Migratory shorebird adheres to Bergmann’s Rule by responding to environmental conditions through the annual lifecycle

The inverse relationship between body size and environmental temperature is a widespread ecogeographic pattern. However, the underlying forces that produce this pattern are unclear in many taxa. Expectations are particularly unclear for migratory species, as individuals may escape environmental extremes and reorient themselves along the environmental gradient. In addition, some aspects of body size are largely fixed while others are environmentally flexible and may vary seasonally. Here, we used a long-term dataset that tracked multiple populations of the migratory piping plover Charadrius melodus across their breeding and non-breeding ranges to investigate ecogeographic patterns of phenotypically flexible (body mass) and fixed (wing length) size traits in relation to latitude (Bergmann’s Rule), environmental temperature (heat conservation hypothesis), and migratory distance. We found that body mass was correlated with both latitude and temperature across the breeding and non-breeding ranges, which is consistent with predictions of Bergmann’s Rule and heat conservation. However, wing length was correlated with latitude and temperature only on the breeding range. This discrepancy resulted from low migratory connectivity across seasons and the tendency for individuals with longer wings to migrate farther than those with shorter wings. Ultimately, these results suggest that wing length may be driven more by conditions experienced during the breeding season or tradeoffs related to migration, whereas body mass is modified by environmental conditions experienced throughout the annual lifecycle

Migratory shorebird adheres to Bergmann’s Rule by responding to environmental conditions through the annual lifecycle

The inverse relationship between body size and environmental temperature is a widespread ecogeographic pattern. However, the underlying forces that produce this pattern are unclear in many taxa. Expectations are particularly unclear for migratory species, as individuals may escape environmental extremes and reorient themselves along the environmental gradient. In addition, some aspects of body size are largely fixed while others are environmentally flexible and may vary seasonally. Here, we used a long-term dataset that tracked multiple populations of the migratory piping plover Charadrius melodus across their breeding and non-breeding ranges to investigate ecogeographic patterns of phenotypically flexible (body mass) and fixed (wing length) size traits in relation to latitude (Bergmann’s Rule), environmental temperature (heat conservation hypothesis), and migratory distance. We found that body mass was correlated with both latitude and temperature across the breeding and non-breeding ranges, which is consistent with predictions of Bergmann’s Rule and heat conservation. However, wing length was correlated with latitude and temperature only on the breeding range. This discrepancy resulted from low migratory connectivity across seasons and the tendency for individuals with longer wings to migrate farther than those with shorter wings. Ultimately, these results suggest that wing length may be driven more by conditions experienced during the breeding season or tradeoffs related to migration, whereas body mass is modified by environmental conditions experienced throughout the annual lifecycle

Breeding biology of the 'Io (Buteo Solitarius)

Western Region, National Park Servic

A review of vertebrate community composition in seasonal forest pools of the northeastern United States

Seasonally-flooded wetlands occur throughout the world and provide important foraging, resting, and breeding habitat for a broad array of organisms. This review summarizes our current understanding of vertebrate community composition at seasonal forest pools in the northeastern United States. These wetlands typically have hydroperiods that range from temporarily flooded to intermittently exposed, which reduces densities of many potential predators (e.g., fish). Current research has shown that pool hydroperiod, canopy closure, vegetation structure within pools, presence of potential predators, and landscape structure surrounding pools are the key factors determining vertebrate diversity at seasonal forest pools. Of 25 species of amphibians in the region, frogs (10 of 12 species) are more likely to breed in seasonal forest pools than salamanders (6 of 13 species). Seven of 10 amphibian species that breed in seasonal forest pools are state-listed as threatened or endangered. Among 27 species of reptiles, 3 of 15 species of snakes, and 6 of 12 species of turtles utilize seasonal pools during at least one stage of their annual cycle. Seasonal forest pools are important foraging and basking habitat for three species of turtles listed as threatened or endangered. Compared to other vertebrate taxa, most species of mammals are habitat generalists, with 50 of 63 mammal species potentially foraging at seasonal pools during part of their annual cycle. Chiroptera (bats; all 9 species) are believed to actively forage at seasonal pools and some Insectivora, particularly Sorex palustris Richardson and S. fumeus (Miller) and Condylura cristata (L.), are detected regularly at seasonal pools. Breeding birds are less likely to utilize seasonal pools than other vertebrate taxa, although 92 of 233 species might forage or breed near seasonal pools. Several species of Anatidae, Rallidae, and some Passeriformes use seasonally flooded pools. All vertebrates that use seasonal forest pools use other habitats during some stage in their life cycle; thus gaining a clear understanding of their habitat requirements is critical to their long-term persistence. © Springer 2005

Salamander dispersal across a forested landscape fragmented by a golf course

We assessed dispersal behavior of 78 radiotagged adult spotted salamanders (Ambystoma maculatum) at a 36-hole golf course in southeastern Connecticut, USA. Lake of Isles Golf Course is atypical of most golf courses in North America because it is much larger (461 ha) than average 18-hole golf courses (54 ha) and deciduous forests accounted for 70% landscape composition on the course. We tracked individuals an average of 164 days as they emigrated from 3 seasonal pools surrounded by golf course fairways and one pool located in contiguous forest (control pool) from March through December 2004. Males and females dispersed similar distances at the control pool, averaging 71 ± 10 m. However, females migrating across the golf course dispersed twice as far (214 ± 25 m) as males on the golf course (102 ± 15 m) and both genders at the control pool. Over 40% the salamanders at the golf course crossed fairways; thus, fairways were not a dispersal barrier to adult spotted salamanders. Previous researchers have suggested establishing a 164-m life zone around breeding ponds to protect pond-breeding amphibian populations. Our results suggest that strategies that protect core upland habitat within 164 m of wetland boundaries would include 82% of adult males and only 50% of adult females. Empirical estimates based on our telemetry study suggest that core terrestrial habitat would have to extend 370 m to protect 95% of adult females, which is much farther than previous estimates

Assessing habitat selection by foraging egrets in salt marshes at multiple spatial scales

We assessed salt marsh use by foraging egrets in coastal Rhode Island, USA. Two species [great egret (Ardea alba) and snowy egret (Egretta thula)] nest in mixed-species colonies on islands in Narragansett Bay and regularly forage in adjacent salt marshes. We surveyed 13 salt marshes approximately twice weekly during the breeding and post-breeding seasons in 2001 and 2002. Based on resource selection functions, foraging great and snowy egrets strongly preferred pools within salt marshes, while mosquito control ditches were rarely used. Foraging egrets were never detected in stands of common reed (Phragmites australis). The number of egrets using individual marshes varied considerably, although density estimates were far less variable. Salt marsh area was better at predicting the mean number of foraging egrets using a marsh than landscape-level parameters, such as distance to the nearest nesting colony or the total area of salt marsh within 5 km. Carefully designed salt marsh restoration projects could benefit local egret populations because it appears that foraging habitat availability may be a limiting factor. To ensure use by foraging egrets, salt marsh restoration designs should increase the availability of pool and open water habitat, reduce common reed, and modify deep ditches and channels to make them more accessible for foraging egrets. © 2006, The Society of Wetland Scientists

Emigration behavior of spotted salamanders on golf courses in southern Rhode Island

Few studies have investigated the emigration behavior of adult ambystomatid salamanders in fragmented landscapes. We assessed the emigration behavior of 30 Spotted Salamanders (Ambystoma maculatum) by implanting transmitters in 2003. Study sites, all in southern Rhode Island, included an active golf course, a golf course under construction, and a closed-canopy forest that served as a control site. Maximum dispersal distances from breeding ponds ranged from 44-467 m (mean = 145, SE = 20 m), with the maximum distance twice as far as prior studies on this species. Spotted Salamanders exhibited distinct preferences for terrestrial habitats by avoiding fairways and selecting forested uplands and forested wetlands. The use of forested wetlands was unusual because most past research has suggested avoidance of this habitat by Spotted Salamanders. We documented adult Spotted Salamanders crossing fairways to adjacent forest patches; thus, fairways were not a dispersal barrier. Compared to random points, adult Spotted Salamanders selected cool microhabitats with greater leaf litter depth, more coarse woody debris, more canopy cover, less herbaceous cover, and high densities of vertical and horizontal small mammal burrows. These results suggest that maintaining extensive upland and wetland forested habitats near breeding ponds, with significant amounts of deep leaf litter, coarse woody debris, and high small mammal densities will help sustain Spotted Salamanders. Copyright 2006 Society for the Study of Amphibians and Reptiles

Population trends and habitat use of Harlequin Ducks in Rhode Island

To assess population trends of Harlequin Ducks (Histrionicus histrionicus) in Rhode Island (U.S.A.), we analyzed Christmas Bird Counts and other historical surveys and also conducted surveys during the winter of 2005-2006. We estimated sex and age ratios, evaluated the effects of tidal regime and time of day on survey precision, and quantified habitat use. The population in Rhode Island experienced logistic growth from 1976 to 2004, with approximately 150 birds now wintering at three primary sites in the state. We estimated that the current ratio of males to females in the region was 1.6:1 (62% males) and that 13% of males were first-winter birds. Most Harlequin Ducks were observed in rocky habitats within 50 m of the shore or offshore islands. We detected the greatest numbers of birds, with the least amount of variation, during morning surveys at low tide, suggesting that this may be the most appropriate time for population monitoring. Increases in the Rhode Island population and male-biased sex ratios may indicate a local population recovery resulting from a hunting ban initiated in 1990. Although most Harlequin Ducks in eastern North America winter in Maine, the population in Rhode Island represents one of the largest in the southern part of their range. ©2007 Association of Field Ornithologists

Assessing detection probabilities of larval amphibians and macroinvertebrates in isolated ponds

Isolated ponds provide vital habitat for an array of vertebrates and invertebrates. Given the potential decline in protection of isolated ponds and the increase in urbanization in northeastern North America, knowledge of the condition of this aquatic resource is essential for developing revisions to existing regulations, conservation efforts, and restoration initiatives. We were interested in the ability of rapid assessment methods, which require only one site visit, to estimate the condition of isolated ponds. During 2008, we conducted dip-net surveys at 10-day intervals from mid-May to late July 2008 at each of 36 isolated ponds in Rhode Island. We calculated detection probabilities for larval amphibian species and predatory macroinvertebrate families and assessed factors influencing detection probabilities. Most taxa displayed distinct seasonal phenologies in detection probabilities. Pond depth and vegetative characteristics also influenced detection probabilities of many taxa. Based on seasonal variation in detection probabilities, rapid assessment methods would not be effective to monitor overall biodiversity of isolated ponds in southern New England. Rather, multiple visits would be required to estimate occupancy rates of pondbreeding amphibians or aquatic macroinvertebrates if they were used as ecological indicators of pond condition. © Society of Wetland Scientists 2010

Long-term shifts in autumn migration by songbirds at a coastal eastern north American stopover site

We investigated long-term trends in mean autumn capture dates of 19 species of migratory passerines including 11 long-distance migrants and eight short-distance migrants. Birds were captured between 1960 and 2007 at a banding station in southern Rhode Island. We detected annual trends in the highest ranked models with mean capture dates of seven species significantly delayed by an average of 3.0 days per decade; 38% of long-distance migrants and 50% of short-distance migrants studied significantly delayed migration. We found no evidence of long-term shifts in autumn migration timing for seven species and mean capture dates of five species exhibited non-linear annual trends. Mean autumn temperature was an important factor in explaining annual trends for eight species. Changes in annual capture rates for some species may have an equal or greater role than year or temperature in explaining long-term trends in autumn migration timing. Our analysis suggests that some migratory bird species are now departing the region later than in the 1960s. Important differences among species and regions are likely to influence species-specific responses to changes in climate patterns. © 2011 by the Wilson Ornithological Society