Factors influencing the density and distribution of breeding waterfowl in North-Central Montana

Abstract

Continental waterfowl population declines in the early 1980s led to the development and implementation of the North American Waterfowl Management Plan. The plan identified wetland and grassland losses in the Prairie Pothole Region (PPR) of Canada and the United States as the major causes of low continental duck populations. North-central Montana is the only remaining PPR area in the United States without a ground-based annual survey to monitor breeding duck populations and quantify breeding duck habitat. The purpose of this study was to establish an annual breeding duck survey in north-central Montana to 1) develop species-specific breeding pair predictive models, and 2) apply the models to estimate the density and distribution of breeding ducks and identify priority areas for conservation actions. 1969 indicated breeding duck pairs were observed on approximately 700 wetland basins in 2008 and 2009. A competing model analysis was used to identify local- and landscape-scale habitat characteristics to predict breeding duck pairs on wetland basins. The five most commonly observed species were modeled separately; those species were mallard (Anas platyrhynchos), northern pintails (A. acuta), gadwall (A. strepera ), northern shoveler (A. clypeata) and blue-winged teal (A. discors). At the local scale, wetland basin area, the square root transformation of wetland basin area and wetland basin class were important predictors for all species. Northern pintail, gadwall and blue-winged teal exhibited a strong location effect, occurring more in the northern and eastern portions of the study area. At the landscape scale, the proportion of agricultural lands surrounding a sample basin was associated with the greater abundance of all species. Northern pintail and blue-winged teal breeding pair abundance increased when the proportion of seasonal and semipermanent basin wetland surface area in the landscape around sample basin decreased. Results from this study provide land managers with initial information on where breeding waterfowl are settling across the PPR landscape of north-central Montana. The continuation of this research for several more breeding seasons will enable conservation partners to efficiently target important breeding waterfowl habitat for conservation actions.