Effect of annual rainfall and temperature on the selection of habitat and overwintering home range of grassland birds

Resumen

Objective: To determine the effect of annual precipitation and winter temperature on the habitat and size of the overwintering home range of two grassland birds in a native grassland in northern Durango, Mexico.

Design/ Methodology/ Approach: Using telemetry techniques during four consecutive winters (2016-2019), we estimated the size of the home range (HR; by the Kernel method) of Centronyx bairdii and Ammodramus savannarum. Likewise, the coverage of grassland, scrubland, bare soil, dead vegetation, and animal excrement was estimated and the seeds available in the soil (biomass, g m^-2) of the habitat were counted. We correlated these dependent variables with non-parametric statistics, to the minimum and maximum annual rainfall (mm) and temperature (°C) of the site.

Results: Grassland sparrows used sites with equitable cover of grass, herbaceous plants, shrubs, bare soil and others (Kruskal-Wallis, p≤0.05). Overall, annual precipitation has no effect on structure and vegetation cover. The HR was negatively correlated (Spearman, p≤0.05) with the annual precipitation for C. bairdii (r^s=-0.90, n=45) and for A. savannarum (r^s=-0.80, n=33). When the maximum temperature was higher, both species had lower HR. In contrast, when the minimum temperature was low, the HR increased for C. bairdii and decreased for A. savannarum.

Study Limitations/ Implications: We demonstrated the importance of considering quantifying the greatest number of variables when research is required on the selection and use of grassland bird habitat.

Findings/ Conclusions: This study allowed us to increase our knowledge about the winter ecology of grassland birds and demonstrated that environmental variables such as annual precipitation and temperature influenced the habitat selection of C. bairdii and A. savannarum.