Environmental unpredictability drives cooperative breeding in Savannas birds

Savannas bird species show more altruistic tendencies compared to others, to the extent that rather than start a family of their own, they will stick around longer to help a relative raise their young, according to a new study appearing online in the journal Current Biology.

Washington, Aug 17 : Savannas bird species show more altruistic tendencies compared to others, to the extent that rather than start a family of their own, they will stick around longer to help a relative raise their young, according to a new study appearing online in the journal Current Biology.

In the study, Dustin Rubenstein of the University of California, Berkeley and the Cornell Laboratory of Ornithology, examined the pattern of breeding behaviour exhibited by 45 species of African starlings in relation to the environments in which they lived. The regions included the savannas, deserts and tropical forests.

The team also examined the rainfall patterns typical of each of those environments in 47 African countries as far back as 147 years ago.

Findings revealed evidence of different starling species having independently evolved the cooperative breeding system upon moving to savannas, where the amount of year-to-year variation in rainfall was greatest.

Rubenstein said the birds displayed cooperative breeding probably because it was advantageous in environments that showed variations.

This allowed for reproduction in harsh years, as well as sustained breeding during benign years, he said.

"When the unpredictability of your environment is high, you don't know in advance what conditions you will be facing when the next breeding season rolls around," said Rubenstein.

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

ANI