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COWBIRDS (GENUS MOLOTHRUS)

(3 species). Medium-size to large blackbirds of open and

semi-open country, often found around livestock. Ages/sexes differ slightly to distinctly, attain adult

appearance in a few months; males slightly to distinctly larger than females. Brood parasites of various

species; hence begging young cowbirds are found singly, being fed by sundry species but not by cowbirds.

BRONZED COWBIRD  Molothrus aeneus 19–22cm, male>female. Ranchland

(often around livestock), open country with scattered trees, hedgerows, parks in

towns and urban areas; more often woodland and forest edge in breeding

season. Singles and small groups in breeding season; flocks locally to 100s at

other times. Feeds on ground, tail often slightly cocked; roosts communally in

trees, often with grackles. Perches readily in trees and on phone wires; male in

display expands neck ruff and hovers in front of female, singing. Flight strong

and direct, often in fairly tight, slightly undulating flocks. Best identified by

stout, deep-based bill, reddish eyes (fiery-red on male, duller on female and

imm.); adult male wings have glossy bluish sheen. Juv dark sooty brown to dull blackish overall, sometimes

with fine pale wingbars, faint pale streaking on belly, like duller version of adult by winter. Cf. Shiny

Cowbird. SOUNDS: High, thin, tinny whining trills and wheezy squeaks, at times suggesting European

Starling Sturnus vulgaris. Spluttering, chattering rattle, 1–2 secs (mainly female). Song a varied series of

high whining whistles, at times mixed with short quiet gurgles. STATUS: Uncommon to fairly common on

both slopes, locally to 1800m; least numerous in drier Northwest. (Mexico and sw. US to Panama.)

SHINY COWBIRD  Molothrus bonariensis Male 23–24cm, female 20–21.5cm.

Ranchland (often around livestock), open country with scattered trees, parks in

towns and urban areas, feeders. Habits much like Bronzed Cowbird, and at

times can be found together with that species. Shiny is slightly larger than

Bronzed, with shallower, more pointed bill. Male has glossy purplish-blue head

and body, dark eyes; also cf. Melodious Blackbird. Female distinctive, with

plain pale gray-brown underparts. Juv. warmer-toned than female with dark

streaking above and below (unlike plain, dark juv. Bronzed Cowbird), like

duller version of adult by winter. SOUNDS: Male gives high thin seeíh; both sexes

(mainly female) give clucking or bubbling rattle, 1–2 secs, averaging lower than Bronzed Cowbird. Song

a high, slightly metallic to fairly sweet warble, usually overall descending, 1.5–4 secs, often preceded by

series of (usually 4–8) low, wet gulping grunts that can be given separately. STATUS: Uncommon and local

on s. Pacific slope, rare to uncommon locally but spreading to n. Pacific slope and on Caribbean slope;

mainly below 1500m, rarely wanders to 2400m. First recorded Costa Rica in 2004. (Caribbean and S

America.)

GIANT COWBIRD  Molothrus oryzivorus Male 32–36 cm, female 28–30.5cm.

Semi-open country and ranchland with taller trees, hedgerows, forest edge and

clearings; brood parasite of oropendolas and caciques. Mostly seen in flight,

often fairly high overhead, as singles or small loose groups: note distinctive,

strong, flap-flap-flap-glide progression, unlike steadier wingbeats of Great-tailed

Grackle. Feeds on ground around livestock, along riverbanks, but arboreal at

oropendola colonies. Much larger than other cowbirds; note thick neck that

contributes to rather small-headed look; in flight note pointed wings, thick

neck, squared-off tail; cf. grackles. Juv. has pale bill, pale to brownish eye; soon

resembles duller version of adult. SOUNDS: Sharp clucks and chatters mainly in interactions. Song a short,

slightly jerky or discordant series of harsh, semi-metallic whistles. STATUS: Uncommon to fairly common

on Caribbean slope and s. Pacific slope, less numerous and more local on n. Pacific slope; locally to

1800m. (Mexico to S America.)