When parents let kids go hungry

Scientists creating fake crises at bird nests have confirmed a theory about

parents protecting themselves at their offspring’s expense.

According to theorists, this type of behavior should occur in species that live

relatively long and bear only a few young at a time. Species with shorter lives

and that produce more offspring per batch should take the opposite path: Parents

ought to risk their own lives for the sake of offspring. Field studies have

confirmed these proposed behavior patterns, say Cameron K. Ghalambor of the

University of California, Davis and Thomas E. Martin of the University of Montana

in Missoula.

They analyzed life patterns for 182 songbirds. Southern Hemisphere species tend to

live longer and lay smaller clutches than northerners, the researchers report in

the April 20 Science. Ghalambor and Martin identified five pairs of species with

similar ecology but living in opposite hemispheres. For example, they matched a

robin with a rufous-breasted thrush.

Playing calls of hawks, which eat adult birds, near a nest prompted more self-protective behavior among the southern species. These birds, with a smaller

relative investment in any particular clutch than their northern counterparts,

chose to avoid feeding runs and remain hidden, even though their young went

hungry. The northern birds, however, risked such runs.

When these braver parents heard calls of a jay, which kills nestlings but not

adults, they curtailed feeding runs, which might have revealed their nest’s

location. However, their less invested counterparts hazarded such trips, the

researchers observed.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.