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Name: Nancy A.
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: Saturday, May 18, 2002


Question:
A small brown bird has made a nest near our back door here in north eastern Illinois. I have not gotten a good look at it because it flies off when it hears the door open. It has laid 2 or 3 tan eggs with brown speckles. However, this morning I also noticed 3 more light grayish blue eggs as well. I believe I remember learning that certain birds will be interlopers, and lay their eggs in others' nests, hoping that their progeny will survive over the original nestlings. Is this true? What sorts of birds exhibit this kind of behavior? Is it common? My kids (10, 8, and 5) are scandalized at the thought of the original babies not getting their mom's full attention! I explained that birds do not think in the same ways as people, and that nature sometimes may seem cruel to them, but I would love to give them more information. I have scanned the Internet, and have not found anything. I would love for my kids to gain a real passion for learning about birds. I am hoping this will spark their interest further. Thanks so much for your help and information. What a terrific service you provide!


Replies:
Nancy,

Yes, there is such a bird in Illinois. The Common Cowbird female does exactly what you have suspected. The female after mating will observe nest building of another species and lay one egg in the same nest when the other birds are occupied elsewhere. The eggs she lays will (to the nest owners) look like thier own. However, during incubation, the cowlbird eggs will hatchfirst. The large cowbird chick is accepted by the surrogate parents and the chick will remove, by a stretching-liken behavior, the other eggs in the nest so it is the only one present. It gentica,ly knows it is a cowbird and will stay with the parents it has for as long as it needs, fled (leave) and never return. The surrogate parents do not know that difference.

There is usually only one cowbird egg per nest. I am sure there may be exceptions.

For the most part, all birds are born with the behaviors it needs to survive. This is one of many examples of how a species survives successfully. There is no indications that I have read that would indicate that the Cowbird does damage to any species. No, man does all of that all by himself!

If you haven't already, puchase a Bird Identification book to learn about which birds you may see around your house. In Northeastern Illinois during the spring, a experienced birdwatrcher may see over 120 different species of birds in a few hours (early to mid May).

Steve Sample


Here are two informative links I found using the Newton search engine:

http://146.139.100.40/webpages/askasci/zoo00/zoo00207.htm
http://146.139.100.40/webpages/natbltn/300%2D399/nb346.htm

If the host birds understood what was happening, chances are they would be more upset than your children are. After all, it is their resources that are going to another species at the expense of their own reproduction.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois


The only nest parasite of the U.S. is the brown-headed cowbird; Some European cuckoos are nest parasites, but American cuckoos are not. Cowbirds probably developed parasitism as they evolved following buffalo herds on the great plains and thus did not stay in one place long enough to build their own nest. For more information about cowbirds, try this site, type in the name in the search window and you will get a page with good basic information, and on the page will be a link to the text on cowbirds from the A.C. Bent books, Life Histories of North American Birds, originally published by the Smithsonian. Those books are old so much information has been updated but they are incredibly detailed.

http://www.birdzilla.com/sub.asp?strType=omnibus_intro&strTitle=Birdzilla:+ Wild+Bird+Omnibus

Another birding site of interest is

http://www.birdnature.com/index.html

Audubon Society has a bird page with links:

http://www.audubon.org/bird/

And you can find many more with a little searching. Encourage your kids to understand, as you have started, that while we should not expect wild creatures to behave the way we do, sometimes wild things do need our help.

J. Elliott


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