Landscape openness, not patch size or grassland amount, drives area sensitivity of songbirds in northern tall-grass prairies

Context Area sensitivity, a behaviour whereby smaller patches of habitat are avoided, is of significant conservation concern for North American grassland birds. However, it is unclear whether area sensitivity is caused by patch size per se, or whether it results from factors such as landscape openness, which often covaries with patch size. Objectives We aimed to determine which characteristics of a grassland patch or the landscape surrounding it most influence habitat use by tall-grass prairie birds. Methods Using point-count data collected from 20 tall-grass prairie patches in Southern Manitoba, Canada, we determined which spatial extent and landscape characteristics contributed most to area sensitivity for five species of grassland passerines and grassland bird species richness. We assessed the relative importance of patch size, landscape composition within spatial extents ranging up to 8000 m from sampling locations, and edge proximity then compared the importance of landscape characteristics to that of local habitat structure. Results The proportion of open landscape dominated by low-stature plants had a positive effect on species richness and the relative abundances of all focal species, and was generally more important than patch size, habitat amount, edge proximity, or local habitat structure. Conclusions These results suggest that landscape openness, not patch size or habitat amount, drives area sensitivity of grassland birds. Grassland patches embedded in open landscapes are less susceptible to area sensitivity and may be of high conservation value for grassland birds, even when small.

Automated summary

The openness of the landscape is more influential on area sensitivity of grassland birds than patch size or habitat amount. Grassland patches embedded in open landscapes are of high conservation value for grassland birds, even when small.