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

S Dutta,Y Jhala

doi:10.3354/esr01126

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.

Highlights

Fourteen percent of the world’s birds are threatened (IUCN 2018), with steep declines among Indo-Malayan species (Butchart et al 2004)
We developed resource selection functions (RSFs) for each behavior and a common RSF for all behaviors by testing ecological predictions with used vs. available habitat data using binomial generalized linear models (GLMs) in an information-theoretic framework (Manly et al 2002)
We examined the goodness of fit (GOF) and variance inflation factors of the global models (Quinn & Keough 2002)

Summary

Introduction

Fourteen percent of the world’s birds are threatened (IUCN 2018), with steep declines among Indo-Malayan species (Butchart et al 2004). Information on habitat use is lacking for many threatened species. This is concerning for grasslands that are rapidly changing and require urgent conservation interventions (White et al 2000). Species depend on landscape complementation when their abundance at larger scales is constrained by the availability of complementary resources at smaller scales (Dunning et al 1992). For these species, availability of complementary resources can enable higher usage of an area, by reducing energetic costs of movements, diminishing predation risk and attracting birds (Choquenot & Ruscoe 2003). Bustards (family Otididae), a group of globally threatened grassland birds, offer an ideal system to test this postulate because of their requirement for heterogeneous habitats and growing dependence on conservation efforts (Collar et al 2017)

Methods

Results

Conclusion