UNIVERSITY OF KENTUCKY Lexington, Kentucky, United States
Abstract: Group foraging occurs when individuals in a population form groups while searching for resources. Fitness advantages that drive group formation include reduced per capita predation risk as well as increased resource uptake. While there are many drivers of group size, its relation with overall population density has not been studied. Here, we described a model which predicts how optimal group size is determined by population density in bird populations. Per capita costs and benefits of group formation in our model are represented by predation risk and intragroup competition, respectively. Under this model, group size is predicted to be density dependent due to the differences in the density dependence of the factors that drive group formation. We then conducted a meta-analysis to test the predicted relationship. We digitized and analyzed the relationship between population abundance and group size across 24 species of foraging birds. We found evidence that population density is a factor driving group formation and therefore per capita fitness. This confirmed that the preliminary analysis of our data was consistent with our theoretical predictions. Future implications of this study include understanding how optimal group size and social behaviors can drive the stability of populations.
