Skewed Age Ratios of Breeding Mallards in the Nebraska Sandhills

Understanding demographic structures of populations allows managers to better evaluate factors affecting populations and increase efficiency of conservation efforts. Recent studies suggest low productivity, but high survival characterizes mallard (Anas platyrhnchos) populations in the Nebraska Sandh...

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Bibliographic Details
Published in:The American midland naturalist 2016-04, Vol.175 (2), p.280-285
Main Authors: Cunningham, Zach J, Powell, Larkin A, Vrtiska, Mark P, Stephens, Scott E, Walker, Johann A
Format: Article
Language:English
Subjects:
Age
Age discrimination
Age distribution
Age distribution (Demography)
Animal age determination
Animal behavior
Bias
Bird nesting
Breeding
Breeding sites
Demographic aspects
Ducks
Ecosystems
Female animals
Females
Grasslands
Mallard
Note and Discussion Pieces
Notes and Discussion Piece
Ornithological research
Population
Ratios
Studies
Waterfowl
Wetlands
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Summary:Understanding demographic structures of populations allows managers to better evaluate factors affecting populations and increase efficiency of conservation efforts. Recent studies suggest low productivity, but high survival characterizes mallard (Anas platyrhnchos) populations in the Nebraska Sandhills. We studied age ratios of decoy-trapped and observer-shot mallards in the Sandhills during 2007–2008. Observed age distribution (second-year:after-second-year) of mallards was 2.8:1 for females and 0.8:1 for males. Age ratios of trapped females were skewed towards young females relative to other studies, and the age ratio of trapped females was not different than the age ratio of the sample we collected by shooting. The skewed age ratios we observed provide additional context to the low reproductive success that has been reported for nesting mallards in the Sandhills. Second-year mallard females tend to invest fewer resources and take fewer risks associated with nesting. As a result the Sandhills population may not contribute significantly to productivity of the continental mallard population but act as a reservoir of young female mallards available to disperse to more productive breeding areas in future years.
ISSN:0003-0031
1938-4238
DOI:10.1674/0003-0031-175.2.280