Renesting characteristics of captive wild-strain mallards (Anas platyrhynchos) were investigated on experimental ponds in southcentral North Dakota during the breeding seasons of 1976-81. Renesting efforts and egg production increased during the 1st 3 years. Post-yearling females that experienced clutch loss during early incubation produced 3 clutches of eggs during the breeding season. All of the birds produced 4 clutches and 50% produced 5 during the study. Birds provided with an unlimited food supply produced an average of 10.36 ? 1.03 (SD), 9.97 ? 1.09 (SD), 9.59 ? 0.91 (SD), 8.47 ? 0.94 (SD), and 8.50 ? 0.50 (SD) eggs during each successive nesting attempt. Clutch size differed (P < 0.01) among birds, ages, and nesting attempts. Renesting intervals for mallard females on unlimited food averaged 7.13 ? 1.24 (SD) days and ranged from 5 to 10 days. Intervals differed (P < 0.01) among birds and interval sequences. When food availability was reduced, renesting intervals increased and clutch size decreased. J. WILDL. MANAGE. 50(1):32-38 Ground-nesting waterfowl lose many nests to severe weather, predators (Kirsch 1969, Higgins 1977), and agricultural practices such as tillage and haying. Females compensate for such egg losses through renesting (Swanson et al. 1985). The importance of renesting by groundnesting birds to annual production has been shown by numerous authors (Gates 1962, Pospahala et al. 1974, Donham et al. 1976, Nilsson 1983). The characteristics of renesting ducks, however, are not well documented (Sowls 1955, Coulter and Miller 1968, Cowardin and JohnThis content downloaded from 157.55.39.253 on Wed, 08 Jun 2016 04:55:22 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 50(1):1986 MALLARD RENESTING * Swanson et al. 33 son 1979). Renesting has been demonstrated with wild marked birds, but the proportion of females that renest after their clutch is destroyed is not known (Sowls 1955, Keith 1961, Gates 1962, Strohmeyer 1967, Coulter and Miller 1968). Renesting is difficult to document because nests destroyed during early laying usually are not found, and renesting can occur outside of a study area. Early-nesting species, such as mallards, initiate laying soon after arrival on the breeding grounds, can establish several nests through continuous laying (Gates 1962), and may continue to renest into late June and early July (Swanson et al. 1985). Birds captured during the early stages of laying often abandon their nests and, as a result, the 1st attempt may not be documented. Here we describe the characteristics of renesting, wild-strain mallards on experimental ponds. Appreciation is extended to D. H. Johnson for aid in statistical analysis, and H. F. Duebbert and A. T. Klett for critically reviewing the manuscript.