vultures is highly restricted spatially, and both the reproductive and
non-reproductive fractions of the population coexist. The decision of some individuals to get into a trio as a subordinate also has clear adverse consequences for the
whole population. However, since it appears as a result of ecological constraints,
this behaviour could be reversed through management.
15.4.4 Conservation Implications Related
with the Apparition of Polyandrous Formations
This unusual mating behaviour is thus compromising the conservation effort
directed to this endangered species; management to encourage floaters to settle in
other suitable but unoccupied areas may be beneficial. Our findings have direct
implications for conservation. To our knowledge, this would be another example of
the detrimental effects of food supplementation programmes on the conservation of
threatened species (Robertson et al. 2006). Reducing food supply or progressively
moving feeding stations outside of the Pyrenees may encourage floaters to settle in
other areas where they could find breeding opportunities (see Margalida et al.
2008a, 2013). The translocation of floaters of the endangered Seychelles
magpie-robin Copsychus sechellarum from a population-saturated island to an
unoccupied one was a successful conservation strategy, since individuals become
breeders (Kokko and Sutherland 1998). A similar situation could be expected if
ecological and behavioural cues exposed in this paper are linked to direct conservation actions for this endangered vulture.
15.5 Density-Dependent Productivity Depression
and Supplementary Feeding Management
Two different hypotheses relate density-dependent changes in demographic
parameters to population regulation in territorial species. The interference
hypothesis suggests that reductions in fecundity and/or survival coinciding with an
increase in population size are caused by a homogeneous reduction in the quality of
available resources due to an increase in agonistic encounters between individuals
(Dhondt and Schillemans 1983; Sillett et al. 2004). The habitat heterogeneity
hypothesis, however, suggests that the progressive occupation of low-quality territories as density increases causes a decline in the average per capita productivity
and/or survival of a population even when its variation increases, leading to
density-dependent regulation (Rodenhouse et al. 1997; Krüger and Lindström 2001;
Sergio and Newton 2003). Here, dominant or early-arriving individuals occupy
high-quality areas and, by means of territorial behaviour, relegate subordinate or
late-arriving individuals to inferior territories or, when these places are also
15 Importance of Long-Term Studies to Conservation …
353
non-reproductive fractions of the population coexist. The decision of some individuals to get into a trio as a subordinate also has clear adverse consequences for the
whole population. However, since it appears as a result of ecological constraints,
this behaviour could be reversed through management.
15.4.4 Conservation Implications Related
with the Apparition of Polyandrous Formations
This unusual mating behaviour is thus compromising the conservation effort
directed to this endangered species; management to encourage floaters to settle in
other suitable but unoccupied areas may be beneficial. Our findings have direct
implications for conservation. To our knowledge, this would be another example of
the detrimental effects of food supplementation programmes on the conservation of
threatened species (Robertson et al. 2006). Reducing food supply or progressively
moving feeding stations outside of the Pyrenees may encourage floaters to settle in
other areas where they could find breeding opportunities (see Margalida et al.
2008a, 2013). The translocation of floaters of the endangered Seychelles
magpie-robin Copsychus sechellarum from a population-saturated island to an
unoccupied one was a successful conservation strategy, since individuals become
breeders (Kokko and Sutherland 1998). A similar situation could be expected if
ecological and behavioural cues exposed in this paper are linked to direct conservation actions for this endangered vulture.
15.5 Density-Dependent Productivity Depression
and Supplementary Feeding Management
Two different hypotheses relate density-dependent changes in demographic
parameters to population regulation in territorial species. The interference
hypothesis suggests that reductions in fecundity and/or survival coinciding with an
increase in population size are caused by a homogeneous reduction in the quality of
available resources due to an increase in agonistic encounters between individuals
(Dhondt and Schillemans 1983; Sillett et al. 2004). The habitat heterogeneity
hypothesis, however, suggests that the progressive occupation of low-quality territories as density increases causes a decline in the average per capita productivity
and/or survival of a population even when its variation increases, leading to
density-dependent regulation (Rodenhouse et al. 1997; Krüger and Lindström 2001;
Sergio and Newton 2003). Here, dominant or early-arriving individuals occupy
high-quality areas and, by means of territorial behaviour, relegate subordinate or
late-arriving individuals to inferior territories or, when these places are also
15 Importance of Long-Term Studies to Conservation …
353