Spatial modeling of Sarus Crane nest site suitability in Cambodia to help target conservation of breeding areas

Robert N. van Zalinge, Jeb Barzen, Stephen T. Garnett

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Abstract

To understand the breeding habitat requirements of the small, highly threatened migratory population of Eastern Sarus Crane (Grus antigone sharpii) in Cambodia and Vietnam, we assessed nest site selection at two different spatial scales: at the scale of individually occupied wetlands within the deciduous dipterocarp forests of Kulen Promtep and Chep Wildlife Sanctuaries, and at a landscape scale covering all such forested areas in northern Cambodia. To model the likelihood of nest occupancy within the landscape, results of aerial surveys for Sarus Crane nests, conducted in 2001, were combined with topographical and environmental spatial data. A second model incorporated deforestation and road development in the landscape between 2001 and 2016.

We found that Sarus Cranes in Cambodia typically nested in remote rain-fed wetlands that formed on flat terrain in the upper reaches of drainage basins. Within these small, forested wetland units, nests were often placed in deeper, well-defined ponds, although three-quarters of all nests were placed randomly in relation to water level. Nest locations were further from roads and agricultural areas than random points. Most of the best nesting habitat, including Kulen Promtep and Chep Wildlife Sanctuaries, was located on Cambodia’s Northern Plains (247 km2 of habitat with a predicted occupancy likelihood of >75 % inside pro- tected areas and 77 km2 outside), with smaller patches of highly suitable areas scattered across the Eastern Plains (15 km2 inside protected areas and 11 km2 outside).

Between 2001 and 2016, 14,215 km2 (15 %) of the original deciduous dipterocarp forest cover was cleared for agriculture, 1,605 km of road was constructed and the area of habitat with a predicted occupancy likelihood of >75 % shrank by 69 % in the Northern Plains (66 % inside protected areas and 79 % outside) and 73 % in the Eastern Plains (80 % inside and 64 % outside). In Kulen Promtep and Chep, cranes continued to nest but in areas modeled as having lower suitability. We recommend (i) strengthening protection of Kulen Promtep and Chep Wildlife Sanctuaries in the Northern Plains and of remaining nesting habitat in other protected areas; (ii) surveying for active nesting in areas having the highest suitability classes based on the 2001 model but not currently protected, particularly south of Kulen Promtep; (iii) in the meantime, take immediate steps towards protecting as much remaining habitat as possible, that was modeled as highly suitable, to allow for population recovery or in case subsequent surveys find it occupied
Original languageEnglish
Article number120703
JournalForest Ecology and Management
Volume529
Early online date10 Dec 2022
DOIs
Publication statusPublished - 1 Feb 2023

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