By Susan Milius
When barn swallow nestlings open wide and say “Ah,” parents may check their health much as human moms and dads peer anxiously down Junior’s throat.
Parents of barn swallows, however, may be looking for the healthiest throats so they can pop food into the youngsters most likely to survive, according to Nicola Saino of the University of Milan in Italy and her colleagues. In the Jan. 7 Proceedings of the Royal Society of London B, they propose that the gape redness of a begging nestling indicates whether the young bird is battling infection.