Abstract

The Osprey, Pandion haliaëtus, started to breed 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, and in particular the installations of artificial nests where natural nests or trees holding nests had fallen down, favoured and sped up the colonisation of new sites by breeding pairs thereby creating a small population in central France. In 2007, 22 pairs were breeding, resulting in an average annual growth rate of the population of 15.1% per year since 1985. research program (R. Wahl) with a capture-mark-recapture design, allowed to describe the breeding phenology and to estimate key demographic parameters for this population. Since 1995, nearly 300 fledglings were ringed as well as a few adults. In average, each breeding pair produced 1.8 ± 1.2 fledglings per year. 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 3.7 ± 1.0 years for females, and 4.6 ± 1.5 years for males. Recapture probability was high and averaged 0.911. Adult survival probabilities were high and were lower for younger breeding females (0.798 ± 0.076, IC95% : 0.611 – 0.908) than for older females and males (0.921 ± 0.024, IC95% : 0.859 – 0.957). Survival probabilities during the first year of life was 0.379 ± 0.057 (IC95% : 0.276 - 0.495). A matrix population model with four age classes was built to model the dynamics of this population for the next 20 years. The population growth rate estimated with environmental stochasticity was 1.105, indicating that the population should continue to increase in the near future at an average rate of 10.5% per year. 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 below the observed rate of increase (1.151). The immigration of individuals, particularly from eastern parts of Germany, probably explains this difference.

Key words: Osprey, Population dynamics, Breeding, Survival.

 

 

Context

 

 

¨ First breeding discovered in Loiret in 1984

¨ Increase in breeding pairs since 1984

¨ National Restoration Plan for Ospreys since 1999:

    ¡ Monitoring breeding pairs

    ¡ Training courses on the management and conservation of the Osprey (nature reserves,    national agencies, private land)

    ¡ Building of artifical nest platforms

    ¡ Conferences

    ¡ Surveys among hunters and fishermen

 

 

Aims of the talk

 

  ¨ Update of the demographic parameters for the Osprey population in mainland France

 

 ¨ Modeling the population dynamics of this population

 

 

Study area

 

 

 

 

 

 

 

 

          

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                         Adult survival

 

 

 

Population size

 

 

 

Reproduction

 

 

 

Reproduction

 

 

 

 

Reproduction

 

 

 

Density dependence

 

 

Adult survival – best model

 

 

 

 

 

Adult survival - time dependent model

 

 

 

 

Population dynamics

 

 

 

Migration and wintering sites

 

 

 

 

 

Near future of the population

 

 

 

 

Acknowledgements

 

 

 

 

Publications

 

 

 

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