Avian Ecology & Management I

Contributed Paper
ROOM: CC, Room 20

1:10PM Evaluating Interactions between Space-Use Sharing and Defense Under Increasing Density Conditions for the Group-Territorial Red-Cockaded Woodpecker
James E. Garabedian; Christopher E. Moorman; M. Nils Peterson; John C. Kilgo
Information about how bird species respond to increasing density conditions through either space-use sharing or increased territoriality, and how those changes affect fitness, is essential for effective conservation planning. We used a case study of endangered Red-cockaded Woodpeckers Leuconotopicus borealis (RCW) space-use characteristics and territorial behaviors to address these questions. We documented over 36,000 locations from 44 RCW groups in three density conditions on two sites in South Carolina, USA between April 2013 and March 2015. The frequency of neighboring group interactions differed among density conditions and was greatest for high-density groups. RCW home ranges and core areas were larger under low-density conditions (Home range = 88.4 ha, Core area = 21.0 ha) than under medium (Home range = 68.29 ha, Core area = 16.6 ha) and high-density (Home range = 76.3 ha, Core area = 18.6 ha) conditions. Neighboring RCWs maintained overlapping home ranges with nearly exclusive core areas across density conditions, but overlap tended to increase as neighboring group density increased. Under high-density conditions, home-range overlap correlated inversely with clutch size (β ± se = -0.19 ± 0.09), nestling production (β ± se = -0.37 ± 0.09), and fledgling production (β ± se = -0.34 ± 0.08). Our results indicate that RCWs dedicate more effort to territorial defense under high-density conditions, potentially at the expense of greater foraging efficiency and time allocated to reproduction, as evidenced by reduced fitness. High home-range overlap indicated limited territoriality farther away from cavity trees, but exclusive core areas suggest RCW groups defend habitat closer to cavity trees. Thiessen partitions used to allocate critical foraging habitat offered comprehensive habitat protection for RCW, but appear flawed for spatially-explicit habitat assessments because they do not accurately delineate space used by individual RCW groups.
1:30PM Impacts of Climate Change on Boreal Bird Communities: Going Beyond Climatic Suitability Models
Junior A. Tremblay; Yan Boulanger; Dominic Cyr; Anthony R. Taylor; David T. Price; Diana Stralberg; Peter Solymos
Increased anthropogenic climate forcing in the coming decades is anticipated to strongly alter boreal forest composition and age structure through changes at both stand- (e.g., mortality, competition, reproduction, growth) and landscape-scales (e.g., natural disturbances). Such changes are, in turn, likely to affect the distribution of boreal species habitats. Coupled with the climate-change threat, there are also conservation concerns resulting from rapid rate of industrial development, including forestry, energy, and mineral resource extraction in boreal regions, which could dramatically alter forest habitat over coming decades. In this study, we use the LANDIS-II forest landscape model to project the impacts of climate change and anthropogenic disturbance (forest harvesting) on boreal bird community in northeastern Alberta (>100 bird species). More specifically, we project changes in forest landscapes, and associated bird population trends according to four climatic forcing scenarios (Baseline, RCP 2.6, RCP 4.5, RCP 8.5), and 3 management scenarios. Both forest harvesting and climate-related drivers are predicted to have great impacts on forest in this region, notably by triggering sharp declines in the abundance of coniferous tree species. Accordingly, bird species associated with coniferous habitat, especially those depending on older forest stands would be negatively impacted by both climate-related drivers and harvesting. Under mild and moderate anthropogenic climate forcing, lower harvesting rates mitigate the impact of climate change on bird populations. Our study highlights the importance of adapting forest management to conserve and maintain old coniferous forest habitats.
1:50PM Multi-Season Movements of Red-Headed Woodpeckers in Managed Oak Savannas of the Midwest
R. Kyle Pagel; Elena H. West; Henry M. Streby
The Red-headed Woodpecker (Melanerpes erythrocephalus) is a flagship species of the oak savanna ecosystem found in small isolated areas throughout the Midwest. Populations have declined by 70% across the species’ breeding range over the past 50 years. Landscape management has increased oak savanna cover in recent years; however, populations continue to decline. To identify drivers of these population declines and identify important habitat characteristics during both the breeding and non-breeding seasons, monitoring movements of individuals across the annual cycle is vital. In 2017 and 2018, we used radio telemetry to track daily movements of fledglings and adults at Oak Openings Preserve Metropark in northwestern Ohio, Cedar Creek Ecosystem Science Reserve in central Minnesota, and Fort Custer State Recreation Area in southwestern Michigan, USA. Daily locations, parental care, and habitat use of fledglings were recorded to identify movement patterns and potential factors influencing survival. In addition, we used pinpoint GPS units to monitor the annual movements of adults from two of these sites. The daily movements of individuals at three distinct populations across the Midwest provide us with better knowledge of cover-type associations of various age classes. In general, fledglings used oak savanna and surrounding forest cover-types and remained within ~350m of their nest cavity during the dependent post-fledging period. Preliminary results from pinpoint GPS units indicate that location estimates were highly accurate and adults remained within ~1km of their nest during the breeding season. Migratory timing, movements, and winter home ranges will be discussed. Together, these annual-cycle habitat use data can provide the basis for informing conservation and management plans and future research objectives.
2:10PM Effects of Warming Temperatures on Reproductive Demography: Sagebrush Songbirds and Climate Change
Embere Hall; Anna D. Chalfoun
Warming temperatures are altering ecosystem dynamics, species composition and extinction probabilities. Despite these trends, however, relatively little is known about the long-term demographic effects of warming temperatures, and in particular, how climate change might impact reproduction, a key driver of population trends in many species. Sagebrush-obligate songbirds offer an excellent system to evaluate demographic effects of climate change, as they nest in exposed, arid environments, and their altricial offspring are highly sensitive to variation in temperature. Using Brewer’s sparrows (Spizella breweri) as a model, we addressed the extent to which climate variation influenced reproductive investment and output. We collected fitness-related data from 3,189 nests across 4 study areas (45 sites) in the sagebrush steppe, USA, 2002-2016. Each nest was linked with temporally matched, gridded daily temperature values. This allowed us to quantify the strength and spatial consistency of the relationship between temperature and critical fitness components, including the number of young fledged from each nest. On average, Brewer’s sparrows produced 2.97 (SD = 0.87) offspring per reproductive attempt. We found a strong quadratic effect of temperature, with decreased per-nest productivity at both high and low mean temperatures. The magnitude of this result, however, varied substantially by study area (σ = 4.71), suggesting strong context dependency in the influence of climate on reproductive output. As warming temperatures continue to manifest, efforts to understand and quantify species’ vulnerability to changing climate dynamics will be enhanced by considering the influence of climate-related stressors, including thermoregulatory risk, during key life-history periods.
2:30PM Refreshment Break
3:20PM Describing Spatial Use of Bicknell’s Thrush in Industrial Forest Landscapes in North-Cental New Brunswick, Canada
Christopher Ward; Tony Diamond
Bicknell’s Thrush (Catharus bicknelli) is a rare, neotropical migratory songbird which breeds in high elevation stunted-growth forests in north-eastern United States and eastern Canada. In New Brunswick, Bicknell’s Thrush occupy industrial forest stands regenerating after clear-cutting, and have declined at 11.5% annually from 2002-2011. Current population estimates are derived from point-count surveys combined with rough habitat models that are inaccurate for the region. Assessing population density and habitat use are vital next steps to improve New Brunswick population estimates. We focus on measuring home range size in an occurrence patch of 4100 ha in size. We tagged eight male and eight female Bicknell’s Thrush with VHF radio tags and tracked them over two summer breeding seasons. We found mean home range areas of 19.8 ± 17.3 ha (male), and 48.94 ± 53.7 ha (female). From home range size and overlap, we estimated a female Bicknell’s Thrush population within the patch to be 111 ± 28 female individuals. When extrapolated to a potential habitat model within New Brunswick, we estimated 5895 ± 1490 female Bicknell’s Thrush, translating to 17685 individual Bicknell’s Thrush in New Brunswick (calculated at a 2:1 ratio of males to females). Our estimate is much greater than previous estimates (2734 – 10573 individuals) from male-only point count surveys. We discuss the population estimate and the high variability in home range sizes of both sexes in relation to their breeding stage and general habitat.
3:40PM Population Trends of Vermivora Warblers Are Linked to Strong Migratory Connectivity
Gunnar R. Kramer; David E. Andersen; David A. Buehler; Petra B. Wood; Sean M. Peterson; Justin A. Lehman; Kyle R. Aldinger; Lesley P. Bulluck; Sergio Harding; John A. Jones; John P. Loegering; Curtis Smalling; Rachel Vallender; Henry M. Streby
Identifying the drivers of population trends in migratory species can be especially challenging but is crucial for informing effective management strategies. Golden- and blue-winged warblers (Vermivora chrysoptera and V. cyanoptera, respectively) are closely related Neotropical-Nearctic migrant songbirds exhibiting varied regional population trends within and between species. Intensive landscape management focused on increasing cover types associated with nesting for both species has not resulted in observable responses in breeding population trends suggesting that factors during the nonbreeding period may be limiting breeding populations of these species. To investigate the potential for factors during the nonbreeding period to differentially influence breeding population trends of these species we used light-level geolocators to track the annual movements of 41 golden-winged warblers, 25 blue-winged warblers, and 4 phenotypic hybrids from 22 sites across both species’ breeding distributions in eastern North America. Blue-winged warblers demonstrated weak connectivity with individuals across their breeding distribution occurring throughout Central America during the nonbreeding period. Conversely, golden-winged warblers exhibited strong connectivity with eastern, declining populations occurring exclusively in northern South America during the nonbreeding period, and western populations occurring throughout Central America. Our results suggest that nonbreeding-site factors, specifically conversion of forest to other land-cover types, may explain differences in population trends observed in golden-winged warbler breeding populations, but not trends in blue-winged warbler populations. Blue-winged warblers showed weaker connectivity and occurred in similar areas during the nonbreeding period as stationary or increasing, western-breeding golden-winged warbler populations (i.e., Central America). We discuss the management implications of species- and population-specific nonbreeding distributions and migratory connectivity. Specifically, our results suggest that ongoing breeding-grounds management of golden-winged warblers intended to increase population sizes may be futile unless there are also efforts to provide forest cover types that serve as nonbreeding habitat in Central America and northern South America.
4:00PM Canada Warbler Environmental Correlates in the Central Appalachian Mountains, West Virginia
Gordon W. Dimmig; Christopher T. Rota; Petra B. Wood; Christopher M. Lituma
The Canada Warbler (Cardellina canadensis) is a species of conservation concern due to continued population decline over the past 60 years. While this species breeds widely throughout Canada and the northeastern United States, its breeding distribution also extends south through the high elevation areas of the Appalachian Mountains. Past findings on Canada Warbler habitat associations vary across its range and few studies have investigated this species in the Appalachian region. Avian point count data from the Monongahela National Forest, West Virginia was used to determine if this species has unique environmental correlates in the southern extent of its range. We modeled Canada Warbler occupancy as a function of several environmental variables while also accounting for heterospecific interactions between two potentially competing species (Black-throated Blue Warbler and Hermit Thrush). Canada Warblers were detected along a gradient of elevations, but had a higher probability of occupying sites at intermediate elevations. We also found that Canada Warbler occupancy was positively correlated with a well-developed deciduous understory, which is consistent across most of its breeding range. Unique to the Appalachian region, occupancy showed a strong positive association with the density of rhododendron (Rhododendron maximum). Additionally, Canada Warblers had a high probability of co-occurring with Black-throated Blue Warblers, but were negatively associated with Hermit Thrush occupancy. These results indicate that Canada Warblers exhibit some specific environmental associations in the Appalachian Mountains which may guide future conservation and management in this region.
4:20PM Estimated Density and Abundance From a Stratified Rangewide Survey of the Eastern Breeding Population of Painted Bunting
Clinton T. Moore; Dean Demarest; Rua S. Mordecai; Bruce Peterjohn
The eastern breeding population of Painted Bunting (Passerina ciris) has been a focus of broad conservation interest since the 1990s. Concern has been motivated by perceived threats due to habitat loss and unquantified take for the cage bird trade, coupled with the bird’s limited distribution and apparent decline suggested by the North American Breeding Bird Survey. A working group of managers and scientists from state, federal, and university organizations designed and implemented a rangewide survey of the population in 2007-2009, using methods to assure statistical validity and representativeness of estimates, repeatability of protocols, and adjustment for detectability. The survey protocol relied on fixed-radius point counts arranged in routes or clusters, each visited up to 3 times during a brief sampling window, and with time of first detection recorded for each bird counted. Our objective was to estimate density and abundance for survey years 2008-2009 at the rangewide level, for each of the four states comprising the breeding range (Florida, Georgia, South Carolina, North Carolina), and for two ecoregion strata (coastal and interior). Treating the detections as removals from the sample, we fit a hierarchical N-mixture model with adjustment for temporary emigration, a reasonable allowance for a mobile species in which geographic closure across the repeated visits may be hard to justify. The model included route/cluster-level effects for density to account for patterns in spatial heterogeneity associated with proximal grouping of sample points within routes or clusters. We compare results from our model to estimates from other mostly local studies, and we discuss them in the context of continued conservation attention for this population of Painted Bunting. Finally, we summarize the utility of statistically robust surveys to gain fundamental information about population demography and to base conservation decision making on their output.
4:40PM Composition of Forest Assemblages as the Basis for Predicting Avian Community Composition
Bryce Adams; Stephen Matthews
Of the factors that determine faunal resource use, the vegetative community of an area is of prime importance because it unmistakably functions as the physical habitat for other organisms, such as birds. Subsequently, the diversity in vegetation structure has served as a strong generalizable framework in assessing patterns in avian assemblages and habitat quality, whereas the composition of the vegetative community has received less attention. By utilizing a recent statistical approach, called co-correspondence analysis, accommodating the direct prediction of one assemblage (birds) by another (woody plants), plant composition (cross-validatory fit: 11.22%) emerged as a better predictor (statistically greater at P < 0.05; 999 permutations) of the species composition of avian assemblages over vegetation structure (cross-validatory fit: 7.35%) in our study encompassing a wide compositional and physiognomic spectrum of point count stations in the Central Hardwoods Forest Region of southern Ohio. In addition, vegetation structural variables, quantified by remote sensing (LiDAR) and field-derived methods, poorly predicted the species composition of the woody plant assemblages (2.66% and 3.45%, respectively). Plant composition is likely a better predictor because of its comprehensive nature, integrating aspects of structure, environmental conditions, and, most importantly, species-specific preferences for certain plant species. We advocate for more detailed information on the floristics of vegetative communities in predicting variation in avian diversity and community structure responsible for guiding sound management strategies as strong proximate signals of shifting vegetation pressures imply abrupt regional and global transitions in forest communities over the coming decades.
12:50PM Quantifying Land Use and Climate Pressures on Avian Distribution By Looking Back to Understand the Magnitude of Future Projections
Stephen N. Matthews; Matthew Shumar; Paul Rodewald
Species distributions, while often considered stable over decadal time horizons, are dynamic. The impact of changing landuse patterns on avian distributions demonstrates how these directional perturbations can bring about strong conservation action. Climate change is another pressing global issue impacting species across the globe. Thus, there is great need to anticipate future changes and quantify these impacts relative to other pressures. Here we combine two analyses (both using randomForest methodologies) to intersect the contemporary directional changes in bird distributions with projected future change in forest bird habitat. First we examined distributional data for 103 species from two breeding bird atlases in Ohio (1982-1987 and 2006-2011). Species distributions during the second atlas were modeled and incorporated both climate and landcover data. To assess performance, models were back-projected with environmental data from the first atlas to quantify actual change. Mean true skill statistic (TSS) for 70 species indicated good model performance to capture spatial patterns on change. Model variable importance showed 45 species models were dominated by land cover while 22 were strongly influenced by climate space. Mean TSS for land cover dominated models was 0.54 (sd = 0.14) and for climate species model was 0.48 (sd = 0.16). Going forward, and at the eastern US extent, we modeled these same forest bird distributions based on North American Breeding Bird Survey data with predictors of climate, elevation, and tree species abundances (from FIA data). These models were projected to assess potential trajectories of habitat changes in bird distribution for each decade until 2070 when climate change in the eastern US is likely to have reached or exceeded ~2ºC. Finally, by intersecting these two approaches, we show the importance of both landcover and climate in capturing past and future changes in avian distributions and quantify the increasing pressures of climate change.


Contributed Paper
Location: Cleveland CC Date: October 8, 2018 Time: 12:50 pm - 5:00 pm