Linking density, productivity and trends of an endangered species: The Bonelli's eagle in Spain

Abstract

It is controversial if regional population density is a good indicator of environmental quality according to demographic variables such as breeding success or short-term population trends. In this paper we analyze the interrelationships among regional population density, breeding success and recent population trends of an endangered species, the Bonelli's eagle in the Iberian Peninsula. It is also analyzed the different influence of geographical, climatic, landscape structure and human impact variables on regional variation in those demographic variables. Breeding success was higher and population decrease was lower in those areas where the population density of Bonelli's eagle was greater. The tightly related productivity, density and recent population trends of Bonelli's eagle increased from northern to southern Iberian Peninsula (with highest figures at intermediate latitudes), and as sun radiation increased, and altitude decreased. Breeding success and population density were significantly lower in the periphery of the distribution range than in core areas in the Iberian Peninsula. Population trends between 2000 and 2005 were also more negative (decreasing) in the periphery. Overall, these results suggest that population density in this endangered species of large home-range is a good indicator of environmental quality and reproductive output, and that peripheral populations occupy low suitability areas with lower breeding success, and more probable negative short term population trends.

An approach to consider behavioral plasticity as a source of uncertainty when forecasting species' response to climate change

“…These factors were selected because topography and Mediterranean climate are consistent factors influencing the distribution of the species in Spain at different spatial scales; from a national scale (Muñoz et al. ; Carrascal and Seoane ), to more local scales centered in the near vicinity of the nesting sites (Gil‐Sánchez et al. ; López‐López et al.…”

Effects of rearing conditions on natal dispersal processes in a long‐lived predator bird

“…This means that Bonelli’s eagles rarely recruit into a new territory. Under this scenario, the recruitment of nonadult individuals could be enhanced by a sudden rise in adult mortality, which will increase the probability that juvenile floaters find and/or occupy a vacant territory or mate with the remaining owner of the territory (Carrascal & Seoane, 2009; Carrete et al., 2006; Penteriani et al., 2003). This phenomenon may explain why males recruit at a younger age than female Bonelli’s eagles, as mortality rates are higher in males than in females in the studied population (Hernández‐Matías, Real, Pradel, Ravayrol, et al., 2011).…”

“…Our study species is threatened in Europe, and considerable conservation efforts are being undertaken to protect its remaining populations (Cadahía et al., 2010; Carrascal & Seoane, 2009; Hernández‐Matías et al., 2015; Real & Mañosa, 2001). This means that managers will need further scientific knowledge of dispersal processes as a tool for implementing conservation actions more efficiently.…”

“…In addition, it is vital to improve habitat and prey availability (Ferrer et al., 2014; Real, Bosch, Tinro, & Hernández‐Matías, 2016) and/or to reduce disturbances caused by human outdoor activities and/or the construction of new infrastructures in those territories where chicks are reared under poor conditions (Bosch, Real, Tintó, Zozaya, & Castell, 2010). In all cases, conservation efforts would be best invested in areas of high potential environmental suitability (Carrascal & Seoane, 2009). …”

“…The study and assessment of dispersal areas in management and conservation are vital as such areas may be heavily affected by human disturbance and so may be excluded from typical management plans (Cadahía et al., 2010; Carrascal & Seoane, 2009; Penteriani & Delgado, 2009; Rollan, Hernández‐Matías, & Real, 2016). In fact, reducing juvenile mortality in dispersal areas is a crucial conservation strategy for long‐lived species and may have an important effect on the viability of the reproductive fraction of a population (Fasciolo et al., 2016; Hernández‐Matías et al., 2015).…”