[Douglbirds] House Finches: When Danger Lurks, It's Ladies First

[KarenSMetz at cs.com]

Some of you may be interested in this brief article concerning House Finches.

> 
> By Rhitu Chatterjee
> ScienceNOW Daily News
> 18 September 2006
> 
> When her nest is invaded by bloodsucking mites, the female house finch 
> juggles the birth order of her future offspring. She first lays eggs that will 
> bear daughters--which tend to be hardier--and saves the eggs of her more 
> sensitive sons for last. The strategy ensures that vulnerable male chicks spend less 
> time with the mites and may help explain why the house finch has been so 
> successful in adapting to new environments.
> 
> The house finch (Carpodacus mexicanus ) is the conquistador of the bird 
> world. Confined to the western United States and Mexico until about 1940, the 
> bird quickly set up shop around the country when a few individuals were set 
> loose in New York. Each population has had to overcome the hardships of its new 
> environment, and scientists have long suspected that the secret to the bird's 
> success is an ability to adapt very quickly to small changes in its 
> surroundings.
> 
> To find how these birds fare in the face of an aggressive adversary, 
> evolutionary biologist Alexander Badyaev and his colleagues at the University of 
> Arizona in Tucson turned to a group of house finches that has lived in Arizona 
> for hundreds of years. During the breeding season in late spring, the 
> bloodsucking nest mite (Pellonyssus reedi) attacks mothers and chicks. As in most 
> bird species, the male chicks are especially vulnerable to danger when born.
> 
> Badyaev and his team observed more than 100 finch nests over two breeding 
> seasons. In the winter, when the mites are not on the scene, the researchers 
> found that mothers laid their clutch of four or five eggs in no particular 
> order. Boys were born more sensitive to their environment than girls, and 
> although mothers laid one egg a day, all chicks left the nest at about the same 
> time.
> 
> When mites started popping up in the spring, however, things changed. The 
> mothers laid daughters before sons. The team suspects that's because the 
> mothers pay a bit more attention to these late bloomers, funneling extra hormones 
> and nutrients to them while they're still inside the safety of the egg. 
> Besides allowing boys to be born in better shape, the strategy minimizes the amount 
> of time males are in the nest, because they take off around the same time 
> their sisters do. The practice helps the mothers reduce the mortality of their 
> sons by 12.5%, the team reports online this week in the Proceedings of the 
> National Academy of Sciences.
> 
> Invasive finches in other parts of the country could be relying on similar 
> mechanisms to adapt to other environmental challenges, says Badyaev. 
> Evolutionary biologist David Harper of the University of Sussex in the U.K. agrees. 
> The study takes some of the mystery out of the "mystifying flexibility" of 
> house finches, he says.
> 
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