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J.R. Goldsberry

Publications and source records attributed to J.R. Goldsberry.

5 recordsLinked to original sources
USGS2002

Sources of variation in breeding-ground fidelity of mallards (Anas platyrhynchos)

Generalizations used to support hypotheses about the evolution of fidelity to breeding areas in birds include the tendency for fidelity to be greater in adult birds than in yearlings. In ducks, in contrast to most bird species, fidelity is thought to be greater among females than males. Researchers have suggested that fidelity in ducks is positively correlated with pond availability. However, most estimates of fidelity on which these inferences have been based represent functions of survival and recapture-resighting probabilities in addition to fidelity. We applied the modeling approach developed by Burnham to recapture and band recovery data of mallard ducks to test the above hypotheses about fidelity. We found little evidence of sex differences in adult philopatry, with females being slightly more philopatric than males in one study area, but not in a second study area. However, yearling females were more philopatric than yearling males in both study areas. We found that adults were generally more philopatric than yearlings. We could find no relationship between fidelity and pond availability. Our results, while partially supporting current theory concerning sex and age differences in philopatry, suggest that adult male mallards are more philopatric than once thought, and we recommend that other generalizations about philopatry be revisited with proper estimation techniques.

Behavioral Ecology↗
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↗
USGS1985

An aerial photographic census of Chesapeake Bay and North Carolina canvasbacks

We used conventional 35-mm photography to conduct an aerial photographic census of canvasbacks ( Aythya valisineria ) throughout Chesapeake Bay (tidal Maryland and Virginia) and coastal North Carolina, 26-30 January 1981. Flock size and sex ratio characteristics were determined from examination of color transparencies of 165 canvasback flocks totaling over 95,000 birds. A sex ratio of 2.91 males/female was determined from 68,769 birds, 80% of the birds in 150 flocks. Sex ratio for the Atlantic Flyway was projected as 2.90 males/female. We recorded the greatest number of canvasbacks and the widest range of flock size in Maryland waters; the fewest canvasbacks and the smallest average flock size in Virginia; and the fewest but on average the largest flocks of canvasbacks in North Carolina. Sex ratio varied latitudinally in the flyway with a tendency for males to occupy more northern and females more southern latitudes in winter. Sex ratio (males/female) was highest in Maryland (3.98), slightly lower in Virginia (3.71), and lowest in North Carolina (1.70). Locally, sex ratio varied with flock size. In Chesapeake Bay, small flocks (<100 birds) had lower sex ratio (P < 0.05) than medium (100-1,000) or large (>1,000) flocks. By providing large- sample sex ratio information, as well as exact counts of birds, we conclude that low-level 35-mm aerial photography is the most efficient and accurate means of determining canvasback population status in eastern coastal habitats.

Maryland, North Carolina, Virginia↗