cerulean warbler Management Guidelines for Enhancing Breeding Habitat in Appalachian Hardwood Forests February, 2013 Authors Petra Wood1, James Sheehan2, Patrick Keyser3, David Buehler3, Jeff Larkin4, Amanda Rodewald5, Scott Stoleson6, T. Bently Wigley7, Jeremy Mizel2, Than Boves3, Greg George2, Marja Bakermans5, Tiffany Beachy3, Andrea Evans4, Molly McDermott2, Felicity Newell5, Kelly Perkins2, Matt White4 1 U.S. Geological Survey, West Virginia Cooperative Fish and Wildlife Research Unit, West Virginia University, Morgantown, WV, USA. 2 West Virginia Cooperative Fish and Wildlife Research Unit, Division of Forestry and Natural Resources, West Virginia University, Morgantown, WV, USA 3 Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN, USA 4 Department of Biology, Indiana University of Pennsylvania, Indiana, Pennsylvania, USA 5 School of Environment and Natural Resources, Ohio State University, Columbus, Ohio, USA 6 U.S. Forest Service, Northern Research Station, Irvine, PA, USA 7 National Council for Air and Stream Improvement, INC. Clemson, SC, USA Recommended citation: Wood, P.B., J. Sheehan, P. Keyser, D. Buehler, J. Larkin, A. Rodewald, S. Stoleson, T.B., Wigley, J. Mizel, T. Boves, G. George, M. Bakermans, T. Beachy, A. Evans, M. McDermott, F. Newell, K. Perkins, Cerulean Warbler. Bill Hubick and M. White. 2013. Management guidelines for enhancing Cerulean Warbler breeding habitat in Appalachian hardwood forests. American Bird Conservancy. The Plains, Virginia. 28 pp. Cerulean Warbler Management Guidelines...........................................................................................................i Acknowledgments This research was an outgrowth of the many integrated efforts of the Cerulean Warbler Technical Group for conservation of Cerulean Warblers. Development of this habitat management guidelines document was funded through a grant from the U.S. Fish and Wildlife Service, (USFWS) Northeast region Division of Migratory Birds. Funding for publication provided by American Bird Conservancy through the Appalachian Mountains Joint Venture. Data on which the guidelines primarily are based were collected in a research study funded by National Fish and Wildlife Foundation, National Council for Air and Stream Improvement, Inc, USFWS, U.S. Forest Service (USFS) Monongahela National Forest and Daniel Boone National Forest, MeadWestvaco Corporation, Kentucky Department of Fish and Wildlife Resources, Ohio Division of Wildlife, Tennessee Wildlife Resources Agency, Department of Forestry, Wildlife and Fisheries at the University of Tennessee, The Nature Conservancy through a USFWS HCP planning grant with the Tennessee Wildlife Resources Agency, West Virginia Division of Natural Resources Wildlife Diversity Program, and U.S. Geological Survey West Virginia Cooperative Fish and Wildlife Research Unit. This research was conducted on USFS Daniel Boone National Forest and Monongahela Appalachian breeding habitat. Than Boves National Forest, on public lands owned by the Tennessee Wildlife Resources Agency and the West Virginia Division of Natural Resources, and on private lands owned by Forest Land Group/Wagner Forest Management and MeadWestvaco. We appreciate the cooperation and assistance of these agencies/groups and the efforts of their forest management personnel for assistance with study site selection, design of harvesting treatments, and especially implementation of harvests. We thank cooperating universities: Indiana University of Pennsylvania, Ohio State University, West Virginia University, and University of Tennessee. This study was completed under the auspices of IACUC protocols from Ohio State University (#2004A0047, 2007A0015, and 2010A0003), West Virginia University (#04-0302, 07-0303), and University of Tennessee (#561). Technical review of this publication was provided by: Frank Ammer, Barbara Breshock, Gwen Brewer, Randy Dettmers, Mary Ann Fajvan, Todd Fearer, Christine Kelly, Ben Jones, Glen Juergens, Cathy Johnson, Paul Hamel, Jim McCann, Mike Reynolds, Ken Rosenberg, Sara Rothemel, Brian Smith, and Scott Somershoe Publication design and layout by Debra Reynolds, USFWS Photos: Cover: Clockwise: Appalacian landscape, Charlie Choc; Cerulean Warbler, Bill Hubick, http://www.billhubick.com; Fledgling, Marja Bakermans; Shelterwood, Scott Stoleson; Female, Bill Hubick Cerulean Warbler Management Guidelines..........................................................................................................ii Table of Contents Introduction..............................................................................................1 Goals...........................................................................................................2 Conservation.............................................................................................3 Cerulean Warbler Habitat Associations................................................4 Landscape and Topography.......................................................4 Stand Structure and Composition............................................6 Male Cerulean Warbler. Marja Bakermans Cooperative Cerulean Warbler Forest Management Project..............8 Findings Relevant to Silvicultural Prescriptions..................................12 Territory Density.........................................................................12 Nest Success.................................................................................14 Habitat Use..................................................................................15 Changes in Allied Bird Communities.....................................16 Management Considerations..................................................................18 Landscape-scale Considerations..............................................18 Stand-scale Considerations.......................................................19 Temporal and Silvicultural Considerations.............................21 Summary....................................................................................................22 References Used in These Guidelines....................................................23 Cerulean Warbler Management Guidelines.........................................................................................................iii Introduction The Cerulean Warbler (Setophaga cerulea) is a migratory songbird that breeds in mature deciduous forests of eastern North America. Cerulean Warblers (hereafter, ceruleans) require heavily forested landscapes for nesting and, within Appalachian forests, primarily occur on ridge tops and steep, upper slopes. They are generally associated with oak- dominated (Quercus spp.) stands that contain gaps in the forest canopy, that have large diameter trees (>16 inches diameter breast height (dbh)), and that have well-developed understory-and upper-canopy layers. Ceruleans primarily use the mid- and upper-canopy where they glean insects from the surface of leaves and conceal their open cup nests. Because they are severely declining across Figure 1. Cerulean Warbler distribution and trends in abundance across their breeding much of their range (Fig. 1), habitat range from Breeding Bird Survey data (1966-2010; Sauer et al. 2011). The Appalachian Mountains Bird Conservation Region boundary is in black. management is a high priority. Management for this species can also improve conditions for a number of other wildlife species that depend on the same structure. Adult Cerulean Warbler feeding chick. Wayne Miller Cerulean Warbler Management Guidelines...........................................................................................................1 Goals This document provides land managers in the Appalachian Region with guidelines for retaining and enhancing habitat for Cerulean Warblers and a diverse bird community based on the current available science. They are intended for use by federal, state and private foresters, biologists, and other land managers. These management guidelines are based to a large extent on the recently completed Cooperative Cerulean Warbler Forest Management Project (CWFMP) but also incorporate relevant findings from other research projects. All literature incorporated into this document is listed in the Reference section. The guidelines apply primarily to upland oak-dominated habitats where the majority of the research reported was completed. Figure 2. Cerulean Warbler abundance (number per route) estimated from Breeding Bird Survey data for the Appalachian Mountains Bird Conservation Region (BCR) (adapted from Shumar 2009). Study areas from the Cerulean Warbler Forest Management Project (CWFMP) are in the core range of the species. Cerulean Warbler Management Guidelines...........................................................................................................2 Conservation About 80% of the total cerulean population breeds within the Appalachian Mountains Bird Conservation Region (BCR; Fig. 1), and they are particularly abundant within the central part of the region (Fig. 2). Declines have occurred across most of their range (Fig. 1). A range-wide loss of ~70% of the population (Fig. 3) led to their designation as a species of national conservation concern by the U.S. Fish and Wildlife Service (USFWS) and as a Continental Watch List species by Partners in Flight. Cerulean declines are primarily related to the loss and reduced suitability of habitat on breeding, migration, and wintering grounds. On breeding Male Cerulean Warbler. Than Boves grounds, the second growth forests that occur throughout most forested landscapes often lack the complex forest structure favored by ceruleans. Old-growth forests naturally develop a more open and complex canopy structure, as well as multi-layered shrub and mid-story layers. Maintaining older, structurally diverse forest within cerulean breeding range may be important to sustain populations in the long-term and to support the ecosystems on which they and other organisms depend. In managed forests, however, foresters and landowners can use silviculture as a tool to develop stands with structural and compositional characteristics that are favorable for cerulean and associated species. Partial harvesting to benefit ceruleans can be consistent with forest management goals such as promoting oak regeneration and managing for a diverse wildlife community. Figure 3. Cerulean Warbler population decline modeled using Breeding Bird Survey data from 1966-2006 (W. Thogmartin, unpubl. analyses). Cerulean Warbler Management Guidelines...........................................................................................................3 Cerulean Warbler Habitat Association Cerulean breeding density is variable across the Appalachian region (Fig. 2). Their distribution is often patchy in part due to the patchy nature of canopy disturbance in mature forests and their strong association with ridge tops. In a southern West Virginia study, for example, they occurred at 40% of randomly placed sample points. Landscape and Topography Small forest tract size and the presence of large-scale edge (e.g., agricultural lands, mountaintop mines) can limit use of a site by ceruleans. Although the minimum forest tract size required by ceruleans to breed successfully is not known, smaller, more fragmented forest patches tend to have lower densities of territories and lower nest success. Ceruleans will use relatively small forest patches (~25 ac), but typically in landscapes that are primarily forested (e.g. >75% forest cover within ~6 miles of the project area). In landscapes with a relatively low proportion of forest cover (e.g. those that are dominated by Figure 4. Cerulean Warbler territories on a topographic map of the Lewis Wetzel agriculture), ceruleans are less likely to occur within small forest tracts. In the Wildlife Management Area, West Virginia, heavily deforested Mississippi Alluvial Valley, ceruleans require ~4000 acre showing territories aligned along ridgelines tracts, in the highly fragmented Mid-Atlantic region ~1730 acres, and in the and clustering near areas of local relief. more forested Ohio Hills ~60 acres. Ceruleans are often associated with canopy gaps and also use internal forest edges including narrow roads, narrow utility rights-of-way, narrow- cut strip mines, edges of small timber harvests, and trails. However, they are less abundant near abrupt or “hard” edges between forest cover and large expanses of open land (e.g., commercial, residential, and industrial development). In southern West Virginia, for example, cerulean abundance decreased near mountaintop mine edges and in northern West Virginia, they avoided edges of a large powerline right-of-way that was ~75 feet wide. In the Appalachians, ceruleans primarily occur along ridges and steep, upper slopes and appear to cluster near areas of local relief such as knobs and bluffs (Fig. 4). The soil characteristics and topography of these features contribute to stratification of canopy trees so that ridge top forests often have a complex overstory structure containing large oaks with expansive crowns. Thus, ridge top forests often offer the structure and composition sought by breeding ceruleans. Within ridge top forests, ceruleans often favor mesic, north- and northeast-facing slopes, although other aspects are used. In some sections of the Appalachians (e.g. Delaware River valley), ceruleans are most dense at lower slope positions and along major waterways. Cerulean Warbler Management Guidelines...........................................................................................................4 Appalachian landscape. Than Boves Minimum patch size used by ceruleans depends on the amount of forest cover in the landscape. Cerulean Warbler Management Guidelines...........................................................................................................5 Stand structure and Composition Before extensive clearcutting in the late 19th and early 20th century, tree mortality from old age, wind- throw, ice storm damage, and fire contributed to the development of structurally complex and relatively open stands in which oaks were dominant. In the even-aged stands that developed following those extensive harvests, natural canopy disturbances tended to be unevenly distributed and relatively small thereby creating a relatively homogenous canopy structure (e.g., a closed canopy forest with an undeveloped understory and/or mid- story). Important Components of Cerulean Habitat Large Diameter Trees Ceruleans place territories and nests in hardwood forests with well- spaced, large diameter trees (>16 inches dbh). Nests are typically in the largest trees available at a site. Canopy Gaps and Structure Ceruleans favor the complex canopy structure characteristic of uneven- aged stands and old growth forest. Canopy gaps allow mid- and upper- canopy trees the growing space to form long horizontal branches and Upland forest used by Cerulean Warbler. Marja Bakermans develop dense foliage. Tree species composition is relatively diverse with shade-intolerant species abundant in Heterogenous stand structure including large trees, the overstory. canopy gaps, and understory vegetation promote density and reproductive success of ceruleans. Cerulean Warbler Management Guidelines...........................................................................................................6