Does ecology and life history predict parental cooperation in birds? A comparative analysis

In animals, species differ remarkably in parental care strategies. For instance, male-only care is prevalent in teleost fishes, while biparental care predominates in birds and female-only care is widespread in mammals. Understanding the origin and maintenance of diversified parental care systems is a key challenge in evolutionary ecology. It has been suggested that ecological factors and life-history traits play important roles in the evolution of parental care, but the generality of these predictions has not been investigated across a broad range of taxa. Using phylogenetic comparative analyses and detailed parental care data from 1101 avian species that represent 119 families of 26 orders, here we investigate whether parental strategies are associated with ecological variables (i.e., food type, nest structure, and coloniality) and life-history characteristics (i.e., chick development mode and body size). We show that parental care strategies are in relation to coloniality (solitary, semi-colonial, colonial) and chick development mode (altricial vs. precocial). Colonial and altricial species provide more biparental care than solitary and precocial species, respectively. In contrast, food type (plant, invertebrate, vertebrate), nest structure (open vs. closed), and body size do not covary systematically with parental care patterns in birds. Taken together, our results suggest that living in groups and/or having high-demand offspring are strongly associated with biparental care. Towards the end, we discuss future research directions for the study of parental care evolution.