Devil is in the detail: behaviorally explicit habitat selection by the Critically Endangered great Indian bustard

Abstract

Habitat management to accommodate ecological needs of threatened species can help abate biodiversity decline. Some species require contrasting microhabitats for different functions, and may prefer patches with ample, diverse microhabitats. We examined this problem for the Critically Endangered great Indian bustard Ardeotis nigriceps in 175 km2 breeding habitat in Kachchh, India. We developed behaviorally explicit resource selection functions (RSFs) by comparing used vs. available microhabitats using binomial generalized linear models that tested hypothesized habitat responses in an information theoretic framework. We identified suitable resource units based on fitted RSF values. We examined if availability of complementary resource units influenced density/usage at the patch level, using line transect distance sampling. Birds preferred agro-vegetation mixture, grassland, high fruit abundance and intermediate grazing density, and they avoided Prosopis thickets for foraging. They preferred moderately tall sward for day resting but shorter sward and less Prosopis for roosting. Nesting females preferred grasslands with relatively tall sward and abundant insects, while displaying males preferred grasslands with shorter sward, far from settlements. Thus, microhabitat selection differed between behaviors and differed from habitat availability. The RSF without behavioral segregation failed to capture these nuances and was non-informative for habitat management. Density/usage at the patch level was correlated with the availability of complementary microhabitats. Thus, protected area management to accommodate diverse life-history requirements may reduce species’ movements over large hostile landscapes and associated mortality. Overall, species requiring complementary microhabitats will benefit from management that promotes habitat heterogeneity. However, habitat use analysis based on behaviorally inexplicit occurrence cannot capture the habitat quality of such species.