Assessing Breeding Populations of Ducks by Ground Counts.

Waterfowl inventories taken during the breeding season are recognized
as a basic technique in assessing the number of ducks per unit
area. That waterfowl censusing is still an inexact technology leading
to divergent interpretations of results is also recognized. The
inexactness stems from a wide spectrum of factors that include
weather, breeding phenology, asynchronous nesting periods, vegetative
growth, species present and their daily activity, previous field
experience of personnel, plus others (Stewart et al., 1958; Diem and
Lu, 1960; Crissey, 1963a). In spite of the possible errors, accurate
estimates are necessary to our understanding of production rates of
all North American breeding waterfowl. Statistically adequate censuses
of breeding pairs and accurate predictions of young produced per pair
still remain as two of the primary statistics in determining yearly
recruitment rate of species breeding in particular units of pond
habitats. Without precise breeding pair and production data, the
problems involved in describing the reproductive potential of any
species and its environmental or density-dependent limiting factors
cannot be adequately resolved.

The purposes of this paper are to (1) describe methods used to
estimate yearly breeding pair abundance on two study areas, one in
Manitoba and the other in Saskatchewan; (2) assess the relative
consistency, precision, and accuracy of pair counts as related to the
breeding biology of duck species; and (3) recommend census methods
that can more closely approximate absolute populations breeding in
parkland and grassland habitats.