on abdominal 2 mm. Down also found on wings (Mousley 1932, Walkinshaw 1939).

Juvenal Plumage

Plumage recognizable by 12th d post hatching, but feathers still growing. Crown, nape, ear coverts and back, buff; rump, olive brown fading to sulphur yellow to white upper tail coverts; Throat and side neck olive yellow; breast and flanks clay color; belly clay color shading to white vent. Remiges and rectrices, dusky brown (male) or dark grayish brown (female) with clay color white tips and margins on both edges but more extensive on leading edge of proximal 3 secondaries; remiges with large terminal white areas on inner vane; males with extensive white on leading edge of medial primaries extending beyond coverts (Middleton 1974); greater coverts dusky brown, broad clay color tips; median coverts dusky brown, broad clay colored tips; lesser coverts olive yellow.

Basic I Plumage

Prebasic I molt from mid-Sep through early Jan (Middleton 1977b). Complete body (i.e. not remiges, rectrices) molt, except greater and usually median primary and secondary coverts. Early fledglings molt earlier than later fledglings.

Male: compared to Juvenal plumage, dorsal surface is darker brown, strongly tinged with olive yellow on head and often elsewhere; grayish neck collar; upper tail coverts are smoky gray with brown edgings. Ventral surface duller; abdomen and under tail coverts white; breast brownish olive gray; sides and flanks strongly washed with wood brown. Throat yellow.

Female: very similar to male except females have duller and less extensive yellow throat and less olive yellow tinging elsewhere.

Alternate I Plumage

Male: through prolonged Prealternate I molt (Fig. 6; Middleton 1977b), sex becomes identifiable with gradual appearance of sulphur yellow feathers on chin, throat, and foreneck, and isolated black crown feathers. Main molt occurs mid-Mar to mid-Jun to produce sulphur yellow body feathering (range may vary through spectrum yellow to orange yellow); forehead, crown, and lores black; Juvenal remiges, rectrices and coverts retained, clay colored tips worn.

Female: molt pattern similar to male. Head, sides of neck, and back citrine shading to olive yellow on rump; throat, breast, flanks olive yellow; belly sulphur yellow; vent white. Some females can be brighter with sulphur yellow being predominant body color. Juvenal remiges, rectrices, and coverts retained, now distinctly fuscous, possibly through fading, tips worn.

Definitive Basic Plumage

Plumage acquired during complete (i.e. all feathers) Prebasic II molt, requires about 75 d (Middleton 1977b), extending from mid-Sep to mid-Dec (Fig. 6 ). Males begin molt about a week in advance of females and complete molt earlier. Considerable individual variation depending on stage of nesting cycle (Middleton 1977b ), and geographical location (Mundinger 1972, Wiseman 1975). Bulk of breeding population at Guelph, ON, molt between mid-Aug and late Oct to early Nov (Fig. 6 ; Middleton 1977b). Molt begins with shedding of first primary and ends with complete growth of 9th primary. Primaries molted centrifugally from 1–9. Secondary molt begins with shedding of #8 when primaries 3 or 4 shed; completed before primary molt ends. Secondaries 1–6 molted centripetally simultaneously with 8, 7 and 9, in given order. Coverts molted with corresponding remiges. Alular feathers molted simultaneously between shedding of 4th or 5th primary and before 9th primary dropped. Tail molt begins with shedding of primaries 4 or 5; completed before primary molt. Rectrices molted centrifugally from 1–6. Body molt begins on head; proceeds posteriorly. Difficult to determine precise start and finish (Middleton 1977b).

Male: body feathering resembles Juvenal plumage but distinctly citrine on crown, nape, lores, back and flanks; chin, throat, and breast straw yellow; belly and vent white. Remiges and rectrices jet black with distinct white margination, more extensive on proximal 3 secondaries. White leading edge of medial rectrices no longer projects beyond coverts. White on vane of rectrices noticeably more extensive than in Juvenal plumage. Greater coverts jet black, white tipped; median and lesser coverts straw yellow.

Female: body feathering resembles Juvenal plumage but distinctly more olive green on crown, nape, lores, back and flanks; chin, throat, and breast olive yellow; belly and vent white. Remiges and rectrices fuscous, faint clay color to white margination, more extensive on proximal 3 secondaries. White on vane of rectrices more extensive than in Juvenal plumage. Greater coverts fuscous, faint clay colored to white tipped; median and lesser coverts citrine.

Definitive Alternate Plumage

Fig. 6 ; Middleton 1977b). At Guelph, ON, first birds in “recognizable” Alternate plumage appear with regularity in second week of Apr. Resembles Alternate I plumage, in both sexes, except remiges, rectrices, and greater coverts, retained from First Basic plumage, now jet black and white tipped (males), or fuscous with faint clay color to white tips (females). Secondary and lesser coverts either sulphur yellow (male) or olive yellow (female).

No subsequent age-related changes known; Basic and Alternate plumages continue to replace each other annually. Basic contour plumage heavier than Alternate plumage (Dawson and Carey 1976, Middleton 1986). For C. t. salicamans in California, all molts 1–2 mo earlier than for other subspecies (Dwight 1902). In some areas, Prealternate molt apparently suppressed and individuals never gain complete Alternate plumage (Tyler 1968).

Coloration

Alternate Plumage

Considerable attention paid to the nature and function of sexually selected carotenoid pigmentation in feathers and bill. Canary xanthophylls, metabolically derived from two dietary carotenoids (lutein and zeaxanthin), color the plumage and beak of both sexes (McGraw et al. 2001); almost no melanin is present in yellow feathers of males (McGraw 2004a). Yellow feathers reflect some ultraviolet (UV) light, which is the result of full-spectrum light scattering from white feather keratin; carotenoids create color by absorbing light in the middle (indigo-blue; 435-485 nm) wavelengths, leaving UV and yellow wavelengths to be reflected (Shawkey and Hill 2004). Variation in carotenoid concentration explains the majority of variation in feather coloration (Shawkey et al. 2006). Color expression not age dependent (McGraw and Hill 2000, MacDougall and Montgomerie 2003).

Correlationally, plumage and beak color linked to body condition, and some attributes of plumage color (back plumage and cap symmetry) associated with genetic diversity (Tarvin and Rosen 2006), suggesting important short- and long-term information content of these traits. Experimentally, dietary manipulations of carotenoids influence extent of coloration (McGraw et al. 2002), as occurs for most such avian ornaments. Interestingly, in captivity individuals are capable of growing orange plumage if fed orange or red dietary pigments (i.e. canthaxanthin) (McGraw et al. 2001), although females still prefer to mate with naturally yellow-colored males (Hill and McGraw 2004). Certain natural pigments (i.e. zeaxanthin) appear more valuable for synthesizing the canary xanthophylls that are used in coloration (McGraw et al. 2004), but in wild birds the most colorful individuals are those with more of all types of dietary and plumage pigments (McGraw and Gregory 2004).

Calorie restriction also impairs carotenoid coloration (McGraw et al. 2005), presumably via its impact on pigment metabolism, which occurs in the feather follicles and beak keratinocytes themselves (McGraw 2004b). Considerable variation shown on standard diet suggests physiological control of color as well (McGraw and Hill 2001), which may include disease impacts (see Mortality And Disease). Although carotenoids commonly play a role as antioxidants and immuno-enhancers in animals, no such evidence in this species (Navara and Hill 2003).

Basic Plumage

Colors equally if not more variable than in the Pre-Alternate plumage; individuals with larger black areas of color in the cap during winter have yellower body plumage, leaving open the possibility of a non-breeding-season function to these ‘remnant’ colors (McGraw 2004).

Cranial Ossification

Pattern of skull ossification is unusual, beginning posteriorly and progressing anteriorly (as opposed to peripheral pattern of most small passerines) so that near completion of ossification only a remnant of unossified, skull remains at the anterior margin of the skull adjacent to the posterior orbital margin (Yunick 1979). Ossification is slow and may not be completed until at least Feb of their second year. Earliest date of complete ossification is unknown (C. Thompson pers. comm.).

Bare Parts

Bill

Color changes concurrently with plumages. Change under hormonal control and indicative of breeding condition (Mundinger 1972). Juvenal condition and throughout first winter, bill dark grayish brown. With Prealternate molt, bill gradually changes color, from base of bill outwards, to orange yellow (extreme spectrum orange). See Coloration above for discussion of beak color variation among individuals. Dark tip persists. Reversion to basic dark grayish brown begins with Prebasic molt. During breeding season, bill more intensely colored in males than females. In nestlings, gape flanges cream color, mouth lining geranium pink.

Iris

Iris dusky brown. No known change with age or sex.

Legs And Feet

Color changes in harmony with plumages. Juvenal and throughout first winter, legs and feet dark grayish brown. With Prealternate molt, legs and feet raw umber, with some even approaching buff. Carotenoid-containing, though dilute compared to beak and feathers (KJM). Reversion to basic dark grayish brown occurs with Prebasic molt. Little difference in color between the sexes.