Mangrove Swallow
Tachycineta albilinea
A relatively small swallow, the mangrove swallow is 11–12 centimetres (4.3–4.7 in) long and weighs about 14 grams (0.5 oz). The adult has iridescent blue-green upperparts, white underparts, rump, and undertail- and wing-coverts, and blackish tail and flight feathers. The feathers are greener when fresh and bluer when worn. The white underparts sometimes have faint, dark shaft streaks. The bill is small and black, about 11 millimetres (0.43 in) long. The iris is a dark brown, and the tarsus and toes range in colour from black to fuscous-brown.
ID text from Wikipedia, CC BY-SA 4.0
Tree Swallow
Tachycineta bicolor
The tree swallow has a length between about 12 and 14 cm (4.7 and 5.5 in) and a weight of approximately 17 to 25.5 g (0.60 to 0.90 oz). Wingspan ranges from 30 to 35 cm (12 to 14 in). The male has mostly glossy blue-green upperparts, the wings and tail being blackish. The underparts and the cheek patch are white, although the underwing coverts are gray-brown. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is duller in color than the male, and sometimes has a brown forehead. Voice: The tree swallow's song consists of three parts: the chirp, the whine, and the gurgle. These sections may be repeated or omitted, and all can stand alone.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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