Savanna habitat drives birds, and perhaps others, to cooperativ...( Berkeley -- Delaying having kids to ...)

Berkeley -- Delaying having kids to help raise the offspring of others seems like a bad choice if you want to reproduce, but many African starlings have adopted this strategy to deal with the unpredictable climate of their savanna habitats, according to a new study by University of California, Berkeley, and Cornell University biologists. It appears in the Aug. 21 issue of the journal Current Biology.

This behavior, called cooperative breeding, is typical of many animals, from insects and shrimp to birds and even humans, but the reasons underlying its evolution and distribution among such a wide array of species have been unclear.

In the new study, behavioral ecologist and evolutionary biologist Dustin Rubenstein, a Miller Fellow in the Department of Integrative Biology and the Museum of Vertebrate Zoology at UC Berkeley, looked at the complete group of African starlings and found that all of the cooperative breeders among these birds live in savannas - highly seasonal habitats with great variation in rainfall, and thus food, from one year to the next. The species that do not engage in cooperative breeding are found mostly in forests, which have more reliable annual food resources.

"Faced with an uncertain and unpredictable environment, it pays evolutionarily to live and breed in social groups that will help you weather the bad times and make the most of the good times," he said. "Living in cooperative family groups may be like a form of insurance against the unpredictable nature of the environment, because it allows individuals to maximize their reproductive success over the course of their lifetimes."

Cooperative breeding is defined as one member of a group delaying breeding to assist another breeding couple. Because cooperative groups in most birds consist of extended families with grandparents, parents, offspring and other close relatives, helpers are typically related to the group members. Among most birds, females leave
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