Incomplete search effort: a potential source of bias in estimates of Adelie penguin breeding populations in the Australian Antarctic Territory

PotentialAdelie penguin Pygoscelis adeliae breeding habitat in the AustralianAntarctic Territory (AAT: 45◦E–136◦E, 142◦E–160◦E) was mapped using a geographic information system (GIS), and the literature reviewed for evidence of the mapped habitat being searched for presence or absence of breeding Adelie penguins. It is concluded that incomplete search effort is a possible source of substantial negative bias of Adelie penguin breeding abundance derived from published count data in some regions of the AAT. The extent of search effort in other regions of Antarctica could be determined using the same approach applied here, because GIS data required for mapping potential habitat are available for the entire continent.We would expect that regions with more scientific and tourist activity, such as the Antarctic Peninsula, are likely to have greater search effort than the AAT.