Black-tailed Gnatcatcher
Polioptila melanura
The black-tailed gnatcatcher reaches about 4.5 to 5 inches in length, much of it taken up by a long black tail lined with white outer feathers. The body is blue-grey, with white underparts, and while it is similar to the blue-grey gnatcatcher, the two birds are differentiated by the amount of black in the tail feathers. The male has a black cap during the summer that extends to the eyes. Females and winter males, lacking the black cap, are difficult to distinguish from the blue-grey gnatcatcher.
ID text from Wikipedia, CC BY-SA 4.0
Blue-grey Gnatcatcher
Polioptila caerulea
It is 10–13 cm (3.9–5.1 in) in length, 6.3 in (16 cm) in wingspan, and weighing only 5–7 g (0.18–0.25 oz). Adult males are blue-gray on the upperparts with white underparts, slender dark bill, and a long black tail edged in white. Females are less blue, while juveniles are greenish-gray. Both sexes have a white eye ring. Voice: The songs (and calls) are often heard on breeding grounds, (usually away from nest) and occasionally heard other times of the year. Calls: "zkreee, zkreee, zkreee", Songs: "szpree zpree spreeeeey spree spre sprzrreeeee"
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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