Factors Affecting Flushing Distance in Incubating Female Greylag Geese Anser Anser

Abstract

We studied risk-taking behaviour of breeding greylag geese Anser anser in western Poland. Our objectives were to test predictions resulting from the parental investment theory by observing variation in flushing distance for incubating females in relation to clutch size, stage of incubation, nest type and number of human visits to the nests. We found that the best predictor of flushing distance was the stage of breeding; a negative relationship was observed between the number of incubation days and the observed flushing distance. Hence, females showed more risky behaviour (shortening their flushing distance) in clutches with a higher probability of hatching, i.e. in agreement with the parental investment theory. We found only a small effect of clutch size in relation to flushing distance and not in the direction expected from the parental investment theory, i.e. females incubating the largest clutches demonstrated the largest escape distance. This finding may be due to unknown age and experience of particular females which, at least potentially, may underlie the observed variation in flushing distance. We also found that females adjusted their flushing distance depending on nest location and potentially different concealment. We found no effect of repeated human visits. Flushing distance was nearly significantly shorter in unsuccessful females (whose nests were later destroyed) than in successful females. Hypotheses explaining risk-taking differentiation patterns in greylag geese are discussed. Our findings suggest that using exclusively flushing distance (or another single behavioural measure of response to human disturbance) might be misleading and should be used carefully for managing access to wildlife areas.