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Aerial surveys are often used to estimate the density of wildlife populations.A common problem is underestimation of population density due to animals being missed.This visibility bias can be quite serious and in this paper we review various methods of attempting its estimation.A variety of methods based on comparison with ground counts, use of a subpopulation of marked animals, mapping with multiple observers, line transect sampling, and multiple counts on the same areas are considered.All of the methods are model based and the various model assumptions are discussed and compared.
Pollock et al. (Wed,) studied this question.