Fall movements patterns of adult female American woodcock (Scolopax minor) in the western Great Lakes region

Abstract

In 2002 and 2003, I collected movement and habitat data for 58 adult female woodcock during fall across 3 pairs of study sites in Minnesota, Wisconsin, and Michigan. Distances between subsequent daily locations were highly variable (C.V. = 2.188), and the majority (90.9%) of distances between subsequent daily locations of woodcock were <400 m, with 47.7% of distances <50 m. Habitat variables related to food, weather, and predator avoidance were used in general mixed linear models using Information-theoretic methods to assess the importance of these variables as predictors of distance between subsequent daily locations of individual woodcock. Models incorporating all movements explained 71.56% of the process variation among individual birds. Woodcock were more likely to make large movements (>500 m) and forage in new areas when environmental conditions were not favorable, such as in the case of low earthworm abundance (biomass). Large movements into new foraging areas were correlated with the interaction between soil porosity and rainfall, presumably because earthworm availability increased following precipitation. Woodcock were also more likely to make longer movements in warmer temperatures with >2/3 of movements >500 m occurring when the daily low temperature was above the median low temperature of 2.4º C. My results suggest that the primary determinants of woodcock movements during fall (prior to migration) were low local food availability and the potential for increased food availability elsewhere. Longer movements were influenced by weather conditions, and there was little evidence that predator avoidance influenced movements between subsequent days. Adult female woodcock appear to incorporate prior knowledge of previously used areas into the decision of foraging location on a particular day, and generally return to the previous day’s foraging area unless conditions become more favorable elsewhere.