Deahn M. Donner

Spatial and Temporal Habitat-Use Patterns of Wood Turtles at the Western Edge of Their Distribution

Abstract Wood Turtles (Glyptemys insculpta) are a state threatened species at the western edge of their geographic distribution in Minnesota, United States. There is currently little published information regarding habitat use of western populations to assist with conservation initiatives. The primary purpose of this study was to investigate habitat use of a population of Wood Turtles in northeastern Minnesota to determine if habitat-use patterns were similar to other regions. In addition, we assessed the efficacy of two land-cover data sets (National Land Cover Dataset and LANDFIRE Existing Vegetation Type), relative to an aerial-photo–based habitat layer, for assessing habitat use and delineating preferred or avoided habitat classes. We performed this analysis to gauge the value of widely used habitat layers for Wood Turtle management and research. We used radio telemetry data collected on 8 males and 14 females between May and November 1990 to assess habitat associations and space-use patterns. We found that Wood Turtles heavily used and generally remained within 100 m of flowing water. Individuals also appeared to prefer other aquatic and semiaquatic habitats when not in or adjacent to flowing water. Despite this population inhabiting a primarily forested landscape, we found little evidence that forest habitat classes were preferred by this species; however, forest age could be an important variable, with younger, more open forest types being used more frequently. We found that neither NLCD nor LANDFIRE were adequate for assessing habitat associations or delineating habitat classes at the scale at which Wood Turtles use the landscape.

Beaver colony density trends on the Chequamegon-Nicolet National Forest, 1987-2013

The North American beaver (Castor canadensis) is a managed species in the United States. In northern Wisconsin, as part of the state-wide beaver management program, the Chequamegon-Nicolet National Forest removes beavers from targeted trout streams on U.S. Forest Service lands. However, the success of this management program has not been evaluated. Targeted removals comprise only 3% of the annual beaver harvest, a level of effort that may not affect the beaver population. We used colony location data along Forest streams from 1987–2013 (Nicolet, northeast Wisconsin) and 1997–2013 (Chequamegon, northwest Wisconsin) to assess trends in beaver colony density on targeted trout streams compared to non-targeted streams. On the Chequamegon, colony density on non-targeted trout and non-trout streams did not change over time, while colony density on targeted trout streams declined and then stabilized. On the Nicolet, beaver colony density decreased on both non-targeted streams and targeted trout streams. However, colony density on targeted trout streams declined faster. The impact of targeted trapping was similar across the two sides of the Forest (60% reduction relative to non-targeted trout streams). Exploratory analyses of weather influences found that very dry conditions and severe winters were associated with transient reductions in beaver colony density on non-targeted streams on both sides of the Forest. Our findings may help land management agencies weigh more finely calibrated beaver control measures against continued large-scale removal programs.

Using a full annual cycle model to evaluate long-term population viability of the conservation-reliant Kirtland's warbler after successful recovery

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 the population dynamics. The Neotropical migratory songbird Kirtlands warbler Setophaga kirtlandii (Baird 1852) is listed as endangered under the U.S. Endangered Species Act and Near Threatened under the IUCN Red List. This conservation-reliant 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 Kirtlands 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 the continuation of current management conditions, reduced productivity and carrying capacity due to the changes in habitat suitability from the creation of experimental jack pine Pinus banksiana (Lamb.) plantations, and reduced productivity from alteration of the brown-headed cowbird Molothrus ater (Boddaert 1783) removal programme. Linking wintering grounds precipitation to productivity improved the accuracy of the model for replicating past observed population dynamics. Our future simulations indicate that the Kirtlands warbler population is stable under two potential future management scenarios: (i) continuation of current management practices and (ii) spatially restricting cowbird removal to the core breeding area, assuming that cowbirds reduce productivity in the remaining patches by =41%. The additional future management scenarios we assessed resulted in population declines. Synthesis and applications. Our study indicates that the Kirtland’s warbler population is stable under current management conditions and that the jack pine plantation and cowbird removal programmes continue to be necessary for the long-term persistence of the species. 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 the model performance.