IsabellaLinton wrote:
Dog-cat, deer-cow, and human-monkey is different than bird-bird.
There are lots of dog-dog breed mixes.
They're called mutts (or sometimes expensive new breeds).
.
They are NOT different. The species I mentioned are all mammals. Just like birds are all birds. Both the class aves (birds), and the mammalia (mammals) are 'classes'. The same level of taxa. So if mammal species dont interbreed so why would expect bird species to?
Blue jays are to robins what cows are to deer. Two different species. Dog breeds are not analogous to separate species of songbirds. A better analogy (though even this not an exact analogy) to dog breeds would be human 'races' - subdivisions of the same one species: canis familiaris (the domestic dog). However domestic dogs do interbreed with wolves, coyotes, and dingos, which are classified as seperate species from the domestic dog. But closely related.
Some closely related species of songbirds do actually hybridize in the wild. But nothing like jays with robins. More like one kind of sparrow with another almost identical looking species of sparrow that looks almost the same because they are so closely related.