Effects of weather and timing on counts of breeding Snipe Gallinago gallinago

Abstract

Capsule: Snipe numbers are assessed most accurately at dusk and at low wind speeds. Aims: To identify factors affecting the variability and efficiency of breeding Snipe surveys and to assess the validity of current survey methods for estimating breeding densities or monitoring population change. Methods: The effects of cloud cover, rain, wind, diurnal and seasonal timing on estimated densities of breeding Snipe were assessed using data from early morning and evening surveys on moorland during mid-April to early June. The effects of diurnal and seasonal timing of surveys were examined using data from counts of Snipe made at three-hour intervals throughout the day on four dates. Results: Estimated total Snipe densities and densities of drumming Snipe declined as wind speed increased (25% and 39% lower, respectively, at force 2-3 on the Beaufort scale and 46% and 83% lower at force 4-5 compared to force 0-1). Drumming Snipe density estimates were 266% higher in light rain than dry conditions. Numbers of drumming Snipe were highest at dusk and low numbers of Snipe were encountered during the middle of the day. There was seasonal variation in drumming activity, with little drumming during late April and early May. Conclusions: Surveys of breeding Snipe should not be undertaken when wind exceeds force 3 on the Beaufort scale (or 19 km/h). In situations where only small areas need to be surveyed but absolute numbers are desirable, point counts at dusk will be the most effective method. © 2006 British Trust for Ornithology.