Projects Completed This Year

Evaluating the Western Prairie Habitat Restoration Area as a Grassland Bird Conservation Area

Investigator:                       Christine A. Ribic, USGS, University of Wisconsin-Madison

Funding:                             US Geological Survey (Science Support Partnership Program)

Expected Completion:        December 31, 2018

Beyond the recognized importance of protecting large areas of contiguous habitat, conservation efforts for many species are complicated by the fact that patch suitability may also be affected by characteristics of the landscape within which the patch is located. Currently, little is known about the spatial scales at which species respond to different aspects of the landscape surrounding a patch of habitat. Using grassland bird point count data, we described an approach to evaluating scale-specific effects of landscape composition on patch occupancy. We used data from 793 point count surveys conducted in idle and grazed grasslands across Wisconsin, from 2012-2014 to evaluate scale-dependencies in the response of 4 species of grassland birds to landscape composition. Patch occupancy models were used to evaluate the relationship between patch occupancy and landscape composition at various scales. Bobolink exhibited a pattern indicating selection for grassland habitats at all spatial scales while selecting against other habitats. Eastern meadowlark displayed evidence of scale sensitivity for all habitat types. Grasshopper sparrow showed a strong positive response to pasture and idle grass at small scales and negatively to cropland at large scales. Patch occupancy by Henslow’s sparrow was primarily influenced by patch area. For all species except Henslow’s sparrow, patch occupancy was more strongly influenced by scale-specific landscape composition than by patch size. Our results highlight the importance of considering species-specific patch and landscape characteristics for effective grassland bird conservation.

Range-wide Assessment on the Impacts of Changing Climate on the Endangered, Migratory Kirtland’s Warbler Population

Investigators:                      Christine A. Ribic, USGS, University of Wisconsin-Madison

Funding:                             US Geological Survey (Science Support Partnership Program)

Expected Completion:        June 30, 2018

Long-term management planning for conservation-reliant migratory songbirds is particularly challenging because habitat quality in different stages and geographic locations of the annual cycle can have direct and carry-over effects that influence population dynamics. The Neotropical migratory songbird Kirtland’s warbleris listed as endangered under the U.S. Endangered Species Act and Near Threatened under the IUCN Red List. This conservationreliant species is being considered for U.S. federal delisting because the species has surpassed the designated 1000 breeding pairs recovery threshold since 2001. To help inform the delisting decision and long-term management efforts, we developed a population simulation model for the Kirtland’s warbler that incorporated both breeding and wintering grounds habitat dynamics, and projected population viability based on current environmental conditions and potential future management scenarios. Future management scenarios included continuation of current management conditions, reduced productivity and carrying capacity due to changes in habitat suitability from the creation of experimental jack pine plantations, and reduced productivity from alteration of the brown-headed cowbird removal program. Our future simulations indicate the Kirtland’s warbler population is stable under two potential future management scenarios: 1) continuation of current management practices and 2) spatially restricting cowbird removal to the core breeding area, assuming cowbirds reduce productivity in the remaining patches by ≤ 41%. The additional future management scenarios we assessed resulted in population declines. This study represents one of the first attempts to incorporate full annual cycle dynamics into a population viability analysis for a migratory bird, and our results indicate that incorporating wintering grounds dynamics
improved model performance.

Because of the link between the wintering grounds and Kirtland’s warbler productivity on the breeding grounds, we assessed how future climate change scenarios might affect wintering habitat of Kirtland’s Warbler on the Bahamian archipelago. We used ensembles of general circulation models to project precipitation and temperature patterns across the archipelago over the winter period, from baseline average, until the end of the century. We also used topography layers to define Kirtland’s Warbler winter habitat (open lands) and then made land-cover loss projections for open lands using 1- and 2-m sea-level rise scenarios. Our results indicate the Bahamian islands used by Kirtland’s Warbler will become warmer and wetter during the winter months, except during March when central islands are predicted to go through a drying trend. Moreover, the greatest habitat loss of coastal open land due to sea level rise was predicted for the northern, lower-elevation islands. If we consider both potential changes in habitat quality and quantity from changing climate, the north-central islands, which currently contain the majority of the wintering population, are likely the critical islands on which to focus climate adaptation strategies.

We then modeled the potential impacts of changing environmental conditions to the Kirtland’s Warbler breeding habitat distribution, quantity, and quality in the near future. Kirtland’s warblers are habitat-specialists that nest exclusively within dense jack pine (Pinus banksiana) forests between ca. 5 – 20 years of age. We predicted changes in distribution and growth rate of jack pine under future scenarios. Results indicate the projected distribution of jack pine will contract considerably (ca. 75%) throughout the Lake States region in response to projected environmental conditions in 2099 under RCP 4.5 and 8.5 climate scenarios regardless of climate model. Reduced suitability for jack pine regeneration across the Lake States may constrain management options, especially for creating high stem-density plantations nesting habitat. However, conditions remain suitable for jack pine regeneration within their historical and current core breeding range in northern Lower Michigan and several satellite breeding areas. Projected changes in jack pine growth rates varied within the core breeding area, but altered growth rates did not greatly alter the duration that habitat remained suitable for nesting by the Kirtland’s Warblers. These findings contribute to Kirtland’s Warbler conservation by informing habitat spatial planning of plantation management to provide a constant supply of nesting habitat based on the spatial variability of potential loss or gain of lands environmentally suitable for regenerating jack pine in the longterm.

Fitting the Climate Lens to Grassland Bird Conservation: Assessing Climate Change Vulnerability using Demographically-informed Species Distribution Models

Investigator:                       Benjamin Zuckerberg, Department of Forest and Wildlife Ecology, and Christine A. Ribic, USGS, University of Wisconsin-Madison

Funding:                             US Geological Survey (NE Climate Science Center)

Completion Date:              July 31, 2018

Temperate grasslands and their dependent species are exposed to high variability in weather and climate due to the lack of natural buffers such as forests. Grassland birds are particularly vulnerable to this variability, yet have failed to shift poleward in response to recent climate change like other bird species in North America. However, there have been few studies examining the effect of weather on grassland bird demography and consequent influence of climate change on population persistence and distributional shifts. We estimated the vulnerability of Henslow’s Sparrow, an obligate grassland bird that has been declining throughout much of its range, to past and future climatic variability. We conducted a demographic meta-analysis from published studies and quantified the relationship between nest success rates and variability in breeding season climate. We projected the climate-demography relationships spatially, throughout the breeding range, and temporally, from 1981-2050. These projections were used to evaluate population dynamics by implementing a spatially explicit population model. We uncovered a climate-demography linkage for Henslow’s Sparrow with summer precipitation, and to a lesser degree, temperature positively affecting nest success. We found that future climatic conditions — primarily changes in precipitation — will likely contribute to reduced population persistence and a southwestward range contraction. Future distributional shifts in response to climate change may not always be poleward and assessing projected changes in precipitation is critical for grassland bird conservation and climate change adaptation.

Grassland bird distributions and abundances often correlate with gradients in climate, but few studies have explored the consequences of weather on the demography of multiple grassland birds inhabiting a range of grassland fragments. To do so, we modeled the effects of temperature and precipitation on nesting success rates for a dozen grassland bird species comprising 21,000 nests from 81 individual studies across North America. We found that higher amounts of precipitation in the preceding year (bioyear) were associated with higher nesting success, but wetter conditions during the active breeding season reduced nesting success. In terms of temperature, extreme cold and hot springs were associated with lower rates of nesting success. Notably, the direct and indirect influence of temperature and precipitation on nesting success was moderated by grassland patch size. The positive effects of bioyear precipitation on nesting success were strongest for birds occupying smaller grassland patches, with little effect in larger grasslands. Conversely, warmer spring temperatures reduced nesting success in small grassland patches, but increased nesting success in the larger grasslands. Mechanisms underlying these differences may be patch-size induced variation in microclimates and predator activity. While the exact cause is not clear, large grassland patches, the most common metric of grassland conservation, appears to moderate the consequences of weather on grassland bird demography and could be an effective component of climate change adaptation.