Experimental evaluation of a new ground-based survey method for estimating the density and abundance of nesting Adelie penguins Pygoscelis adeliae

A new ground-based technique for estimating the density of nesting Adelie penguins (Pygoscelis adeliae) within occupied habitat is described and evaluated using an experimental approach with model penguins. In this set-up, an operator takes photos with a camera mounted on a 3-m pole at pre-determined sampling locations within habitat occupied by nesting penguins, and the actual boundaries of the plot in which penguin density is estimated are added post-survey. Density estimates are calculated by overlaying slope-specific templates delineating plot boundaries and distances of known dimensions onto the digital photos to allow a distance-sampling analysis to correct for any negative bias in counts arising from a proportion of penguins being obscured. Experimental assessment of biases in density estimates because of misclassification error was < 2% when compared to true density, indicating that this survey method is effective at accurately estimating penguin density and, therefore, abundance.