Research Abstracts
Department of Natural Resource Ecology & Management, OSU (2006-)
Project Title: Advancing broad scale ecological assessment using bird community indicators.
In recent years, several authors have developed ecological indicators for broad scale assessment that are based on the condition of landbird assemblages. These indicators are typically referenced to a physiographic province or geopolitical region, and rely on specific knowledge of life history of breeding birds. In some regions, bird-based indicators have been used in concert with land cover and other taxa-specific indicators to provide integrated assessments of ecological condition, but efforts to expand that approach to other regions have been slowed by a lack of indicators and/or source data to which those indicators could be applied. I investigated the application of conservation value (CV) scores derived from Partners in Flight prioritization ranks and applied to data from the North American Breeding Bird Survey (BBS) as a remedy for the current shortage of geographically dependent indicators. I compared CV scores to scores of existing indicators (the Bird Community Index) in the Central Appalachians and Mid-Atlantic Coastal Plain based on random selections of BBS data from 1973 and 2000. To demonstrate the approach in a region for which no other indicator was available, I derived CV scores for random selections of BBS data from the Northwestern Great Plains, also for 1973 and 2000. Results indicated that average CV scores across regions generally provided similar information to Bird Community Index scores, but CV scores were less closely associated with net land cover change over time. The CV scores offer potential for use as broad scale indicators, but may be most useful in targeted studies of specific management effect.
FIGURE 3. Change in BCI and PIF CV scores for BBS route data for the Central Appalachians, 1973–2000. Dashed lines indicate the upper and lower bounds of the standard deviation in mean change in scores for the region.
Project Title: The distribution of breeding Cerulean Warblers (Dendroica cerulea) in Oklahoma
Cooperators: Vince Cavalieri, Chip Leslie
Funding Sources: Oklahoma Department of Wildlife Conservation, State Wildlife Grant
Recent field work for Oklahoma’s Breeding Bird Atlas failed to locate Cerulean Warbler, raising concerns of range contraction for this former uncommon breeder. In 2006 and 2007, we conducted point counts at 150 sites throughout the species’ historical range in Oklahoma. We located Cerulean Warblers at 5 (3.3%) of the sites surveyed. These sites were located on north slopes in the Ouachita Mountains, near ridge tops between 641 and 721 m elevation. We encountered 8 adult males and 4 adult females at the 5 sites. We confirmed breeding from separate observations of pairs feeding fledglings in June 2006 on Lynn Mountain, and in June 2007 on Rich Mountain, both locations in LeFlore County. Compared to sites where we did not encounter Cerulean Warblers, sites where they were detected supported a taller and more densely vegetated canopy and were restricted to the region’s highest ridges.
Male Cerulean Warbler photographed on Lynn Mountain by Jason Heinen.
Project Title: A bird community on the edge: habitat use of forest songbirds in eastern Oklahoma
Cooperators: Vince Cavalieri, Chip Leslie
Funding Sources: Oklahoma Department of Wildlife Conservation, State Wildlife Grant
Several species of forest songbirds reach a western limit of their respective distributions in eastern Oklahoma. The relative influence of various habitat variables on patterns of occurrence in this region may differ from those same influences in the core of species’ ranges. We examined the influence of 16 habitat variables on the occurrence and density of a suite of forest songbirds. We sampled breeding birds with four, fixed radius point counts along 1-km transects at 75 forested sites in eastern Oklahoma in 2006. Forest cover at fine scales varied by numerous structural characteristics (e.g., canopy cover) as well as species composition (e.g., pines vs. hardwoods). We performed both Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) ordinations using 16 environmental variables and 37 bird species to examine bird habitat relationships. Forward Selection in CCA indicated that the most important environmental variables effecting bird habitat relationships were percent forest cover, canopy height, and elevation.
Project Title: Influence of old world bluestem (Bothriochloa ischaemum) monocultures on breeding density of three grassland songbirds in Oklahoma.
Cooperators: Andy George, Karen Hickman, Chip Leslie
Funding Sources: Oklahoma Department of Wildlife Conservation, State Wildlife Grant
Despite persistent and widespread declines of grassland birds in North America, few studies have assessed differences between native grasslands and seeded monocultures as songbird habitat. In the Great Plains, many fields enrolled in the Conservation Reserve Program have been seeded to Old World Bluestems (OWB), but there is evidence to suggest that OWB may not provide suitable conditions for several grassland bird species. Our objectives were to investigate the influence of OWB monocultures on vegetation structure, composition, and breeding densities of three common grassland bird species. In 2007, we used distance sampling to survey breeding songbirds in 6 native mixed grass prairie and 6 OWB fields in Garfield, Grant, and Alfalfa counties, Oklahoma. Native mixed grass prairie supported taller and more dense vegetation, as well as greater forb cover than OWB fields. Grasshopper Sparrow densities were significantly higher in OWB monocultures, while density of Dickcissel and Eastern Meadowlark was similar among field types.
Project Title: Influence of invasive eastern redcedar on density of breeding warblers in cross timbers forest.
Cooperators: Jason Heinen
Funding Sources: Oklahoma Department of Wildlife Conservation, State Wildlife Grant
Several species of North American wood-warblers with population centers in the eastern U.S. reach the southwestern limit of their breeding range in Oklahoma cross timbers forest. Historically, the cross timbers was dominated by post oak (Quercus stellata) and blackjack oak (Q. marilandica), but increasingly, these patches are influenced by eastern redcedar (Juniperus virginiana) encroachment. We investigated the influence of eastern redcedar on songbird community metrics and breeding density of three focal species of Neotropical migrant warblers: Kentucky Warbler (Oporornis formosus), Black-and-White Warbler (Mniotilta varia), and Louisiana Waterthrush (Seiurus motacilla). During May and June of 2007, we surveyed eight cross timbers forest patches in central Oklahoma. The 29 study plots within these patches represented a gradient of condition from low to high prevalence of redcedar. We used repeated samples of a modified spot-mapping approach for focal species, and fixed-radius point counts to reflect the larger breeding bird assemblage. Our results suggest that overall songbird species richness, diversity and Partners in Flight conservation value were not affected by cedar encroachment; however, breeding density of Kentucky Warbler was negatively correlated with the abundance of eastern redcedar in cross timbers forests.
Project Title: Bird species assemblage turnover during autumn migration.
Cooperators: Jason Heinen
Funding Sources: Unfunded undergraduate research project
During a twelve-week period in the autumn of 2006, we surveyed bird species assemblages at four sites in north-central Oklahoma. Our objective was to identify seasonal peaks in species turnover during autumn migration. Compared to the first week of sampling (8/29-31), mean Chao-Sorensen Abundance-based similarity over the 12 week survey period was 0.60, with a minimum of 0.44 observed during the 11th week (11/7-9). Similarity declined throughout the autumn from a mean of 0.67 during the period 9/5-28, to 0.56 during the period 10/3-19, to 0.49 during the period 10/24-11/16. Week to week similarity throughout the sampling period averaged 0.83. Similarity was high (0.99) during the first two sampling periods but dropped off sharply thereafter. We obtained a similarity estimate of 0.68 from 9/5-7 to 9/12-14 and 0.53 from 9/12-14 to 9/19-21. Following that September dip in weekly similarity, estimates increased and stabilized so that mean week-to-week similarity from 9/19-21 to 11/14-16 was 0.87. We interpret this result as pointing to mid- to late-September as the time of greatest species assemblage turnover. The period of peak species assemblage turnover did not coincide, however, with the arrival or departure of migratory species as initially predicted. Most of the incoming migrants arrived during subsequent weeks. This may indicate that local movements and changes in flocking behavior may have contributed more to species turnover estimates than the arrival or departure of individual species.
Department of Zoology, OSU (2003-2006)
Project Title: Indirect effects of wind farm development on breeding songbird densities in mixed grass prairie.
Cooperators: Martin Piorkowski, Rene Braud (FPL Energy)
Funding Sources: FPL Energy
Direct mortality from birds colliding with wind turbines has been well studied; comparatively less is known about the indirect effects of habitat loss from modern wind development areas. We estimated breeding density of songbirds adjacent to wind turbines, and in similar habitats 1-5 km and 6-10 km distant. All sites were located in mixed-grass prairie in proximity to the 68-turbine Oklahoma Wind Energy Center (OWEC). We sampled breeding birds in 2004 and 2005, using point-based counts along 26 transects to which post-hoc removal models were applied to account for detection probabilities and facilitate density estimation. For 19 of 22 species analyzed, density was lower at the OWEC than in similar habitats at least 1km away from the turbines, but those differences were significant for only five species. Of these, only Greater Roadrunner and Western Meadowlark potentially avoided an area around turbines that was larger than each structure’s construction footprint, and the apparent distribution of these species could have been influenced by factors other than habitat type and distance to turbines. Thus, our data do not suggest that the presence of wind turbines negatively influenced the breeding density of grassland songbirds at the Oklahoma Wind Energy Center.
Project Title: Estimates of bat and bird mortality from collisions with wind turbines in mixed-grass prairie.
Cooperators: Martin Piorkowski, Rene Braud (FPL Energy)
Funding Sources: FPL Energy
From May-July in 2004 and 2005, we studied bird and bat mortality from collisions with wind turbines at a 102 megawatt, 68-turbine wind farm in the southern Great Plains. Standardized searches around turbine bases yielded 122 total carcasses of which 92 (75%) were found within 20 m of the turbine bases. We identified 111 carcasses of seven bat species and 11 carcasses of six bird species among the casualties. Brazilian free-tailed bats (Tadarida brasiliensis) made up 85% of bat carcasses collected. We corrected turbine collision estimates using searcher efficiency trials and a range of carcass removal trials from the literature. Estimated bat turbine collisions ranged from 1.19 – 1.71 fatalities/turbine (1.03–1.37/MW). Spatial analyses indicate no consistent patterns in mortality estimates relative to ground cover or topographic position, but collision mortality was higher at several individual turbines. These data provide some of the first evidence for a steady rate of collision mortality of Brazilian free-tailed bats at a North American wind farm, most likely due to the site’s proximity (~15 km) to a maternity colony. Understanding patterns of mortality among individual turbines may lead to management actions that can reduce the collision rate.
Project Title: Breeding habitat and estimated population size of Mountain Plover in Oklahoma.
Cooperators: Scott McConnell, Chip Leslie, John Shackford
Funding Sources: State Wildlife Grant, Oklahoma Department of Wildlife Conservation
Population estimates for the Mountain Plover (Charadrius montanus) are complicated by the low density of Breeding Bird Survey routes throughout the breeding range. Researchers have turned to specific inventories at local scales to estimate numbers. In western Oklahoma, a small breeding population has been known since at least the 1920s, but no reliable population estimate had been obtained. We implemented a randomized point count survey of agricultural sections in an area where Mountain Plovers were known to breed, and conducted additional reconnaissance across a broader area to better delimit the distribution. We used a removal model to estimate detection probability for raw counts obtained from 1104 point counts in 2004 and 2005, and derived a state level population estimate using the detection-adjusted counts. Mountain Plovers used flat, bare, cultivated fields for nesting, and their distribution was closely tied to the presence of clay loam soils. We estimated that at least 101–126 Mountain Plovers bred in Oklahoma in 2004–2005. The future of the species in Oklahoma may be determined by changing agricultural practices forecasted for the shortgrass plains.
Project Title: Land-cover associations of breeding habitat for three sympatric Buteos in shortgrass prairie.
Cooperators: Scott McConnell, Chip Leslie, John Shackford
Funding Sources: State Wildlife Grant, Oklahoma Department of Wildlife Conservation
Three species of Buteo hawks nest sympatrically in the U.S. southern Great Plains. Because dietary overlap among them is broad, we tested the hypothesis that these species partition their breeding habitat spatially. We compared landcover and topography around 224 nests of three species of Buteos breeding in shortgrass prairie in 2004 and 2005. Red-tailed Hawks (Buteo jamaicensis) nested almost exclusively in riparian timber surrounded by prairie (95% prairie landcover around nests) and disproportionately used areas with greater topographic relief within prairie landscapes. Swainson’s Hawks (B. swainsoni) commonly nested in low-relief areas dominated by small-grain production agriculture but generally used habitats in proportion to availability. Most nest sites of the Ferruginous Hawk (B. regalis) were in prairie (78% prairie landcover around nests), but some nests were in agricultural areas. Ferruginous Hawks had at least two times more sandsage around their nests than their two congeners. We conclude that sympatric breeding Buteos on the southern Great Plains spatially partitioned nest sites according to subtle differences in land cover and topography. Because Red-tailed and Ferruginous hawks were already nesting prior to the spring arrival of Swainson’s Hawks, we also conclude that species-specific affinities were maintained in the absence of agonistic encounters.
Project Title: Modeling post-CRP land use for optimum environmental benefits using GIS
Cooperators: Cosmas Lungu
The Conservation Reserve Program (CRP) started in 1986 with the enactment of Title XII of the Food and Security Act of 1985 passed by Congress. Land is retired for 10 to 15 years and planted with either trees or grass. Studies have shown environmental benefits of the CRP. This study addresses the question of how these environmental benefits can be maintained after the expiration of the CRP contracts in Texas County Oklahoma.
The CRP has brought change to the Texas County landscape resulting in increase in minimum patch size (17%), reduction in number of patches (-15%), and total edge (-4%). The CRP has targeted areas important for natural resource conservation by converting areas of concern to CRP tracts shown by reduction of such areas e.g. fallow (-41%), small grains (-16%), row crops (-22%), and wetland (-19%). However, conversion of pre-CRP grassland has resulted in loss of habitat for some native species except for those that could use CRP tracts as habitat e.g. mean patch size reduced for those species that could not use CRP tracts as habitat. This study has demonstrated that environmental benefits can still be maintained by using part of the CRP coming out of contract for row crops (9.13%), pasture (6.58%), and wildlife (84.29%). Additionally, 13.53% of the CRP tracts should be monitored for groundwater quality and 62.18% for surface water quality. Modeling of crop production shows that crops can be produced profitably with minimum soil loss in the CRP tracts. We recommend that some CRP tracts should be returned to row crop production, about 9.13%. About 33-50% of the CRP tracts should be reserved for wildlife. Some areas should be monitored for water quality, soil and wind erosion. There should be a policy change in CRP to allow commercial use of CRP tracts for wildlife and give tax incentives instead of continued rental payments. Some CRP tracts should be retained as buffers.
Penn State Cooperative Wetlands Center, The Pennsylvania State University (1994-2003)
Project Title: Classifying and Prioritizing Watersheds for Protection and Restoration
Cooperators: Rob Brooks, G. P. Patil (Center for Statistical Ecology and Environmental Statistics, Department of Statistics, Penn State), George Constanz (Canaan Valley Institute)
Funding Source: USEPA-STAR Grant Program
Natural resource managers need to be able to put watersheds into categories for several reasons, including identifying reference conditions, understanding the types of environmental degradation, designing monitoring studies, and narrowing the restoration options. For example, a defensible “bundling” of watersheds according to their characteristics, problems, and restoration feasibilities may allow “off-the-shelf” TMDL plans. We will develop, validate, and apply a hierarchical, geographically-independent classification of watersheds based on pre-existing environmental data. Although focused on the Mid-Atlantic Highlands, our scheme will be useful anywhere. Our project has three major parts. (1) Using multivariate statistics, we will build a Characterization Model to classify watersheds based on their natural features and observed stressors. (2) Using linear ordering and echelon analysis, we will build a Prioritization Model to classify basins according to disturbance, susceptibility to impairment, and feasibility of restoration, where the last includes technical and economic measures. Both the Characterization and Prioritization models will be validated with in-stream and terrestrial biotic data sets (e.g., IBIs). (3) We will compare the results of our taxonomies of watershed types and priorities to the findings of other classifications. Products include: synoptic GIS coverages of environmental data for the Mid-Atlantic Highlands, a model graphical and statistical process for classifying watersheds by their features and restoration priorities, a taxonomy of Mid-Atlantic watersheds, and a set of monitoring and restoration options for each watershed class that can assist managers in the development and implementation of TMDL plans.
Project Title: Design and Survey Protocols for the 2nd Pennsylvania Breeding Bird Atlas
Cooperators: Rob Brooks, Joe Bishop, Mike Lanzone
Funding Sources: Cooperative Agreement with the PA Game Commission and a grant from the Wild Resources Conservation Fund
This project served as the “kick-off” for Pennsylvania’s 2nd Breeding Bird Atlas Project, 2004-2008. Guided by the ultimate direction of the Atlas Steering Committee (a subset of the Pennsylvania Society for Ornithology), the CWC formed a core Design Team of five members: an ornithologist and a GIS specialist from the CWC, the Chair of the Atlas Steering Committee, and the Coordinator and Assistant Coordinator for the 2nd Atlas. Our overriding goal was to design sampling protocols to allow rigorous statistical comparisons of distribution and abundance for all Pennsylvania breeding birds using data collected by volunteer and select paid staff atlasers. We also developed an interactive computer infrastructure for data entry, analysis, and archival in concert with BirdSource, a joint organization of the National Audubon Society and Cornell Laboratory of Ornithology. Significantly, and we think unique among all atlas projects thusfar, volunteers for Pennsylvania’s 2nd Atlas will be able to view and print detailed maps of potential habitat for conservation priority species based on 187 predictive habitat models produced as part of Pennsylvania’s Gap Analysis Project. The models are based on multiple GIS layers, and were reconfigured specifically for the 2nd Atlas using land cover data from Landsat 7. This feature will allow Atlas volunteers to locate specific habitat patches for a given species that might not otherwise have been apparent from topographic maps alone. The ability to identify specific habitat patches for priority species will foster more efficient and objective general atlasing, as well as anchor specific abundance sampling efforts for wetland and nocturnal birds. The 2nd Atlas will include an abundance sampling protocol with randomly located, eight-stop mini-routes in 3,931 non-border Atlas blocks. We anticipate that this component will take 2-3 dozen select field observers three field seasons to complete. Because of the need for multiple observers, we will apply post hoc analyses using count removal models to correct for observer and species detection biases and facilitate direct abundance and density comparisons among observers for many species. Again, the scale at which we are proposing is unprecedented among atlas projects, and indeed, other large-scale monitoring programs.
Project Title: Using Bioindicators to Develop a Calibrated Index of Regional Ecological Integrity for Forested Headwater Ecosystems
Cooperators: Rob Brooks, Joe Bishop, Terry Master (East Stroudsburg University), and Bob Mulvihill (Powdermill Nature Reserve, Carnegie Museum of Natural History)
Funding Sources: USEPA-STAR Grant
We developed an integrated and calibrated indicator of ecological integrity for forested headwater streams in the Mid-Atlantic States. Ecological indicators provide a quick, objective, and relatively easy method to gauge the condition of a particular resource, and aid greatly in the establishment of conservation priorities and development of restoration goals. Headwater systems are degraded by point source stressors, like acid mine drainage, and also by more cumulative and insidious stressors that operate at large scales, such as forest fragmentation. Ecological indicators exist that respond to site-level attributes, like water quality. Recently, new indicators have emerged that respond to landscape-scale attributes, like bird communities. We investigated the utility of a new indicator that would be sensitive to stressors at both the site and landscape scale in forested headwaters (i.e., integrated). This indicator was developed through application of existing indicators such that the assessments of multiple indicators could be compared directly (i.e., calibrated). Primarily due to its dependence on both high stream water quality and large patches of mature forest, we saw great potential in the Louisiana Waterthrush (Seiurus motacilla) to provide meaningful biological data to incorporate in our new indicator. Thus, our primary objective was to investigate aspects of Louisiana Waterthrush (a.k.a. LOWA) ecology as the basis for a calibrated and integrated indicator of forested headwater stream condition. The resulting indicator, the Headwater Stream Assessment, incorporates information on local landscape condition, instream water chemistry (pH), and a biological element (either LOWA breeding density or richness of the riparian songbird community) to provide a rapid assessment of overall riparian condition.
Project Title: A Bird Community Index for the Southeastern United States
Cooperators: Rob Brooks, Mike Lanzone, Joe Bishop
Funding Sources: USEPA-STAR Grant
As part of an effort to develop guild-based assessment tools for bird communities that convey information on ecosystem condition, we constructed a new Bird Community Index (BCI) for the Piedmont and Coastal Plain physiographic provinces of the mid-Atlantic and Southeastern United States. To build the new “Southeastern BCI,” we sampled breeding songbird communities, ground level vegetation, and landscape characteristics from approximately 80 sites in PA, MD, DE, VA, and NC in 2001. Sample sites represented a gradient of condition from older growth broadleaf forest and mature fire-maintained pine savanna to intensive urban development. Primary land cover stressors in this region included intensive crop production, urban sprawl, short-rotation forestry for pulp and paper, and fire suppression. We recognize two distinct states of “natural” condition at landscape scales in uplands of the study region: a mature, mesic, broadleafed or mixed forest that is infrequently disturbed by natural forces, and a pine and oak savanna maintained by frequent low-intensity fires. Like our previous research in the Appalachians, we found traditional community measures such as richness and Shannon diversity were unreliable indicators of anthropogenic disturbances. In contrast, life history groups such as “ground nesting forest birds” exhibited statistical relationships to varying degrees of landscape level disturbance. We envision the resulting Southeastern BCI to be applicable to near-coastal upland environments from southern New England to northern Florida and west to the Mississippi River. Combined with our original “Appalachian” BCI, the Southeastern BCI provides assessment coverage for roughly the eastern third of the United States, and provides a major advancement toward the production of a “National Environmental Scorecard.”
Project Title: The North American Breeding Bird Survey as Source Data for Assessments of Ecological Condition with The Bird Community Index
Cooperators: Rob Brooks, Joe Bishop
Funding Sources: USGS-Patuxent Wildlife Research Laboratory, USEPA
We examined the use of data from the North American Breeding Bird Survey (BBS) for assessments of ecological condition using an avian community-based indicator, the Bird Community Index (BCI). In previous research, the BCI was developed and applied to a random sample of sites in the Mid-Atlantic Highlands. The goal of providing national scale assessments with bird community indicators hinges on a demonstration that existing monitoring programs, like the BBS, can be tapped as source data for the indicators. Our goal was to compare a BBS-based assessment of the Mid-Atlantic Highlands to our original assessment based on random sampling locations. We subsampled three iterations of BBS route data from the study area to account for spatial and temporal scale differences between 40 km BBS routes and the original 1 km transects sampled to develop the BCI. All three iterations of BBS subsamples provided lower overall assessments of ecological condition for the Mid-Atlantic Highlands relative to our original research. Land cover analysis, however, revealed that BBS routes sampled land cover types in proportion to their actual prevalence in the region. Thus, we conclude that BBS data are appropriate as source data for broad scale ecological assessments with indicators such as the BCI. For numerous analytical and logistical reasons, we recommend 10-stop subsamples of BBS data as the preferred scale at which to apply bird community indicators of ecological condition.
Project Title: Changes in Small Mammal Communities of Riparian Corridors on a Gradient of Urban Land Cover
Cooperators: Carolyn Mahan (Penn State-Altoona)
Funding Sources: Centre Community Foundation, Hamer foundation, Land Studies, Inc.
As part of a larger effort to conduct natural history inventories of select urban parks in Centre County, Pennsylvania, we documented community-level changes in the small mammal fauna on a gradient of disturbance. Using mark-recapture analysis of live-trapped mammals, we compared the fauna of a relatively undisturbed, mature riparian forest in the Rothrock State Forest with that of seven county parks in various states of management for active (e.g., playing field) to passive (e.g., nature study) recreation. All parks supported a predominantly riparian environment. Preliminary results suggest that urban parks can potentially support a native small mammal fauna similar to that of an undisturbed riparian forest or meadow, but specific management practices (e.g., mowing to the stream banks) can dramatically influence species composition and reduce abundance.
Project Title: Forest birds in the Mid-Atlantic Highlands: Informing conservation through patterns of occurrence
Cooperators: Rob Brooks, Joe Bishop, Laura Jackson (USEPA)
Funding Sources: Unfunded analysis of USEPA-EMAP data
We analyzed patterns of occurrence for 107 breeding birds to determine which species responded primarily to forest cover, and derive a management target for mature forest habitats suitable for multiple species. We conducted point counts in 1995 and 1996 at 126 randomly selected sites in the Mid-Atlantic Highlands. To determine which species were forest-dependent, we tested for associations between species abundance and percent mature forest mapped in a GIS in a 314 ha circular area around bird survey locations. Twenty seven species were positively associated with percent forest at the 314 ha scale. We used principal components analysis and best subsets regression to explore relationships among stand- and site-level variables with a response variable based on the percentage of forest species that occurred at sites. The response variable was best predicted by a model incorporating percent forest, land cover diversity, herbaceous cover, slope, and canopy height. Most sites supported about 33% of the potential forest species; only sites in excess of 80% forested supported one standard deviation above the mean, i.e., 52% of the potential forest species. We intend our results to advance conservation management objectives for forest breeding birds in the Mid-Atlantic Highlands ecoregion by illustrating a basis for management targets at a scale relevant to regional planners.
Project Title: An Avian Indicator of Ecological Condition for the Mid-Atlantic Highlands
Cooperators: Rob Brooks, Laura Jackson (USEPA)
Funding Sources: USEPA-EMAP, USGS
This research involves the development, evaluation, and application of the Bird Community Index (BCI). The BCI is an analytical tool for ecological assessment at large scales, e.g., landscapes, ecoregions, and, ultimately, continents. The theory behind the BCI is that native ecological specialists should be more vulnerable to human disturbances (e.g. habitat loss and degradation) than ecological generalists. The BCI converts a list of breeding songbirds in an area into a matrix of proportions for 16 life history guilds representing structural, functional, and compositional elements. Guilds are divided into “specialists” (sensitive to human disturbance) and generalists (tolerant of human disturbance) and assigned numeric ranks based on the proportion of the species in the breeding bird community representing each guild. A bird community is assigned high values for good representation of specialist guilds and poor representation of generalist guilds. Thus, a community dominated by specialists will receive high rankings for all 16 guilds. Ranks are summed to indicate an overall BCI score. We developed and verified the BCI in central Pennsylvania using independent data from multiple taxonomic groups. We then applied the BCI to 126 randomly-selected sites from the entire Mid-Atlantic Highlands Assessment area to more fully describe its behavior relative to landscape features and perform an assessment of condition across the region. Because the BCI responds well to land cover features, we see tremendous potential in its application to land use planning.
Independent research (1991-1994)
Project Title: Avian Window Strike Mortality at A Suburban Office Park
From May 1993 to May 1994, I recorded incidences of window strike mortality at four glass-surfaced buildings in a corporate office park in suburban Richmond, Virginia. Each building was checked for dead birds by walking the perimeter of the building approximately weekly. Individual victims were counted and identified to species, depending on the state of preservation. I documented 116 individuals of 40 species killed at the four buildings, with a mean annual mortality rate of 29 individuals killed per building. This rate is nearly three times the carefully derived and independently verified estimated rate of ten birds/building/year, suggesting that structures with high rates of bird strikes can indeed compensate for structures with low incidences of bird strikes in continental scale estimates of window-strike mortality. Unlike previously published reports on bird-window collisions, mortality in this study was significantly higher in the spring and fall than in winter. I also documented a disproportionately low incidence of mortality among birds attracted to feeders and a high incidence of mortality in long distance migrants. Window-strike mortality at office parks, therefore, may mimic more closely the type of mortality documented at certain well-known skyscrapers than it does the mortality observed at private residences with feeding stations.
The College of William and Mary in Virginia (1989-1991)
Project Title: Gull predation limits nest success of terns and skimmers on the Virginia barrier islands
Cooperators: Ruth Beck (College of William and Mary)
Funding Source: Williamsburg Bird Club, Northern Neck of Virginia Audubon Society, Virginia Department of Game and Inland Fisheries
We studied seven mixed-species colonies of terns and skimmers on the Virginia barrier islands in 1990 and 1991 to determine the effect of gull predation on nest success. We compared intensity of gull predation and other agents of egg or chick mortality between tern and skimmer colonies on islands that also contained nesting gulls and colonies on islands that lacked nesting gulls. Terns and skimmers fledged about 3% of all eggs produced, with confirmed gull predation (27%) and tidal flooding (21%) accounting for the majority of nest failures. Gull-present colonies experienced significantly greater rates of disturbance from Herring and Great Black-backed gulls than did gull-absent colonies. Overall levels of gull predation were similar between gull-present and gull-absent colonies, likely due to the added impact of aerially-foraging Laughing Gulls. Anecdotal evidence suggests that nest site competition with Herring and Great Black-backed gulls may have led to many terns and skimmers nesting in areas that were prone to frequent tidal flooding. In addition, floods may have indirectly prevented terns and skimmers from adequately protecting their surviving eggs and young, thus rendering flooded colonies more susceptible to gull predation.
Cornell University (1985-1989)
Project Title: Is the chemical defense of Eurycotis floridana a deterrent to small mammal predators?
Cooperators: Nathan Reagle (Penn State undergraduate student), Thomas Eisner (Jacob Gould Schurman Professor of Chemical Ecology at Cornell University).
Adults of the subtropical cockroach Eurycotis floridana emit a defensive chemical spray from their abdomens consisting primarily of (E)-2-hexenal. Nymphs are similar in size to the adults, but lack the chemical defense. The ability of the defensive spray to repel predators has received relatively little study. We conducted feeding trials with two species of mice, Peromyscus gossypinus and P. polionotus, that are abundant in the natural habitats that support Eurycotis in central Florida, and potentially important predators on Eurycotis. We offered captive mice Eurycotis nymphs, adults, and nymphs with a solution of (E)-2-hexenal applied either to the head or the abdomen. Both species of mice were adept at handling untreated nymphs. Both species of mice were visibly distressed when exposed to (E)-2-hexenal. P. polionotus proved largely unable to handle adult Eurycotis because of the inability of this mouse to deal with the chemical defense. In contrast, P. gossypinus dealt well with adult Eurycotis by thrusting the roach’s abdomen into the substrate and feeding from the head to avoid exposure to the chemical defense. We conclude that the chemical defense of Eurycotis is an effective deterrent to small mammal predators, but that at least some individuals of P. gossypinus adopt a behavior to neutralize that defense.
