Long-term response of northern pintails to changes in wetlands and agriculture in the Canadian Prairie Pothole Region / Kevin M. Podruzny, James H. Devries, Llwellyn M. Armstrong, and Jay J. Rotella

Includes bibliographical references (pages 1007-1008).

From 1955 through the late 1970s, northern pintail (Anas acuta) populations closely tracked the abundance
of spring ponds. Declines in numbers of both northern pintails (hereafter, pintails) and ponds were evident
during years of drought. However, since the early 1980s, the strength of the relationship between pintails and
ponds has weakened greatly. Agricultural expansion on primary breeding grounds has been implicated as the
cause of sustained pintail declines, but previous studies investigated pintail response only at large geographic scales
(e.g., prairie-wide, stratum level). Potentially important effects of localized or multiscale changes in wetlands and
agriculture on pintails are not well understood. Using data from the Canadian Prairie Pothole Region for 1961 to
1996, we investigated spatial and temporal covariation of pintail numbers with environmental factors (pond numbers
and wetness indices) and agriculture at various scales. Models best supported by the data indicated that pintails
responded positively to winter precipitation but with important regional variation and positively to pond numbers
in some locations (southwestern Saskatchewan and southern Alberta). Results also indicated that pintail
settling was better explained (increases in R2 values of 0.05-0.06) using information about specific agricultural
practices than about overall increases in farmed area. At a prairie-wide scale, we detected a negative association
between settling and increased cropland area. At regional scales, settling was positively associated to various
degrees with area in fallow (i.e., summerfallow-land tilled but not planted to crop in a given year). Both associations
were strengthened with higher winter precipitation. Because cropland stubble is used readily as a nesting
habitat by pintails and spring tillage of fields not used for summerfallow destroys nests, a shift from summerfallow
to continuous cropping in the Prairie Pothole Region of Canada may have reduced the reproductive capacity of
pintails in important breeding areas. In regions with characteristics that historically have attracted pintails to settle,
we encourage land managers to promote agricultural practices that minimize use of spring tillage, convert
cropland to perennial forages and pasture, and protect and restore wetland and upland habitat.