Chickless Birds Help To Guard Relatives’ Nests

A new research study has revealed why some birds choose not to reproduce, and instead help to guard the nests of their close relatives.

AsianScientist (Dec. 26, 2013) – A new research study has revealed why some birds choose not to reproduce, and instead help to guard the nests of their close relatives. This occurs in about nine percent of all bird species.

The findings, published in the journal Science, showed non-breeders helped drive off birds like cuckoos, which lay their eggs in the nests of other birds.

“Birds like cuckoos are called brood parasites, which means they are reproductive cheats. They lay their eggs in the nests of other birds, imposing the costs of rearing on their hosts, who often lose their entire brood of chicks as a result,” said Australian National University’s lead investigator, Dr. Naomi Langmore. “Biologists have long wondered how this strategy, termed cooperative breeding, could be evolutionarily successful.”

When it comes to guarding the nest, if there is extra help for the breeding pair, it enhances protection against brood parasites, and the chances that their own chicks will survive, says University of Melbourne’s Dr. Michelle Hall and Associate Professor Raoul Mulder, who are coauthors on the study.

The global distribution of cooperative breeders and brood parasites is tightly linked and concentrated in two major geographic hotspots: Australasia and sub-Saharan Africa.

Using data from over 100 families of superb fairy wrens living at Serendip Sanctuary, near Melbourne and Campbell Park, near Canberra, the researchers showed that nests of larger family groups were less likely to contain cuckoo eggs than nests of small family groups.

Experiments with model cuckoos conducted at Serendip Sanctuary showed that bigger host groups of birds aggressively mob the invading cuckoos at their nests much more than smaller groups.

“Understanding this interaction between cooperative breeding and brood parasites also helped explain the uneven global distribution of cooperative breeding birds,” said Hall.

The article can be found at: Feeny W et al. (2013) Brood Parasitism and the Evolution of Cooperative Breeding in Birds.

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Source: University of Melbourne.
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