In the real world there's no such thing. You're going to have to be a lot more specific in order for us to pick out which specific mythological creature you might be talking about, but I'll take a guess:
A harpy is a mythological creature which has the lower body and wings of a bird, and the head of a human. In between, whether the body is birdlike or humanlike varies from source to source, but usually they are described as having human breasts (harpies are almost invariably female).
At 37,000 feet, the bird is likely a High-flying bird such as bar-headed geese or Rüppell's griffon vulture.
no
The word "Ba" represented as a bird or a human headed bird.the word "Ba" means soul
yes
eagle
The distinctive elements of a bird-headed man, a bison, and a rhinoceros lie in their symbolic and representational meanings in art and mythology. The bird-headed man often symbolizes a connection between the spiritual and earthly realms, while the bison represents strength, endurance, and the natural world. The rhinoceros, with its formidable presence, can embody power and resilience. Together, these figures highlight the interplay between human traits, animal symbolism, and cultural narratives.
The Striped-headed Tanager is the representative bird of Puerto Rico.
brown headed cow bird
A Cotton Headed Ninny Muggins
The most well-known bird to do this is the Cuckoo.
Yes
The Sphinx structure was headed The Lion