Cassin's Kingbird
Tyrannus vociferans
Adults have a gray head with slightly darker cheeks; a dark unforked tail with a buffy fringe and gray-olive underparts. They have a pale throat and deep yellow lower breast. Juveniles are duller and have pale edges on their wings. Measurements: Length: 8.3–9.1 in (21–23 cm) Weight: 1.6 oz (45 g) Wingspan: 41 cm Cassin's kingbird and the western kingbird are similar in appearance. Cassin's is a little larger than the western and the upper parts are a darker gray than the western.
ID text from Wikipedia, CC BY-SA 4.0
Grey Kingbird
Tyrannus dominicensis
The adult gray kingbird is an average-sized kingbird. It measures 23 cm (9.1 in) in length and weighs from 37 to 52 g (1.3 to 1.8 oz). The upperparts are gray, with brownish wings and tail, and the underparts are white with a gray tinge to the chest. The head has a concealed yellow crown stripe, and a dusky mask through the eyes. The dark bill is heavier than that of the related, slightly smaller, tropical kingbird. The sexes are similar, but young birds have rufous edges on the wing coverts, rump and tail.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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