LAUSR

Despite decades of comparative research, how selection shapes the evolution of cognitive traits remains poorly understood [1-3]. Several lines of evidence suggest that natural selection acts on spatial memory in food-caching species [3-6]. However, a link between reproductive fitness and spatial memory ability has yet to be demonstrated in any caching species [1, 3, 6]. Here, we show that memory performance influences reproductive success differentially for males and females in a caching songbird, the New Zealand robin (Petroica longipes). Males' memory performance in a spatial task during winter influenced their subsequent breeding success; individuals with more accurate performance produced more fledglings and independent offspring per nesting attempt. Males with superior memory performance also provided an increased proportion of large prey items to chicks in the nest and spent less time flying while foraging and provisioning. No such effects were found for females. Previous research reveals that trade-offs may constrain selection and act to maintain variation in cognitive traits [7]. The gender dimorphism in the reproductive benefits of robin memory performance suggests an additional role for divergent selection between the sexes in constraining runaway selection on male memory ability [8], ultimately maintaining variation in this cognitive trait.