DAY-NIGHT VARIATION IN HABITAT USE BY WILSONS PLOVERS IN NORTHEASTERNVENEZUELA

We quantify the temporal variation in day and night habitat use by Wil son's Plovers (Charadrius wilsonia connamominus) in the Chacopata lago on complex, in northeastern Venezuela, during the non-breeding season. The overall (day + night) time spent by plovers on foraging habitats did not vary seasonally. However, the duration of their presence on fo raging sites during daylight was very short from November to January. but was compensated by an increase during nighttime. The day and night distribution of plovers over the lagoon complex differed substantiall y. Wilson's Plovers were gregarious and roosted most of the time durin g daylight. After dusk, they left their diurnal roosts and repositione d themselves solitarily throughout the lagoon mudflats. or flew to the ir nocturnal individual roosts close to mangroves. They foraged during low tides, but never during the entire low-tide periods, neither duri ng daytime nor during nighttime. The plovers spent more time on foragi ng sites during the first part of the night than thereafter, and on mo onlit nights, although they often occurred on feeding habitats during moonless nights. This appears to be correlated with the observation th at Uca cumulanta, their main prey, is active during this portion of th e night and on moonlit nights. The main reason why Wilson's Plovers ar e largely nocturnal appears to be the avoidance of diurnal predators.