Home range size and foraging niche predict lead exposure variability in terrestrial birds.

Ecological risk assessments estimate chemical exposures in wildlife from contaminant concentrations within their surrounding environment. This approach precludes a detailed understanding of interactions between biota and contaminant sources. It also overlooks how the uneven and irregular use of space by animals influences variability in exposure. Here, we conducted a meta-analysis to examine whether site-specific variability in lead exposure was associated with the home range size and movement-related traits of terrestrial bird species. We constructed a series of linear models to test the effect of ecological and environmental predictors on variability in lead exposure, which we quantified using the coefficient of variation for site-specific feather lead concentrations. Accounting for variance across study, site, species, and phylogeny, we show that birds with larger home ranges exhibited more variable levels of lead exposure than those with more restricted movement patterns. This relationship was moderated by foraging niche and was significant in ground foraging birds but non-significant in generalists and arboreal-aerial foragers, which may relate to differences in dietary lead sources and niche complexity. Site-specific variability in feather lead concentrations was further structured by feather type, with contour feathers exhibiting lower variability than wing, tail, or mixed feather samples. Our findings highlight how the use of space at varying scales might influence divergent patterns of chemical exposure in terrestrial birds. We discuss how incorporating movement-related traits into wildlife risk assessments can reduce uncertainties associated with spatial variability in exposure and improve the ecological relevance of monitoring outcomes.