On the Origin of Parental Care and the Early Evolution of Male and Female Parental Roles in Birds

Abstract

In over 90% of bird species both parents participate in care of eggs and young. The reasons for this unique phenomenon are not adequately understood. The comparative approach shows that in Eoaves, the most primitive of extant birds, paternal care constituted the ancestral state. As uniparental paternal care is unknown in reptiles, most probably it had to be derived from the state of absence of care. Thus, the lineage of reptiles without postovipositional attendance of eggs constitutes a point of departure. I address two main questions: how avian care could have evolved from such a state, and how male and female parental roles have been shaped. I propose that the evolution proceeded initially through stages without parental care (main adaptations to flight appeared then) but with increasing investment in eggs, resulting in the appearance of sequential ovulation and of very large eggs producing superprecocial young able to fly shortly after hatching. I suggest that parental care appeared only at that stage....