Definition of "birddom"

The parrot particularly, which may be considered the autocrat of the feathered tribes leads all birddom in the number and variety of diseases to which it is subject.

1895, Walter F. Webb, The Museum: A Journal Devoted to Research in Natural Science, volumes 1-3, page 337

As March creeps into April, the panoply of summer birddom has begun to reassemble.

1996, Tom Horton, An Island Out of Time: A Memoir of Smith Island in Chesapeake Bay, page 280

I doubt there is a zoo in the world which doesn't have at least a few of these gorgeous creatures strutting through the grounds, from time to time deigning to show off the most extravagant plumage in all of birddom.

2006, David Moyle, Living With Peacocks, page 1