What are the reasons for population changes in rare species?

The populations of the hoopoe and the wryneck declined sharply in Switzerland between 1950 and 2000. Both species are priority species, migratory birds, cavity breeders in arable land and foraging specialists. Possible causes of the decline include reduced accessibility or density of prey, reduced availability of breeding sites or deterioration of wintering habitats. However, the relative importance of these possible causes of decline is largely unknown, making effective conservation efforts challenging.

Since 2000, around 700 nesting boxes for the two species have been installed in the Valais and the population has been monitored. Breeding success is recorded and young and adult birds are marked. Integrated population models can be used to investigate which demographic processes (reproduction, survival, immigration, emigration) primarily impact the population. Conventional (ring analysis) and new methods (stable isotopes, geolocator) will be used to learn more about the wintering areas.

The demography of the two species is surprisingly similar. Their populations are mainly influenced by breeding success and immigration. The breeding success of both species depends on the weather, even more so for the hoopoe than for the wryneck.

Hoopoes from the Valais overwinter in the Sahel, with wintering grounds extending over a vast area from Niger to Senegal. Wrynecks from the Valais breeding population, on the other hand, winter in southern Spain and northern Morocco, making them short-distance migrants.

• Abteilung Conservation Biology der Universität Bern

• Schweizerischer Nationalfonds
• Ella & J. Paul Schnorf Stiftung
• Janggen-Pöhn-Stiftung
• UniBern Forschungsstiftung
• Accentus Stiftung