Habitat Determinants and Density of the Endemic Sicilian Rock Partridge Alectoris graeca whitakeri on Mt. Etna, Sicily, Italy

Abstract

The assessment of the conservation status of a species is the first step to prevent local extinction and to plan appropriate, effective and scientifically sound conservation actions, hence knowledge of the distribution, population trends and characteristics of preferred habitat is crucial for the conservation of a species. Galliformes are facing increasing threats related to overhunting, habitat loss and fragmentation, and human disturbance. The Sicilian Rock Partridge (hereafter Rock Partridge) Alectoris graeca whitakeri is a significant conservation unit endemic to Sicily (Italy) classified as Near Threatened by the IUCN due to a decreasing population. Few studies have been conducted on the occurrence and population density of this subspecies. Here, we estimated its population density and identified which habitat factors drive the occurrence of this species on Mt. Etna. We used a combination of sampling methods (speciesspecific play-back calls, distance sampling, camera-trapping) to collect count and presence/absence data, which were then integrated into a single habitat model (presence vs. absence). We obtained 24 responses from play-back calls (plus 8 individuals observed while performing the play-back calls), 8 sightings from distance sampling, 6 detections from camera-trapping. Probability of occurrence of Rock Partridge on Mt. Etna was positively driven by shrub and meadow vegetation, whereas its occurrence decreased with an increase in both woody areas (coniferous and deciduous) and elevation. Population density estimated using play-back call data resulted in 0.80 pairs/km2 (95% CI: 0.17–2.22) over an area of 53.7 km2. The density of Rock Partridge on Mt. Etna appeared to have slightly declined and its distribution undergone a contraction since the previous survey. Several potential threats to the Rock Partridge in Sicily are currently increasing and should be mitigated to ensure the long-term survival of this unique population on Mt. Etna, as well as in the whole island of Sicily.