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Wildlife Monographs

Determinants of Breeding Distributions of Ducks


Breeding Distributions of the Species

Northern Pintail.—Pintails reached very high densities in several northern strata as well as in the southwestern part of the prairie provinces (Fig.10A). Within the prairie and parkland region, densities tended to decline away from the primary breeding area.

gif --Northern Pintail Distribution

Figure 10. (A) Average species density by stratum, 1955-81; (B) correlation between species density and local pond counts, 1955-81; and (C) correlation between species density and total pond counts, 1955-81.

The pintail is the most numerous wintering species in California. Additional pintails winter in Mexico and along the Gulf Coast (Bellrose 1980). It appears that only about 40% of spring migrants use the southern portal to the breeding grounds; the remainder use the western portal or proceed directly to far-northern breeding grounds.

Densities of this species covaried with local pond densities in the surveyed area more closely than any other species (Table 3). Correlations were consistent throughout that area (Fig. 10B), but tended to be larger where pintails were most common. Correlations were high also in western and central South Dakota, although pintail densities there were low.

The pintail exhibited very strong positive correlations with total ponds throughout the southern part of its range (Fig. 10C). In the northern strata, associations were clearly negative.

Pintails may home at a high rate when habitat conditions are stable (Sowls 1955, Bellrose 1980). Henny (1973) suggested that pintails that overfly to the north in 1 year are likely to return there the next, even if wetland conditions in the south improve. Nonetheless, pintails generally prefer temporary wetlands (Smith 1970, Stewart and Kantrud 1973); therefore, homing likely occurs at a low rate. In fact, pintails have responded opportunistically to newly available wetlands (Stoudt 1971, Hochbaum and Bossenmaier 1972) and appear to be highly sensitive to drought conditions (Crissey 1969, Smith 1970, Henny 1973, Derksen and Eldridge 1980). A reasonable hypothesis is that pintails entering along the southern corridor respond initially to wetland conditions in South Dakota, next to conditions in North Dakota, and eventually proceed northward. Birds arriving from the southwest are influenced initially by wetland conditions in southeastern Alberta and southwestern Saskatchewan. If conditions there are not suitable, they move northward. Many pintails migrate directly to the far north, bypassing the prairies and parklands entirely.

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