Insights into movements of a clandestine forest bird

We aim for two main goals in this study. First, we investigate the preferred breeding habitat characteristics within forest habitats to enhance the basis for implementing habitat conservation measures, Second, we investigate the start dates to autumn migration to estimate the potential effects of autumn hunting on the Swiss breeding population.

We captured a total of over 100 woodcock individuals in the Jura mountains from 2016 to 2018 using different methods. Sixty individuals were tagged with radio transmitters and tracked for several months. Thirty individuals were tagged with ARGOS transmitters. The localizations of the transmitters allowed us to apply resource selection functions to identify habitat preferences at two spatial scales, within the landscape and within home ranges. The ARGOS transmitters were suitable for identifying departure to autumn migration.

The research project is relevant for the conservation of the woodcock and the protection of its forest habitats. Although the species has shown declining populations in recent years and is listed on the Red List of endangered bird species in Switzerland, it is still hunted. Results of the habitat selection analyses can contribute to design measures to protect the most suitable forest habitats, while results on migration dates will allow for recommendations to prevent Swiss breeding birds from hunting threats.

Woodcocks breeding in Switzerland start their autumnal migration in mid-October, and towards the end of November almost all birds have left. Woodcock in the Jura mountains prefer forests with a well-developed shrub layer and a soil pH value between 5 and 6. An additional study showed that the mass of earthworms is greatest in soils with pH around 6. The forests avoided were those fragmented by many paved roads or by open pastures, and those with a high exposure to artificial light.

• Federal Office for the Environment FOEN
• Centre Suisse de Cartographie de la Faune CSCF