Variance sensitivity theory predicts that optimal foragers should take into account not only the mean but also the variance in rewards offered by alternative foraging options. Whereas a positive energy budget should favor variance aversion, a negative one should favor variance-prone choices. The...

Cooperatively breeding bell miners (Manorina melanophrys) have numerous male helpers assisting at multiple nests. Helpers are often related to the brood they aid, consistent with kin selection. However, there are also unrelated helpers for which other direct fitness benefits are likely to...

Despite many studies on the evolution of cooperative breeding and helping at the nest, relatively few have explored the possibility that helping functions as a signal to gain social advantage within groups (the "pay to stay" and "social prestige" hypotheses). One of the most promising candidates...