Working together: the role of nest predation in the evolutionary transition to avian sociality

In this study we will reveal whether reduced nest predation risk is a benefit of cooperation that can explain the evolutionary transition to sociality in birds.

Cooperative breeding, a social system where non-reproductive helpers assist in raising the offspring of others, serves as a model to understand the major evolutionary transitions to sociality, family-living and cooperation across the animal kingdom. An important long-standing goal in evolutionary biology is to identify the selective force underlying such transitions and their stability, which requires identifying the ecological circumstance(s) under which cooperative breeding improves productivity of the group over that of non-cooperative individuals. Several studies have investigated potential links between cooperative breeding and ecological factors such as climate, latitude, and species’ pace of life, but the general relevance of these factors across taxa and geographical regions remains unclear. This has led to the conclusion that “the grand synthesis remains elusive”.

So far, however, one crucial environmental factor has largely been overlooked: offspring predation risk. Nest predation in birds strongly impacts individuals’ reproductive success and is an almost ubiquitous selection pressure shaping species’ life-histories. If helpers can reduce the significant negative impact of predation on productivity, nest predation risk might represent the missing link in understanding the evolutionary transition to cooperation. Nonetheless, most research on cooperative breeding hardly even touches upon nest predation, illustrating that there is an urgent need to incorporate nest predation into current and future hypotheses about the evolution of social systems. To fill this gap, we aim to reveal whether nest predation underlies the evolution of avian cooperative breeding. To do so, we will first investigate the global geographical link between prevalence of cooperatively breeding birds and species that predate nests. Subsequently, we will test the mechanisms that might underpin global patterns in a detailed field study of multiple wild bird species by assessing whether and how cooperative breeding can lead to reduced chances or costs of nest predation. By investigating both the global associations and mechanistic links between nest predation risk and cooperative breeding, we will produce important new insights in the ongoing effort to explain the evolution and stability of cooperative breeding and animal sociality.