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July 10, 2008 [LINK / comment]

Those lazy, deadbeat Cowbirds!

Is this an ugly bird, or what? You may not know this, but Cowbirds also have an ugly behavior pattern, at least by our standards. They are "parasitical nesters," which means they don't build their own nests or raise their own young. Instead, the female Cowbird searches for another bird's nest in which to lay her eggs, and in many cases, the unwitting hosts raise the chicks until they fledge. (The instinct to reproduce can be overwhelming, some times.) Usually, the baby Cowbirds are bigger than the other birds in the nest, and they push them over the side. Nature is indeed cruel.

Cowbird male

This Brown-headed Cowbird was out back a few days ago.

Why do Cowbirds reproduce this way? Well, as with most instances of animal behavior, it evolved over the millenia as an adaptation. Cowbirds live mainly on insects that swarm around cattle and livestock manure, and many centuries ago, such animals roamed freely across the plains, which made it impossible to raise young in a particular breeding location. Thus, some of them gave up on building a nest, and left that task to other birds. Enough of the offspring survived that the behavioral trait became permanently ingrained in their genes. It's a case study in welfare state mentality, you might say.

In Europe, Cuckoos are parasitical nesters, but the American species of Cuckoos build their own nests, albeit rather sloppy ones. I haven't been on any serious birding trip lately, but hope to in the next couple days. I have updated my Wild Birds USA photo gallery page.

Ospreys learn to poop

A photographic record of a "poop lesson" in an Osprey nest was posted by Fred Miranda, and it's pretty funny, though it takes a while to load those big images. Hat tip to Stacey Morris.

Posted (or last updated or commented upon): 10 Jul 2008, 4: 54 PM

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Blog highlights have been compiled for the years 2010-2012 thus far, and eventually will be compiled for earlier years, back to 2002.


The "home made" blog organization system that I created was instituted on November 1, 2004, followed by several functional enhancements in subsequent years. I make no more than one blog post per day on any one category, so some posts may cover multiple news items or issues. Blog posts appear in the following (reverse alphabetical) order, which may differ from the chronological order in which the posts were originally made:

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