[CT Birds] Bird Thugs
crepasz at hotmail.com
Thu Mar 22 16:52:30 EDT 2007
Scott you are not missing anything. I kept some facts out trying to keep my post to a thumbnail sketch. No smaple size was given n=? That should be in the journal article.
The experiement was done with Prothonatary Warbler nests that had baffles to prevent predation. There was a group that had the cowbird eggs removed then a front placed on the box that had a hole to small for cowbirds to enter. The eggs were untouched.
> Date: Thu, 22 Mar 2007 16:41:52 -0400> From: kbosch at gmail.com> To: ctbirds at lists.ctbirding.org> Subject: Re: [CT Birds] Bird Thugs> > I would love to know how big that sample size was - "clearly it is> retaliation" is an assumption without proof, unless I'm missing something.> The researchers even stated they did not witness the cowbirds destroy the> nest/eggs. It could have been a coincidence with many other species of> birds, or even mammals/snakes, committing the acts. Or maybe the act of> removing the cowbird eggs from those nests by researchers caused something> else. Catbirds recognize the eggs, but they do not suffer this same fate,> correct? In my opinion, I think the simplest answer of the fact the parents> do not recognize the foreign egg(s) still sounds good - but I'd love to hear> other thoughts.> > > And speaking of Bird Thugs - the top thugs, European Starlings, have an even> bigger bully here - Monk Parakeets. One Starling was trying to eat my suet> today while a Parakeet was trying to climb onto the cage. It decided it> couldn't fit on the cage with the Starling, and it couldn't push it off very> well, so it bit down on the Starling's leg as it held onto the cage. He flew> off as fast as he could. It's been a week full of pests in addition to the> rarities.> > Scott Kruitbosch> > On 3/22/07, Craig Repasz <crepasz at hotmail.com> wrote:> >> > Bird Thugs> >> > >From "Science News" March 10, 2007 vol. 171> >> > We all know that Brown Headed Cowbirds parasitize other birds by laying> > their own eggs into the nests. They then fly off leaving their eggs to be> > incubated by the parent couple. The fledgling cowbirds usually grow faster> > and out feed the other chicks. This leaves the parents bird with a big> > demanding mouth to feed often at the expense of their own brood. One may> > wonder why the parent birds do not toss the foreign egg out of the nest.> > Researchers of the Illinois Natural History Survey in Champaign have> > concluded that Brown Headed Cowbirds will retaliate against a nest if their> > efforts to parasitize have been undermined.> >> > Researchers have removed the cowbird eggs from warbler nests to find that> > more of the warbler eggs were later smashed or carried off (56% destruction)> > compared to warbler nests that left cowbird eggs in place (6% destruction.).> > Clearly it is retaliation.> >> > Oddly enough the researchers did not witness the cowbirds in their> > destructive acts.> >> > Nests that had cowbird eggs removed produced 40% as many warblers as nests> > that kept the cowbird eggs. There is a degree of starvation of warbler> > chicks in nests that host an interloper, however, nesting success is still> > higher then nests that were destroyed by retaliating cowbirds.> >> > Paper to be released in "Proceedings of the National Academy of Sciences."> >> >> > Personal note: The warblers are forced to take the lesser of two evils.> > The real problem may be forest de- fragmentation as a result of urban sprawl> > that creates both the grass-forest border habitat that is ideal for cowbirds> > and splinters the warbler's breeding habitat.> >> >> > _________________________________________________________________> > Your friends are close to you.Keep them that way.> > http://spaces.live.com/signup.aspx> > _______________________________________________> > This list is provided by the Connecticut Ornithological Association (COA)> > for the discussion of birds and birding in Connecticut.> > For subscription information visit> > http://lists.ctbirding.org/mailman/listinfo/ctbirds_lists.ctbirding.org> >> > > > -- > Scott Kruitbosch> Stratford, CT> kbosch at gmail.com> _______________________________________________> This list is provided by the Connecticut Ornithological Association (COA) for the discussion of birds and birding in Connecticut. > For subscription information visit http://lists.ctbirding.org/mailman/listinfo/ctbirds_lists.ctbirding.org
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