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We examined habitat use by Wilsonia canadensis (Canada Warbler), a migratory songbird population in a 40-year decline. We used a long-term forest bird monitoring program in Vermont to compare the structural components of sites of warbler presence and absence. Habitats occupied included lowland Picea-Abies (spruce-fir), northern hardwood, and Quercus-Carya (oak-hickory) forests, and Acer rubrum-Thuja (Red Maple-cedar) and cedar-fir swamps. Northern hardwood forest detections were explored in greater detail due to the greater extent of coverage in Vermont, the higher number of survey points (n = 80), and high percentage of Canada Warbler detections at those points (29%). Within the northern hardwood forests, warblers occurred in patches with a lower canopy height and higher percent ground cover of shrubs and ferns than patches where warblers were not detected. These three parameters were also the strongest set of competing Akaike's information criterion model scores based on the patch attributes. In the northern hardwoods of the northeast, the conditions of reduced average canopy height and increased ground cover are created naturally by wind throw, ice storms, and insect damage, as well as under some forms of timber management. Canada Warblers appear to prefer these forest structural conditions because they provide abundant foraging strata, conceal nesting sites, and expose song perches.
Somateria mollissima (Common Eider) is an important game species throughout its circumpolar range, including eastern Canada and northeastern United States. In eastern Canada, the largest harvest of Common Eiders occurs in Newfoundland; however, the age, sex, and subspecific composition (S. m. borealis and dresseri are both present) of this hunted population is not well quantified. The species, subspecies, age, and sex composition of the harvest was determined by examining heads collected from 1672 eiders (including Somateria spectabilis [King Eider]), taken mostly by hunters, from 1980–1996. Band-recovery information for Common Eiders banded in Newfoundland and Labrador were also summarized, including data from a release program of hand-reared ducklings in northern Newfoundland from 1988–1996. The composition of the eider harvest varied across the province. In northern and eastern areas, borealis Common Eiders made up the bulk of the harvest. King Eiders were also taken in these areas. In southern areas, most Common Eiders taken were dresseri. Sex ratios tend to be near 1:1, and immature birds comprised most of the harvest. Recovery distributions showed that Common Eiders breeding in Newfoundland and Labrador were mainly taken within the province, but also contributed to harvests in Québec and Nova Scotia, and to a lesser extent, Maine. Hand-reared ducklings had direct recovery rates of 0.047 and were most likely to be recovered within the province in the year of banding, but contributed to harvests in Atlantic Canada and New England as they aged. The harvest of eiders in Newfoundland varies regionally and seasonally; therefore specific harvest regulations could be implemented to manage the variety of populations present in the province throughout the year.
Ceryle alcyon (Belted Kingfisher) and Riparia riparia (Bank Swallow) rely on vertical eroded banks for nesting. We inventoried Belted Kingfisher and Bank Swallow nesting banks along a 91.6-km section of the Connecticut River in Massachusetts, New Hampshire, and Vermont, including stretches where bank stabilization projects are completed, under construction, or planned. In the case of Bank Swallows, we also assessed the availability of potential nesting habitat in the study area. Forty-four Belted Kingfisher nesting sites and 12 Bank Swallow colonies were detected in the study area. Both species used banks with a low percentage of vegetative cover and a steep slope. Belted Kingfishers used high narrow banks. Bank Swallows used wide banks composed of well-drained, fine sandy loam soils. Potential Bank Swallow nesting sites were limited and in comparison to the sites actually used by Bank Swallows, they were narrower, more vegetated, and composed of more coarse soils. The impact of bank stabilization on Belted Kingfishers is probably minimal. However, bank stabilization eliminated three of twelve Bank Swallow colony sites that served as habitat for ≈20% of nesting pairs in the study area between 1999 and 2005.
Edge created through forest fragmentation can have significant impacts on the avian community, increasing predation and nest-parasitism rates and changing species richness and abundance patterns near edges. Although considerable research has demonstrated edge effects during the breeding season, few studies have considered how proximity to an edge affects migrant communities in stopover habitat. We studied bird communities in southern Pennsylvania (Adams, Chester, and Montgomery counties) to determine if richness and abundance of migrants were impacted by edges during spring and fall 1999–2001. The three categories of study sites were north-facing forest-herbaceous edges, south-facing forest-herbaceous edges, and interior forest (>300 m from an edge); sites were located in Gettysburg National Military Park-Eisenhower National Historic Site (GETT-EISE) and Valley Forge National Historical Park. During fall migration, Nearctic-Neotropic migrant species richness was significantly (P = 0.03) higher in interior forest compared to edges, whereas species richness of other guilds was not significantly different among edge types. During spring migration, richness of both permanent residents (P < 0.001) and temperate migrants (P < 0.001) were higher at both edges compared to interior sites. Only two species, Dendroica caerulescens (Black-throated Blue Warbler) (P = 0.03 during fall, P = 0.002 during spring) and Vireo olivaceus (Red-eyed Vireo) (P = 0.03 during fall, P = 0.05 during spring), showed differences among edge types during both spring and fall migration. Although the parks differed in amount of forest and in landscape composition, differences in richness and abundance patterns of birds between the parks also may be based on active management of Odocoileus virginianus Zimmerman (White-tailed Deer) at GETT-EISE that has resulted in vegetation differences. Overall, we found differential impacts of fragmentation (edge) on guilds and during different migratory periods, illustrating the importance of considering habitat use during each season individually for conservation of migratory songbirds.
On 6 May 2003, a tornado severely damaged 284 ha of Mermet Lake State Forest and Wildlife Area in southern Illinois. We used mist nets and Anabat ultrasonic detectors to determine if community composition and habitat use of bats differed between the tornado-disturbed forest and surrounding undisturbed forest during the summers of 2004 and 2005. Ten species of bats (118 individuals) were caught using mist nets on sites in undisturbed forest; 4 species (11 individuals) were mist-netted on disturbed sites (χ2 = 34.24, df = 1, P < 0.0001). The Anabat system documented six species on both habitat types with no difference in the number of bat passes detected acoustically. We suspect that apparent differences in mist-net data reflect the greater ability of bats on the disturbed sites to avoid nets. Telemetry data and field observations confirmed bats used disturbed and undisturbed areas for roosting and foraging. Unless precluded by higher fire danger, we suggest that tornado-disturbed areas remain non-salvaged because they provide additional roosting and foraging habitat for many bat species.
We used nest boxes to study communal nesting and breeding habits of Glaucomys volans (Southern Flying Squirrel) at high elevations over a wide geographic range in western Virginia from 1985 to 1996. Of 320 occupied nest boxes, 19.1% contained litters, 20.3% contained solitary adults, 45.9% had adult aggregations, and 14.7% contained individuals or aggregations of unknown age. Aggregation size ranged from 2–12 individuals. Group size appeared larger during winter months, while the greatest number of aggregations peaked between June and August; however, neither trend was significant. Females were significantly more numerous than males in mixed-age aggregations, while males were significantly more abundant than females in adult aggregations. The breeding season, from first conception to last weaning, lasted 46–48 weeks, from the fourth week of January through the second week of December. Two distinct parturition peaks were evident in late March to mid-April and mid-August to mid-September. Our data support the hypothesis that reproductive activity of Southern Flying Squirrels varies by latitude and is primarily determined by photoperiod length, at least in temperate areas.
Use of global positioning system (GPS) collars to improve our understanding of bear movements and habitat use has increased markedly in the last 10 years. Habitat use has been better defined using this technology, but variation in acquisition rates across covertypes and with varying antenna orientation could bias results. I assessed the effects of vegetative habitat characteristics and antenna orientation on percent of successful fixes and 3-dimensional (3D) fixes for GPS collars designed for Ursus americanus (American Black Bear) in Michigan during April–July, 2001–2002. I placed collars in 5 habitats with varying tree density, diameter, and canopy cover and also in an unobstructed area with antennas oriented 0–90° from horizontal. Basal area was the only habitat parameter measured that influenced fix success; the correlation was negative. Percent of successful locations obtained in the open area decreased as antenna orientation increased away from the vertical position. Habitat characteristics and antenna orientation appeared to influence the percent of total fixes and 3D fixes obtained, which could have adverse effects on accuracy. Thus, bear or other wildlife use of certain covertypes and behavior (e.g., sleeping) can reduce GPS collar acquisition rates. Variation in acquisition rates among cover-types and antenna orientation warrants consideration for development of correction factors based on habitats encountered and animal behavior.
Three groups of Tsuga canadensis (Eastern Hemlock) trees were analyzed to compare their chemical composition and the potential for naturally occurring resistance to Adelges tsugae (Hemlock Woolly Adelgid [HWA]). Potentially resistant “parent” trees located in southern Connecticut were compared with rooted propagules from those same trees and control trees located in northern Vermont, outside of the current HWA range. For trees in each group, we quantified Ca, P, K, C, and N and developed terpenoid profiles using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC/MS). There was no significant variation in terpenoid profiles between the three groups of hemlock trees. Propagules retained elevated levels of Ca and N from fertilization during propagation, suggesting that their chemical composition does not mirror the parent trees. The potentially resistant “parent” trees had higher levels of K compared to control trees. This may impart some level of tolerance/resistance to HWA and explain their persistence in hemlock forests that have otherwise been decimated by HWA. Comparison to regional foliar chemistry databases suggest that while rare, such elevated K levels do exist in natural hemlock populations. Such individuals may persist as HWA continues to spread across the region.
Poutwater Pond Bog is a National Natural Landmark located in Holden, MA. As present-day species inhabiting this bog have been described, this study presents an insight into earlier inhabitants of the area during the mid- to late Holocene. A 5-m coring of peat was collected 10 m from the pond edge. Radiocarbon analysis of 10 sections of the core shows a nearly linear accumulation rate of peatland from 8500 years ago to the present. The presence of mineral matter at the base of the core suggests paulidification as the mechanism for formation of the bog. Microfossils were isolated from sections of the peat core by density-buoyant centrifugation, and examined using a scanning electron microscope. High-resolution images of pollen, sponge remains, and algae are presented. Circumneutral and acidobiontic diatoms were found at different depths of the core, indicating a changing water environment over time. Arboreal pollen grains were documented spanning 8500 years of vegetative history, permitting insight into the biodiversity that once existed.
Tributary and mainstem corridors represent important fish-connectivity avenues in large riverscapes. We evaluated the connectivity of 40 Monongahela River tributaries in southwestern Pennsylvania and their respective mainstem junctions using a variety of gears. Twelve tributaries were so fragmented by physical and water-quality impediments, comparisons could not be made. Among the 28 remaining tributaries, classified as adventitious (lst–3rd order) or ordered (4th–5th order), we evaluated fish communities using the Jaccard coefficient of similarity, a cluster analysis, and a Venn diagram. Adventitious tributaries shared 82% of their total faunal complement with ordered tributaries and 29% with the mainstem, while 70% of the ordered ichthyofauna was common to the mainstem. The ichthyofauna of the adventitious tributary network was more distinct and isolated from the mainstem than that of ordered tributaries. In fragmented riverscapes such as this, islands (tributaries) of biodiversity may warrant special protection.
Lythrurus fasciolaris (Scarlet Shiner) and Lythrurus umbratilis (Redfin Shiner) are closely related minnow species usually exhibiting a parapatric distribution in the Ohio River basin; however, areas of sympatry do exist and hybridization has been documented. In Eagle Creek (Kentucky River drainage), a stream capture event is likely responsible for creating the contact zone, providing a unique opportunity to study hybridization. In this paper, we conduct a morphological analysis of nuptial males from six Lythrurus populations in Eagle Creek. Our results show longitudinal variation in morphology. Individuals from downstream areas exhibit a novel phenotype with a robust body and low meristic counts. In contrast, upstream areas contain individuals resembling Redfin Shiner. Overall, 62% of individuals examined in Eagle Creek have the novel phenotype and 27% have the Redfin Shiner phenotype. Local selection pressures and apparent geographical isolation may be fostering the development of a distinct phenotype via introgressive hybridization.
Basking is common in emydid turtles and is generally accepted to be a thermoregulatory behavior. In 2004, we quantified and described the basking behavior of turtles in the Central Canal of Indianapolis. This canal system flows through an urban landscape that is dominated by fragmented woodlots, residential areas, and commercial areas. We observed that basking turtles exhibited variable basking behavior, with spatial and temporal shifts in basking behavior from east-facing banks in the morning to west-facing banks in the afternoon. Turtles in the Central Canal are subject to frequent disturbance, which altered basking behavior. Many turtles forewent aerial basking on emergent substrates for aquatic basking on vegetation mats, which maintained warmer and more consistent temperatures than either emergent substrates or the surrounding water. Living in an intensively managed urban habitat, turtles in the Central Canal are susceptible to frequent anthropogenic perturbations, and future management should consider the life history and ecology of urban turtle populations
The postlarval stage, or megalopa, of Ocypode quadrata (Atlantic Ghost Crab) has distinctive morphological characteristics, with large size being its most recognizable character. Nevertheless, there is little biological or ecological information on this critical stage in the crab's life cycle. Over a 20-year period (1980–2000) of field work, only five specimens have been collected incidentally along the sandy beaches of southern New Jersey, near the northern limit of its geographic range. Megalopae were obtained via seine, hand net, and sediment core samples from September 6 to October 6, even though some of the locations were sampled throughout the year. Mean carapace width (CW) and length (CL) for the five megalopae were 4.85 ± 0.59 mm by 6.14 ± 0.68 mm, respectively; CW ranged from 4.01–5.43 mm and CL from 5.18–7.01; mean CW/CL ratio was 0.790 ± 0.023. Carapace dimensions of New Jersey specimens were compared with megalopae recorded in the literature from the shores of Long Island, NY and North Carolina, as well as data from two eastern Pacific species, Ocypode gaudichaudii and O. occidentalis. Morphology of the megalopa appears to be adaptive for survival through metamorphosis into the first crab stage. Recruitment of O. quadrata to sandy beaches in the northern part of its range is probably in the fall.
Determining planktonic larval species composition and abundance data can serve to elucidate local patterns of distribution, determine an area's importance as a nursery ground, and help clarify broad-scale trends of adult distribution and spawning ranges. Although the Saco River and estuary is the fourth largest waterway system in Maine, this ecosystem has remained relatively unstudied over the last thirty years, and research describing the temporal ichthyoplankton composition and distribution is virtually absent. The present study examined the structure of the ichthyoplankton community and determined the temporal and spatial variation in species diversity and abundance within the Saco Bay estuary system. Weekly sampling trips during the months of June, July, and August in 2007 revealed ten species of ichthyoplankton present in the study area. Ulvaria subbifurcata (Radiated Shanny) and Tautogolabrus adsperus (Cunner) dominated the abundance data followed by Hippoglossoides platessoides (American Plaice) and Myoxocephalus octodecimspinosus (Longhorn Sculpin).
We provide locality data for stream populations of Procambarus clarkii (Red Swamp Crawfish) in Maryland. This non-native species is now established in 14 watersheds in the Coastal Plain, including all watersheds where it was historically raised in aquaculture ponds. Our surveys indicate that the introduction of Red Swamp Crawfish in Maryland has largely resulted from aquaculture, although the aquarium, biological supply, and live-bait industries are other potential vectors. The effects of Red Swamp Crawfish on the composition and diversity of stream fauna and flora in Maryland are unknown. The establishment of this species may have negative effects on native crayfishes, especially the congeneric P. acutus (White River Crawfish). These locality records provide baseline information for future monitoring of this non-native species and assessment of its effects on Maryland's stream ecosystems and native crayfishes.