Cooperative breeding behavior emerges early in restored populations of the Brown-headed Nuthatch (Sitta pusilla)

Abstract

We monitored the emergence of cooperative breeding behavior in 2 Brown-headed Nuthatch (Sitta pusilla) populations that were reintroduced to formerly occupied sites in south Florida. Individuals from presumed family groups were captured and moved (n = 48) in the first reintroduction attempt (1998–2001) on Everglades National Park, Florida, USA. Two cooperative breeding groups were observed in the second breeding season (2000) and the proportion of cooperative breeding groups increased to ∼20% of the territories present in year 5. The second reintroduction attempt focused on capture and release of juveniles (n = 30) onto Jonathan Dickinson State Park, Florida, USA. A cooperative breeding group was observed in the first breeding season (2019) of this second attempt and in the 2 breeding seasons that followed (2020–2021). Cooperative breeding behavior was observed in both reintroduction attempts when nuthatches occupied a small fraction of the available habitat. Habitat saturation has been linked to cooperative breeding behavior in other avian taxa, but our observations point to the potential influence of other factors in promoting cooperation in the nuthatch. Recent studies suggest these factors might include mate limitations, benefits derived from group activities, and direct benefits of co-breeding among >2 adults.