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Journal ArticleDOI

Relative Distribution of Mallard and Black Duck in Winter

01 Jul 1943-The Auk-Vol. 60, Iss: 3, pp 438-439
About: This article is published in The Auk.The article was published on 1943-07-01. It has received 5 citations till now.
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Journal ArticleDOI
TL;DR: Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.
Abstract: ASTRACT: Changes in general fall and winter distributions of Mallards and Black Ducks over the past century have resulted in markedly increased sympatric contact during pair formation between these two forms, and have been responsible for increased opportunities for hybridization. Bureau of Sport Fisheries and Wildlife records of hybrids from 34 states indicate a minimal current hybridization rate that is about 4% of the frequency expected on the basis of mating according to mathematical probabilities of chance contact. Thus, hybridization is most frequent where both forms are almost equally abundant, indicating that no reinforcement of differences reducing hybridization in the primary zone of contact is detectable. The primary zone of sympatry has moved eastward approximately 300 miles during the past half century and will almost certainly continue to do so. Owing to its much smaller gene pool, the Black Duck is vulnerable to eventual swamping through hybridization and introgression, although the present hybridization rate is sufficiently low as to make this unlikely in the foreseeable future.

49 citations


Cites background from "Relative Distribution of Mallard an..."

  • ...Table 1 presents an updated version of the information presented earlier (Wing, 1943; Johnsgard, 1961b), summarizing Audubon Christmas Count information on Mallards and Black Ducks in the Johnsgard in American Midland Naturalist (January 1967) 77(1)....

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  • ...State-wide Mallard: Black Duck ratios for the- first 40 years, from 1900 to 1939, were first calculated by Wing (1943), and provide an estimate of relative state wintering-ground distributions for this period....

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  • ...Table 1 presents an updated version of the information presented earlier (Wing, 1943; Johnsgard, 1961b), summarizing Audubon Christmas Count information on Mallards and Black Ducks in the...

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Journal ArticleDOI
TL;DR: For example, Johnsgard as discussed by the authors traced the distributional changes of wintering Mallards and Black Ducks in the eastern states from 1900 to the present using data compiled by the Audubon Society's annual Christmas Counts.
Abstract: Through the use of data compiled by the Audubon Society's annual Christmas Counts, an attempt has been made to trace the distributional changes of wintering Mallards and Black Ducks in the eastern states from 1900 to the present. During this period the Black Duck has increased relative to the Mallard in few if any states (the Great Lakes region), whereas the Mallard has increased nearly everywhere else (except in the extreme northeast), particularly in the southern coastal states. Deforestation and changes in land use are suggested as probable reasons for this trend, which is not likely to be reversed. Although several rather spectacular shifts in the distributions of various American species of birds have become evident in recent years, the "colonization" of the eastern states by the Mallard (Anas platyrhynchos) has not been so generally recognized. The magnitude of this range extension has been great nevertheless, and the probable reasons for it have been discussed elsewhere (Johnsgard, 1959, 1961). Concomitant with the increase of the Mallard in the eastern states, the native Black Duck (Anas rubripes) has suffered a decline in numbers, and apparently for some of the same reasons as the Mallard has increased. Since this trend is not likely to be reversed in the future, it will be of interest o follow it carefully and thus possibly to predict the fate of the Black Duck. Wing (1943) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to, 1939. He found that the average ratios for that period (which, because of the continuously increasing number of counts, is probably typical of the situation somewhat after the midpoint of 1920) indicated that the zone of equal ratios fell in a northsouth line between Michigan and western Florida. East of this line the Black Duck was markedly dominant over the Mallard and west of it the Mallard was equally dominant. Wing's data are presented in Table I, but they are converted from simple Mallard: Black Duck ratios to the alternative method of calculating the relative percentages of each form in the combined sample. This latter means of presenting ratio data has certain statistical advantages (Hickey, 1957). Arguments supporting the use of these data as unbiased estimates of wintering Mallard and Black Duck populations have been presented elsewhere (Johnsgard, 1959), and so will not be repeated here. To test the possibility that these counts might indicate the degree to which the Mallard has moved eastward in recent years, it was de477 Johnsgard in American Midland Naturalist (October 1961) 66(2). Copyright 1961, University of Notre Dame. Used by permission.

11 citations


Cites background from "Relative Distribution of Mallard an..."

  • ...Wing (1943) became interested in the ratios of Mallards to Black Ducks throughout he eastern states before the range shift was at all apparent, and calculated state ratios for the two forms on the basis of the data provided by the annual Audubon Society Christmas counts for the forty years 1900 to,…...

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Journal ArticleDOI
01 Jan 2018
TL;DR: The American black duck (Anas rubripes) population declined by 50% between 1955 and 1985, prompting more than three decades of intensive scientific research and strategic management, but even with restrictive hunting regulations implemented in the mid 1980s, populations have not recovered.
Abstract: The American black duck (Anas rubripes) population declined by 50% between 1955 and 1985, prompting more than three decades of intensive scientific research and strategic management. Analyses of band recovery data suggest that the historical declines may have been caused in part by harvest, but even with restrictive hunting regulations implemented in the mid 1980s, populations have not recovered. Increasing competition and hybridization with mallards (Anas platyrhynchos), coupled with habitat loss and fragmentation on northern breeding grounds are hypothesized to have contributed to a lower continental black duck population. Simultaneously, there is a concern that declines in the quantity and quality of wintering habitat—coastal salt marshes of the eastern United States—may have deleterious cross-seasonal effects on black duck demographics. Black ducks have a long legacy of intensive research and management, and ongoing threats to their populations make this a well-rooted and timely case study in science-based conservation.

3 citations


Cites background from "Relative Distribution of Mallard an..."

  • ...The mallard range, initially restricted to the central northern prairies, had been expanding into the range of the east coast black duck since at least the 1940s [22, 23]....

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01 Jan 1987
TL;DR: Merola and Wingate-Ehrhorn as mentioned in this paper used the Connecticut DJLP for allowing access to hunter-killed ducks, and thanks to Beth Wingate Ehrhorn for help with everything.
Abstract: Paul Merola of the Connecticut DJLP. for allowing access to hunter-killed ducks. Many thanks to Beth Wingate-Ehrhorn for help with everything.