Any substance that triggers an immune response is an antigen(s).
We do quite often have mutt birds. (the correct name for such a mutt is a hybrid. <span>They are way more common than most people think, but unless you are a birdwatcher you probably wouldn’t even spot them. People often see an odd looking birds and simply think it’s a type they haven’t seen before, when in fact it is a hybrid of two well-known species.
Having said that, for birds to hybridized they have to be fairly closely related to start with. Robins and blue jays are no more closely related than humans are to baboons. You wouldn’t expect a human and a baboon to be able to mate and produce babies would you? So no, robins and blue jays can’t interbreed.
However there are many different species of animal that CAN interbreed and produce offspring. But the different species need to be fairly closely related, far more closely than human and baboon… or a blue jay and a robin.
For example we can interbreed horses and donkeys to produce baby mules, and we can breed cattle and buffalo, or camels and llamas. And the same is true of birds. While blue jays can’t be bred with robins in the wild we quite frequently find mutt birds.
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Ducks are particularly noted for forming wild mutts and many if not all north American mallards for example are of mixed species ancestry.</span>
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Solar eclipse
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