As a very birdie lady, I have this to say about that.
Some birds — like finches — flock together. The Goldfinches show up in bunches, often more than a dozen at a time and they don’t mind taking in the House and Purple Finches who also live in the woods with them. They apparently don’t care whether you are red, raspberry, or bright yellow.
On the other hand, while the Cardinal often shows up with his mate, he will not tolerate the presence of another male Cardinal in his “patch” of woods. If they meet, they go at it like World War 1 aces, whirling and attacking each other in the air. It’s quite a thing to see.
The Hairy Woodpecker doesn’t like anything or anyone but will tolerate his mate if she doesn’t get in his way. The Red-Bellied Woodpecker will tolerate other birds nearby … as long as they don’t poach on his piece of feeder. The Tufted Titmouses show up in groups, but not flocks and all the other birds are perfectly okay with them. Ditto the Nuthatches. Bluebirds only show up in groups (protection?).
In the watery world of fowl, Canada Geese and Swans hate each other. Meanwhile, Herons will eat the eggs of any other fowl if they can find the nests.
But all of these fighting birds are happy to hang around with ducks. No other bird has a problem with ducks and when the ducks hang out, they don’t care what kind of duck you are. Whatever feathers you wear are fine with all the ducks.