Mallard nest-site selection in an altered environment : predictions and patterns / David W. Howerter, Jay J. Rotella, Michael G. Anderson, Llwellyn M. Armstrong, and James H. Devries.

Includes bibliographical references (pages 452-454).

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 for
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.