Posted on 08/15/2002 4:28:04 PM PDT by 1bigdictator
Science - Reuters
Birds Check Out the Chicks Before Moving In Thu Aug 15, 4:38 PM ET By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Birds check out the chicks before they move to a new neighborhood -- assessing how many nestlings there are in the homes of older residents, researchers said on Thursday.
When researchers stole baby birds from nests in one area, new birds avoided moving there and some birds left, the researchers report in Friday's issue of the journal Science.
This shows that counting chicks may be a kind of short-cut for birds trying to figure out where the best places are to live, Blandine Doligez of the University of Bern and her colleagues said.
Working on the Swedish island of Gotland, Doligez and colleagues manipulated the nests of collared flycatchers -- migrating birds that live in holes in trees.
They moved baby birds from nests in one plotted area to nests elsewhere.
"We tried to mimic predation," Doligez said in a telephone interview. "This sometimes happens in this population -- a woodpecker or squirrel comes and just eats all the young."
Doligez said her team did not look at what the bereft parent birds did after losing their young, but they did watch what happened to the bird populations as the seasons passed.
Sure enough, birds moved away from areas where the young were stolen and moved to areas where baby birds were added to nests.
People may do something similar -- it is what Doligez calls the restaurant effect.
"If you want to choose where to go, you just look through the windows and see if people look happy with what is on their plates," she said.
Looking for crowds is not enough, she said -- which is why birds are not simply drawn to nesting areas where there are lots of other adult birds.
"With the restaurant, maybe everybody goes there because the cinema is close and it is worth going even though the food is bad," she said. "The idea is you look for the focal activity -- here it is eating but for the birds it is breeding. If you look at that, you cannot go wrong."
But the birds were not always taking everything into account, said Doligez, who worked with colleagues in France and Sweden. Flycatchers were happy to welcome strange chicks into their nests, but became overwhelmed.
"When you add some nestlings into the nest, then it causes a hard time for the parents," she said. "They are not able to feed them enough. The young are in poorer condition by the time they leave the nest."
So in areas where nestlings were piled in, the resident birds tended to move away, Doligez said -- while immigrant birds, apparently not aware of the poor condition of the fledglings, moved in.
Other researchers have confirmed similar behavior in kittiwakes, another species of bird, and Doligez said she believes it will hold true in many species. "It could be a quite general phenomenon," she said.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.