close to release areas (Griffon Vultures, Gyps fulvus, in France; Sarrazin et al.
1996), to increase food supply (Piper et al. 1999), or even as a potential solution to
reduce poisoning (California Condor, in the United States; Meretsky et al. 2000).
Our results suggest that these management actions aimed at increasing the
number of breeding pairs within the present distribution of the species and those
attracting nonbreeders within the spatial range of the breeding population of
bearded vultures should be reconsidered. In particular, the strategy of food supplementation should be reviewed because it seems to be one of the main potential
factors promoting the congregation of non-breeding birds around breeders.
Decisions to disperse or to remain in the local population are influenced by local
intraspecific competition (Clarke et al. 1997; Perrin and Mazalov 1999; Gandon and
Michalakis 2001; Lambin et al. 2001; Serrano et al. 2004). Thus high food availability within the geographical range of the breeding population could be keeping
dispersing birds in their natal areas. The expected consequences of reducing food
availability would be both an increase in the movements of floaters outside the
distribution range of breeding birds, thereby reducing direct interactions in territories located near feeding points, and a geographical expansión of the breeding
population to other suitable areas, as is proposed in the Recovery Plan of the species
in Spain. Supplementary feeding sites were opened on the basis of their importance
in increasing juvenile survival (Heredia and Heredia 1990). In this sense, direct
evidence of a causal link between food supplementation and juvenile survival is
lacking, although suggested according to the behaviour and survival values
obtained (Oro et al. 2008; Margalida et al. 2011a, 2014b). Juvenile populations may
have increased as a result of other factors such as an increase in wild ungulate
populations (Razin and Bretagnolle 2003) or the reduction in direct human persecution through legislation since early 1980.
15.6 Demography: Effects of Poisoning
and Supplementary Feeding
The provision of supplementary food at artificial or supplementary feeding stations
or ‘‘vulture restaurants’’ (hereafter SFS), a well-established management tool in the
conservation of scavenger populations (Cortés-Avizanda et al. 2010; Moreno-Opo
et al. 2015; Cortés-Avizanda et al. 2016), appears to be a potentially useful solution
worldwide. SFS has frequently been used to facilitate the recolonization of abandoned areas (Mundy et al. 1992), or to provide safe food sources in areas where
carcasses are baited with poisons to control carnivores (e.g. Wilbur et al. 1974) or
livestock has been treated with veterinary drugs (Gilbert et al. 2007). To the contrary, adverse effects of artificial feeding stations on demographic parameters of
some species (Carrete et al. 2006a) are a concern and prompt us to correctly assess
their effect on the demography of target populations.
358
A. Margalida
1996), to increase food supply (Piper et al. 1999), or even as a potential solution to
reduce poisoning (California Condor, in the United States; Meretsky et al. 2000).
Our results suggest that these management actions aimed at increasing the
number of breeding pairs within the present distribution of the species and those
attracting nonbreeders within the spatial range of the breeding population of
bearded vultures should be reconsidered. In particular, the strategy of food supplementation should be reviewed because it seems to be one of the main potential
factors promoting the congregation of non-breeding birds around breeders.
Decisions to disperse or to remain in the local population are influenced by local
intraspecific competition (Clarke et al. 1997; Perrin and Mazalov 1999; Gandon and
Michalakis 2001; Lambin et al. 2001; Serrano et al. 2004). Thus high food availability within the geographical range of the breeding population could be keeping
dispersing birds in their natal areas. The expected consequences of reducing food
availability would be both an increase in the movements of floaters outside the
distribution range of breeding birds, thereby reducing direct interactions in territories located near feeding points, and a geographical expansión of the breeding
population to other suitable areas, as is proposed in the Recovery Plan of the species
in Spain. Supplementary feeding sites were opened on the basis of their importance
in increasing juvenile survival (Heredia and Heredia 1990). In this sense, direct
evidence of a causal link between food supplementation and juvenile survival is
lacking, although suggested according to the behaviour and survival values
obtained (Oro et al. 2008; Margalida et al. 2011a, 2014b). Juvenile populations may
have increased as a result of other factors such as an increase in wild ungulate
populations (Razin and Bretagnolle 2003) or the reduction in direct human persecution through legislation since early 1980.
15.6 Demography: Effects of Poisoning
and Supplementary Feeding
The provision of supplementary food at artificial or supplementary feeding stations
or ‘‘vulture restaurants’’ (hereafter SFS), a well-established management tool in the
conservation of scavenger populations (Cortés-Avizanda et al. 2010; Moreno-Opo
et al. 2015; Cortés-Avizanda et al. 2016), appears to be a potentially useful solution
worldwide. SFS has frequently been used to facilitate the recolonization of abandoned areas (Mundy et al. 1992), or to provide safe food sources in areas where
carcasses are baited with poisons to control carnivores (e.g. Wilbur et al. 1974) or
livestock has been treated with veterinary drugs (Gilbert et al. 2007). To the contrary, adverse effects of artificial feeding stations on demographic parameters of
some species (Carrete et al. 2006a) are a concern and prompt us to correctly assess
their effect on the demography of target populations.
358
A. Margalida