The importance of social information in breeding site selection increases with population size in the Eurasian Griffon VultureGyps fulvus

Abstract

Animals can select breeding sites using non‐social information (habitat characteristics) and social information (conspecific presence or abundance). The availability of both types of information is expected to vary over time during the colonization of a new area, conditioning their use by colonizers. However, if and how both types of information are exploited during the colonization process remains unclear. We hypothesized that non‐social information should be predominant at the beginning of a colonization episode (when conspecific presence is low) and that social information should gain in importance as the colonization progresses. We tested this hypothesis by studying habitat selection by the Griffon Vulture Gyps fulvus, a long‐lived colonial raptor, during a natural colonization process spanning 40 years. In NW Spain, the population showed a sharp increase from 15 breeding pairs in three colonies in the 1970s to 586 breeding pairs in 120 colonies in 2008, expanding its range from 90 km2 in the 1970s to 6403 km2 in 2008, with directions of expansion following areas rich in nesting cliffs. The main determinants of habitat selection varied over time. Livestock density and the characteristics of nesting cliffs were the main predictors of settlement at the onset of colonization. Breeding density of conspecifics increased its importance over time, having the greatest relative weight in habitat selection later in the colonization process. Our results indicated a prevalent use of non‐social information during the early stages of the colonization and an increasing role of social information as the expansion progressed.

An assessment of tree availability as a possible cause of population declines in scavenging raptors

“…This variability in nearest neighbor distance for nests suggests that tree availability rather than territoriality may determine where vultures nest. Furthermore, vultures can have large foraging ranges and some species nest colonially suggesting that nesting density is determined by the availability of trees with desired characteristics and is unlikely to be affected by over-crowding (Jackson et al 2008, Mateo-Tomas and Olea 2011, Phipps et al 2013, Kendall et al 2014). …”

Assessing Species Habitat Using Google Street View: A Case Study of Cliff-Nesting Vultures

“…This area is covered by 3,905 km of paved roads and has a complex topography, with elevations ranging between 340–2,648 m above sea level. Rocky cliffs, mainly of limestone, are abundant all over the study area [14].…”

“…Cliffs can be located through the conventional analysis of the slope of the terrain in GIS (Figure 1) [14]. We aimed to compare the ability of DEM to identify cliffs with that of Google Street View.…”

“…To select the threshold values above which classify a location as a cliff, we considered the slope of all the vulture breeding cliffs recorded in the study area (i.e. our habitat of interest; n  = 148 cliffs) [14]. On this distribution of slopes, we selected three different thresholds [14]: the minimum slope value (0.34), 25 th (0.63) and 50 th percentile (0.68).…”

“…our habitat of interest; n  = 148 cliffs) [14]. On this distribution of slopes, we selected three different thresholds [14]: the minimum slope value (0.34), 25 th (0.63) and 50 th percentile (0.68). These threshold values were used to obtain maps (i.e.…”