Duck nest success declines with and without predator management

The decline in nest success of upland nesting ducks in the Prairie Pothole Region has been hypothesized to have been caused by increased predation coincident with habitat alteration. We tested this by comparing data on nest success from 21 studies conducted between 1937 and 1990 at sites where principally mammalian predators were removed by trapping, shooting or poisoning, or were presumed absent from either islands or fenced exclosures, with data previously compiled from 37 studies conducted between 1935 and 1992 at sites where predators were not reported removed by any means. Nest success was greater (P < 0.0001) on islands and in fenced exclosures than at removal and unmanaged sites. However, nest success declined (P < 0.0001) over time at similar (P < 0.13) rates where predators were managed and unmanaged. Thus, where nest predators can be excluded, increased nest success results, but nest loss to mammalian predators does not appear to be the cause of the long-term decline in nest success.