Recent studies overestimate colonization and extinction events for Adelie Penguin breeding colonies
Résumé
Modeling metapopulation dynamics is potentially a useful and powerful tool for ecologists and conservation
biologists. However, the key processes driving metapopulation dynamics are colonization and extinction events, which
are notoriously difficult to study. A recent global assessment of Adelie Penguin (Pygoscelis adeliae) breeding
populations reported multiple potential colonization and extinction events from occupancy observations using recent
high-resolution satellite imagery and examination of historical occupancy literature, but emphasized that the events
should be confirmed with direct observations. We evaluated these conclusions by developing a comprehensive
database of direct observations of Adelie Penguin breeding site occupancy across East Antarctica. The database
allowed 16 of 19 proposed colonization and extinction events in this region to be evaluated using direct observations
that were concurrent in space and time (same breeding season) with observations from satellite imagery. We
concluded that none of the 16 proposed colonization and extinction events had occurred. One true extinction event
may have been correctly identified from satellite imagery, but a conclusive evaluation was not possible because the
direct and satellite observations were not concurrent in time. The evaluation identified several sources of error in
observations from satellite imagery, including errors of omission through failure to detect small colonies and errors of
commission through misidentification of other biological and physical features as Adelie Penguin guano. The
occupancy database corrected issues of poor precision and accuracy in locations of historical occupancy data. Our
results improve understanding of key parameters for Adelie Penguin metapopulation dynamics and facilitate
improved interpretation of satellite imagery in the future.