Summary
A new ground-based technique for estimating the density of nesting Adélie 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-speciWc 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 misclassiWcation error was <2% when compared to true density, indicating that this survey method is eVective at accurately estimating penguin density and, therefore, abundance.