Survival of Mallard broods in Benton Lake National Wildlife Refuge in north central Montana

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) than through Class II (0.8887) and Class III (0.9531). Total brood loss occurred among 37% of the females and accounted for 60% of all duckling losses. Broods that survived to fledging averaged 5.0 ducklings. The 60-day survival probability (0.4417) of ducklings in broods that hatched early (on or before 10 Jun) was higher (P < 0.05) than survival of late broods (0.3324). Apparent brood size did not differ (P > 0.05) between marked and unmarked adult females.