P. Dupuis | USGS Science

USGS2000

Survival of American black ducks radiomarked in Quebec, Nova Scotia, and Vermont

We monitored survival of 397 radiomarked juvenile American black ducks (Anas rubripes) distributed among Les Escoumins ( n = 75) and Kamouraska, Quebec ( n = 84), Amherst Point, Nova Scotia ( n = 89), and a site on the Vermont-Quebec border ( n = 149) during autumn 1990 and 1991. Eighty-six percent (215 of 250) of all confirmed mortalities during the study was from hunting; 72% of marked ducks were shot and retrieved and 14% were shot and unretrieved. We tested for differences in survival in relation to sex, body mass, year (1990-91, 1991-92), and among the 4 locations for each of 2 monitoring periods (early, EMP; late, LMP). With data from the EMP for Vermont-Quebec in 1990 and 1991, Les Escoumins in 1990, and Amherst Point in 1991, survival of hatching-year (HY) males and females did not differ ( P = 0.357). For sexes combined for the EMP, survival of ducks was greater in 1991 than 1990 ( P = 0.086), and differed among locations ( P = 0.013). Survival (years combined) was greater at Amherst Point than at Kamouraska ( P = 0.003) and Vermont-Quebec ( P = 0.002) during the EMP. The highest survival rate at Amherst Point (0.545 ± 0.056 [SE]) was associated with the latest date (8 Oct) of season opening; the lowest survival rate (0.395 ± 0.043) was at the Vermont-Quebec border, where hunter numbers and activity were greatest. For the LMP, no interaction between years and locations was detected ( P = 0.942), and no differences in survival existed between years ( P = 0.102) and among locations ( P = 0.349). No association was detected between body mass at capture and survival of combined males and females during the EMP ( P = 0.572) or during the LMP ( P = 0.965). When we censored hunting losses for combined years for each period, EMP or LMP, all survival estimates exceeded 0.800 (0.809-0.965). These data emphasize need for an improved harvest strategy for American black ducks in North America to allow for increases in breeding populations to achieve population goals.

Nova Scotia, Quebec, Vermont↗

USGS1994

Habitat use and movements of postfledging American black ducks (Anas rubripes) in the St. Lawrence estuary, Quebec

We used radiotelemetry to determine habitat use and movements of 38 female juvenile American black ducks (Anas rubripes) on the north shore of the St. Lawrence estuary, Quebec, from 28 August to 15 November 1991. Ducks separated into three groups based on habitat use: inland, estuarine, and those using a mixture of habitats. Ducks using mixed habitats used the greatest variety of habitat types, flew the greatest distances and most often between night roosts and day foraging areas, and were unlikely to be shot. The mean distance flown between night-use and day-use areas for all ducks increased nearly 50% after the hunting season began (overall mean = 6104 m, range 1500 - 26384 m). Mean home range size was 27.6 t 6.5 (SE) km2. Ducks exhibited stronger fidelity to wetlands used at night than to those used during the day. Ducks that were shot spent a high percentage of their time on the estuary (90.1 t 7.4 %) and exhibited high fidelity to a day-use area before the hunting season (73 t 7.3 %).

Canadian Journal of Zoology↗