A Crested Caracara (Caracara plancus) Nest Site Inside a Building in Southern Continental Patagonia, Santa Cruz, Argentina

Abstract

Raptors occasionally build nests on novel substrates, including anthropogenic structures, revealing behavioral plasticity. Anthropogenic structures used by caracaras for nesting include telephone and other communication antennas, an electrical substation, a radio tower, utility poles, gas and petroleum drilling platforms, and machinery, highway signs, light towers, building roofs, and telephone network access trunks. Here we report a Crested Caracara nest inside a building, a novel nest location for this raptor. Nesting inside buildings and other anthropogenic structures is common among other groups of raptors and scavengers, including vultures, owls, and several species of kestrels. However, these species do not build nests; rather they lay their eggs directly on the substrate, inside cavities, or on nests built by other species. In contrast, Crested Caracaras build their own nests. For Crested Caracaras, potential benefits of this nest site may include increased protection from extreme weather and mammalian predators, and reduction in the probability of detection by aerial predators, such as the Great Horned Owl present in the area. Some animal behavior patterns can spread quickly, especially in social animals, so it is important to report occurrences of unusual nest sites and to continue monitoring them. Although anthropogenic changes in the Patagonian landscape and in the central Argentina pampas began centuries ago, before our studies on this species in Patagonia there were no reports of anthropogenic structures being used for nesting by the common, highly social, and ubiquitous Crested Caracara in South America. This suggests the use of anthropogenic structures for nesting by this species is recent and limited to southern Patagonia in the southern hemisphere. Our observation of a likely Crested Caracara nest inside a building adds to the mounting evidence of this species’ apparent ability to exploit various and novel anthropogenic substrates for nesting.