Estimating density of animals during migratory waves: A new model applied to marine turtles at nesting sites

Abstract

Migratory species are sensitive to population declines because they require good habitat across their broad geographic distributions. For this reason, populations of migratory species require careful monitoring to permit detection of any change in their conservation status. An easily implemented technique is a census of individuals at a particular location along the migratory route, which can be used as an index of population status. However, in most situations, censuses are only performed during a portion of a particular season, especially when the presence of the species spans several months at a remote place. To be able to make comparisons among years, it is, thus, important to correct for partial counts. Several such procedures have been developed recently for marine turtles at nesting sites, birds during migration and the phenology of flowering in plants. In the current paper, I review different existing approaches, and then present a new statistical framework improving on those previously used. The method was tested with various time-series of marine turtle nest counts during the nesting season. Results demonstrate that the method is very efficient, and has the additional advantage of being easy to use by a wide variety of researchers. © Inter-Research 2010.