When Brains Beat Bonds: How Chickadees Choose Smarter Mates

Mountain chickadees are socially monogamous birds that cache food and rely on spatial memory. New research has shown that females sometimes mate outside the pair bond, and they prefer males with stronger spatial abilities. The team used 'smart' feeder arrays, where each tagged bird learned which one feeder would open for it, so spatial learning was measured in the wild. Over three breeding seasons, DNA tests were used to assign paternity and compare males.

The results show that males with better spatial cognition sire more extra-pair young and produce heavier fledglings. Extra-pair males had significantly better spatial performance than the social males they cuckolded, while females that performed worse on the cognitive tests were more likely to have extra-pair young in their nests. These findings support the idea that sexual selection can act on cognitive traits, and they suggest that memory skills, which are heritable in this species, may provide indirect genetic benefits. Therefore, spatial cognition may influence both survival and reproductive success. However, the likelihood of being cuckolded was not directly related to the social male's own cognitive score. Furthermore, about a third of sampled offspring were sired by extra-pair males, and 70% of nests contained extra-pair young.