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A ROBUST AND COST-EFFICIENT WAY FOR ESTIMATING ABUNDANCE FROM SPECIES DISTRIBUTIONS

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In a recent issue of the Bulletin of the Ecological Society of America (2009, 90(4): 493-495, also the front cover), the editors introduced an upcoming paper by C·I·B scientists and colleagues from Stellenbosch University, SANParks, CSIR and Aarhus University (Hui et al. Extrapolating population size from the occupancy-abundance relationship and the scaling pattern of occupancy — Scheduled to appear in Ecological Applications 19(8), December, 2009).

Abundance is one of the most important measures of species conservation status and an efficient surrogate for species’ ecological functioning. Many techniques, including mark–recapture methods, have been used to estimate species abundance. However, these techniques require fine-scale data, and therefore have only been used for rare species at local scales. As a result, a cost-efficient technique that can be applied at broad spatial scales (e.g., the continental level) and for whole communities (i.e., including common dominant species) is urgently needed. Recent progress in macroecology, and in particular the mechanisms underlying the occupancy–abundance relationship and the scaling pattern of occupancy has provided such potential techniques. Using a dipswitch test with 15 criteria, C·I·B researcher Cang Hui and his coauthors examined the ability of eight models of this kind to estimate the abundance of 610 southern African bird species. Models based on the scaling pattern of occupancy (i.e., those that reflect the scale dependence of species range size) produced the most reliable abundance estimates, and therefore are recommended for assemblage-scale regional abundance estimation. These methods estimate a total of ~2x109 birds in southern Africa (South Africa, Lesotho, and Swaziland). The Bulletin article presents images of four common bird species from the region studied.