On the Reproducibility of Bird and Mammal Transect Counts in Polar Seas

Abstract

Claude R Joiris

In order to make comparisons between seabird and marine mammal data collected at sea, a first step consists in evaluating their reproducibility. The same transects counted during years show huge variations up to one or two orders of magnitude. In this paper, I compare return transects followed in a short period. Out of important heterogeneities such as local hotpot concentrations, results obtained along the same return transect seem to vary by a factor of two to four. Within a same transect, data simultaneously collected by two observers on both sides of the bridge show ratios of mean values (numbers per 30 min counts) remaining below a factor two, with a mean variation by a factor1.4.

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