Survival of Mallard Broods on Benton Lake National Wildlife Refuge in Northcentral Montana

Abstract

We estimated duckling survival in broods of 31 radio-marked female mallards (Anas platyrhynchos) on Benton Lake National Wildlife Refuge (NWR) in northcentral Montana in 1985 and 1986. Overall survival for the 60-day prefledging period was 0.3951, and 87% of all duckling losses occurred within the first 18 days. Survival through the Class I interval (0.4664) was lower (P 0.05) between marked and unmarked adult females. J. WILDL. MANAGE. 54(1):62-66 Low recruitment by mallards and other dabbling ducks over major portions of their breeding range is cause for concern (Greenwood et al. 1987, Hochbaum et al. 1987, Klett et al. 1988). Major determinants of recruitment include nest success, renesting rate, and duckling survival; the latter is perhaps the least understood component (Cowardin et al. 1985:28). However, obtaining precise counts of ducklings is difficult in the dense habitat often used by mallard broods (Talent et al. 1982, 1983; Cowardin et al. 1985). Ringelman and Longcore (1982) encountered similar problems studying black ducks (Anas rubripes). Our objective was to estimate survival rates of mallard ducklings relative to age classes, seasonal chronology of hatch, and body mass of the adult female. We thank N. E. Hall and B. P. Rogers for field assistance, R. J. Everett for manuscript review, and the entire staff of Benton Lake National Wildlife Refuge for encouragement and logistic support. Financial support was provided by the Refuge Division, Region 6, U.S. Fish and Wildlife Service.