Antarctic penguins come on land for just a few short months each summer to breed and raise their chicks. Raising a family in the coldest place on earth is no small feat. Adelie penguins pull it off by tag-team parenting, the researchers explained. Males and females take turns incubating the eggs and guarding the chicks while their mate forages for food.
Males arrive first to claim a territory and build a nest. When the females arrive, the males serenade prospective mates by throwing their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks. Males with more consistent pitch were snatched up more quickly. These males were also heavier and more successful at raising chicks, the researchers found. The fat surrounding the male's voice box changes what his call sounds like and body fat appears to stabilize their calls. By listening to male courtship calls, a female can tell how fat a male is and what kind of father he'll be. Fatter males make better fathers because they have the energy reserves to endure long fasts, so are less likely to leave the nest and desert their chicks.
After choosing a mate the female lays two eggs and returns to sea, leaving the male alone to tend the egg until she returns to take the next shift. For the first two weeks penguin dads do the bulk of babysitting duty without breaking to eat. According to the research findings by relying on stored fat reserves, father penguins can lose more than 20% of their body weight over the course of the summer breeding season and as a result their calls changed too. Therefore a skinny male is unlikely to be able to pretend he's a big fat male.
The reference for this article is: Emma J. Marks, Allen G. Rodrigo, Dianne H. Brunton. Ecstatic display calls of the Adélie penguin honestly predict male condition and breeding success. Behaviour, 2010; 147 (2): 165