Differential intensity of moorhen Gallinula chloropus (Rallidae) feeding at dawn and dusk in spring
- Department of Botany and Zoology, Massey University, Palmerston North, New Zealand
Feeding intensity of moorhens (Gallinula chloropus) in Scotland is indexed by combining frequency of feeding activities with rates of pecking measured on three substrates. Scottish moorhens peck fastest on a grass/herb sward and slowest on water, with mud intermediate. The foraging pattern over spring, with a March peak, is influenced more by changes in pecking rates than by frequency of feeding activities. Because frequency of feeding and rates of pecking are both higher before sunset than after sunrise the hypothesis of equal feeding intensity at dawn and dusk is discarded. Factors possibly contributing to this result are: reduced energy expenditure at night; diurnal variation in the proportion of time taken up by other, especially social, activities; regulation of bodily heat losses; and diurnal variation in availability of invertebrates and in concentrations of nutrients in plants.