Wintering Distribution Changes in Mallards and Black Ducks
Summary (1 min read)
Introduction
- The "colonization" of the eastern states by the Mallard (Anas platyrhynchos) has not been so generally recognized.
- 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.
478 THE AMERICAN MIDLAND NATURALIST 66(2)
- Cided to bring these calculations up to date, by collating the Christmas Count records for the twenty years 1940 to 1959.
- The data for the years 1940 to 1949 show some interesting differences from Wing's data for the preceding forty years.
- Of the states east of the Michigan to western zone, one state exhibits a majority of Mallards in the wintering population.
- Eighteen states exhibit marked declines in Black Duck ratios from those presented by Wing.
- On the other hand, the northern interior states have undergone less pronounced decreases, such as, for example, Michigan, Illinois, Indiana and Ohio.
484 THE AMERICAN MIDLAND NATURALIST 66(2)
- Mallard gene pool and through the constant reduction of its breeding habitat, may eventually disappear as a distinct entity from their fauna.
- -This study was done at Cornell University under the support of fellowships from the Cornell University Graduate School and the National Science Foundation.
- Evolutionary relationships among the North American mallards.
- Evolutionary relationships among the North American mallards.
- Relative distribution of Mallard and Black Duck in winter.
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Citations
12 citations
Cites background from "Wintering Distribution Changes in M..."
...American black ducks (Anas rubripes) are declining, and mallard (A. platyrhynchos) numbers rising, in eastern North American (Johnsgard 1961, 1967; Johnsgard & DiSilvestro, 1976; Dennis, Fisher & McCullough, 1984; Ankney, Dennis & Bailey, 1987)....
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...Some authors suggest that hybridization is common because American black duck females may prefer mallard males as mates (Johnsgard, 1961, 1967; Ankney, Dennis, Wishard et al., 1986; Brodsky & Weatherhead, 1984)....
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11 citations
Cites result from "Wintering Distribution Changes in M..."
...This estimate of hybrid frequencies is more than three times higher than those I summarized for the 1960’s, which included an estimate of 2.7 percent hybrids relative to the overall Atlantic flyway black duck population (Johnsgard, 1961, 1967)....
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10 citations
Cites result from "Wintering Distribution Changes in M..."
...This estimate of hybrid frequencies is more than three time higher than those I summarized for the 1960’s, which included an estimate of 2.7 percent hybrids relative to the Atlantic flyway black duck sample (Johnsgard, 1961, 1967)....
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3 citations
Cites background from "Wintering Distribution Changes in M..."
...Regardless of mechanism, by the 1960s and 1970s, mallards outnumbered black ducks on both the breeding [18] and some wintering grounds [23, 25]....
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...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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...It was hypothesized that extensive logging across the eastern United States paved the way for eastward expansion of the prairie-adapted mallard [23], supplemented by game farm mallards released for hunting [24]....
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References
55 citations
"Wintering Distribution Changes in M..." refers background in this paper
...The magnitude of this range extension has been great nevertheless, and the probable reasons for it have been discussed elsewhere (Johnsgard, 1959, 1961)....
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...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....
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5 citations
"Wintering Distribution Changes in M..." refers background in this paper
...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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