Lesser Scaup - Aythya affinis
A medium-sized (41.9 to 43 cm, 730 to 850 g) black and white diving duck, one of the most abundant and widespread of North American ducks. Adults sexually dimorphic most of year. Male in Definitive Alternate plumage characterized by slaty blue bill; black head with purplish gloss; black neck, breast, and upper mantle; white flanks and belly; gray-flecked lower mantle; and black vent and undertail region. Female is fuscous to chocolate brown with white patch of varying size at base of bill (sometime broken into patches of white); upperparts darker; wing-coverts flecked with gray; bill dark gray. Iris color in males is brilliant yellow, but in females varies with age from olive brown to olive or brownish yellow (Austin et al. 1998).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Normal migration periods in the Bozeman area are April 10 to May 25 and October 1 to November 20, with peak numbers on April 25 and October 25 (Skaar 1969).
In the Bozeman area, habitat is generally restricted to lakes and ponds (Skaar 1969). Throughout fall and winter this species forms large flocks on rivers, lakes, and large wetlands. Pairs and broods typically associated with fresh to moderately brackish, seasonal and semipermanent wetlands and lakes with emergent vegetation such as bulrush, cattail and river bulrush (Austin et al. 1998).
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 (common or occasional) 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 2012, 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 observation 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 listed as associated with 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 listed as 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.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific 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 assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
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: mtnhp.org/requests
) 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.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
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- Commonly Associated with these Ecological Systems
Recently Disturbed or Modified
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Human Land Use
Shrubland, Steppe and Savanna Systems
Mainly aquatic invertebrates such as insects, crustaceans, and mollusks. Seeds and vegetative parts of aquatic plants are important in certain areas (Austin et al. 1998).
At Bowdoin National Wildlife Refige, 25,000 were seen in November 1949. The major cause of unsuccessful nests at Freezeout Lake was skunk predation.
Individuals form new pair bonds during spring migration each year. Female builds nest on the ground near or over water, as well as in uplands, unlike other diving ducks. Eggs are elliptical to nearly oval in shape. The color is pale olive or greenish buff to dark olive buff. Most clutches have 8 to 10 eggs (Austin et al. 1998). Actual nest records are scattered from mid-May to August 10. Hatching dates at Freezeout Lake were from June 1 to August 20. Birds nesting on islands were more successful (60%) than those in other habitat types (average of all was 23.5%). Average clutch size was 9.5.
- Literature Cited AboveLegend: View Online Publication
- Austin, Jane E., Christine M. Custer, and Alan D. Afton. 1998. Lesser Scaup (Aythya affinis). Species Account Number 338. The Birds of North America Online (A. Poole, Ed.). Ithaca, NY: Cornell Laboratory of Ornithology; Retrieved 3/25/2008 from The Birds of North America Online database
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- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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