Effects of Habitat and Predator Manipulations on Breeding Success
of Prairie Ducks: A Review of Hypotheses and the Evidence
ROBERT G. CLARK AND THOMAS D. NUDDS
Canadian Wildlife Service, Prairie and Northern Wildlife Centre, 115
Perimeter Road, Saskatoon, SK S7N OX4, Canada; Department of Zoology,
University of Guelph, Guelph, ON NIG 2WI, Canada
Proposed habitat and predator manipulations to increase population sizes of
some species of prairie-nesting ducks by increasing nest success depend on some
as yet poorly understood relationships among rates of nest predation, type of
nest predator, nest concealment, nest and predator densities, and habitat size.
We reviewed studies which examined nest predation in ducks and other ground
nesting birds, in order to test whether predation and (1) nest concealment,
(2) nest density, and (3) habitat fragmentation (patch size) are related. Nest
(egg) survival was highly dependent on the type of predators. When avian predation
was important, eggs in well-concealed nests had higher survival than those in
poorly concealed nests. When mammals, or a combination of mammals and birds,
were the most important predators, egg survival was not related to concealment.
Most field and theoretical research showed that nest predation rates increased
with increasing nest density except on islands or other predator-free sites.
Our review of literature allows us only to tentatively conclude that increased
habitat fragmentation leads to higher nest predation because direct tests are
needed. Studies which examine the relationships among habitat patch size, nest
predation, predator exclusion, and survival (and homing) of female ducks and
their offspring will assist decisions about land management in the Canadian
prairies.
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