MALLARD NESTING ECOLOGY IN THE GREAT LAKES
Understanding how habitat features influence vital rates that drive population growth is fundamental for delivery of effective conservation programs. Past decisions in management of Great Lakes mallard (Anas platyrynchos) populations were based largely on paradigms established in the mid-continent because regional data were lacking. Recent sensitivity analyses from the Great Lakes Mallard Study show that population growth (i.e., ?) is most sensitive to changes in nest success (16%) and duckling survival (32%).
In spring of 2001 to 2003, as part of the Great Lakes Mallard Study, 536 mallards were radio-marked at nine sites in four states (Michigan, Ohio, Wisconsin, and Indiana). I tested a set of a priori candidate models to evaluate the relative influence of habitat variables on survival rate of mallard nests (DSR) at local and landscape-level scales (2 m and 2-, 5-, and 10-km radii from nest). Nest success (0.156 ± 1.420) varied regionally from a low of 0.101 in Wisconsin to a high of 0.247 in Michigan, and was higher in forested landscapes (21.7 - 24.7%) than in agricultural environments (10.1 16.5%). Mallard nest survival was higher for older females than for second-year birds, and probability of hatching increased with nest age. Concealment within 2 m of a nest increased nest DSR, and amount of tillage agriculture within 5-km of a nest was inversely related to survival.
Models that combined variables at multiple spatial scales explained nest DSR better than any combination of variables that were measured at a single spatial scale. Mallard populations in the Great Lakes states are likely to expand further as forested lands are cleared for agricultural production, and mallards begin to pioneer newly created habitats. Because nest success and duckling survival are the most influential vital rates, we recommend that managers conserve and restore wetlands to increase brood survival in higher forested landscapes where small inclusions of agricultural tillage provide habitat without affecting nest success.
Advisor:David E. Naugle; I. Joe Ball; Richard L. Hutto
School:The University of Montana
School Location:USA - Montana
Source Type:Master's Thesis
Date of Publication:08/07/2008