The Ruddy Duck is a small, chunky, thick-necked duck with a large head, broad bill (blue in the breeding male), and long tail that often is cocked upward. The male has conspicuous white cheeks, especially when breeding, and the female and young have a single dark line across the light cheeks. The breeding male has bright reddish-brown upperparts and the non-breeding males, females, and young are mostly grayish-brown. Ruddy Ducks lack a contrastingly colored speculum.
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.
Ruddy Duck differs from the Masked Duck in that males have white cheeks instead of black and females have a single dark cheek stripe rather than two cheek stripes on each side; Ruddy Duck lacks the conspicuous white wing patches (visible in flight) of the Masked Duck.
Western Hemisphere Range
The migration destination is unknown (west, east or Gulf coasts) (Skaar personal communication). Migration in the Bozeman area occurs April 15 to May 25 and September 15 to November 25 (Skaar 1969).
Breeding is usually on overgrown, shallow marshes with abundant emergent vegetation and some open water. Non-breeding birds are found on large, generally deeper waters with silty/muddy bottoms (Johnsgard 1986). During migration in the Bozeman area, birds prefer open lakes (Skaar 1969).
Takes primarily aquatic insects, crustaceans, zooplankton, and other invertebrates. Typically consumes small amount of aquatic vegetation and seeds. Forage almost exclusively by diving but occasionally forage by "skimming" water surface, straining food from water (Brua 2002).
At Freezeout Lake, hatching dates were from July 21 to August 20. Near Fortine, egg dates range from June 12 to July 1. Brood size averages 8 on a statewide basis; nesting records are from June well into August.