Subject: Strange co-hosts (Was:Parakeet fodder for thought)
Date: Nov 13 09:24:12 1995
From: Serge Le Huitouze - serge at cs.sfu.ca



fredbird at halcyon.com writes:
> ... an article in the Nov.-Dec. Bird
> Watcher's Digest, entitled `Neighbors: Parrots and Owls', by Linda
> Pearson and Alison Oliver. BWD is not usually a source for technical
> ornithological discussions, but this article comes close,
> particularly in light of our periodic debates about invasive
> species. The article centers around the curious sharing of a Monk
> Parakeet nest by resident parakeets and a pair of Great Horned Owls
> in suburban Connecticut. ...
> The owls built their nest atop the parakeet structure, while the
> parakeets continued using the nest, accessing interior chambers
> through holes located on the underside. The owls raised one young
> (1992) and were never observed eating their co-hosts.

This kind of behavior seems to happen in other cases too.
I recall reading about the Red-breasted Goose (I think) _Branta ruficollis_
in the Siberian tundra. Apparently, it tended to place its nest relatively
close to Gyrfalcons and Peregrine Falcons nests, in any case, closer than
what would be expected at random.
The researchers noticed no significant predation on neighboring goslings and
adults from the Falcons, though they would predate this particular species
when nesting away from its own nest. It seems quite surprising (yet another
sampling error???).

The explanation the researchers had for the behavior of the Goose (these
people always come up with an explanation even if they don't have a clue :-)
was that the proximity of the falcons would avoid (at least diminish)
predation by mammals (mostly foxes).
I don't recall any explanation as to why the falcons would not try to take
neighbouring goslings, while still occasionaly feeding on goslings they would
find while hunting away from their nest...


P.S. Being a bushtitomaniac, I reserve the noble use of "eyrie" to these
little sock-like structures, and just call "nest" the place where falcons
raise their young :-)


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Serge Le Huitouze Intelligent Software Group
email: serge at cs.sfu.ca School of Computing Science
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