Do parents with extra help goof off?

A mere human might slack off on the baby care if a nanny suddenly materialized, but a test of house sparrows has found the opposite reaction.

Douglas W. Mock of the University of Oklahoma in Norman compares the experiment to the 1950s television show The Millionaire. It featured stories of people who, out of the blue, received a million dollars from the show's fictional philanthropist. Much of the drama, Mock points out, came from the recipients' lives falling apart.

In an avian version of the million-dollar windfall, Mock and his colleagues provided extra feedings to some nests of sparrows, but not to others. Mock studies the evolutionary stability of monogamy, and he wondered whether the males in the lucky nests would "goof off and participate in skirt chasing."

Not so. He saw no significant jump in parental care among these males. Instead, the birds made almost one-third more food deliveries to their nests than did sparrow dads receiving no assistance. Mock's team found that females put in about the same effort with or without handouts.

Mock says he's still speculating about what this unexpected paternal effort means. It might indicate that chicks chirp more emphatically if extra food has boosted them into better condition. This could suggest, in turn, that a chick's chatter doesn't just indicate hunger but advertises the chick's worthiness of parental effort.