Time‐lagged variation in pond density and primary productivity affects duck nest survival in the Prairie Pothole Region

Abstract

The Prairie Pothole Region (PPR) is the primary breeding region for most species of North American dabbling ducks (Anas spp.). Conservation of these species is guided in part by knowledge of relationships between nest survival probability and habitat features. Positive relationships between duck nest survival and amount and configuration of herbaceous perennial vegetation have been observed in previous studies, but these 2- to 4-year studies might not have adequately characterized the temporal effect of wet-dry episodes on nest survival. Over an eight-year period, we studied nest survival of five species of ducks in the PPR relative to spatial and temporal variation in pond density, primary productivity, and hydrologic status of wetlands, soil, and vegetation on 52 study sites selected to span a gradient of spatial variation in proportion of herbaceous perennial vegetation and in number of wetland basins. We observed the fate of 12 754 nests. Consistent with past studies, 90% of nests that failed to hatch were destroyed by predators. Nest survival probability was positively related to current-year pond density and primary productivity, negatively related to pond density and primary productivity during the previous two years, and positively related to the number of wetland basins on the study site. Predicted relationships between nest survival and proportion or configuration of herbaceous perennial vegetation in the surrounding landscape were not supported. For mallard (Anas platyrhynchos), median estimated nest survival probability ranged from 0.02 (SE = 0.01) to 0.22 (SE = 0.02). Estimated nest survival was greatest on sites with numerous wetland basins that had transitioned from dry, unproductive conditions to wet, productive conditions in the previous 1-2 years. Our results were consistent with time-lagged responses of food webs to resource pulses in a broad array of ecosystems. Our study highlighted the importance of wetland basins and wet-dry episodes to duck nest survival in the PPR. Current habitat conservation efforts focus on landscapes with numerous wetland basins and a high proportion of herbaceous perennial vegetation. Our results suggest that future conservation efforts should focus on preserving high-density wetland complexes across as large a geographic extent as possible even in cropland-dominated landscapes.

Banding age ratios reveal prairie waterfowl fecundity is affected by climate, density dependence and predator–prey dynamics

“…Stratum‐specific PDSI values were a weighted average of the geographic area of overlap between PDSI cells (2.5°) and each stratum. We hypothesized that wetland re‐inundation and maintenance would positively affect fecundity, as nest success and brood density are positively correlated with higher pond counts (Walker, Rotella, Schmidt, et al., ; Walker, Rotella, Stephens, et al., ).…”

“…Positive effects of wetland inundation might also result from reduced predator abundance following droughts, as hypothesized by Walker, Rotella, Stephens, et al. (). However, if this were the case we would have expected a negative effect of previous‐year prey abundance ( BPL1 , SOL1 ) on fecundity, but this effect was only observed in teal.…”

“…Walker, Rotella, Stephens, et al. () postulated that reduced waterfowl nest survival in years following wet conditions was driven by higher densities of nest predators resulting from a strong small mammal prey base that was supported by strong primary productivity associated with the wet conditions. We aimed to test this hypothesis more directly by including indicators of small mammal and duck nest food resource availability in the previous year ( BPL1 and SOL1 ), hypothesizing negative effects on fecundity.…”

“…Age ratios, for example, are frequently collected during migration and wintering when birds are congregated, but since this metric inherently captures a mixture of source populations, inference about regional breeding habitat management is limited. Nest survival is a commonly used fecundity metric that is specific to local breeding areas (Walker, Rotella, Stephens, et al., ); however, it fails to account for breeding effort (Etterson, Bennett, Kershner, & Walk, ) and offspring survival after leaving the nest (Streby & Andersen, ), which includes the entire brood‐rearing period in precocial birds (Amundson, Pieron, Arnold, & Beaudoin, ). Age ratios from late summer banding obtained before birds have initiated extensive postbreeding migration (Mazerolle, Dufour, Hobson, & den Haan, ; Nolet et al., ) represent an opportunity to examine an integrated fecundity index with broad temporal and spatial replication.…”

Variation in mallard vital rates in Canadian Aspen Parklands: The Prairie Habitat Joint Venture assessment

“…Also, grasslands typically undergo more frequent and severe droughts than habitats in the Aspen Parklands (Bird , Lynch , Adams , Bethke and Nudds ), which might affect trophic dynamics in ways that affect this relationship. Recent work by Walker et al () suggests that the temporal dynamics of deluge and drought can have persistent effects on predator–prey relationships, but the reasons for this difference between Aspen Parkland and grassland landscapes remain unclear and merit further study.…”