Mama bird benefits from help

Mother fairy wren.

When mother fairy wrens have helpers that share baby-feeding duties, they save their own strength and lay smaller eggs, researchers report. When mother fairy wrens have helpers that share baby-feeding duties, they save their own strength and lay smaller eggs, researchers report.

These findings should help explain a long-standing mystery about helpers in cooperative animal societies. In many of these systems, babies get food from helper animals as well as the parents. But, the puzzling thing is that these babies don’t seem to grow larger or survive at higher rates than babies who don’t receive the extra food. So where are those extra calories going"

Andrew F. Russell of the University of Sheffield in Sheffield, U.K. and the University of New South Wales in Sydney, Australia and colleagues studied a group of fairy wrens, which help each other out during breeding. They found that baby wrens are born smaller than usual when helpers are present. The mothers invest less of their own energy and resources when laying the eggs.

For the bird mothers, this means they are more likely to survive to the following breeding season. For the bird babies, it means that the extra food provided by the helpers is helping them catch up and become normal-sized.

The study shows that helpers do make important contributions and why their effects have been so hard to find. The research appears in the 17 August issue of the journal Science.

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