Variation of pecking rate with sward height in wild wigeon Anas penelope

We examined how pecking rate changed with sward height in wintering European wigeon Anas penelope in a nature reserve of the French Atlantic coast. Pecking rates were recorded as the time taken to perform 10 or 50 pecks. We found a negative correlation between pecking rate and sward height over a range of heights from 1.0 to 3.5 cm, but no sex effect. Equations based on the time taken to perform 10 or 50 pecks were slightly different, suggesting that scanning (scans of the surroundings) and moving (search for plant items of good quality) had an effect on pecking rate. However, these costs were lower (i.e. a decrease of 6-10% of pecking rate) than the effect of handling time, which remained the dominant foraging process constraining pecking rate (i.e. a decrease of 24% with each 1-cm increase in sward height).