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
Violet-green Swallow
Tachycineta thalassina
The distinct body form of swallows distinguishes them from other passerine birds. Their long pointed wings and slim, streamlined body evolved to catch insects while in flight; the violet-green swallow is no exception. With an average body length of 12–13 cm (4.7–5.1 in), the violet-green swallow is slightly shorter and appears more compact in flight compared to some other members of the genus Tachycineta. The violet-green swallow most closely resembles the tree swallow T. Voice: There are many knowledge gaps surrounding the vocalization behaviour of violet-green swallows. These gaps include vocalizations made during early development, alarm calls and the daily pattern of calls. The little information available suggests two main classes of vocalizations, the chee-chee calls and twitter calls.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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