Importance of environmental nest attributes in the conservation of Juan Fernandez endemic landbirds

Hahn, I., P. Vergara, U. Römer

Abstract

Understanding the particular nesting ecology of Island endemic species represents the first step for identifying suitable micro-habitats and establishing efficient management programs. This could become even more important when island bird assemblages are prone to be invaded by ecologically similar species that may eventually cause niche compression or the extirpation of species already present on the island. In this study we described the nesting ecology of both native and introduced landbird species of the Juan Fernandez Islands and determined to what extent native species could be negatively affected by alien competitors. A total of 119 nests belonging to the 11 resident landbird species were analysed. Landbirds exhibited a wide range of nesting habitat preferences on the different Islands, covering different vegetational types, altitude and ecosystems. By means of a cluster analysis we determined that competition between alien and endemic species apparently does not represent an important factor affecting resource use by endemic birds. Endemic landbirds preferred sites comparatively higher above the ground and with greater slope, as well as larger level of shelter, than alien species. The introduced hummingbird, the Green-backed Firecrown (Sephanoides sephaniodes), had different nesting preferences than the endemic Juan Fernandez Firecrown (Sephanoides fernandensis) whereas the House Sparrow (Passer domesticus) selected nest sites located in humans areas, suggesting that both alien species might be not competing with endemic passerines by nest sites. However, urgent measures are necessary to reduce the potential predation risk of Juan Fernandez Firecrown nests by the alien Austral Thrush (Turdus falcklandii).