Water‐level management is widespread and illustrates how contemporary climate can interact directly and indirectly with numerous biological and abiotic factors to influence reproductive success of wildlife species. We studied common loons, an iconic waterbird sensitive to timing and magnitude of water‐level changes during the breeding season, using a before‐after‐control‐impact design on large lakes in Voyageurs National Park (Minnesota, USA), to assess the effect of anthropogenic changes in hydroregime on their nesting success and productivity. We examined multiple competing a priori hypotheses in an information‐theoretic framework, and predicted that magnitude of changes in loon productivity would be greater in the Namakan Reservoir, where water‐level management was altered to mimic a more natural hydroregime, than in Rainy Lake, where management remained relatively unchanged. We determined outcomes from 278 nests during 2004–2006 by performing boat‐based visits every 3–5 days, and measuring hydrologic, vegetative, and microtopographic covariates. Relative to comparably collected data for 260 total loon pairs during 1983–1986, productivity (chicks hatched/territorial pair) increased 95% in the Namakan Reservoir between the 2 time periods. Nest success declined in both lakes over the 2 study periods but less so in the Namakan Reservoir than in Rainy Lake. Flooding was a primary cause of nest failures (though second nests were less likely to flood). Nest predation appears to have increased considerably between the 2 study periods. Top‐ranked models suggested that timing of nest initiation, probability of nest flooding, probability of nest stranding, and probability of nest success were each related to 2–4 factors, including date of initiation, timing of initiation relative to peak water levels, changes in the elevation of the nest edge, maximum water‐level change between initiation and peak water levels, and maximum water‐level change between initiation and nest outcome. The top model for all variables except stranding each garnered ≥82% of total model weight. Results demonstrate that water‐level management can be altered to benefit productivity of common loons. However, nuanced interactions between land‐use change, invasive species, human development, recreation, climate change, and recovery of top predators may often complicate both management decisions and interpretation of water‐level impacts on wildlife. © 2013 The Wildlife Society.
The Illinois State Wildlife Action Plan targeted the Conservation Reserve Program (CRP) as important improvable acres for grassland and grassland‐successional bird species of greatest need for conservation. A large portion of CRP grasslands in Illinois and elsewhere lack floristic and structural diversity because of the absence of management and the extensive planting of monotypic grasses such as tall fescue (Schedonorus phoenix). The 2006 Farm Bill included the mid‐contract management (MCM) provision requiring landowners with new CRP enrollments to provide habitat improvement midway through the 10–15‐year contract duration. We compared the effects of 3 approved MCM regimes (i.e., fall strip disking, fall glyphosate spraying, fall glyphosate spraying followed by spring legume drill‐seeding) on grassland bird communities in 60 tall fescue‐dominated CRP fields in south‐central Illinois during 2006–2008. We modeled relative density of dickcissels (Spiza americana), Henslow's sparrows (Ammodramus henslowii), and eastern meadowlarks (Sturnella magna) as a function of microhabitat, patch‐level patterns, and landscape composition using a multi‐scale assessment approach. We detected 10 grassland‐associated bird species (e.g., Henslow's sparrow, northern bobwhite [Colinus virginianus], sedge wren [Cistothrus platensis], Savannah sparrow [Passerculus sandwichensis], grasshopper sparrow [Ammodramus savannarum]) that are recognized as species of greatest need for conservation under the Illinois State Wildlife Action Plan. Mean total bird densities and species richness were greater in glyphosate‐sprayed fields (5.0 birds/ha; 11.5 species) and glyphosate drill‐seeded fields (4.4 bird/ha; 12.4 species) than in disked (3.4 birds/ha; 8.7 species) and reference (3.1 birds/ha; 7.5 species) fields. The avian conservation value of glyphosate sprayed and glyphosate drill‐seeded fields increased 34.2% and 32.6% post‐management, respectively, but we did not detect change in disked and reference fields. Our models indicate that density of each of the focal species is likely associated with changes in plant species diversity and habitat structure resulting from management actions but is also influenced by landscape composition. Despite an overall positive response of the grassland bird communities to glyphosate‐based treatment regimes in tall fescue CRP fields in south‐central Illinois, the response of Henslow's sparrow density to glyphosate was not consistently positive. © 2013 The Wildlife Society.
The United States Department of Agriculture (USDA) authorized mid‐contract management (MCM) in 2004 to restore and maintain plant species composition and structural diversity in aging Conservation Reserve Program (CRP) fields for the northern bobwhite (Colinus virginianus) and other grassland‐dependent wildlife. We implemented 3 USDA‐approved MCM regimes (i.e., strip disking, strip glyphosate spraying, and strip glyphosate spraying in combination with legume interseeding) in 60 tall fescue (Festuca arundinaceae) CRP monocultures in south‐central Illinois, USA, during 2005–2008. We hypothesized that adult bobwhite relative densities and brood presence would increase following MCM that effectively restored early successional plant communities in otherwise monotypic stands of tall fescue. We estimated annual adult bobwhite relative densities and brood presence‐absence in managed and unmanaged CRP. We modeled vegetation characteristics and landscape composition to identify factors influencing adult densities and brood presence. Adult relative densities were 2‐fold greater in managed fields than in unmanaged fields, and were negatively correlated with greater percentages of grass cover. Adult densities were positively correlated with greater plant species diversity, and greater percentages of bare ground and legume cover. Logistic regression and odds ratio estimates indicated that fields managed with glyphosate‐interseed and glyphosate treatments were 39.6% more likely to have broods than unmanaged CRP, whereas disked fields were 10.0% more likely than unmanaged CRP. These models indicated that the probability of brood presence was greater in fields with increased percentage of bare ground, greater plant species diversity, and decreased percentage of grass and litter cover. These findings suggest that a 3‐year rotation of glyphosate or glyphosate‐interseed treatments can enhance habitat conditions for adult bobwhites and broods in CRP tall fescue monocultures. © 2011 The Wildlife Society.
Global climate change is increasing the frequency and severity of extreme climatic events (ECEs) which may be especially detrimental during late‐winter when many species are surviving on scarce resources. However, monitoring animal populations relative to ECEs is logistically challenging. Crowd‐sourced datasets may provide opportunity to monitor species' responses to short‐term chance phenomena such as ECEs. We used 14 years of eBird—a global citizen science initiative—to examine distribution changes for seven wintering waterfowl species across North America in response to recent extreme winter polar vortex disruptions. To validate inferences from eBird, we compared eBird distribution changes against locational data from 362 GPS‐tagged Mallards (Anas platyrhynchos) in the Mississippi Flyway. Distributional shifts between eBird and GPS‐tagged Mallards were similar following an ECE in February 2021. In general, the ECE affected continental waterfowl population distributions; however, responses were variable across species and flyways. Waterfowl distributions tended to stay near wintering latitudes or moved north at lesser distances compared with non‐ECE years, suggesting preparedness for spring migration was a stronger “pull” than extreme weather was a “push” pressure. Surprisingly, larger‐bodied waterfowl with grubbing foraging strategies (i.e., geese) delayed their northward range shift during ECE years, whereas smaller‐bodied ducks were less affected. Lastly, wetland obligate species shifted southward during ECE years. Collectively, these results suggest specialized foraging strategies likely related to resource limitations, but not body size, necessitate movement from extreme late‐winter weather in waterfowl. Our results demonstrate eBird's potential to monitor population‐level effects of weather events, especially severe ECEs. eBird and other crowd‐sourced datasets can be valuable to identify species which are adaptable or vulnerable to ECEs and thus, begin to inform conservation policy and management to combat negative effects of global climate change.
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