The role of conservative versus innovative nesting behavior on the 25‐year population expansion of an avian predator

Abstract

Species ranges often change in relation to multiple environmental and demographic factors. Innovative behaviors may affect these changes by facilitating the use of novel habitats, although this idea has been little explored. Here, we investigate the importance of behavior during range change, using a 25-year population expansion of Bonelli's eagle in southern Portugal. This unique population is almost exclusively tree nesting, while all other populations in western Europe are predominantly cliff nesting.During 1991-2014, we surveyed nest sites and estimated the year when each breeding territory was established. We approximated the boundaries of 84 territories using Dirichlet tessellation and mapped topography, land cover, and the density of human infrastructures in buffers (250, 500, and 1,000 m) around nest and random sites. We then compared environmental conditions at matching nest and random sites within territories using conditional logistic regression, and used quantile regression to estimate trends in nesting habitats in relation to the year of territory establishment. Most nests (>85%, n = 197) were in eucalypts, maritime pines, and cork oaks. Nest sites were farther from the nests of neighboring territories than random points, and they were in areas with higher terrain roughness, lower cover by agricultural and built-up areas, and lower road and powerline densities. Nesting habitat selection varied little with year of territory establishment, although nesting in eucalypts increased, while cliff nesting and cork oak nesting, and terrain roughness declined. Our results suggest that the observed expansion of Bonelli's eagles was facilitated by the tree nesting behavior, which allowed the colonization of areas without cliffs. However, all but a very few breeding pairs settled in habitats comparable to those of the initial population nucleus, suggesting that after an initial trigger possibly facilitated by tree nesting, the habitat selection remained largely conservative. Overall, our study supports recent calls to incorporate information on behavior for understanding and predicting species range shifts. K E Y W O R D SAquila fasciata, behavioral innovation, conditional logistic regression, conservation, habitat selection, quantile regression, range expansion

Genetic diversity is retained in a bottlenecked Cinereous Vulture population in Turkey

“…These observations may possibly be explained by high rates of post-fledging mortality at the winter quarters (Yamac ß & Bilgin 2012) or by highly conservative behaviour of adults in nest-site selection (Dias et al 2017, E. Yamac ß unpubl. On the other hand, the lack of any evidence of post-bottleneck expansion is a further cause of worry.…”

“…Despite the much reduced use of poisons recently and the availability of new sources of food near poultry farms (Yamac ß & G€ unyel 2010), the population of Cinereous Vultures in Turkey has neither increased in size nor founded new colonies in the last two decades. These observations may possibly be explained by high rates of post-fledging mortality at the winter quarters (Yamac ß & Bilgin 2012) or by highly conservative behaviour of adults in nest-site selection (Dias et al 2017, E. Yamac ß unpubl. data), respectively.…”

Wild Bonelli’s eagles (Aquila fasciata) as carrier of antimicrobial resistant Salmonella and Campylobacter in Eastern Spain

“…Mediterranean ecosystems [30][31][32]. This species feeds mostly on European wild rabbit (Oryctolagus cuniculus) and red-legged partridge (Alectoris rufa) playing a major dietary role [33].…”

Individual variability in space use near power lines by a long‐lived territorial raptor

“…To our best knowledge, behavioral avoidance of power lines has not been reported in this species, but such potential effect has raised concerns from conservation agencies during the licensing processes of new power lines, sometimes resulting in requests for companies to implement mitigation or compensatory measures. The study was conducted in southern Portugal, focusing on an eagle population that has been regularly monitored in the last 25 years (Dias et al, 2017 ; Palma et al, 2013 ). Since 2006, eagles in this population have been tracked with GPS PTT tags, providing the opportunity to evaluate interactions with both transmission and distribution lines located within their home ranges.…”