UAVs surveys reveals environmental and population changes over time in a large seabird colony of Patagonia, Argentina

Abstract

The use of commercial unmanned aerial vehicles (UAVs) offers numerous potential applications in wildlife research. UAVs enable information gathering in remote areas at relatively low cost and with minimal disturbance to the species under study. In this study, we describe how to use UAVs to acquire aerial data of a large (approximately 6000 breeding pairs) imperial cormorant (Leucocarbo atriceps) colony on the coast of Patagonia, not only in terms of counts and densities, but also in terms of morphometric aspects and changes in the colony substrate over time. We monitored the colony through UAVs for six years from 2014 to 2020. For each year, we built a georeferenced model, which we were able to compare with historical aerial photographs from 1989, 1990 and 1993. This allowed us to identify changes on a large spatial and temporal scale. Over the years, we found a marked increase in the number of imperial cormorants (approximately 60% in 30 years), paired with a significant retreat (roughly 15 m in 30 years) of the original colony substrate due to coastal erosion. This process led to the colony growth inland and the creation of satellite plots on the outskirts, where cliffs, shrubland and otherwise unsuitable areas surround the colony on the internal side. Our approach might shed light on colony responses to environmental change contributing to the advancement of methodological knowledge in wildlife studies.