Bird Mobsters

This Washington Post article about possible evolutionary roots of human behavior contains this rather astonishing example from the animal world:

It all began, he says, when ecologists started removing the eggs of cowbirds from the nests of warblers. Cowbirds leave their eggs in the nests of dozens of other birds. It has long been a mystery why birds such as warblers allow the eggs to hatch and why the hosts then feed the young cowbirds -- sometimes at the expense of their own offspring.

Hoover and colleague Scott Robinson found that when they removed cowbird eggs from the warbler nests, those nests mysteriously got trashed. Turns out that the cowbirds, much like members of the mob, were keeping a close eye on the nests in which they had laid their eggs. If anything bad happened to the eggs, the cowbirds would return and destroy the nest.

Hoover found that, much like the way the mafia operates, the cowbirds begin with detailed surveillance of their potential targets...

"Nice nest you got here...lots of dryer lint, real nice warm place to hatch kids. It'd sure be a shame if somebody with a really sharp beak like mine came in and pecked it to bits, wouldn't it?"