Occupancy as a surrogate for abundance estimation

Call Number:

Keywords:

Abstract:

In many monitoring programs it may be prohibitively expensive to estimate the actual abundance of a bird species in a defined area, particularly at large spatial scales, or where birds occur at very low densities. Often it may be appropriate to consider the proportion of area occupied by the species as an alternative state variable. However, as with abundance estimation, issues of detectability must be taken into account in order to make accurate inferences: the nondetection of the species does not imply that the species is genuinely absent. Here the authors review some recent modelling developments that permit unbiased estimation of the proportion of area occupied, colonization, and local extinction probabilities. These methods allow for unequal sampling effort and enable covariate information on sampling locations to be incorporated. The authors also describe how these models could be extended to incorporate information from marked individuals, thereby enabling finer questions of population dynamics (such as turnover rate of nest sites by specific breeding pairs) to be addressed. The authors believe that these models may be applicable to a wide range of bird species and may be useful for investigating various questions of ecological interest. For example, with respect to habitat quality, they might predict that a species is more likely to have higher local extinction probabilities, or higher turnover rates of specific breeding pairs, in poor-quality habitats.

Notes:

ELECTRONIC FILE - Zoology