Patuxent Wildlife Research Center
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Survival of American Black Ducks During Staging and Migration
Outcome of Aggressive Interactions Between American Black Duck and Mallard
Sizes of Sympatric American Black Duck and Mallard Broods
American Black Duck—The Birds of North America
Effects of intermittent fasting on body composition and reproduction of American black ducks in winter and spring
Effects of fasting on American black ducks in autumn
Changes in numbers of American black ducks counted in the mid-winter survey in Maryland
American black duck breeding success on Smith Island, Chesapeake Bay, Maryland
Dynamics of Wetland Use by American Black Ducks and Mallards
Water Level and Hunters Affect Use of Habitat by American Black Ducks in Lake Champlain, VT
"Black Ducks and their Chesapeake Bay Habitats" Symposium
Eighty-six percent of all confirmed mortalities of 397 radiomarked black ducks in Quebec, Nova Scotia, and Vermont was caused by hunters. Survival of black ducks among locations was 80 to 96 percent when losses from hunting were censored. (Collaborative study with personnel of CWS, FWS, Université du Québec à Montréal, and Provincial and State biologists). Citation: Longcore, et al. 2000. Survival of American black ducks radiomarked in Quebec, Nova Scotia, and Vermont. J. Wildl. Manage. 64:238-252.
Numbers of aggressive interactions initiated were not different between species, but when black ducks initiated interactions with mallards, black ducks were more successful than mallards. Displacement from a wetland by a male or a pair of one species by the other species was infrequent and equal between species. These findings do not support the hypothesis that male mallards are behaviorally dominant over black duck males, and thus do not support behavioral dominance as a mechanism for competitive exclusion. Citation: McAuley et al. 1998. Outcome of aggressive interactions between American black ducks and mallards during the breeding season. J. Wildl. Manage. 62:134-141.
Sizes of black duck and mallard broods at fledging were not different in either agricultural or forested habitats. These findings support the view that mallards do not affect the productivity of black ducks on a variety of wetland types irrespective of wetland fertility. Citation: Longcore et al. 1998. Brood sizes of sympatric American black ducks and mallards in Maine. J. Wildl. Manage. 62:142-151.
A comprehensive account of the life history of the American Black Duck was complied from published and unpublished literature through 2000. The account details all aspects of the life history and includes a discussion of priorities for future research. Citation: Longcore et al. 2000. American Black Duck (Anas rubripes). In The Birds of North America, No. 481 (A. Poole and F. Gill, eds.). The Birds of North America, Inc. Philadelphia, PA.
American black ducks fasted during winter and spring delayed egg laying in spring but did not affect egg size, fertility or percent that hatched. Fasting did increase liver, intestinal tissue, and digesta mass of females but not of males. Black ducks combine flexibility of food intake with plasticity of the digestive tract, liver, and adipose tissue when food supply is interrupted during winter. Females modulate body mass to survive and defer reproduction when food supply is interrupted in spring. Citation: Barboza and Jorde, 2002. Intermittent fasting during winter and spring affects body composition and reproduction of a migratory duck. J. Comp. Physiol. B 172:419-434.
Intermittent feeding of American black ducks reduced metabolizability of dry matter, energy, protein, and acid detergent fiber. Birds on short fasts were heavier and fatter then those on long fasts but body water and protein were similar between groups. Omnivorous waterfowl combine ingestive and digestive flexibility with plasticity of body lipid to contend with uncertain food availability. Citation: Barboza and Jorde. 2001. Intermittent feeding in a migratory omnivore: Digestion and body composition of American black duck during autumn. Physiol. and Biochem. Zool. 74:307-317.
Black ducks have been counted during the mid-winter survey since 1955 in Maryland and since 1957 in adjacent Virginia. Numbers of black ducks counted in Maryland declined until 1983 when the trend reversed concomitant with more restrictive harvest regulations. The distribution of black ducks in the Chesapeake Bay changed from use in the upper Bay to use in the mid-Bay Eastern Shore and Potomac River sites. Redistribution of wintering black ducks seemed associated with habitat change, loss of submerged aquatic plants, and degradation of water quality, whereas decline in black duck numbers to 1983 seemed related to level of harvest. Citation: Jorde and Stotts. 2002. The mid-winter survey of black ducks, locally and regionally. In Perry, M. C., editor, Proceedings of a Symposium: Black Ducks and their Chesapeake Bay Habitats: KU.S. Geological Survey, Biological Resources Division, Information and Technology Report, USGS/BRD/ITR 2002-2005, in press
The low rate of nesting (37%), lack of renesting, and low hatching success (31%) confirmed that the island salt marsh habitats were a harsh environment for breeding. Most nests (85%) were in needlerush (Juncus roemerianus), where they were vulnerable to tidal flooding and egg predators. Shoreline meadows of widgeon grass (Ruppia maritima) provided foraging sites for ducklings, but high salinity may have affected duckling growth. Citation: Haramis, et al. 2002. Breeding productivity of Smith Island black ducks. In Perry, M. C., editor, Proceedings of a Symposium: Black Ducks and their Chesapeake Bay Habitats: KU.S. Geological Survey, Biological Resources Division, Information and Technology Report, USGS/BRD/ITR 2002-2005, in press
Composition of breeding black ducks and mallards on wetlands at any given time is extremely variable. Up to 26 different combinations of mallards and black ducks were observed on wetlands, and 51% of the wetlands had at least 6 pair combinations. Instantaneous, single-visit surveys to determine use by black ducks and mallards of a wetland are unreliable. Presence of one species or the other during a single visit is insufficient information to characterize a wetland as exclusively used by a mallard or black duck. Citation: manuscript in internal review.
Palustrine emergent wetlands were used preferentially by black ducks irrespective of water level. Palustrine scrub-shrub wetlands were seldom used in the low-water year but used in proportion to availability in the high-water year. Lacustrine emergent wetlands were avoided during hunting season but were used extensively after hunting ceased. Radiomarked ducks avoided refuge wetlands open to hunting regardless of habitat type. (Collaborative study with FWS, Missisquoi NWR, University of Maine) Citation: manuscript in internal review.
The symposium "Black Ducks and Their Chesapeake Bay Habitats," held October 4, 2000, in Wye Mills, Maryland provided a forum for scientists to share research about the American black duck (Anas rubripes). The black duck is an important breeding and wintering waterfowl species dependent upon the Chesapeake Bay habitats. Black ducks have declined significantly in the last 50 years and continue to be a species of management concern. The symposium, sponsored by the Wildfowl Trust of North America and the U. S. Geological Survey, highlighted papers and posters on a range of topics, from the traditional concerns of hunting, habitat, and hybridization to the more recent concerns of human disturbance and neophobia. Other presentations provided a historical perspective of black duck management. The direction that black duck conservation initiatives could or should take in the future was also discussed. As populations of humans in the Chesapeake Bay region continue to increase, we can expect that the black duck and these subjects will receive increased discussion in the future. The proceedings of this symposium, edited by Matthew Perry of USGS-Patuxent Wildlife Research Center, are in press and should be available in the Spring of 2003.