Survival and Philopatry of Female Dabbling Ducks in Southcentral Saskatchewan

Abstract

Survival and emigration are important processes affecting population dynamics, but these parameters are poorly known for most species of prairie waterfowl. We used mark-resighting analyses to estimate local survival and resighting probabilities of nasal-marked female dabbling ducks (Anas spp.) on the St. Denis National Wildlife Area in southcentral Saskatchewan during 1982-93. Annual resighting probabilities averaged 0.65 (SE = 0.05) for mallards (A. platyrhynchos), 0.75 (SE = 0.09) for gadwalls (A. strepera), 0.44 (SE = 0.09) for northern shovelers (A. clypeata), 0.61 (SE = 0.10) for American wigeons (A. americana), and 0.20 (SE = 0.07) for blue-winged teal (A. discors). We believe that lower resighting probabilities for teal and shovelers resulted from temporary emigration from the study area. Annual adult survival probabilities averaged 0.56 (SE = 0.06) for mallards, 0.57 (SE = 0.05) for gadwalls, 0.51 (SE = 0.06) for shovelers, 0.64 (SE = 0.10) for wigeons, and 0.49 (SE = 0.13) for teal. For gadwalls and wigeons, local survival was negatively correlated with wetland conditions in year i+1. Juvenile survival averaged 0.55 (SE = 0.07) for mallards, 0.00 (SE = 0.17) for gadwalls, 0.32 (SE = 0.09) for shovelers, 0.57 (SE = 0.14) for wigeons, and 0.29 (SE = 0.13) for teal. Lower survival by juveniles relative to adults could reflect lower true survival, greater permanent emigration, or both. Survival estimates from our study were generally comparable to previous estimates based on band recoveries, but they were substantially higher than apparent return rates, demonstrating the inappropriateness of return rates as survival surrogates. We suggest that mark-resighting analysis may have wide use for estimating female survival rates in other species of waterfowl.