Variation in colony sizes of weavers from a citizen science project

Abstract

The project PHOWN (PHOtos of Weaver Nests) is a citizen science project that collects breeding distributions and colony sizes of weaverbirds (Ploceidae) globally. PHOWN began in mid-2010 and has collected nearly 30 000 records in 9.5 years. This paper provides quantitative colony size data for 80 weaver species. In contrast, general handbooks provide either qualitative information or limited quantitative data. The project has resulted in many ornithological insights and we provide some of these in the context of coloniality here. For instance, most species (66%) had a mean colony size of less than 10 nests. Six species had a mean colony size of >50 nests. Colony size is strongly influenced both by breeding biology and by fluctuating environmental conditions, so that the PHOWN database can serve as a guide for future studies.