Northern Prairie Wildlife Research Center
Mallard Recruitment in the Agricultural Environment of North Dakota
Recruitment of a mallard (Anas platyrhynchos) population was assessed
on a 10,041-km2 study area in central North Dakota during
1977-80. We equipped 338 hens with radio transmitters and monitored them during
the breeding season. Two hundred thirty-five of these hens furnished data reported
here. Habitat use, nest site selection, fate of nests, and the rate of renesting
were measured. Survival of hens during April-September and survival of young
were determined. There was a high negative correlation between nest initiation
date and mean April or May temperature. Hens selected nest sites most frequently
in grassland and least frequently in cropland, but habitat use compared to availability
indicated preference for road right-of-way and odd areas of cover and rejection
of cropland. Use of other habitats was in proportion to their availability.
Nest success was only 8% during the study. Hen success, a function of nest success
and renesting rate, averaged 15% and varied among years because of increased
renesting in wet years. In all years, 2-year-old and older hens were twice as
successful as first-year nesters. Nesting effort was correlated with water conditions
as derived from aerial photographs. April-September survival of hens averaged
80% because predation was heavy when hens were on nests. Only 74% of the hens
that hatched a clutch were observed later with at least 1 surviving duckling.
On average, hens in the spring population recruited only 0.27 young females
to the fall population. Based on this recruitment estimate, published survival
estimates, and a model previously developed for a closed population, we predict
a 20% annual population decline. Nest success of 15% and a resulting hen success
of 31% would be required for a stable population. The results suggest that the
population on the study area is not maintaining itself but is being supplemented
by pioneering birds. A serious recruitment problem has resulted from nest predation.
Additional research is needed to determine the geographic extent of the problem.
If the problem is widespread, management techniques must be devised to overcome
nest destruction, mortality of hens, and mortality of ducklings.
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