Kestrel and the Western Barn Owl

      Compared to the 1960s, the Western Barn Owl and the Kestrel have become much rarer in the Swiss Central Plateau. The decline is thought to be primarily due to a lack of suitable breeding sites as well as reduced supply and accessibility of food as a result of intensified farming.

      Aims

      The goal is to increase the populations of Kestrel and Barn Owl, two of the priority species in the Swiss species recovery programme for birds, by providing nest boxes and by ecological improvement of the utilised agricultural area. The effectiveness of the measures is evaluated locally. Simultaneously, a population monitoring will help to identify critical stages in the life cycle of these typical farmland species, thus enabling a comprehensive assessment of the state of their populations. An applied research project investigates the habitat needs of the Barn Owl outside of the breeding season.

      Approach

      Throughout Switzerland, volunteer groups support the Kestrel and the Barn Owl by installing and maintaining nest boxes. The study sites are ecologically distinct areas with a population of at least 10 breeding pairs or covering an area of at least 10 square kilometres. Besides increasing the availability of nesting sites, the purpose of placing nest boxes is to encourage farmers to provide suitable ecological compensation areas close to the nests, especially wild flower strips and extensively managed meadows.

      To assess the success of the recovery measures, the breeding population is surveyed annually, the numbers of eggs and fledglings are recorded, and the young and some adult birds are ringed and measured. Data from the volunteer groups are incorporated into the integrated population monitoring of Kestrel and Barn Owl. Some of the teams have even installed web cams in selected nest boxes, allowing fascinating insights into the breeding behaviour of these two bird species: Pro Riet, Naturschutzverein Lausen.

      To date, little is known about range use and habitat needs of the Barn Owl outside of the breeding season. Food supply, spatial distribution of resources and their use by the owls are unknown. In this study, we investigate how the home ranges of Barn Owls change in the course of the year, and which landscape structures are important in each season. To collect these data, adult Barn Owls are equipped with small GPS loggers that record nighttime coordinates for a period of eight months. In addition, we determine the availability of small mammals by counting mouse tracks along transects and on tracking plates. The results of this survey will help to improve conservation efforts for the Barn Owl.

      Significance

      With their data, the many volunteer groups provide a valuable basis from which the population trends of Kestrel and Barn Owl can be assessed more accurately both at a local level and nationwide.

      The recovery programme for these two popular bird species offers an opportunity to appeal to farmers, encouraging them to implement ecological farming practices for the benefit of endangered species. A fact sheet especially for farmers (“Supporting Kestrels and Barn Owls”) was designed in collaboration with SVS/BirdLife Switzerland and AGRIDEA. The fact sheet introduces specific measures for the conservation of both species on farms and explains how accidents involving the birds can be avoided.

      Results

      In 2015, volunteers managed a total of 3472 nest boxes. Between 2002 and 2015, 7105 kestrel broods and 1583 barn owl broods were recorded. In the process, 18,560 nestling Kestrels and 344 adults as well as 5913 nestling Barn Owls and 513 adults were ringed and measured. Thanks to the recovery efforts, the Kestrel population increased in almost all project areas between 2002 and 2015. Barn Owl populations, on the other hand, are subject to considerable fluctuations, including some dramatic collapses of the breeding population, especially after cold winters with heavy snowfall.

      The results of 14 years of coordinated species recovery programme were summarised in a report (Michler et al. 2016). Publications on habitat use and breeding biology of the Kestrel in the various project areas can be found in the list below.

      Project management

      Stephanie Michler (recovery project)
      Bettina Almasi, Nadine Apolloni (range use of the Barn Owl in the course of the year)

      Partners

      Le Groupe Broyard de Recherches Ornithologiques (GBRO)
      Pro Riet Rheintal
      Several teams of volunteers
      Nature and bird conservation groups/Sections of BirdLife Switzerland

      Publications

      Zellweger-Fischer, J., M. Schaub, C. Müller, M. Rudin †, M. Spiess & L. Jenni (2011):
      Der Bruterfolg des Turmfalken Falco tinnunculus: Resultate und Erkenntnisse aus fünf Jahren integriertem Populationsmonitoring.