Vermont Center for Ecostudies

Manchester Center, VT, United States

Vermont Center for Ecostudies

Manchester Center, VT, United States
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Perlut N.G.,University of New England at Biddeford | Renfrew R.,Vermont Center for Ecostudies
Wilson Journal of Ornithology | Year: 2016

The Bobolink (Dolichonyx oryzivorus) is the only landbird species that is known to stop every year in Galapagos while migrating; however, its stopover ecology while on the islands is unknown. In October 2015, we searched for and captured Bobolinks in the highlands of San Cristóbal. We found Bobolinks in two fields, separated by 9.15 km, at ∼425 m elevation. Average daily counts of Bobolinks on these two fields were 3.2 ± 1.8 and 4.8 ± 2.3 individuals. We caught nine individuals; body mass and fat reserves varied from 22.5-40.0 g and no fat reserves to 50-100% reserves, respectively. Both fields were dominated by grasses ranging in height from 30 cm to >100 cm, and included purple cuphea (Cuphea sp.). Other habitats we surveyed, where we did not observe Bobolinks, included closely cropped grass (5-10 cm), taller grasses with seed and with scattered to dense guava trees (Psidium guajava), and small (0.1-0.3 ha) corn plantations with seed. Six of the birds we caught had seeds of Drymaria cordata entwined in their feathers; while native to the Galapagos, this plant is highly invasive in other parts of the world.

Parsons K.C.,Manomet Center for Conservation science | Mineau P.,Environment Canada | Renfrew R.B.,Vermont Center for Ecostudies
Waterbirds | Year: 2010

Waterbird use of agricultural wetlands has increased as natural wetlands have declined. Use of rice (Oryza sativa) habitats by some waterbird species is considered essential to sustaining populations. Although use of rice habitats by waterbirds has been documented throughout the world, little information is available on potential risks as a result of chemicals used in rice cultivation. The current review summarizes understanding of the use and consequences to birds of pesticide applications in rice habitats. Historically, organochlorine pesticides known to be applied for pest management in rice cultivation included dichlorodiphenyltrichloroethane (DDT), aldrin, dieldrin, endrin, heptachlor, technical hexachlorocyclohexane (HCH), toxaphene, endosulfan and sodium pentachlorophenate. Endosulfan and purified HCH (the gamma isomer lindane) are still in use. Cholinesterase-inhibiting insecticides currently used in rice include carbofuran, monocrotophos, phorate, diazinon, fenthion, phosphamidon, methyl parathion and azinphos-methylmany products known to cause acute poisoning in birds. In addition, herbicides, fungicides, molluscicides and other pesticide types are used in rice cultivation. Some of the chemicals are highly toxic to birds and associated with mortality; several have the potential of causing adverse reproductive effects. Because of the large area under rice cultivation worldwide, the volume of pesticides applied to rice fields is significant. Innovations within the past few decades in rice production have increased pesticide use resulting in biodiversity losses in production areas and pollution of water resources. Management practices that address adverse effects of pesticide use in rice fields include increased adoption of Integrated Pest Management principles and less toxic products.

Studds C.E.,Smithsonian Conservation Biology Institute | Mcfarland K.P.,Vermont Center for Ecostudies | Aubry Y.,Environment Canada | Rimmer C.C.,Vermont Center for Ecostudies | And 3 more authors.
Diversity and Distributions | Year: 2012

Aim: Measuring dispersal is crucial for estimating demographic rates that inform conservation plans for rare and threatened species. We evaluated natal dispersal patterns in Bicknell's thrush (Catharus bicknelli) across most of the breeding range using a 10-year data set of stable-hydrogen isotope ratios in feathers (δ 2H F) grown on the natal area and sampled 1 year later at the first breeding site. Location: North-eastern United States and south-eastern Canada. Methods: We used δ 2H F values of adult thrushes sampled at 25 breeding sites as prior information for assigning first-time breeders to their natal site. We calculated the minimum distance birds moved from their natal to first breeding site and fit these data to three statistical distributions for characterizing the importance of long-distance dispersal: the exponential, Weibull and half-Cauchy. Finally, we assessed differences in the probability of dispersal across the breeding range and through time to understand spatio-temporal variation in demographic connectivity. Results: The δ 2H F values of first-time breeders were lower compared with those of adults, a difference that was greater at the southern compared with northern breeding range extreme. Assignment tests accounting for age differences in δ 2H F suggested that most birds dispersed < 200 km from their natal area and within the centre of the breeding range, whereas comparatively few individuals dispersed up to 700 km. A Weibull distribution provided the best fit to these data. Two of three corrections for age differences in δ 2H F indicated that natal dispersal probability declined by 30-38% from 1996 to 2005. Main conclusions: Our findings suggest that estimating natal dispersal with δ 2H F measurements may contribute to understanding the resilience of geographically isolated Bicknell's thrush populations. Declining natal dispersal may be symptomatic of observed population declines and could compound this trend by limiting demographic exchange between habitat patches predicted to be increasingly isolated by natural and anthropogenic habitat changes. © 2012 Blackwell Publishing Ltd.

Sly N.D.,Cornell University | Townsend A.K.,Cornell University | Rimmer C.C.,Vermont Center for Ecostudies | Townsend J.M.,New York University | And 2 more authors.
Molecular Ecology | Year: 2011

With its large size, complex topography and high number of avian endemics, Hispaniola appears to be a likely candidate for the in situ speciation of its avifauna, despite the worldwide rarity of avian speciation within single islands. We used multilocus comparative phylogeography techniques to examine the pattern and history of divergence in 11 endemic birds representing potential within-island speciation events. Haplotype and allele networks from mitochondrial ND2 and nuclear intron loci reveal a consistent pattern: phylogeographic divergence within or between closely related species is correlated with the likely distribution of ancient sea barriers that once divided Hispaniola into several smaller paleo-islands. Coalescent and mitochondrial clock dating of divergences indicate species-specific response to different geological events over the wide span of the island's history. We found no evidence that ecological or topographical complexity generated diversity, either by creating open niches or by restricting long-term gene flow. Thus, no true within-island speciation appears to have occurred among the species sampled on Hispaniola. Divergence events predating the merging of Hispaniola's paleo-island blocks cannot be considered in situ divergence, and postmerging divergence in response to episodic island segmentation by marine flooding probably represents in situ vicariance or interarchipelago speciation by dispersal. Our work highlights the necessity of considering island geologic history while investigating the speciation-area relationship in birds and other taxa. © 2011 Blackwell Publishing Ltd.

Townsend J.M.,New York University | Driscoll C.T.,Syracuse University | Rimmer C.C.,Vermont Center for Ecostudies | Mcfarland K.P.,Vermont Center for Ecostudies
Environmental Toxicology and Chemistry | Year: 2014

High-elevation ecosystems of the northeastern United States are vulnerable to deposition and environmental accumulation of atmospheric pollutants, yet little work has been done to assess mercury (Hg) concentrations in organisms occupying montane ecosystems. The authors present data on Hg concentrations in ground-foraging insectivorous songbirds, a terrestrial salamander, and forest floor horizons sampled along a forested elevational gradient from 185m to 1273m in the Catskill Mountains, New York, USA. Mean Hg concentrations in Catharus thrushes and the salamander Plethodon cinereus increased with elevation, as did Hg concentrations in all forest floor horizons. Mean Hg concentrations in organic soils at approximately 1200m elevation (503.5±17.7ng/g, dry wt) were 4.4-fold greater than those at approximately 200m. Montane ecosystems of the northeastern United States, and probably elsewhere, are exposed to higher levels of atmospheric Hg deposition as reflected in accumulation patterns in the forest floor and associated high-elevation fauna. This information can be used to parameterize and test Hg transport and bioaccumulation models of landscape-specific patterns and may serve as a monitoring tool for decision makers considering future controls on Hg emissions. Further investigation is needed into the potential effects of increased Hg concentrations on high-elevation fauna. © 2013 SETAC.

Rimmer C.C.,Vermont Center for Ecostudies | Miller E.K.,Ecosystems Research Group Ltd. | McFarland K.P.,Vermont Center for Ecostudies | Taylor R.J.,Texas A&M University | Faccio S.D.,Vermont Center for Ecostudies
Ecotoxicology | Year: 2010

We investigated mercury (Hg) concentrations in a terrestrial food web in high elevation forests in Vermont. Hg concentrations increased from autotrophic organisms to herbivores < detritivores < omnivores < carnivores. Within the carnivores studied, raptors had higher blood Hg concentrations than their songbird prey. The Hg concentration in the blood of the focal study species, Bicknell's thrush (Catharus bicknelli), varied over the course of the summer in response to a diet shift related to changing availability of arthropod prey. The Bicknell's thrush food web is more detrital-based (with higher Hg concentrations) in early summer and more foliage-based (with lower Hg concentrations) during late summer. There were significant year effects in different ecosystem compartments indicating a possible connection between atmospheric Hg deposition, detrital-layer Hg concentrations, arthropod Hg concentrations, and passerine blood Hg concentrations. © 2009 Springer Science+Business Media, LLC.

van der Hoek Y.,CUNY - College of Staten Island | Renfrew R.,Vermont Center for Ecostudies | Manne L.L.,CUNY - College of Staten Island
PLoS ONE | Year: 2013

Background: Identifying persistence and extinction thresholds in species-habitat relationships is a major focal point of ecological research and conservation. However, one major concern regarding the incorporation of threshold analyses in conservation is the lack of knowledge on the generality and transferability of results across species and regions. We present a multi-region, multi-species approach of modeling threshold responses, which we use to investigate whether threshold effects are similar across species and regions. Methodology/Principal Findings: We modeled local persistence and extinction dynamics of 25 forest-associated breeding birds based on detection/non-detection data, which were derived from repeated breeding bird atlases for the state of Vermont. We did not find threshold responses to be particularly well-supported, with 9 species supporting extinction thresholds and 5 supporting persistence thresholds. This contrasts with a previous study based on breeding bird atlas data from adjacent New York State, which showed that most species support persistence and extinction threshold models (15 and 22 of 25 study species respectively). In addition, species that supported a threshold model in both states had associated average threshold estimates of 61.41% (SE = 6.11, persistence) and 66.45% (SE = 9.15, extinction) in New York, compared to 51.08% (SE = 10.60, persistence) and 73.67% (SE = 5.70, extinction) in Vermont. Across species, thresholds were found at 19.45-87.96% forest cover for persistence and 50.82-91.02% for extinction dynamics. Conclusions/Significance: Through an approach that allows for broad-scale comparisons of threshold responses, we show that species vary in their threshold responses with regard to habitat amount, and that differences between even nearby regions can be pronounced. We present both ecological and methodological factors that may contribute to the different model results, but propose that regardless of the reasons behind these differences, our results merit a warning that threshold values cannot simply be transferred across regions or interpreted as clear-cut targets for ecosystem management and conservation. © 2013 van der Hoek et al.

Frey S.J.K.,Oregon State University | Strong A.M.,University of Vermont | McFarland K.P.,Vermont Center for Ecostudies
Ecography | Year: 2012

Changes in site occupancy across habitat patches have often been attributed to landscape features in fragmented systems, particularly when considering metapopulations. However, failure to include habitat quality of individual patches can mask the relative importance of local scale features in determining distributional changes. We employed dynamic occupancy modeling to compare the strength of local habitat variables and metrics of landscape patterns as drivers of metapopulation dynamics for a vulnerable, high-elevation species in a naturally fragmented landscape. Repeat surveys of Bicknell's thrush Catharus bicknelli presence/non-detection were conducted at 88 sites across Vermont, USA in 2006 and 2007. We used an organism-based approach, such that at each site we measured important local-scale habitat characteristics and quantified landscape-scale features using a predictive habitat model for this species. We performed a principal component analysis on both the local and landscape features to reduce dimensionality. We estimated site occupancy, colonization, and extinction probabilities while accounting for imperfect detection. Univariate, additive, and interaction models of local habitat and landscape context were ranked using AICc scores. Both local and landscape scales were important in determining changes in occupancy patterns. An interaction between scales was detected for occupancy dynamics indicating that the relationship of the parameters to local-scale habitat conditions can change depending on the landscape context and vice versa. An increase in both landscape- and local-scale habitat quality increased occupancy and colonization probability while decreasing extinction risk. Colonization and extinction were both more strongly influenced by local habitat quality relative to landscape patterns. We also identified clear, qualitative thresholds for landscape-scale features. Conservation of large habitat patches in high-cover landscapes will help ensure persistence of Bicknell's thrushes, but only if local scale habitat quality is maintained. Our results highlight the importance of incorporating information beyond landscape characteristics when investigating patch occupancy patterns in metapopulations. © 2011 The Authors. Ecography © 2011 Nordic Society Oikos.

Renfrew R.B.,Vermont Center for Ecostudies | Kim D.,Platte River Whooping Crane Maintenance Trust Inc. | Perlut N.,University of New England at Biddeford | Smith J.,The Nature Conservancy | And 2 more authors.
Diversity and Distributions | Year: 2013

Aim: In the Northern Hemisphere, bird migration from the tropic to the temperate zone in spring is thought to proceed at a rate determined in large part by local phenology. In contrast, little is understood about where birds go or the factors that determine why they move or where they stop during the post-breeding period. Location: Study sites were in Oregon, Nebraska and Vermont, and location data we collected extend south to Argentina. Methods: We deployed light-level geolocators on individual Bobolinks from three populations across the breeding range and compare their southbound movement phenology to austral greening as indicated by the Normalized Difference Vegetation Index. Results: Bobolinks from all breeding populations synchronously arrived and remained for up to several weeks in two sequential, small non-breeding areas that were separated by thousands of kilometres, before staging for pre-alternate moult. Similar to the migration patterns of birds to northern breeding areas, movements into the Southern Hemisphere corresponded to increasing primary productivity. Main conclusions: Our findings suggest that the Bobolink's southbound migration is broadly constrained by resource availability, and its non-breeding distribution has been shaped by the seasonal phenology of grasslands in both time and space. This is the first documentation of individual birds from across a continental breeding range exhibiting phenological matching during their post-breeding southward migration. Known conservation threats overlap temporally and spatially with large concentrations of Bobolinks, and should be closely examined. We emphasize the need to consider how individuals move and interact with their environment throughout their annual cycle and over hemispheric scales. © 2013 John Wiley & Sons Ltd.

Townsend J.M.,New York University | Rimmer C.C.,Vermont Center for Ecostudies | McFarland K.P.,Vermont Center for Ecostudies
Auk | Year: 2010

We used radiotelemetry to investigate the spatial behavior of wintering Bicknell's Thrushes (Catharus bicknelli) at a mid-elevation rainforest site and a high-elevation cloud-forest site in the Dominican Republic. We also analyzed blood stable carbon isotopes and fecal samples to compare thrush diets at these two floristically and climatically distinct sites. Birds consumed a primarily fruit-based diet at the mid-elevation site and a primarily arthropod-based diet at the high-elevation site. Despite these dietary differences, individuals at both sites defended and maintained exclusive, minimally overlapping core use areas and home ranges. The mean size of both core use areas and home ranges was similar between males and females and between adults and first-winter birds. Presence of nonterritorial or "floater" individuals was low at both sites (2.7% and 5.6%). Birds at the arthropod-dominated site were observed significantly more often on or within 1 m of the ground than birds at the fruit-heavy site, which were more often observed in the mid-canopy structure above 2 m. Birds at both sites displayed agonistic behaviors toward conspecifics and toward playback of conspecific vocalizations. Exclusive territoriality was the predominant winter social system, and we suggest that both arthropods and fruit are defensible resources for wintering Bicknell's Thrushes. © 2010 by The American Ornithologists' Union. All rights reserved.

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