Appearance

The Caribbean Martin is a typical Progne martin: it is large, steel-blue swallow with a forked tail.  The adult male also has a white belly. The female and immature are similar, but the forecrown is sooty brown, and the throat and breast are gray or gray-brown.

The Caribbean Martin is the most widespread breeding species of Progne martin in the Caribbean, and typically does not overlap with other martins at this season. Purple Martin (Progne subis) is a vagrant to the breeding range of Caribbean Martin. Male Purple Martins are entirely purplish blue (lacking the white belly). Female and immature Purple Martins are more similar to Caribbean, but have a pale forehead, paler sides to the neck, less contrast between the white belly and the dark breast, and the breast usually is paler gray with a scaled pattern.

The nonbreeding distribution of Caribbean Martin is unknown, as are the nonbreeding distributions of several similar species of martins (Cuban Martin Progne cryptoleuca) and Sinaloa Martin (Progne sinaloae). Identification of Caribbean Martin at this season is difficult at best. The male Cuban Martin (Progne cryptoleuca)  is entirely purplish blue, and so easily is distinguished from Caribbean Martin. The male Sinaloa Martin has the same plumage pattern as male Caribbean Martin, but is slightly smaller. Females of Cuban and Sinaloa martins perhaps are not distinguishable from female Caribbean Martin in the field.

The following description primarily is based on Turner and Rose (1989) and Turner (2004); see also Ridgway (1904):

Wings are pointed and the tail of is moderately forked.

Adult male: Most of the body (upperparts, throat, and upper breast) is glossy steel-blue or violaceous steel-blue. The lower breast, belly, and undertail coverts are pure white, except for some dark spots or a dark band across the undertail coverts. Underwing coverts and axillars are gray-brown. Wings and tail are black with a bluish gloss.

Adult female and first-year male: Resembles adult male but duller. The forecrown is sooty-brown. The wings and tail have a greenish-blue gloss. The sides of the head and neck are grayish brown or sooty, the auriculars glossed with steel blue. The malar region, chin, throat, breast, sides, flanks, axillaries, and underwing coverts are sooty-gray or grayish brown; the feathers of the chest (and sometimes the throat) also have indistinct pale gray tips. The lower breast, belly, and undertail coverts are pure white

Juveniles of both sexes are also similar to adult female but with fainter steel-blue gloss on the upperparts.

No information.

The bill is black. Eyes are brown. Legs and feet are brown.

Males (measurements are means of seven small samples, n = 1-7, from different islands; Ridgway 1904):

Wing length (chord): 140.8-148 mm

Tail length: 73.7-76 mm

Depth of fork in tail: 17-20.5 mm

Bill (exposed culmen): 10.9-12 mm

Tarsus length: 13.8-15 mm

Females (measurements are means of six small samples, n = 1-4, from different islands; Ridgway 1904):

Wing length (chord): 135.5-148 mm

Tail length: 69-74 mm

Depth of fork in tail: 14.5-20.2 mm

Bill (exposed culmen): 10-12 mm

Tarsus length: 14-15 mm

Measurements from Hispaniola (Wetmore and Swales 1931):

Males:

Wing length: mean 142.5 mm (range 139.6-146.4 mm, n = 10)

Tail length: mean 72.9 mm (range 69.1-77.3 mm, n = 10)

Culmen from base: mean 12.0 mm (range 11.6-12.8 mm, n = 9)

Tarsus: mean 14.9 mm (range 14.3-15.6 mm, n = 10)

Females:

Wing length: mean 140. 9 mm (range 138.3-144.4 mm, n = 4)

Tail length: mean 71.1 mm (range 68.7-72.5 mm, n = 4)

Culmen from base: mean 12.3 mm (range 11.7-12.7 mm, n = 3)

Tarsus: 14.3 mm (range 13.8-14.9 mm, n = 4)

Mass: 1 male, 38 g; 4 unsexed, mean 40 g (range 39-42 g) (ffrench 1991)