Animal social interactions have an intrinsic spatial basis—individuals must be close in space to interact, whether directly (e.g., co-occurrence, allo-grooming) or indirectly (e.g., interact with latrines or with parasites at communal nests). This presents a dilemma when determining causality: do individuals interact socially because they happen to share space, or do they share space because they are socially linked? We present a method that uses demographic turnover events as a natural experiment to investigate the links between social associations and space use in the context of inter-annual winter site fidelity in a migratory bird. We previously found that golden-crowned sparrows (Zonotrichia atricapilla) show consistent flocking relationships across years, and that familiarity between individuals influences the dynamics of social competition over resources. Using long-term data on winter social and spatial behavior across 10 years, we show that (i) sparrows exhibit inter-annual fidelity to winter home ranges on the scale of tens of meters and (ii) the precision of inter-annual spatial fidelity increases with age, but (iii) this fidelity is weakened when sparrows lose social partners from the previous year. Furthermore, the effect of social partner loss on spatial fidelity was higher for older birds, suggesting that social fidelity may play an increasingly important role on spatial behavior across the lifetime of this migratory bird. Our study provides evidence that social relationships can influence spatial fidelity, and shows the potential of long-term studies for disentangling the relationship between social and spatial behavior.

Flocks of golden-crowned sparrows were observed during the winter (October-March) from 2009-2019 at the University of California Santa Cruz Arboretum in Santa Cruz, California. Birds were captured using potter traps, fitted with unique combinations of color bands, and DNA samples were collected to identify sex. Flocks were followed on foot through the Arboretum and individual flock memberships and locations were recorded on a 10mx10m grid cell overlay on a map of the study site. 

Dominance interactions were observed for golden-crowned sparrows at seed piles throughout the arboretum. This data was collected separately from flock observations. The included dominance data has been filtered to exclude the individual behavioral observations that were not used in this analysis. 

Banding and attribute files were filtered to exclude morphological and behavioral data not included in this analysis.

There are four files for download, one of which is a rdat file that containing 32 dataframe objects in R. The text files are saved as non-propietary comma separated files, and all analysis was completed in the open-source software, Rstudio. Rstudio is required to open, edit, and run code scripts that are included as R files.