Mallard (Anas platyrhynchos) Science Article 10
Mallard (Anas platyrhynchos) breeding densities in the prairie pothole habitat of eastern North Dakota during 1961-1980 varied from 2.28 birds/km2 in 1977 to 9.47 birds/km2 in 1963 and were correlated with pond abundance (r = 0.543, P < 0.05). The number of basins used by pairs declined with drought, as did home-range size. Nesting activity also varied with the number of ponds holding water/km2, ranging from high (including substantial renesting) under favorable water conditions to low during extreme drought. The span between first and last nest initiations declined by 19 days from a wet to a dry year.
GARY L. KRAPU, ALBERT T. KLETT, DENNIS G. JORDE, The Auk 100: 689-698. July 1983