Appearance

The Chilean Swallow is a standard Tachycineta, blue above with white underparts; like several other species of Tachycineta, it also has a white rump.

The Chilean Swallow is one of five species of South American Tachycineta swallows with a white rump; the other species are Tumbes Swallow (T. stolzmanni), White-winged Swallow (T. albiventer), White-rumped Swallow (T. leucorrhoa), and Mangrove Swallow (T. albilinea). The Chilean Swallow is more blue above than these congeners, lacking the greenish tones on the upperparts of the other species. It also does not overlap geographically with Tumbes and Mangrove Swallows. White-winged Swallow easily is distinguished by the large amount of white on inner wing coverts and secondaries.

The Chilean Swallow is closely similar to the White-rumped Swallow, however, and although the breeding ranges have little or no overlap, the Chilean Swallow migrates north into the range of the White-rumped. In addition to the somewhat greener tones to the upperparts, the White-rumped Swallow has a narrow white line on the lores, a feature that is absent (typically) or greatly reduced in Chilean (Ridgely and Tudor 1989). Also, the underwing coverts of White-rumped Swallow are paler (white, rather than light gray as in Chilean; Schulenberg et al. 2007).

The following description is based on Turner and Rose (1989) and Fjeldså and Krabbe (1990):

Adult: The upperparts are deep metallic blue, other than a white rump; some feathers on the rump may have a small dark spot along the shaft. The uppertail coverts are black. The lores are black, although there sometimes there are a few white feathers over the bill or on the lores; the auriculars are black with a blue gloss. The feathers of the lower breast, especially those at the side of the breast, have dark bases, sometimes producing a narrow dark mark on the sides of the breast. The remiges are brownish black, the tertials and inner secondaries with narrow white tips when fresh. The under wing coverts are light grayish or grayish brown.

Tail slightly forked.

Juvenile: Similar to the adult, but duller and browner above, with only upper back and wing coverts glossy.  Upper tail coverts blackish tipped with white instead of being completely black.  Usually has a narrow line of white feathers above the lores.

No information.

Data from Turner and Rose (1989):

Iris dark brown.

Bill, tarsi, toes black.

Linear measurements from Turner and Rose (1989):

Mass: mean 17 g (range 15-20 g; Turner and Rose 1989); mean 14.9 g (range 14-16 g, SD 0.6, n = 21 males; Egli 1996, in Dunning 2008).