© Ruedi Aeschlimann
The whitethroat is a characteristic bird species of the open farmland with herbaceous field boundary strips and low hedges and bushes for nesting. Due to habitat loss, the once widespread species is now missing in large parts of the Swiss plateau. Therefore, specific habitat improvements aim at promoting populations of the whitethroat.
A relatively large population of whitethroats still occurs along the southern foot of the Jura mountains (canton Vaud). We aim at conserving this population by both enhancing existing and creating new habitats. To increase our understanding of the species´ habitat requirements, specific questions are being addressed within the framework of this recovery programme.
The whitethroat is one of 50 species in the Swiss species recovery programme, which lists species in need of specific conservation measures for continued persistence in Switzerland.
In 2006 and 2007, whitethroats were censused along the southern foot of the Jura mountains to increase knowledge on the preferred breeding habitats. In 2006, whitethroats were additionally censused in an area near Geneva (Champagne genevoise) and in two sites near Lake Neuchâtel (Grosses Moos, canton Bern and Combremont-Nuvilly, cantons Vaud/Fribourg). Afterwards, habitat composition was compared between occupied sites and randomly selected, but unoccupied sites close by.
The findings of this study have been incorporated into a land management course for farmers. The course shows how suitable habitat can be created for the whitethroat and other species.
The major aim of this project is to show what measures should be taken to promote the whitethroat in agricultural landscapes. In addition, we hope to raise the farmers´ awareness of and interest in implementing suitable conservation schemes. We expect other bird species (e.g. red-backed shrike, stonechat, yellowhammer, brown hare) to benefit from the measures taken in favour of the whitethroat.
The censuses along the southern foot of the Jura Mountains revealed 70 whitethroat territories in 2006, but only 44 territories in 2007. This decrease was most probably caused by the removal of numerous wildflower strips as well as by unfavourable weather conditions during the breeding season. Results from the 2006 censuses in the other study sites were as follows: 43 territories in both the Champagne genevoise (canton Geneva) and the Grosses Moos (canton Bern), 8 territories in Combremont-Nuvilly (cantons Vaud/Fribourg). The whitethroats did not only settle in hedges, ruderal areas and (railroad) embankments, but often also in wildflower strips. Sporadically, singing whitethroats were observed in rape fields.
In the context of this project we collected data of various habitat factors in whitethroat territories and in corresponding reference points nearby. In order to evaluate the important factors for habitat selection, habitat data were analyzed either for territories in hedgerows or for territories in fields. Our analyses showed that in case of territories located in fields the "presence and number of a few important plants (as for example Common teasel Dipsacus sylvestris)" and "vegetation density", whereas in case of territories located in hedgerows the "number of thorny shrubs" and "presence of brambles" were important factors for habitat selection.