Habitat suitability assessment for the endangered Nilgiri Laughingthrush: A multiple logistic regression approach

Bombay Natural History Society, 400 023, Mumbai, India; Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, USA; Indian Institute of Remote Sensing, Department of Space, Government of India, 248 001, Dehradun, India; Present address: Centre for Biodiversity Studies, Baba Ghulam Shah Badshah University, Rajouri, India
Current science (Impact Factor: 0.91). 06/2008; 94(11):1487-1494.

ABSTRACT Application of remote sensing and Geographic Informa-tion System (GIS) tools has assumed an increasingly important role in conservation biology and wildlife management by providing means for modelling poten-tial distributions of species and their habitats, unlike the conventional ground surveys. We present here a predic-tive model of habitat suitability for the Nilgiri Laugh-ingthrush, Garrulax cachinnans based on a synergistic use of field surveys and digitally processed satellite im-agery combined with features mapped using GIS data layers. Collateral data were created in a GIS framework based on ground surveys comprising layers such as land-use, measures of proximity to likely features of distur-bance and a digital terrain model. Multiple binomial logistic regression approach was used for modelling, and the model performance was assessed by the area under the receiver operating characteristics (ROC) curve. About 320 km 2 , 25.12% of the area of the Nilgiris considered for modelling was predicted to be suitable for the Nilgiri Laughingthrush. The area under the ROC curve was found to be 0.984 ± 0.003 (R 2 : 0.93 at P < 0.0001), implying a highly effective model. The as-sessed suitable habitat was highly fragmented and comprised of 1352 patches (natural as well as man-made) distributed all over the study area. The smallest suitable patch identified by the model was 400 m 2 and the largest patch 17.65 km 2 . Also, ca. 92% of all patches were smaller than 0.5 km 2 . We presume that some suit-able habitat patches may be unoccupied due to strong fidelity of the species to shola (montane wet temperate forest) patches, low colonization rates, or large inter-fragment distances. Also, larger fragments might serve as source or 'exporters' of surplus individuals to main-tain sink populations throughout the rest of the range. We discuss the implication of habitat fragmentation and narrow geographical range and anthropogenic pressure for the conservation of the Nilgiri Laughing-thrush.


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