Resolving uncertainty in historical observations of the Adélie penguin breeding distribution in southern Prydz Bay, East Antarctica

Abstract The sophisticated spatial reference tools that exist today greatly facilitate studies of spatial ecology. Historically, however, the lack of such tools meant that spatial data were often imprecise, ambiguous or sometimes inaccurate. This can hinder or confound assessments of whether species distributions have changed in the past over decadal timescales. This is the case for Adélie penguins breeding at the southern limit of their breeding range in East Antarctica. In this short note, we resolve uncertainties in the locations of Adélie penguin breeding sites observed in the first population survey in Prydz Bay in 1981 by examining the original working notes of that work in combination with data from a recent survey in 2009 and a recently published spatial reference and identification system for coastal East Antarctica. By clarifying the historical locations, we conclude that the Adélie penguin breeding distribution has remained unchanged in this region over the past three decades, and we provide a robust baseline for assessing change in the future.