Appearance

Amaurospiza seedeaters are small finches with a thick conical bill. Male Blue Seedeaters are uniform blackish with a noticeable blue gloss. Females are warm cinnamon brown and otherwise unmarked. Juveniles are similar to females but are brighter and more rufous below, with cinnamon wingbars.

Blue Seedeater overlaps, from southern Mexico south to Honduras, with the similar Blue Bunting (Cyanocompsa parellina). Blue Bunting usually occupies thickets and forest edge, not bamboo, and is stockier with a larger bill. Male Blue Bunting is dark blue, but is lighter blue on the forecrown and face, wing coverts, and rump. Plumages of female Blue Seedeater and Blue Bunting are very similar; female Blue Bunting is best distinguished by its larger bill and by habitat. Blue-black Grosbeak (Cyanocompsa cyanoides) is much larger than Blue Seedeater, with a much larger, thicker bill. Slaty Finch (Haplospiza rustica) has a more slender, pointed (less conical) bill. Blue-black Grassquit (Volatinia jacarina) is much smaller and occopies more open habitats.

The following description is based on Ridgway (1901), Wetmore et al. (1984), and Howell and Webb (1995), and refers to nominate concolor; see also Geographic Variation:

Adult male: Body and wing coverts slate blue. Remiges black, edged with slate blue.

Adult female: Upperparts cinnamon brown. Remiges dusky brown, edged cinnamon brown. Underparts tawny.

Immature: Similar to adult female.

Juvenile: Similar to adult female, but plumage brighter, with dull cinnamon wingbars.

Little information. The second Basic Molt (sensu Howell et al. 2003) is complete (Orr and Ray 1945).

Iris: brown, dark brown

Bill: dark gray, or bill dusky, terminal third of mandible whitish

Tarsus and toes: dark gray, dusky

Bare parts color data from Griscom (1934) and Wetmore et al. (1984).

Total length: 11.5 cm (Stiles and Skutch 1989), 12-14 cm (Howell and Webb 1995), 12.5 cm (Ridgely and Greenfield 2001b)

Linear measurements (from Wetmore et al. 1984; concolor):

male (n = 10)

wing length: mean 62.2 mm (range 60.0-67.0 mm)

tail length: mean 49.8 mm (range 42.0-53.3 mm)

bill length (culmen from base): mean 11.5 mm (range 10.5-12.3 mm)

tarsus length: mean 16.9 mm (range 15.1-19.0 mm)

female (n = 10)

wing length: mean 60.1 mm (range 58.0-62.0 mm)

tail length: mean 50.0 mm (range 47.6-53.1 mm)

bill length (culmen from base): mean 11.4 mm (range 10.2-12.7 mm)

tarsus length: mean 17.2 mm (range 16.0-18.1 mm)

linear measurements (relicta; from Griscom 1934 and Orr and Ray 1945)

male (n = 3)

wing length: mean , 69.7 mm (range 69-70.2 mm)

tail length: mean 61.1 mm (range 59-63.0 mm)

bill length: 9.5 mm (n = 1; Griscom 1934)

tarsus length: 19 mm (n = 1; Griscom 1934)

female (from Orr and Ray 1945; n = 1)

wing length: 68.1 mm

tail length: 58.3 mm

linear measurements (aequatorialis; from Hellmayr 1938)

wing length 61 mm (male? n = 1?), female 55-57 mm; tail length 47-52 mm; bill length 9-10 mm

Mass: mean 13.1 g (range 12-15 g, n = 6, sexes combined; Dunning 2008)