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Re: nest predation
>The cowbird control program where I frequent ( stomping a cowbird or
>sparrow chick to death ) is still not bringing down the populations of
>these two parasites. As a matter of fact, you are not allowed to kill
>any birds for any reason unless you have permission.
This would be the Migratory Bird Act. IIRC, it actually specifies certain
introduced species that may be killed. The cowbird control programs in
central Texas used miniature gas chambers connected to the exhaust pipes of
cars, and were operated by one or another state or federal agency.
Cowbirds were netted and gassed in specific areas.
National Geographic had a photo of this a couple of years ago, and it
brought out all kinds of outrage - how can we judge one species, and look
at how cruel this is, and all that. But the fact is, it works. I don't
know if the Michigan program uses the same technology, but the total
worldwide population of Kirtland's warblers (they nest only in Michigan)
jumped from 500 to 2000 after cowbird control started. Similar success
stories are told for some populations of golden-cheeked warbler and
black-capped vireo from central Texas - it's gruesome, but where habitat
preservation has failed, this succeeds.
I don't like wholesale slaughter of animals at all, but cowbirds are
expanding their range and numbers as a direct result of human activity, and
this does threaten several other dinosaur species. The goal of these
programs is not to eradicate cowbirds, but to control their numbers in
specific places where threatened parasitized species occur.
To answer the question that brought this thread up - the presence of small
dromaeosaurid material in an oviraptorid nest is interesting, but could
just as easily have washed in secondarily, or have been part of a meal
(either the parent's or intended for the hatchlings). It's also
problematic that nest parasitism of this nature occurs only within certain
bird groups - nonavian reptiles don't do this at all, with the possible
exception of turtles piggybacking croc nests - and in this case, they're
just coopting some of the nest heat. This means that one cannot actually
optimize nest parasitism on a tree such that nonavian theropods would be
predicted to show nest parasitism. Still, it could happen.
Postdoctoral Research Scientist
Department of Geology
Field Museum of Natural History
Lake Shore Drive at Roosevelt Road
Chicago, IL 60605 USA
phone: 312-922-9410, ext. 469