Gadwall - Anas strepera
Species sexually dimorphic. Males in alternate plummage have gray brown body with a white abdomen and black rump. Black and chestnut portions of some inner median and lesser wing-coverts, slate gray bill, and yellow legs. Females overall brownish color with distinctive bill color (orange yellow with dark longitudinal midsection and gray black lateral spots), and presence of white speculum.
Western Hemisphere Range
Summary of Observations Submitted for Montana
Number of Observations:
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Map Help and Descriptions
(direct evidence "B")
(indirect evidence "b")
No evidence of Breeding
(regular observations "W")
(at least one obs. "w")
(Observations spanning multiple months or years are excluded from time charts)
Normal migration periods in the Bozeman area are from March 20 to May 20 and from October 1 to November 10, with peak numbers reached on April 20 and October 15 (Skaar 1969).
At Bowdoin National Wildlife Refugem, Gadwall nest density was highest in saline lowlands, followed by dense nesting cover, panspots, and silty/ shallow clay. Nest success was highest in saline lowlands, then clay, panspots, silty sites and dense cover (Holm 1984).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
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- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
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Diet consists mainly of submerged aquatic vegitation, seeds and aquatic invertebrates.
The primary cause of nest loss was depradation (67%) from (in order of importance): Striped Skunk, Red Fox, Coyote, Richardson's Ground Squirrel, Raccoon, avian, and American Mink. At Freezeout Lake, Striped Skunks were the major cause of unsuccessful nests.
The brood size was 6.2 in rest-rotation grazing pastures in north-central Montana. Nesting occurred from late May to the third week of August. At Freezeout Lake, island nesters were most successful (75%). The average of all types was 28%. The average clutch size was 11.9 and hatching dates were from May 21 to August 10.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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