Snake species richness predicts breeding distribution of short-toed snake eagle in central Italy

Abstract

Birds of prey, as top predators, play a key role in ecosystem functioning by regulating prey populations and, by means of cascade effects, promoting biodiversity. This makes them adequate sentinels of ecosystem health. Here we analyse the relationship between the occurrence of breeding short-toed snake eagle (Circaetus gallicus) and both the richness of potential prey species and landscape characteristics by taking into account two different spatial scales (i.e. nest-site scale and landscape scale). The short-toed snake eagle offers an interesting case study for investigating the relationships between top predators, prey diversity, and habitats, because it is an extremely specialised raptor that feeds on mesopredators, mostly snakes. Additionally, short-toed snake eagles are mainly threatened by changes in agriculture and land use in Europe, which have reduced the extent of suitable hunting habitats, and by the decrease in snake populations. Our study was conducted in the Latium Region (central Italy) in 2007, where most of the Italian breeding population is concentrated. By means of habitat selection analyses using generalised linear models, our results showed that the species selected breeding areas characterised by low elevations, rugged slopes, and high snake species richness at the nest-site scale (1 km 2 ). At the landscape scale (25 km 2 ), the

Habitat suitability and nest-site selection of short-toed eagle Circaetus gallicus in Tolfa Mountains (Central Italy)

“…Interestingly, neither habitat diversity nor the extent of edge between forests or shrublands and open areas were key factors explaining the presence of the species. Similar results were found in another study carried out in central Italy showing no relationship between the presence of the species and edge extent (Cecere et al 2018). However, other studies have reported that ecotonal and heterogeneous habitats are the preferred hunting areas for the short-toed eagle (Petretti 1988, Sánchez-Zapata & Calvo 1999, Ontiveros 2016).…”

“…As Cecere et al (2018) hypothesized, we argued that the importance of landscape heterogeneity for the species might arise at higher spatial scales than we analysed, therefore we did not find any significant effect.…”

“…Therefore, we believe that this is a genuine relationship and that steeper slopes might enable eagles to reach the nest more easily (Petretti 1988). Alternatively, eagles could select these sites to take advantage of rising thermal updrafts, which are used for soaring and searching for food, as has also been concluded by other researchers (Lopez-Iborra et al 2011, Cecere et al 2018.…”