A. “Many birds occasionally mate with members of other bird species, producing hybrid offspring,” said Irby J. ... Lovette said, about 10 percent of the world's 10,000 bird species are known to have bred with another species at least once, either in the wild or in captivity.

Are there any bird hybrids?

In the wild, some of the most frequently reported hybrids are waterfowl, gulls, hummingbirds, and birds-of-paradise. ... Numerous gamebird, domestic fowl and duck hybrids are known. Captive songbird hybrids are sometimes called mules. Numerous hybrid macaws exist in aviculture and occasionally occur in the wild.

Can Cardinals and Bluejays crossbreed?

But whatever color a blue jay/cardinal mix might be, Marilyn's answer was that the birds "belong to different species, so they won't crossbreed." She is right about blue jays and cardinals--no crossbred specimens are known.