The Unique Cowbird

[Driftless]

Brown head cowbirds are very common in the Midwest They are nondescript and blend in with the other birds in the area quite well. There is one thing about them that makes them very unique. They are parasitic birds. They do not make their own nests and they usurp the nests of other birds.

Definition of USURP

a : to seize and hold (as office, place, or powers) in possession by force or without right

This cowbird mother was not very picky and laid her egg in a non-speckled egg nest. The blue bird mother didn't know the difference.

Brown headed cow birds begin laying their eggs in the middle to late April. They typically stop in the middle of July laying eggs. Cowbirds typically lay about six eggs a day and wait a few days, and then start again. Usually only one Cowbird egg is found in each nest . It is very rare to find two cowbird eggs in one surrogate's nest. It does happen if the nests to chose from are limited.

Female Cowbirds scout out nests in advance. They perch on shrubs or trees to watch for other birds building nests. They try to flush nesting birds by flying in and landing noisily in the nest they are hijacking. They tend to prefer species with eggs smaller than their own and in active nests with at least two host eggs in the nest. Cowbirds seem to prefer open cup nests and the nests of other birds that also lay speckled eggs. They also prefer to usurp bird nests that the mother bird is laying her eggs after sunrise. They are opportunists and will lay their eggs in none speckled eggs nests.

Brown-headed Cowbird eggs are usually oval, but the shape can vary to short, rounded and or oval. The shell is moderately glossy. It is white or grayish white with dots and blotches also described as brown or chocolate in color. The markings are all over the egg.

I watched the mother red winged black bird leave this nest. The cow bird really doesn't discriminate on what nest it hijacks.

Egg laying usually takes only 20 - 40 seconds. The female usually sneaks into the nest minutes before sunrise to quickly deposit an egg. The mother cowbird either eats a couple of the host's eggs or drops them to the ground. If they are in a hurry they will just break the shells of a couple host eggs so they don't mature and are ejected from the nest by the surrogate mother at a later time.

The brown cowbird's young typical grows much faster than the young of the nest their mother usurped. The stronger and bigger cow bird takes all of the food offered by its foster mother and the babies of the real mother grow weak and die and are pushed out of the nest. The surrogate mother raises the cowbirds like her own and completes the cowbird mother's assignment.

[Steve Foss]

Len, nice pics that show the lifestyle (a successful one, I might add) of the cowbird. Nature has so many different forms of expression. More than parasites, it's the invasive species that can really wreak havoc on an established ecosystem. Thanks for sharing!

[ShawnZ]

I like how detailed your information is...and nice job with the nest photography.

In the first image, you identified the nest as a bluebird nest....Eastern Bluebird? I was not aware that they nested outside of cavities...?

Another interesting piece of information about the Brown Headed Cowbird that disturbs me is how they are live trapped in some parts of the country, and then the females are "manually extirminated" by a person, as a form of "cowbird control". This is ironic to me, due mainly to the fact that cowbirds used to have a more limited range prior to people expanding there range through development. Cue the sarcasm....More great "after the fact" natural resource management....but I digress....

Here is a question for anyone that promotes "cowbird control"....If the cowbird were a bright red bird with flashy wings, or a deep blue with some type of beautiful nape or crown, would they be viewed and or treated the same way?

[Steve Foss]

Here is a question for anyone that promotes "cowbird control"....If the cowbird were a bright red bird with flashy wings, or a deep blue with some type of beautiful nape or crown, would they be viewed and or treated the same way?

I think the contempt so many hold for the cowbird is partly because you have to look deep to find beauty in a bird with such an appearance, and just as much (or even more) because of its non-nesting strategy. Make it gorgeous and some would still not like it because the "parasitic" nature of its life goes against their ethical/moral beliefs.

Me, I figure Ma Nature knows more about that kind of stuff than I do. I'm pretty matter-of-fact, rather than judgmental, about such things. Just the way I look at it.

[Dotch]

I too was a bit taken aback by the claim the first pic is that of a bluebird nest. While some bluebirds lay white eggs and others lay blue eggs, I don't recall their nests being woven with quite such craftsmanship. First I've heard they nest outside of a cavity too. I hear ya Steve. I occasionally find cowbird eggs in a robin or grackle nest but generally speaking, there seem to be plenty of grackles and robins to go around. I let nature take its course. One can only imagine while watching the ewes graze on the hillside with cowbirds on their backs picking insects what it must've looked like in the days the bison roamed the prairie.

[ShawnZ]

I'm not sure if it's allowed to post this type of link...if it is not, I'm sure it will be moderated. However, if it is okay...Please check out this very well written article. I think it highlights some very important concepts to consider in regards to brown-headed cowbirds.

Regards,

Shawn Zierman.

Click here for link