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Histrionicus histrionicus (Harlequin Ducks) that winter along the east coast of North America are listed as a population of special concern in Canada, and they use several coastal wintering sites in southern New England that are subject to varying degrees of urbanization. We studied patterns of habitat use by Harlequin Ducks at 12 known wintering sites in southern New England. An average of 327 ± 114 Harlequin Ducks were found at the sites during the winters of 2001–2003. More Harlequin Ducks wintered at sites south of Cape Cod, MA that had greater mollusk (709,133 ± 504,568 versus 97,154 ± 72,427 kcal ha−1) and crustacean (27,907 ± 16,312 versus 1412 ± 1675 kcal ha−1) prey energy density, and a higher index of hunting activity (2.4 ± 1.2 versus 1.4 ± 0.5) than sites to the north. We used logistic regression analysis at 12 sites inhabited by Harlequin Ducks and 12 nearby sites of similar geomorphology that did not support Harlequin Ducks to identify habitat characteristics that best explained their distribution in southern New England. Our analysis identified two habitat characteristics that affected the likelihood a site was used by Harlequin Ducks: 1) the proportion of residential, commercial, and industrial land use within a 100-m radius of the perimeter of the site; and 2) distance to the nearest Harlequin Duck wintering site. However, other factors, including those related to their extremely low population size, need to also be considered as recommendations are developed for the conservation of east coast Harlequin Ducks.
Ticks are common ectoparasites on birds, but little work has examined the effects of ticks on migrating birds. In this study, we examined the incidence of ticks on migrants during spring and fall migration on Appledore Island, ME. Because ticks are not indigenous to the island, birds with ticks are very likely to have transported them from elsewhere. During spring, 2.4% of migrants captured were parasitized by at least one tick, whereas during fall, 0.6% of migrants were parasitized by ticks. These trends occurred in several of the commonly captured species, although there was substantial variation among species. The average number of ticks per infested bird did not differ between the seasons among our commonly captured species. Males and females had similar tick loads within most species. We did not find a consistent pattern of difference in condition (fat and mass) among birds that were parasitized by ticks compared with those that were not. Furthermore, comparison of birds parasitized by ticks with those that were not indicated no significant difference in either the recapture rate or the stopover length between these two groups. Although parasites may greatly impact the fitness of individual birds, our results suggest that ticks are not impacting the species of migrant birds that use this stopover site during migration.
The ability to detect and monitor exotic invasive plants is likely to vary depending on the sampling method employed. Methods with strong qualitative thoroughness for species detection often lack the intensity necessary to monitor vegetation change. Four sampling methods (systematic plot, stratified-random plot, modified Whittaker, and timed meander) in hemlock and red oak forests in the Delaware Water Gap National Recreation Area were compared for their ability to detect and monitor understory exotic invasive plant species. The timed-meander method best detected exotic invasive plants and documented richness. The stratified-random method was similar to the timed-meander method in terms of detection of exotic invasives and defining richness, but also provided estimates of species abundances and diversity. An initial combination of the timed-meander and stratified-random sampling designs followed by monitoring with the stratified-random method is suggested as a standard approach.
Hemigrapsus sanguineus (Asian shore crab) first arrived at Rye, NY in 1994. The intertidal abundances of H. sanguineus, Carcinus maenas (green crab), and the native crabs Eurypanopeus depressus (flatback mud crab), Cancer irroratus (Atlantic rock crab), and Libinia emarginata (spider crab) were censused from 1998–2005. Asian shore crab densities (estimated in June) increased from 1998–2001 to ca. 120 crabs m−2, and then declined to 80 crabs m−2 from 2002–2005. The flatback mud crab declined in abundance by about 95%. Decreases in the abundances of Atlantic rock crabs, green crabs, and spider crabsmay also have occurred, though these species were uncommon at the outset of the study. The lower intertidal density of the gastropod Littorina littorea (common periwinkle) decreased by about 80%, and the decline was coincident with the expansion of the Asian shore crab population. In June, small Asian shore crabs were disproportionately more abundant in the upper intertidal zone compared with lower zones, where large crabs were more abundant. January intertidal populations were dominated by small Asian shore crabs, and these were restricted to the lower half of the intertidal zone.
Freshwater mussels (Bivalvia: Unionidae) are sensitive to pollution of stream habitats. However, there has been no analysis of whether mussel density is correlated with measurements from commonly used rapid water assessment protocols. This study tested which water quality parameters are correlated with the density of freshwater mussels found in selected locations of the middle Allegheny River, PA. No correlation was found between mussel density and either temperature or chemical water quality parameters. However, there was a strong positive correlation between mussel density and the modified EPA physical habitat parameters tested. These results suggest that the physical habitat variables are a useful tool to assess the suitability of stream habitat for unionid mussels, and should help ecosystem managers make informed decisions about the maintenance or restoration of the ecosystem function that these mussels perform.
Storm-water drainage catch basins are manmade structures that often contain water and organic matter, making them suitable environments for various organisms. We censused organisms inhabiting catch basins in southern Rhode Island in 2002 in an effort to begin to describe these communities. Catch-basin inhabitants were mostly detritivores, including annelids, arthropods, and mollusks that could withstand low oxygen levels and droughts. Our results suggest that catch-basin inhabitants were mostly washed in with rainwater, and populations increased over the summer season as biotic activity resulted in increased nutrient levels later in the summer. In contrast, mosquitoes and other Diptera larvae were abundant earlier in the summer because the adults actively sought catch basins for oviposition sites. Mosquito larvae were likely to be abundant in catch basins with shallow, stagnant water that had relatively low dissolved oxygen and pH, and relatively high total suspended solids, carbon, and nitrogen.
We surveyed little-known ray-finned fish assemblages from Maryland's coastal bays in order to establish species-habitat relationships for common species. From 1996–1999, 25 sites were sampled monthly with otter trawls in the coastal bays of Maryland. Anchoa mitchilli (bay anchovy) constituted nearly 50% of the catch for each year, and species composition was largely similar across years, with some differences likely related to variation in recruitment. For example, Clupea harengus (Atlantic herring) was particularly abundant during 1996 and 1999 following their spawning season. We used canonical correspondence analysis to determine how assemblages were related to temperature, dissolved oxygen (DO), salinity, and land-use variables during summer (June–September) and throughout the rest of the year. A gradient correlated with temperature and DO significantly structured assemblages throughout most of the year; during summer, the proportion of wetland habitat was important. We demonstrate that environmental gradients important for structuring fish assemblages differ between summer and non-summer months and there is a general shift in habitat use during summer from the lower estuary to other areas of the coastal bays. Our data also provide support for earlier observations that temperature was the major factor influencing changes in fish assemblage structure in the coastal bays. Our results point to better characterization of fish habitats in order to effectively manage coastal ecosystems of Maryland.
Fundulus diaphanus (banded killifish) were the most abundant fish collected in the shallow water areas of Presque Isle Bay, making up 86% of fish collected. Peak spawning dates based on gonadosomatic index and ovary observations were July 9, 2003 and July 18, 2004. Females became sexually mature at age 1. During 2004, the majority of spawning occurred over a 20-day period between July 9 and July 29. Total fecundity increased with both size and age, and the mean total number of eggs produced was 526 ± 37 at age 1 (67 mm ± 1.8), 744 ± 38 at age 2 (79 mm ± 2.4), and 1062 ± 43 at age 3 (93 mm ± 4.1). Based on comparison of the total number of eggs and number of eggs with yolk contained within ovaries, three clutches of eggs may be released during each spawning season. Diets were similar between summer and fall; banded killifish fed almost exclusively on cladocerans and benthic macroinvertebrates.
In Canada, Thamnophis sauritus (Eastern Ribbon Snake) is found only in southern Ontario and a small area of southwestern Nova Scotia. Although the Nova Scotia population is nationally designated as threatened, its distribution, seasonal activity, movement patterns, and over-wintering sites remain undescribed. We used radio-telemetry, capture-mark recapture, and direct observation to: 1) assess abundance, summer activity, and movement; and 2) to locate and characterize a hibernaculum for Eastern Ribbon Snakes in Kejimkujik National Park, NS. A total of 105 individuals were marked; among these, 13 free-ranging adults were surgically implanted with radio-transmitters and tracked from June until mid-November 2001. From late May to September, snakes were always found within 5 m of water, with summer ranges on land that rarely exceeded 5 × 10 m. From September to mid-October, snakes moved up to 173 m away from the shoreline. Eleven observations of snakes feeding on anurans (Ranidae) and fish (Cyprinidae) were made at temporary pools, marginal to the lake. Despite the use of radio-telemetry, only one hibernaculum was found. Our observations indicate that the Eastern Ribbon Snake is relatively sedentary; its low activity rate and small activity range may make it vulnerable to local extinction.
This study examines changes in the frequency/abundance of prey selection among five size classes of 183 Ambystoma jeffersonianum (Jefferson Salamanders) within a natural, unmanipulated environment. Significant differences were found in prey selection among size classes in vertebrate and macroinvertebrate (specifically coleopteran and dipteran) prey groups, but not microinvertebrates. Predator-size thresholds were noted as diet shifted from predominantly microinvertebrates to increasingly larger macroinvertebrates to the final dietary selection of other vertebrates. This study augments the catalogue of ingested Ambystoma prey and re-examines the nature of ontogenous dietary selection.
Xanthoria parietina, a conspicuous orange foliose lichen, has been doubtfully recorded as part of the Ontario lichen flora because the previous documented reports were very old (1868 and 1917) and it had never been reported since. Here, we document a number of new sightings, all in southern Ontario. A previous report of this lichen from “Longulac” that was interpreted as Long Lake in Frontenac County is corrected to Longlac in the Thunder Bay District, and the specimen proved to be Xanthomendoza hasseana. A search for the lichen around Belleville, one of the original localities, proved fruitless. It is still not clear whether the new sightings of Xanthoria parietina represent a reintroduction of this coastal species to the inland sites, or whether the lichen has persisted in southern Ontario for almost 140 years, but was never reported. Substrate enrichment (eutrophication due to agricultural activity) in the region is one explanation for the spread of the lichen in southern Ontario.
We report the season of emergence from the nest of hatchlings of five species of freshwater turtles from a wetlands/stream/lake complex in southcentral New Hampshire from 1988–1994. Only hatchling Chrysemys picta (Painted Turtle) overwintered in the nest and emerged the following spring, although there were some cases of autumn emergence, as well as some nests with hatchlings that emerged in both seasons. In nests monitored over the winter, mortality ranged from 26–100%. Hatchlings of the other four species—Chelydra serpentina (Snapping Turtle), Glyptemys insculpta (Wood Turtle), Clemmys guttata (Spotted Turtle), and Emydoidea blandingii (Blanding's Turtle)—emerged only in autumn.