Brown-chested Martin
Progne tapera
The brown-chested martin is 16 to 18 cm (6.3 to 7.1 in) long and weighs 30 to 40 g (1.1 to 1.4 oz). The sexes have the same plumage. Adults of the nominate subspecies have a mostly sandy brown head with a white chin and throat. Their upperparts are sandy brown. Their tail is slightly forked; it and their wings are a darker brown than the upperparts. Their underparts are mostly white with an indistinct brown band across the breast. Subspecies P. t. fusca is larger and overall darker than the nominate with a more defined breast band and dusky markings on the lower breast and belly. Voice: The brown-chested martin's song is "harsh and guttural with series of gurgling sounds". It has been described in more detail as "a series of liquid, rolling, descending trills, for example trr-tee-tuk-TEEERRR...trr-tee-tuk-TEEERRR...". Its calls are "a dry, buzzy djzeut and a more musical dureet".
ID text from Wikipedia, CC BY-SA 4.0
Grey-breasted Martin
Progne chalybea
The grey-breasted martin is 16–18 cm (6.3–7.1 in) in length and weighs 33–50 g (1.2–1.8 oz). It has a forked tail and relatively broad wings. The adult male is glossy blue-black with the grey-brown throat, breast and sides contrasting with the white lower underparts. The female is duller than the male with a paler throat; the juveniles have dull brown upperparts.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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