Individual-level social associations and social information use predict foraging success in winter mixed-species flocks

The acquisition of social information to improve foraging efficiency is considered one of the primary drivers of mixed-species flocks (MSFs). This flow of social information occurs among individuals of multiple species, but analyses of MSFs at the level of species fail to capture the nuances of this dynamic. We investigated how individual-level social associations in North American MSFs impact discovery of novel feeders presented alongside vocal cues. We used radio-frequency identification (RFID) data loggers to track arrivals of individually tagged black-capped chickadees (Poecile atricapillus), white-breasted nuthatches (Sitta carolinensis), and downy woodpeckers (Dryobates pubescens) at fixed feeders, and during novel feeder trials paired with chickadee, nuthatch, or white noise playbacks. For chickadees, a higher number of total associations and conspecific playbacks improved novel feeder discovery. The foraging benefits in nuthatches and woodpeckers were predicted by their individual-level associations with chickadees and these benefits only manifested during chickadee playbacks. We demonstrate that the advantages of mixed-species flocking are not uniformly distributed across species; rather, they are contingent upon individually maintained social associations and the presence of social information. These findings highlight the necessity of quantifying individual variation to accurately assess the evolutionary drivers and fitness consequences of species interactions.