Screaming Cowbird
Molothrus rufoaxillaris
The screaming cowbird has mildly iridescent black plumage; the lesser under-wing coverts are rufous. The female is slightly duller in colour than the male. The legs are black and the iris is reddish brown. Adult body length is 18–21 cm and mean adult weight is 58 g for males and 48 g for females. The call of the screaming cowbird was first described as "impetuous screaming notes"; however, a more useful description for field identification is noisy, explosive and piercing with rasp-like calls also produced. Screaming cowbirds are mostly seen in pairs or small flocks.
ID text from Wikipedia, CC BY-SA 4.0

Shiny Cowbird
Molothrus bonariensis
The physical appearance of the shiny cowbird adult depends on the subspecies. Sizes range from 31–40 grams (1.1–1.4 oz) in mass and 18 cm (7.1 in) in length (M. b. minimus), to 55–65 grams (1.9–2.3 oz) in mass and 22 cm (8.7 in) in length (M. b. cabanisii). Basic adult plumage for M. b. bonariensis is black with purple-blue iridescence for males, and dusty gray-brown for females. M. b. cabanisii males have plumage similar to M. b. bonariensis, while females are paler in colouration. M. b. aequatorialis males have violet iridescence and females are dark in colour. M. b.
ID text from Wikipedia, CC BY-SA 4.0

Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Screaming Cowbird and Shiny Cowbird.