15.7.2 Effects of Illegal Poisoning and Reduced Food
Supplies on Adult and Pre-adult Survival
The model garnering the greatest support (model 1) showed that the closure of some
feeding stations slightly changed survival and did so differently for juveniles (1–
2 years old, the age class exploiting feeding stations with higher frequency) and
immature (2–3 years old) and subadults (4–5 years old), whereas adults (>6 years
old) showed a temporal decline in survival over the study. Survival of juveniles
slightly decreased from 0.975 to 0.957, that of immatures and subadults from 0.917
to 0.906, whereas adult survival decreased from 0.975 in 1987–0.901 in 2011
(Table 15.3).
15.7.3 Contradictions Between Health and Biodiversity
Policies
Recent changes in European health regulations provoked apparent contradictions
between the application of sanitary and conservation policies (i.e. to eliminate
corpses avoiding the presence of carrion in the field vs. to conserve scavenger
species; Donázar et al. 2009b; Margalida et al. 2010). Implementation of the sanitation policy appears to have undermined conservation goals, as evidenced by, for
example, in the same area with Eurasian griffon vultures in which an annual
decrease in breeding success, reduced population growth, increased mortality on
young age classes and changes in diet and behaviour is observed (Donázar et al.
2009b, 2010; Zuberogoitia et al. 2010; Margalida et al. 2011d, 2014c). Our results
confirm these observations with empirical, long-term data on another vulture species. After sanitation policies had been enacted, the threatened Pyrenean bearded
vulture population had reduced survival, especially of subadult individuals, and
adults bred later and less successfully than before policy implementation. In this
sense, additional conservation actions, such as supplementary feeding, can buffer
the negative effects of policy change on demographic parameters (Oro et al. 2008).
However, because supplementary feeding can also have detrimental effects (Carrete
et al. 2006b; Robb et al. 2008; Cortés-Avizanda et al. 2016), this tool should only
be used as a precautionary measure until the recovery of the previous scenario (i.e.
availability of domestic carcases in the field) is achieved.
According to our results, reduction of food supply does not affect the proportion
of pairs that start breeding, and so the decision to breed or not was influenced by the
change in carcase disposal legislation. Among the European scavenger guild,
bearded vultures seem to be the least sensitive to the effects of food limitations
(Margalida and Colomer 2012). Their specialised diet based on bone remains
implies a foraging resource for which only conspecifics can compete, which lasts
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371
Supplies on Adult and Pre-adult Survival
The model garnering the greatest support (model 1) showed that the closure of some
feeding stations slightly changed survival and did so differently for juveniles (1–
2 years old, the age class exploiting feeding stations with higher frequency) and
immature (2–3 years old) and subadults (4–5 years old), whereas adults (>6 years
old) showed a temporal decline in survival over the study. Survival of juveniles
slightly decreased from 0.975 to 0.957, that of immatures and subadults from 0.917
to 0.906, whereas adult survival decreased from 0.975 in 1987–0.901 in 2011
(Table 15.3).
15.7.3 Contradictions Between Health and Biodiversity
Policies
Recent changes in European health regulations provoked apparent contradictions
between the application of sanitary and conservation policies (i.e. to eliminate
corpses avoiding the presence of carrion in the field vs. to conserve scavenger
species; Donázar et al. 2009b; Margalida et al. 2010). Implementation of the sanitation policy appears to have undermined conservation goals, as evidenced by, for
example, in the same area with Eurasian griffon vultures in which an annual
decrease in breeding success, reduced population growth, increased mortality on
young age classes and changes in diet and behaviour is observed (Donázar et al.
2009b, 2010; Zuberogoitia et al. 2010; Margalida et al. 2011d, 2014c). Our results
confirm these observations with empirical, long-term data on another vulture species. After sanitation policies had been enacted, the threatened Pyrenean bearded
vulture population had reduced survival, especially of subadult individuals, and
adults bred later and less successfully than before policy implementation. In this
sense, additional conservation actions, such as supplementary feeding, can buffer
the negative effects of policy change on demographic parameters (Oro et al. 2008).
However, because supplementary feeding can also have detrimental effects (Carrete
et al. 2006b; Robb et al. 2008; Cortés-Avizanda et al. 2016), this tool should only
be used as a precautionary measure until the recovery of the previous scenario (i.e.
availability of domestic carcases in the field) is achieved.
According to our results, reduction of food supply does not affect the proportion
of pairs that start breeding, and so the decision to breed or not was influenced by the
change in carcase disposal legislation. Among the European scavenger guild,
bearded vultures seem to be the least sensitive to the effects of food limitations
(Margalida and Colomer 2012). Their specialised diet based on bone remains
implies a foraging resource for which only conspecifics can compete, which lasts
15 Importance of Long-Term Studies to Conservation …
371