Recovery dynamics and viability of the white-tailed eagle (<Emphasis Type="Italic">Haliaeetus albicilla</Emphasis>) in Germany |
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Authors: | Justine Sulawa Alexandre Robert Ulrich Köppen Peter Hauff Oliver Krone |
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Institution: | 1.Leibniz Institute for Zoo and Wildlife Research,Berlin,Germany;2.UMR 7204 MNHN-CNRS-UPMC, Species Conservation, Restoration and Population Survey (CERSP),Muséum National d’Histoire Naturelle,Paris,France;3.Hiddensee Bird Ringing Center,Greifswald,Germany;4.Neu Wandrum,Germany |
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Abstract: | Understanding the effect of protection measures on recovery of endangered populations is crucial for assessing the efficiency
of management plans. Following the ban of DDT, PCB and other detrimental chemicals in the 1970s, the German white-tailed eagle
population recovered rapidly. Using nest monitoring data, dead recovery data and population dynamics models, we examined both
short and long-term viabilities of the population. Between 1991 and 2005 the proportion of breeding pairs with an active nest
among territorial pairs was α = 0.88 ± 0.007. Annual breeding success was γ = 0.62 ± 0.014. Mean fledged brood size was b = 1.50 ± 0.010 fledged/successful breeding pair. The analysis of dead recovery data of 1,273 individuals ringed as nestling
between 1991 and 2006 allowed survival rates to be estimated. We needed to distinguish between “young” (5 years old) and “old”
(older than 5 years) adults. Furthermore the annual survival rate was higher for juvenile and immature birds (0.921 ± 0.024)
than for adults (s
“young” = 0.760 ± 0.097 and s
“old” = 0.875 ± 0.079), a pattern presumably explained by territorial fights. Finally, an age structured model was used to examine
the joint effect of population regulation, environmental and demographic stochasticities. All results indicated that only
pessimistic scenarios could lead to substantial extinction probabilities within 100 years. We conclude that management measures
were successful in removing the main extinction factors of the population and that future conservation efforts need to focus
on the remaining ultimate extinction causes. |
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