Assessing the population size of the European storm petrel (Hydrobates pelagicus) using spatial autocorrelation between counts from segments of criss-cross ship transects.

European storm petrels were counted on criss-cross ship transects on the continental shelf between Ireland and Spain. No element of randomisation was involved in the selection of the sampled area. A geostatistical model which explicitly considers the spatial autocorrelation between observations from transect segments, was therefore used to predict population size in the study area. The model also provides standard errors of the prediction. Although some of the underlying assumptions of the model were questionable, several alternative approaches yielded almost similar predictions, suggesting model robustness. The predictionof the total number of European storm petrels present in the study area is equivalent to 255 000 breeding pairs. This is much higher than previous estimates of the total breeding population of the region, ranging from 50 000 to 100 000 pairs. [ABSTRACT FROM PUBLISHER]