How to Tell Whether Two Animals can Produce Offspring?


Ad Honorem
Jul 2017
Crows nest
Crows and ravens can breed even though one is bigger than the other, and though they do look similar, do have differences and are classed as separate species. It depends on the distance two species are away from the common ancestor, from when they last shared their genes. There is hardly any gap between ravens and crows, so they can interbreed. At the opposite end of the equation we have the South American Oilbird that cannot breed with any other bird as it has not shared it's genes for 73 million years. It has evolved over that time, but only within it's own species and has not produced new branches that it could have potentially interbred with.

One of the reasons for the colorful displays many birds have is not just to shout out to a potential mate, but to say that they are the same species and to "keep it in the family". The reason being that they could potentially mate with another, and close species, in error, as happens with the all black corvids, despite size differences and ravens having "baggy trousers".