why do different types of birds not mate with each other, ie a robin and a cardinal?

Answer 1

There are quite a few hybrids, but they still have to be related to some extent (robin x cardinal is impossible)
There are a lot of duck hybrids:
Mallard x Black duck
Mallard x Pintail
Mallard x American Wigeon
Mallard x etc , there are a lot of mallard hybrids all these guys are in the same genus.

Here are some interesting ones where both species are in different genus

Hooded Merganser x Bufflehead
Hooded Merganser x Barrow's Goldeneye
Hooded Merganser x Wood duck
Etc.

Hybrids aren't restricted to ducks either

Golden winged warbler x blue-winged warbler
Downy woodpecker x red-cockaded woodpecker
Grasshopper sparrow x Savannah sparrow
The list goes on.

It may seem like there are a lot, but why don't we see more ? Genetics first off, if the genes aren't compatible then they can't produce offspring. Birds have various cues for choosing mates and generally stick to their own species, the difference could be color, size, or something as a slight difference in the song. There is also geographical separation if two species are closely related but are found on different ends of the continent what are the odds of them meeting ?

Answer 2

In most cases it's because they're different species. Birds are weird, however, in that the can mate with another species and produce fertile offspring. That's how you get Catalina's and Harlequin Macaws. This is also how the canary fancy developed the red factor canary. In fact, hybridization is so common among domesticated parrots that some breeders don't even know if they have purebred animals. This is evident among sun conure, jenday conure, scarlet and green wing macaw, and eclectus parrot breeders.

Waterfowl such as ducks often produce hybrids in the wild, as do quail and some passerine (perching) birds. With prairie chickens, the resulting offspring are so different from their respective species that they are unable to find mates during the breeding season!

Answer 3

If an animal is too different from another, the resulting mating would be a sterile animal (such as horses to donkeys = mule) or there would be no pregnancy. Further, instinct tells most animals to look for something specific - their own kind.

Answer 4

They're not like dogs and cat who have different breeds. Each kind of bird is a different species.

Answer 5

Why don't you mate with a chimpanzee?

The answer? They're a different species entirely.