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Costs and benefits of natal dispersal have not been fully evaluated in birds. We compared timing of breeding and nesting success for yearling female mallards Anas platyrhynchos returning to or dispersing from their natal areas. Information about natal origins was discerned with feather-isotopes and combined with detailed reproductive histories for 503 radio-marked females monitored at 16 study sites across the Canadian Aspen Parklands, during 1993-2000. A natal origin assignment model based on feather- δS, δD, δN, and δC values correctly assigned 81% (112 of 138) of known-source yearlings to region of origin; region-specific rates ranged from 70-90%. Timing of breeding and nesting success was not related to whether or not a female had dispersed from its region of natal origin in Aspen Parkland (i.e. short-distance dispersal) versus the southern prairies or boreal forest regions (i.e. long-distance dispersal). Rather, nesting success was best modeled to include effects of site-specific wetland and breeding pair abundances and an interaction between local breeding pair and wetland densities. Nest success performance relative to dispersal distance varied among study sites but was unrelated to local upland nest cover, wetland habitat conditions, or conspecific density. Thus, we detected no strong costs of dispersal but some evidence that long-distance dispersers presumably benefitted when they were able to acquire better nest sites. [ABSTRACT FROM AUTHOR]

An animal's reproduction and survival depend critically on the choices it makes when selecting a habitat for breeding. Therefore, we expect animals to select breeding habitats that confer fitness benefits. For mallards (Anas platyrhynchos), previous research has shown that populations are most sensitive to variation in nest survival rates; thus, we expect strong selection lot safe nest sites. We used patterns of nesting success to predict nest distributions. We compared distributions of nests from radio-marked mallard females (n = 1,710) to random locations using logistic regression and modeled how nest-site locations were related to a number of landscape metrics measured at several spatial scales. Consistent with predictions derived from patterns of nesting success, mallard nest sites were best modeled using habitat attributes measured at the scale of the vegetation patch containing the nest. though ultimately habitat features measured at multiple scales improved predictions. Similarly, for most habitat types mallards tended to nest away from habitat edges, as predicted. Conversely. opposite to predictions, mallards nested in smaller habitat patches and nearer to wetlands than expected by chance. Hence, mallards only provide equivocal evidence that nest-site selection is adaptive. Several possible explanations for this lack of correspondence between patterns of nesting success and nest-site selection include the following: insufficient time to adequately sample available habitats, unpredictable environments, nest sites selected to maximize a different vital rate (e.g., adult female survival), and. finally, anthropogenic changes to the landscape may have resulted in a decoupling of evolved cues used to select nest sites and current predation processes. [ABSTRACT FROM AUTHOR]

Assesses nutritional constraints on clutch size in Mallards by observing incidence and consequences of continuous laying. Use of t-test to determine if continuous laying females produced more total eggs than regular nesting females; Comparison between final incubated clutch size of continuous laying females with final clutch size of regular nesting females; Effect of prenesting body mass on total egg production between the two nesting females.