Stage-specific habitat use of the Mountain Plover in Colorado, USA

ABSTRACT Habitat structure, food availability, and predation risk have spatiotemporal variation on the landscape that creates tradeoffs between risk and rewards for animals as they use habitat. These tradeoffs are associated with survival consequences and can vary by life or breeding stage, but stage-specific shifts in these relationships are often not considered in studies of habitat use and survival. We investigated habitat use for nests and broods in the Mountain plover as an example of a ground-nesting species with precocial, mobile young to explore breeding stage-specific responses to vegetation structure, food availability, and predation risk. We located and monitored nests and broods at two study sites in Colorado occupied by geographically separated breeding populations of plovers. We quantified the three covariate categories across standardized site-wide grids in 2021 and 2022. We employed a resource selection analysis to evaluate 10 a priori working hypotheses for how environmental covariates may influence the habitat used by plovers for nesting and brood-rearing. Model comparison results suggest that habitat use relative to availability is best explained by a linear relationship with vegetation structure while conditioning on breeding stage and site, with no effect of food availability or predation risk detected in our dataset. Specifically, probability of use for both nest and brood sites was highest in areas with taller vegetation, contrary to previous research about nest site selection. These unexpected results may be due to the unbalanced sample sizes of the two sites, as previous separate studies have shown opposing habitat use strategies, or due to the coarseness of our covariate data. Regardless of limitations, these results emphasize the importance of investigating stage-specific and potentially site-specific shifts in habitat use patterns for species with precocial young.