Automated mapping of social networks in wild birds

Growing interest in the structure and dynamics of animal social networks has stimulated major conceptual and analytical advances, but recording reliable, time-resolved association data for wild populations has remained exceptionally challenging. While animal-borne ‘proximity’ tags have been available for some time, earlier devices were comparatively heavy, had limited detection ranges, and/or necessitated recovery for data retrieval (see Supplemental Information). We have developed wireless digital transceiver technology (“Encounternet”) that enables automated mapping of social networks in wild birds, yielding datasets of unprecedented size, quality and spatio-temporal resolution. Miniature, animal-borne tags record the proximity and duration of bird encounters, and periodically transfer logs to a grid of fixed receiver stations, from which datasets can be downloaded remotely for real-time analysis. We used our system to chart social associations in New Caledonian crows Corvus moneduloides – a tool-using species that is suspected to transmit and accumulate tool-related information through cultural processes. Analysis of ca. 28,000 encounter logs for 34 crows over a 7-day period reveals a substantial degree of close-range association between non-family birds, demonstrating the potential for horizontal and oblique information exchange.