Damages of carrion crows in farmland

    Carrion crows are known to cause damages in crops, particularly in maize fields. What can be done to prevent such damages?

    Aims

    The Swiss Ornithological Institute compiles and evaluates procedures and measures against carrion crow damages in collaboration with farmers, agricultural institutions, bird conservation and animal protection agencies.

    Approach

    In March 2003, we experimentally tested the effectiveness of gas balloons for deterring carrion crows in a waste dump in the canton of Ticino, Switzerland. We noted numbers and locations of carrion crows on an area of 60 x 90 m in relation to a) no balloons in the air and b) the presence of three balloons during four days. The test balloons were helium-filled red latex balloons 75 cm in diameter attached to ropes 20 m in length.

    In fall 2003, we additionally conducted inquiries by telephone of more than 30 farmers about their experiences with using gas balloons to deter carrion crows.

    Significance

    Each spring, the Swiss Ornithological Institute is contacted by anxious or aggrieved farmers asking for help in relation to carrion crow damages and the possibility of defence strategies. Our project allowed to evaluate the effectiveness of one of the most promising measures of crow deterrence and, based on the results, to give well-founded recommendations. The project is thus primarily of applied value.

    Results

    Both the experiments and the telephone inquiry suggest that gas balloons are suited to scare crows from crops, at least for a limited period of 3-4 days. To achieve long-term protection, however, various deterrence measures have to be applied alternately and in combination. The most promising measures appear to be those related to how crops are grown and to when measures are implemented (ideally during the most vulnerable stage of the crops).

    Project management

    Daniela Heynen

    Partners

    Swiss Association for the Protection of Birds SVS/BirdLife Switzerland
    Swiss Animal Protection SAP
    Forschungsinstitut für Biologischen Landbau FiBL
    Forschungsanstalt Agroscope Changins-Wädenswil ACW
    Forschungsanstalt Agroscope Reckenholz-Tänikon ART
    School of Agricultural, Forest and Food Sciences HAFL
    Agridea

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