Comments on: Why Do Mockingbirds Accept Invaders' Eggs?

By: Kara

Kara — Tue, 03 Jan 2012 15:30:57 +0000

Actually, it’s been found that some brood parasites will watch to see if the eggs they’ve laid are removed by the host. If the eggs are removed by the host, then the brood parasite will exact retribution by returning and destroying all of the host bird’s eggs. So the hosts are forced to decide between raising the brood parasite and less of their own offspring or losing all of their own offspring. So there is certainly no altruistic “adoption” involved nor is it a narrow-minded short term strategy. Raising the brood parasite’s chicks is simply the lesser of two evils.

By: Squatlo

Squatlo — Tue, 27 Dec 2011 16:16:03 +0000

While the egg-in-the-nest theory might hold water, how does one explain the fact that other species of birds will raise and feed the cowbird hatchlings? I’ve seen robins in our yard being followed by their own young, as well as immature cowbirds, and the robins work diligently to feed them all equally well. One would expect the survival of their own to surpass the parental urge to shelter interlopers, but that’s not what we observe in nature.
This might be a trait more akin to higher primates who will “adopt” the offspring of others.

By: MikeG

MikeG — Sat, 24 Dec 2011 12:15:55 +0000

This is very narrow minded short term strategy. If the mockingbirds shoved the parasite eggs out of their nest, it would in the short term drastically reduce the cowbird population size. In the long term, it may result in a behavioral change in cowbirds, forcing them to rear their own young.