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Breeding Range. (Fig. 36). Fairly common (locally common) on the Missouri Coteau; uncommon on the Southern Drift Plain, Northwestern Drift Plain, and in the Turtle Mountains; rare (uncommon locally) on the Northeastern Drift Plain and in the Agassiz Lake Plain Region and Southwestern Slope Region.

Breeding Habitat. The majority of breeding Ruddy Ducks in North Dakota occur in slightly brackish or moderately brackish semipermanent ponds and lakes of cover types 2 and 3 in which cattails, hardstem bulrush, or a mixture of the two comprise the dominant deep-marsh cover. Fair numbers also occur on brackish semipermanent ponds and lakes in which a mixture of hardstem bulrush and alkali bulrush comprise the emergent deep-marsh cover and on seasonal ponds that are dominated by shallow-marsh emergents, chiefly whitetop and slough sedge. Shallow river impoundments that are managed for waterfowl also are utilized to a limited extent.

Nesting. Breeding season: Late May to mid-October; peak, mid-June to late August. A newly completed nest without eggs was found on May 26 [1964] in Stutsman County (RES). Extreme egg dates (81 nests): May 29 [1963] to August 21 [1962] in Stutsman County (RES). Of all nests with eggs that were recorded, 1 percent was observed in late May, 38 percent in June, 45 percent in July, and 16 percent in August. Extreme dates of dependent young (404 broods): July 3 [1962] to October 14 [1964] in Dickey County (RES). Of all broods recorded, 22 percent were observed in July, 68 percent in August, 9 percent in September, and + percent (1 brood) in October.

All of the nests were situated over water in semi-open or dense stands of emergent marsh vegetation. Water depths at 72 nest sites ranged from 5 to 34 inches and averaged 20 inches. Species composition of emergent marsh cover at 80 nest sites varied as follows: pure stands of hardstem bulrush, 58 percent; mixtures of hardstem bulrush and other species including cattails, whitetop and slough sedge, 31 percent; and other species stands or mixtures including cattails, river bulrush, and whitetop, 11 percent.

Indicated clutch size (68 nests): 4 to 15 eggs; mean, 7.7 eggs. One obvious dump-nest containing 23 eggs was found in Stutsman County on July 17, 1964 (RES).

Figure 36. Breeding Range of Ruddy Duck.