While women may cheat on men for personal reasons, superb starling females appear to stray from their mates for the sake of their chicks, according to recent Cornell research published in the Proceedings of the Royal Society of London B.

The study found that superb starling females (Lamprotornis superbus) cheat on their mates for a variety of reasons. Some females mate with subordinate males from within their social group when they need help to raise their chicks. (Superb starlings are cooperative breeders, meaning breeding pairs get help in raising chicks from other family group members.) This additional male then also acquires food and tends to the nestlings, which increases the chicks' survival rates.

While females often leave the group when young, most males live their entire lives with their families and, therefore, are usually related to the chicks. By helping the chicks survive, they pass on familial genes.

In contrast, some females cheat with males outside their group if they sense their mates are too genetically similar to themselves. Mating with strangers increases their brood's genetic diversity, even though it does not reap additional help. As yet, it is unknown how females detect the genetic similarities between themselves and their mates, though other species of birds appear to adopt similar mating strategies.

"This is the first study to show that individuals from the same population mate with extra-pair males and gain both direct (like additional helpers) and indirect benefits (like better genes for the offspring), but that they do so in different contexts," said Dustin Rubenstein, a former Cornell graduate student in neurobiology and behavior and now a research associate at the Cornell Laboratory of Ornithology and a Miller Research Fellow at the University of California-Berkeley.

Usually, if a female bird (and at times if a human female) is caught cheating, the partner punishes her by doing less w
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20-Jun-2007