Diurnal Activity Budgets and Nocturnal Movements of Mallards (Anas platyrhynchos) Wintering at the Hattabara Dam Lake, Western Japan

Abstract

Diurnal activity budgets of Mallard (Anas platyrhynchos) wintering at the Hattabara dam lake in Hiroshima prefecture, western Japan, were investigated during November 2000 to March 2001. Mallards spent 67.9, 16.0 and 14.7% of the time resting, preening, and locomoting, respectively. Less than 1% of the time was spent for each of feeding, alert, agonistic and courtship activities. Activity patterns varied among the months, apparently in response to declining water levels and human disturbances. Resting was the primary activity of Mallards throughout winter. Time spent on resting was highest (P<0.05) during the mid day and evening, while the time spent on locomotion and courtship was highest during the morning (P<0.05). Mallards used a site near the dam for resting during the day. The site was off limits to boaters and sport fisherman. During the night, they used the shallow areas for feeding because these areas were inaccessible during the daytime due to human disturbances. The shallow feeding areas dried up from December to January when water level decreased sharply. Mallards responded by leaving the dam lake at dusk to feed in the adjacent ponds during this period. More than 95% of the area of these ponds was covered by 2-3m tall Common Reeds (Pharagmites australis) and was inaccessible to the Mallards. Appropriate management of the ponds may improve Hattabara dam lake as a waterfowl habitat.