Extinction and return of the peregrine falcon: what are the demographic causes?

Investigation of the demographic causes for the near-extinction of the Peregrine Falcon in Switzerland around 1971 and for its miraculous population recovery. Data from 1960-2022 are analysed with an integrated population model.

An integrated population model (IPM) combines the entire information content of three different data sources from Switzerland: population counts, counts of young in the eyrie and recoveries of ringed peregrines that are later found dead. A large part of this data was collected by the legendary “équipe” around Gabriel Banderet in southwest Switzerland.

The peregrine falcon is a global conservation icon and one of the most charismatic bird species. Its worldwide population collapses have been frequently reported, but the mechanism has hardly ever been truly understood. In particular, the relative importance of productivity and survival for population collapse and recovery is not yet clear. An assessment of this for the Swiss population is one of the main objectives of the project.

The IPM shows that both the decline in productivity (caused, among other things, by the DDT-induced eggshell breaking) and a reduced survival rate were responsible for the population collapse.

The data on which this work is based are largely due to the decades-long commitment of Gabriel Banderet (1936-2020) and his famous “équipe” in a large study area in southwestern Switzerland. Thank you for everything, Gaby !