Osprey Pandion Haliaetus: Population Dynamics and Conservation of in Central France

27 Mar Osprey Pandion Haliaetus: Population Dynamics and Conservation of in Central France

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Abstract

English Abstract

Ospreys,
Pandion haliaetus, started breeding in continental
France (Loiret) in the mid 1980s. In 1999, a
national recovery plan for the conservation of this
species was initiated. The conservation efforts,
especially building artificial nests where natural
nests or trees holding nests had fallen down,
favoured and sped-up the colonisation of new
sites, resulting in to 18 known breeding pairs in
2003, confirming the installation of a small population
in central France. A capture-mark-recapture
research program (R. WAHL) enabled us to
describe the breeding phenology and to estimate
key demographic parameters for this population.
Since 1995, 152 fledglings have been ringed as
well as a few adults. Each breeding pair produced
an average of 2 fledglings per year, yet the number
of fledglings varied between sites and
increased with the size of the colonies. Individuals
were highly philopatric, with nearly all breeding
adults coming back to breed the following year,
and about 40% of the chicks fledged returning to
breed in the study area. Age at first breeding was
3.2 ± 0.4 years for females, and 4.4 ± 1.8 years
for males. Recapture probability was high and
averaged 0.913. Adult survival probabilities were
high and were lower for younger breeding females
(0.870 ± 0.098, IC95%: 0.551 – 0.973) than for
older females and males (0.971 ± 0.036, IC95%:
0.737 – 0.997). Survival probability during the
first year of life was 0,512 + 0 . 1 5 6 (IC95%: 0.236
– 0.781). A matrix population model with four age
classes was built to model the dynamics of this
population. The population growth rate estimated with environmental stochasficity (1.245) indicated
that the population should continue to increase in
the near future. Although the high survival, breeding
success and early age at first breeding could
partly explain the increase of the population size,
the rate of increase estimated by the population
model remained lower than the observed rate of
increase (1.643). The immigration of individuals,
particularly from eastern parts of Germany, could
help explain this difference.