Convergent Evolution

The Audubon lecture last Saturday included a lot about convergent evolution, whereby unrelated families develop in similar ways in different biogeographical regions. A good example are the Old World Oriolidae and the New World Icteridae. Species within these families have occupied similar eco-niches and have converged remarkably: similar gaudy plumage, hammock nests, distinctive oriole-like calls, even diets are similar.
I am not clever enough to say any more about convergent evolution, but I can describe some striking similarities of birds which may not even be related at the level of Orders.
An example: the local flycatcher, the Black Phoebe, in the garden waits and watches and pounces, just like our European Robin. A party of Bushtits flit one after the other through the shrubs, just like a party of Long-tailed Tits. The Icterid Brewer's Blackbirds in noisy flocks bustling busily wherever there is a food supply: they could be Starlings (the first time I saw them, I thought they were a local species of starling).
But there are, of course, local species which have no direct counterpart in the Old World. One of my favourites is the Northern Mockingbird (see picture). Plain grey it is true, but when it flies it flashes huge patches of white in its wings. Its name, though, tells you most about it: it is a a restless chatterer with a song that seems to be a medley of everything it has ever heard. It's only a matter of time before our local Mockingbird starts twittering like our Budgerigar.