Duck Nest Survival in the Missouri Coteau of North Dakota: Landscape Effects at Multiple Spatial Scales

Abstract

Nest survival is one of the most important parameters in the population dynamics of grassland‐nesting ducks (Anas and Aythya spp.) that breed in the Prairie Pothole Region of North America. Grassland habitats used by these species are increasingly threatened by habitat loss and the coincident fragmentation, which may indirectly alter nest survival through effects on predators. Although predators are the dominant cause of nest loss, they are difficult to monitor directly. Thus, indirect analyses of habitat variables are required. Many studies have attempted to address the relationship between fragmentation and nest survival; however, few studies have examined the influence of fragmentation at multiple spatial scales. Understanding how landscape characteristics at multiple spatial scales explain variation in nest survival is important, because no single correct scale is likely to exist for a diversity of landscape metrics. We examined the relationships between habitat variables and duck nest survival (n ≈ 4200 nests) on 18 10.4‐km2 sites selected across a gradient of landscape characteristics in the Missouri Coteau Region of North Dakota. We evaluated both a priori and exploratory competing models of nest survival that considered habitat features measured at nest sites, within nesting patches, and at multiple landscape scales. We used generalized nonlinear mixed‐modeling techniques to model nest survival rates. Information‐theoretic techniques were used to select among competing models. Models that included covariates measured at multiple landscape scales were better than simpler models that included only covariates measured at a single spatial scale. Landscape covariates measured at 10.4 and 41.4 km2 resulted in the best explanation of nest survival. Nest survival was positively related to the amount of grassland habitat, negatively related to the wetland density, and related to the amount of grassland edge in a quadratic manner, with the lowest nest survival at intermediate values of grassland edge. Future research should attempt to determine the causes of these relationships, something we were unable to do with our correlative approach. Conservation efforts focused on maintaining duck populations should seek to maintain landscapes with abundant grassland and to account for the influence of configuration using GIS analyses.

Landscape features and weather influence nest survival of a ground-nesting bird of conservation concern, the greater sage-grouse, in human-altered environments

“…Within this landscape, nest-site placement by female sage-grouse was influenced by landscape variables at multiple spatial scales (Dzialak et al 2011a); however, DSR of nests was most influenced by nest site-specific variables (area ≤ 30 × 30 m), similar to another study by Manzer and Hannon (2005). This finding is in contrast to other studies which found that landscape-level variables were most influential on the success of nests by ground-nesting birds (Stephens et al 2005;Moynahan et al 2007). Examining the variables that were included in the final model revealed potential mechanisms (i.e., visual and olfactory) that predators used to locate nests when considering that nest depredation and direct predation of the incubating female were the most common sources of nest failure.…”

“…Processes on the landscape occur and interact at multiple spatial scales (Wiens 1989), and likely carry-over to influence predator behavior on the landscape because most predators also perceive the landscape at various spatial scales (Chalfoun et al 2002;Stephens et al 2005). For these reasons, we use a multi-scalar approach to examine the relationships between DSR of nests and spatial landscape features (i.e., anthropogenic and landscape features, and topography) important to sagegrouse during nesting.…”

“…Before implementing a hierarchical variable selection approach, we created quadratic terms (quadratic = original 2 ) for the following: the Julian date (first day of incubation); age of the nest (days since incubation began); temperature; humidity; wind speed; shrub height; percentage of bare ground, litter, forbs, grass, total herbaceous vegetation, sagebrush, and shrub; terrain roughness; elevation; and slope at all spatial scales examined. We developed quadratic terms because animals often avoid the lowest and highest values associated with a given landscape feature (Aldridge and Boyce 2007;Johnson et al 2004;Stephens et al 2005;Dzialak et al 2011a). We also natural log-transformed all distance variables (i.e., distance to wells, structures, ancillary features, roads, and mesic habitat) to allow for a decreasing magnitude of influence with increasing distance.…”

“…A primary example of this is through nest depredation (Gregg et al 1994;Conway and Martin 2000;Chalfoun et al 2002;Stephens et al 2005;Moynahan et al 2007). Nest success, often defined as having ≥ 1 egg hatch, is influenced strongly by the choices females make in terms of nest placement because local and landscapelevel features of the nest site are correlated with susceptibility to depredation (Lima 2009;Conover et al 2010).…”

Nest and brood survival of Ring-necked Ducks in relation to anthropogenic development and wetland attributes

“…I included a seasonal trend variable to explain temporal variation in the nesting season, with earlier nests predicted to be more successful than later nests. I also included a model with nest age to allow nest survival to vary during laying and incubation (Klett and Johnson 1982, Stephens et al 2005, Grant and Shaffer 2012. I included a model with annual variability, where year was modeled as a categorical variable.…”