The effects of flooding on piping plover Charadrius melodus reproductive success at Lake Diefenbaker, Saskatchewan,Canada

Up to 5% of the world piping plover Charadrius melodus population breed on the beaches of Lake Diefenbaker, Saskatchewan so reproductive success there is likely important to the future prospects of this species. We collected data on nest initiation dates, nest elevations, hatching and hedging dates, survival rates of chicks and causes of mortality. Study sites were located on beaches where concentrations of plovers were found during the 1991 International Piping Plover Census. In 1992, plovers fledged a mean of 2.0 chicks per pair (n = 30), higher than the mean of 0.1 chicks per pair in 1993 (n = 39) and one of the highest recorded for the species. The major reason for this difference in hedging success between years was due to the loss of unhatched eggs by flooding. Using 1992 and 1993 nest site elevations and reproductive data, we developed a simulation model to assess the effects of flooding on piping plover reproductive success over the last 30 yr. Our model shows that fledging success at Lake Diefenbaker has been below the level recommended for sustainability of the species, in 24 of the last 30 yr. To maximize reproductive success at this location, we recommend that lake levels be managed to prevent or reduce flooding during the breeding season. (C) 1998 Elsevier Science Ltd. All rights reserved.