Extensive Use of Intertidal Habitat by Shorebirds Outside Protected Nesting Areas

Conservation of shorebirds throughout their breeding and migratory ranges has become a priority as shorebird populations decline globally. Along the North Atlantic Coast, management efforts have particularly focused on preserving nesting habitat for piping plovers (Charadrius melodus), which are protected under the Endangered Species Act. It is unclear whether these conservation measures suffice to protect foraging habitat for piping plovers and other shorebirds on stopover during migration along the Atlantic Flyway. To evaluate the extent to which conservation of piping plover nesting areas extends to all habitats used by plovers, and to determine whether these protections also benefited non-breeding migratory shorebirds in the region, we conducted weekly shorebird surveys, recording the number and locations of piping plovers and other species, during northward and southward migration on Fire Island and Westhampton Island, New York, USA, from 2014–2016. We used canonical correspondence analysis (CCA) to assess the degree of spatiotemporal overlap between breeding plovers, foraging plovers, and other migratory shorebirds that temporarily stage at the site. The spatiotemporal distribution of migratory shorebirds matched more closely with piping plovers seen during foraging than piping plovers observed tending nests and engaging in other breeding activities. Migratory shorebirds and foraging piping plovers were more abundant and frequent in wet intertidal zones outside of fenced-off nesting areas, which were not protected under current management regimes. Therefore, additional protection of piping plover foraging habitat could benefit plovers and migratory shorebirds that use similar feeding grounds during stopover on northward and southward migration. © 2020 The Wildlife Society.     

Foraging Ecology of Fall-Migrating Shorebirds in the Illinois River Valley

Populations of many shorebird species appear to be declining in North America, and food resources at stopover habitats may limit migratory bird populations. We investigated body condition of, and foraging habitat and diet selection by 4 species of shorebirds in the central Illinois River valley during fall migrations 2007 and 2008 (Killdeer [Charadrius vociferus], Least Sandpiper [Calidris minutilla], Pectoral Sandpiper [Calidris melanotos], and Lesser Yellowlegs [Tringa flavipes]). All species except Killdeer were in good to excellent condition, based on size-corrected body mass and fat scores. Shorebird diets were dominated by invertebrate taxa from Orders Diptera and Coleoptera. Additionally, Isopoda, Hemiptera, Hirudinea, Nematoda, and Cyprinodontiformes contribution to diets varied by shorebird species and year. We evaluated diet and foraging habitat selection by comparing aggregate percent dry mass of food items in shorebird diets and core samples from foraging substrates. Invertebrate abundances at shorebird collection sites and random sites were generally similar, indicating that birds did not select foraging patches within wetlands based on invertebrate abundance. Conversely, we found considerable evidence for selection of some diet items within particular foraging sites, and consistent avoidance of Oligochaeta. We suspect the diet selectivity we observed was a function of overall invertebrate biomass (51.2±4.4 [SE] kg/ha; dry mass) at our study sites, which was greater than estimates reported in most other food selection studies. Diet selectivity in shorebirds may follow tenants of optimal foraging theory; that is, at low food abundances shorebirds forage opportunistically, with the likelihood of selectivity increasing as food availability increases. Nonetheless, relationships between the abundance, availability, and consumption of Oligochaetes for and by waterbirds should be the focus of future research, because estimates of foraging carrying capacity would need to be revised downward if Oligochaetes are truly avoided or unavailable for consumption.     

Changes in Soil Fungal Communities, Extracellular Enzyme Activities, and Litter Decomposition Across a Fire Chronosequence in Alaskan Boreal Forests

Wildfires are a pervasive disturbance in boreal forests, and the frequency and intensity of boreal wildfires is expected to increase with climate warming. Boreal forests store a large fraction of global soil organic carbon (C), but relatively few studies have documented how wildfires affect soil microbial communities and soil C dynamics. We used a fire chronosequence in upland boreal forests of interior Alaska with sites that were 1, 7, 12, 24, 55, ~90, and ~100 years post-fire to examine the short- and long-term responses of fungal community composition, fungal abundance, extracellular enzyme activity, and litter decomposition to wildfires. We hypothesized that post-fire changes in fungal abundance and community composition would constrain decomposition following fires. We found that wildfires altered the composition of soil fungal communities. The relative abundance of ascomycetes significantly increased following fire whereas basidiomycetes decreased. Post-fire decreases in basidiomycete fungi were likely attributable to declines in ectomycorrhizal fungi. Fungal hyphal lengths in the organic horizon significantly declined in response to wildfire, and they required at least 24 years to return to pre-fire levels. Post-fire reductions in fungal hyphal length were associated with decreased activities of hydrolytic extracellular enzymes. In support of our hypothesis, the decomposition rate of aspen and black spruce litter significantly increased as forests recovered from fire. Our results indicate that post-fire reductions in soil fungal abundance and activity likely inhibit litter decomposition following boreal wildfires. Slower rates of litter decay may lead to decreased heterotrophic respiration from soil following fires and contribute to a negative feedback to climate warming.     

Lines in the mud; revisiting the boundaries of important shorebird areas

Many shorebird populations are declining throughout the world, concurrent with declines and degradation of wetland habitats. Such declines necessitate a more consistent approach towards conserving habitats used by shorebird populations. Individuals of many shorebird species congregate in specific areas during their non-breeding season. Worldwide, non-breeding areas are designated as ‘important’ for shorebird conservation based primarily on the abundance of birds found in an area. However, the boundaries of any area are often defined with incomplete information regarding how shorebirds use that habitat. This paper discusses examples in Australia where improved knowledge of shorebird habitat use led to the identification of very different boundaries of important shorebird areas than those identified originally. We highlight how simple questioning of those who count shorebirds in an area, led to an improved understanding of which areas were apparently used by the same local population of non-breeding shorebirds. Subsequent analysis of available count, recapture and/or home range data of particular shorebird species is needed to verify expert opinion regarding most of these boundaries. We review how enhanced boundaries improve the ability of shorebird monitoring to detect population changes; allow management of shorebird habitats at relevant spatial scales; and lead to appropriate designations of important areas. While the kinds of approaches to boundary setting described here are not new, they are not consistently applied worldwide. We suggest additional guidelines to those produced under the Ramsar Convention in regard to designating important areas. We also call for more studies on the movements of migratory shorebirds during the non-breeding season to direct more consistent boundary setting around important non-breeding habitats used by local populations of migratory shorebirds.     

Identification of significant shorebird areas: thresholds and criteria

Aim Conservation managers designate significant areas for shorebirds based on imperfect data. Significant wetlands for migratory shorebirds have usually been identified on the basis of whether they exceed certain thresholds, defined either by total abundance (usually 20,000 waterbirds) or percentage of a population (usually 1.0%). We evaluate the performance of existing criteria and determine if lowering thresholds would improve shorebird conservation without adding unreasonable numbers of significant sites. Location Australia. Methods We evaluated the best available data, which is used by managers to designate significant areas, to describe the effect of lowering thresholds on the number of significant sites identified and the number of shorebirds these sites support using a range of thresholds in existing criteria. We also investigated factors which may explain interspecific differences evident when lowering thresholds. Results When the threshold for total abundance was lowered from 20,000 to 2000 shorebirds, an additional 45 shorebird areas, holding 65% more shorebirds, were identified. When thresholds for the percentage of a population criterion were lowered from 1.0 to 0.1%, an additional 86 shorebird areas were identified which held 29% more shorebirds. The proportion of a species population counted within wetlands identified as significant by the application of criteria varied widely between species. The percentage of population criterion always identified a network of areas that included more individuals of each species than the total abundance criterion at all threshold levels tested. The percentage of species populations found in networks of significant areas showed greater increase as thresholds were lowered for species that were abundant, widespread and well represented at existing thresholds. Main conclusions Our results suggest lowering thresholds will substantially increase the number of shorebirds in identified significant areas. However, some species will remain under‐represented, partly because of interspecific differences in distribution and inadequate sampling of some shorebird habitats.     

An Experimental Assessment of Vehicle Disturbance Effects on Migratory Shorebirds

ABSTRACT Off-road vehicle (ORV) traffic is one of several forms of disturbance thought to affect shorebirds at migration stopover sites. Attempts to measure disturbance effects on shorebird habitat use and behavior at stopover sites are difficult because ORV disturbance is frequently confounded with habitat and environmental factors. We used a before-after-control-impact experimental design to isolate effects of vehicle disturbance from shorebird responses to environmental and habitat factors. We manipulated disturbance levels within beach closures along South Core Banks, North Carolina, USA, and measured changes in shorebird abundance and location, as well as the activity of one focal species, the sanderling (Calidris alba), within paired control and impact plots. We applied a discrete treatment level of one flee-response-inducing event every 10 minutes on impact plots. We found that disturbance reduced total shorebird and black-bellied plover (Pluvialis squatarola) abundance and reduced relative use of microhabitat zones above the swash zone (wet sand and dry sand) by sanderlings, black-bellied plovers, willets (Tringa semipalmata), and total shorebirds. Sanderlings and total shorebirds increased use of the swash zone in response to vehicle disturbance. Disturbance reduced use of study plots by sanderlings for resting and increased sanderling activity, but we did not detect an effect of vehicle disturbance on sanderling foraging activity. We provide the first estimates of how a discrete level of disturbance affects shorebird distributions among ocean beach microhabitats. Our findings provide a standard to which managers can compare frequency and intensity of disturbance events at other shorebird stopover and roosting sites and indicate that limiting disturbance will contribute to use of a site by migratory shorebirds.     

Evaluating impacts of shellfish and baitworm digging on bird populations: short-term negative effects on the availability of the mudsnail Hydrobia ulvae to shorebirds

Many shorebird populations show evidence of declines. To identify the causes is a key issue in developing comprehensive shorebird conservation plans. In coastal areas, shorebirds are vulnerable to effects of shellfish and baitworm digging, including reduction of the food supply. The mudsnail Hydrobia ulvae is often reported to be the dominant inhabitant of intertidal mudflats, and is common in the diet of migrating and wintering shorebirds. This prosobranch mollusc lives at or just below the surface of intertidal mudflats, so it might be directly damaged and killed or buried within the mud by hand diggers. We studied the short-term effects of digging by hand on the availability of mudsnail to shorebirds. Twenty centimetres deep core samples were collected from undisturbed and recently disturbed intertidal mud. The total mudsnail density and biomass per core sample was similar in disturbed and undisturbed mud. However, mudsnail density and biomass were significantly lower in disturbed mud than in undisturbed mud when only the upper five centimetres of the mud were compared. If only the mudsnails found in this surface layer are potentially available for shorebirds, the available mudsnail density and biomass fraction for shorebirds had decreased by 62.6? ?±? 11.4% and 75.7? ?±? 7.2% in disturbed mud, respectively. The potential impact of this decreasing mudsnail fraction on shorebirds is addressed.     

Migrant shorebird use of Akimiski Island, Nunavut: a sub-arctic staging site

Determining the importance of stopover and staging areas to migrating shorebirds (Aves: Charadriiformes) is essential if such habitats are to be successfully protected. Migration chronology, species composition, length of stay, body condition, and estimated total abundance of shorebirds during spring and fall migratory periods of 2008 and 2009 were documented on Akimiski Island, Nunavut, Canada. Fourteen shorebird species were observed during spring point counts and 18 during fall. Semipalmated (Calidris pusilla) and White-rumped (C. fuscicollis) Sandpipers comprised about 80?% of all individuals observed. A greater number of species and individuals were observed during fall than spring in both years. Radio-transmitters attached to juvenile Semipalmated and Least (C. minutilla) Sandpipers indicated highly variable lengths of stay ranging up to 26?days in both species (Semipalmated Sandpiper averaged 6.5?±?2.67?days, n?=?12; Least Sandpipers averaged 7.25?±?3.79?days, n?=?8). In 2009, Semipalmated Sandpipers captured and weighed later in the season were significantly heavier than those captured earlier suggesting that this species is refueling while on Akimiski Island. A fall migration seasonal density of 5,267 (2,193–8,341) shorebirds/km² was estimated given a residence probability (i.e., the probability of an individual being present in consecutive counts) of 0.906?±?0.181. Assuming similar habitat value and shorebird density, an extrapolation of the seasonal plot density of 5,267 birds/km² to the total 192?km² mudflat habitat on Akimiski Island yields an estimate of 1,011,264 (421,098–1,601,429) shorebirds during fall migration, making Akimiski Island of Hemispheric importance as a staging site for migrant arctic-breeding shorebirds.     

Community composition and migration chronology of shorebirds using the saline lakes of the Southern Great Plains, USA

ABSTRACT.   Shorebirds migrating through the Southern Great Plains (SGP), USA, use freshwater playas and saline lakes as stopovers. The importance of playas is well documented, but the role of saline lakes is not clearly understood. During 2002 and 2003, we conducted surveys to determine the extent to which the saline lakes serve as stopovers. Twenty-eight species were recorded, and total seasonal abundance ranged from 6779 to 29,924 birds. Potential shorebird abundance for extant saline lakes was estimated at 37,000–71,000 shorebirds annually. American Avocets ( Recurvirostra americana ), Western Sandpipers ( Calidris mauri ), Baird's Sandpipers ( C. bairdi ), Least Sandpipers ( C. minutilla ), Snowy Plovers ( Charadrius alexandrinus ), Killdeer ( Charadrius vociferus ), and Wilson's Phalaropes ( Phalaropus tricolor ) were the most abundant species. Community composition of shorebirds differed between saline lakes and regional freshwater playas. Peak spring abundance was generally in April, whereas summer/fall migration was more protracted and shorebird abundance peaked during 6–8 weeks in August and September. Migration chronologies differed among morphologically similar species, and among representative species from different guilds. Such patterns of temporal separation permit partitioning of resources by shorebirds migrating through the SGP. The saline lakes of the SGP should be regarded as stopover sites of regional and international value. To ensure that saline lakes function as stopovers and to help maintain those unique communities that inhabit them, conservation of saline lakes should focus on preserving spring flows and conserving water.     

Trends and Carrying Capacity of Sea Otters in Southeast Alaska

Sea otter populations in Southeast Alaska, USA, have increased dramatically from just over 400 translocated animals in the late 1960s to >8,000 by 2003. The recovery of sea otters to ecosystems from which they had been absent has affected coastal food webs, including commercially important fisheries, and thus information on expected growth and equilibrium abundances can help inform resource management. We compile available survey data for Southeast Alaska and fit a Bayesian state-space model to estimate past trends and current abundance. Our model improves upon previous analyses by partitioning and quantifying sources of estimation error, accounting for over-dispersion of aerial count data, and providing realistic measurements of uncertainty around point estimates of abundance at multiple spatial scales. We also provide estimates of carrying capacity (K) for Southeast Alaska, at regional and sub-regional scales, and analyze growth rates, current population status and expected future trends. At the regional scale, the population increased from 13,221 otters in 2003 to 25,584 otters in 2011. The average annual growth rate in southern Southeast Alaska (7.8%) was higher than northern Southeast Alaska (2.7%); however, growth varied at the sub-regional scale and there was a negative relationship between growth rates and the number of years sea otters were present in an area. Local populations vary in terms of current densities and expected future growth; the mean estimated density at K was 4.2 ± 1.58 sea otters/km² of habitat (i.e., the sub-tidal benthos between 0 m and 40 m depth) and current densities correspond on average to 50% of projected equilibrium values (range = 1–97%) with the earliest-colonized sub-regions tending to be closer to K. Assuming a similar range of equilibrium densities for currently un-occupied habitats, the projected value of K for all of Southeast Alaska is 74,650 sea otters. Future analyses can improve upon the precision of K estimates by employing more frequent surveys at index sites and incorporating environmental covariates into the process model to generate more accurate, location-specific estimates of equilibrium density. © 2019 The Authors. The Journal of Wildlife Management Published by Wiley Periodicals, Inc.     

Susceptibility of burned black spruce (Picea mariana) forests to non-native plant invasions in interior Alaska

As climate rapidly warms at high-latitudes, the boreal forest faces the simultaneous threats of increasing invasive plant abundances and increasing area burned by wildfire. Highly flammable and widespread black spruce (Picea mariana) forest represents a boreal habitat that may be increasingly susceptible to non-native plant invasion. This study assess the role of burn severity, site moisture and time elapsed since burning in determining the invisibility of black spruce forests. We conducted field surveys for presence of non-native plants at 99 burned black spruce forest sites burned in 2004 in three regions of interior Alaska that spanned a gradient of burn severities and site moisture levels, and a chronosequence of sites in a single region that had burned in 1987, 1994, and 1999. We also conducted a greenhouse experiment where we grew invasive plants in vegetation and soil cores taken from a subset of these sites. In both our field survey and the greenhouse experiment, regional differences in soils and vegetation between burn complexes outweighed local burn severity or site moisture in determining the invasibility of burned black spruce sites. In the greenhouse experiments using cores from the 2004 burns, we found that the invasive focal species grew better in cores with soil and vegetation properties characteristic of low severity burns. Invasive plant growth in the greenhouse was greater in cores from the chronosequence burns with higher soil water holding capacity or lower native vascular biomass. We concluded that there are differences in susceptibility to non-native plant invasions between different regions of boreal Alaska based on native species regeneration. Re-establishment of native ground cover vegetation, including rapidly colonizing bryophytes, appear to offer burned areas a level of resistance to invasive plant establishment.     

Foraging strategies involved in habitat use of shorebirds at the intertidal area of Chongming Dongtan, China

Dense flocks of migratory shorebirds from diverse species often concentrate in the intertidal areas for stopover. Trophic structure, food partition, prey availability and selectivity, predation risk, and abiotic factors are often used to explain the differences in habitat use of coexisting shorebirds. We sampled the macrobenthos and surveyed the distribution of shorebird populations to study the effects of foraging strategies on the habitat use of shorebirds at Chongming Dongtan, an important stopover site for shorebirds on the East Asian–Australasian Flyway. Results show that the relative abundance of epifaunal macrobenthos in salt marshes was much higher than that in the bare flats, whereas the relative abundance of infaunal macrobenthos in salt marshes was much lower than that in bare flats. The relative abundance of two life forms of macrobenthos was similar in the transitional zones between the salt marshes and the bare flats. Shorebirds with different foraging strategies exhibited different habitat uses. Pause-travel shorebirds mainly utilized the salt-marsh fringes, while tactile continuous shorebirds relied heavily on the bare flats. There was no significant difference in habitat use for visual continuous shorebirds. The density of tactile continuous shorebirds was positively correlated with bivalve density, and that of visual continuous shorebirds positively with crustacean density. Meanwhile, the relative abundance of pause-travel foraging shorebirds was positively correlated with the relative abundance of epifaunal, but negatively with infaunal macrobenthos. In contrast, the relative abundance of tactile foraging shorebirds had a positive correlation with infaunal but a negative one with epifaunal life form. Therefore, foraging strategies may play important roles in shorebirds’ habitat use in intertidal areas.     

Testing assumptions for conservation of migratory shorebirds and coastal managed wetlands

Managed wetlands provide critical foraging and roosting habitats for shorebirds during migration; therefore, ensuring their availability is a priority action in shorebird conservation plans. Contemporary shorebird conservation plans rely on a number of assumptions about shorebird prey resources and migratory behavior to determine stopover habitat requirements. For example, the US Shorebird Conservation Plan for the Southeast-Caribbean region assumes that average benthic invertebrate biomass in foraging habitats is 2.4 g dry mass m^?2 and that the dominant prey item of shorebirds in the region is Chironomid larvae. For effective conservation and management, it is important to test working assumptions and update predictive models that are used to estimate habitat requirements. We surveyed migratory shorebirds and sampled the benthic invertebrate community in coastal managed wetlands of South Carolina. We sampled invertebrates at three points in time representing early, middle, and late stages of spring migration, and concurrently surveyed shorebird stopover populations at approximately 7-day intervals throughout migration. We used analysis of variance by ranks to test for temporal variation in invertebrate biomass and density, and we used a model based approach (linear mixed model and Monte Carlo simulation) to estimate mean biomass and density. There was little evidence of a temporal variation in biomass or density during the course of spring shorebird migration, suggesting that shorebirds did not deplete invertebrate prey resources at our site. Estimated biomass was 1.47 g dry mass m^?2 (95 % credible interval 0.13–3.55), approximately 39 % lower than values used in the regional shorebird conservation plan. An additional 4728 ha (a 63 % increase) would be required if habitat objectives were derived from biomass levels observed in our study. Polychaetes, especially Laeonereis culveri (2569 individuals m^?2), were the most abundant prey in foraging habitats at our site. Polychaetes have lower caloric content than levels assumed in the regional plan; when lower caloric content and lower biomass levels are used to determine habitat objectives, an additional 6395 ha would be required (86 % increase). Shorebird conservation and management plans would benefit from considering the uncertainty in parameters used to derive habitat objectives, especially biomass and caloric content of prey resources. Iterative testing of models that are specific to the planning region will provide rapid advances for management and conservation of migratory shorebirds and coastal managed wetlands.     

长江口杭州湾鸻形目鸟类群落季节变化和生境选择

在长江口南岸杭州湾北岸滨海滩涂进行了鸻形目鸟类的资源调查,以及鸟类栖息地选择模式分析,2004年3月至2005年1月共统计到鸟类25种,春季优势种为大缤鹬(Calidris tenuirostris)、尖尾缤鹬(Calidris alpine)和红颈滨鹬(Calidris ruficollis);夏季为环颈(Charadrius alexandrinus)、青脚鹬(Tringa nebularia)和蒙古沙(Charadrius mongolus),秋季为环颈、红颈滨鹬和青脚鹬,冬季为黑腹滨鹬(Calidris alpina)、环颈和泽鹬(Tringa stagnatilis),鸟类总体数量呈春季>秋季>冬季>夏季,海堤外(自然滩涂)和堤内(人工湿地)鸟类种数四季大致相等,但鸟类平均密度季节差异显著。通过对样点内鸟类与环境因子进行多元分析,初步总结出堤外滩宽和光滩宽是影响鸟类栖息的最关键因子,海三棱草(Scirpus× mariquete)覆盖比例和潮上坪宽度的影响程度次之。堤内浅水塘比例和裸地比例是影响形目鸟类分布的关键因子,海三棱草覆盖比例也起正向作用。而人类干扰大、芦苇(Phragmites communis)/互花米草(Spartina alternifloral)密植和高水位的区域不利于鸟类利用。     

Investigating Avian Influenza Infection Hotspots in Old-World Shorebirds

Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered.     

Biomass and density responses in tallgrass prairie legumes to annual fire and topographic position

Annually burned tallgrass prairie is purported to be a nitrogen-limited system, especially when compared to unburned prairie. To test the hypothesis that legumes, potential nitrogen-fixers, would increase in relative abundance in annually burned sites, we assessed their density and biomass for two seasons on upland and lowland soils in annually burned and unburned watersheds. Total legume density was significantly higher in burned (8.0 ± 1.0 [SE] stems/m²) than in unburned watersheds (3.0 ± 0.3 stems/m²). Species with higher (P < 0.05) densities in burned than in unburned prairie included Amorpha canescens, Dalea candida, Dalea purpurea, Lespedeza violacea, Psoralea tenuiflora, and Schrankia nuttallii. Desmodium illinoense was the only legume that responded negatively to annual fire. Total legume biomass did not differ between burned (11.3 ± 1.3 g/m²) and unburned prairie (10.5 ± 0.9 g/m²). Biomass productions of Dalea candida and Psoralea tenuiflora were higher (P < 0.05) in burned than in unburned sites, but biomasses of other legumes were similar between burn treatments. Average individual stem masses of Amorpha canescens and Baptisia bracteata were significantly greater in unburned than in burned prairie. Legumes were affected differentially by topographic location. Total legume density was higher (P < 0.05) on lowland soils (6.6 ± 1.0 stems/m²) than on upland soils (4.3 ± 0.5 stems/m²). However, total legume biomass was not different between lowland soils (12.0 ± 1.2 g/m²) and upland soils (9.9 ± 1.0 g/m²). Densities and biomasses of Amorpha canescens, Desmodium illinoense, and Lespedeza capitata were higher on lowland sites than on upland sites, whereas densities and biomasses of Baptisia bracteata and Dalea purpurea were higher on upland than on lowland soils. Most legume species are either fire tolerant or exhibit a positive response to fire and their persistence in annually burned prairie suggests that they may play an important role in the nitrogen budget of this ecosystem.     

Community composition, seasonal dynamics and interspecific correlation of waterbirds in the Qiantangjiang River estuary and Hangzhou Bay

Waterbird surveys were conducted regularly in the Qiantangjiang River estuary and Hangzhou Bay from July 2007 to November 2011. A total of 128 species (nine orders and 18 families) were recorded, including 119 migrants which accounted for 93% of the total species; eleven species were listed as National Protected Species. Inter-specific correlation analysis for 13 shorebird populations and nine duck populations recorded over time found that 21 pairs of shorebirds and 23 pairs of ducks were correlated. By looking at seasonal dynamics and migration patterns we were able to divide the migration process into six stages: (1) late July to late September was the migration peak of shorebirds, which were dominated by Limosa limosa, Calidris ruficollis and Charadrius mongolus. (2) Early October to mid-December was the migration peak of wintering migrants of shorebirds and ducks, which were the first two large groups in our study areas. (3) Late December to mid-February was the wintering period of migration waterbirds. (4) Late February to late March was the peak migration of ducks and the winter migrants of shorebirds dominated by Calidris alpina. (5) Early April to mid-May was the migration peak of passage migrants such as, Calidris ruficollis, Calidris acuminate and Limosa limosa but the population size of shorebird winter migrants dominated by Calidris alpine was still larger than the former. (6) Late May to mid-July was the breeding season of all egrets, summer migrants of gulls and several species of shorebirds. Our surveys show that interaction among species is possibly an important determinant of community composition of shorebirds and wintering ducks during the migration season. It may be the geographical position and community composition of migrant shorebirds across Hangzhou Bay that mean during the northward migration there are far more shorebirds than during the southward migration.     

Intraseasonal patterns in shorebird nest survival are related to nest age and defence behaviour

Nest survival may vary throughout the breeding season for many bird species, and the nature of this temporal variation can reveal the links between birds, their predators, and other components of the ecosystem. We used program Mark to model patterns in nest survival within the breeding season for shorebirds nesting on arctic tundra. From 2000 to 2007, we monitored 521 nests of five shorebird species and found strong evidence for variation in nest survival within a nesting season. Daily nest survival was lowest in the mid-season in 5 of 8 years, but the timing and magnitude of the lows varied. We found no evidence that this quadratic time effect was driven by seasonal changes in weather or the abundance of predators. Contrary to our prediction, the risk of predation was not greatest when the number of active shorebird nests was highest. Although nest abundance reached a maximum near the middle of the breeding season, a daily index of shorebird nest activity was not supported as a predictor of nest survival in the models. Predators’ access to other diet items, in addition to shorebird nests, may instead determine the temporal patterns of nest predation. Nest survival also displayed a positive, linear relationship with nest age; however, this effect was most pronounced among species with biparental incubation. Among biparental species, parents defended older nests with greater intensity. We did not detect a similar relationship among uniparental species, and conclude that the stronger relationship between nest age and both nest defence and nest survival for biparental species reflects that their nest defence is more effective.     

The First Estimates of Marbled Cat Pardofelis marmorata Population Density from Bornean Primary and Selectively Logged Forest

The marbled cat Pardofelis marmorata is a poorly known wild cat that has a broad distribution across much of the Indomalayan ecorealm. This felid is thought to exist at low population densities throughout its range, yet no estimates of its abundance exist, hampering assessment of its conservation status. To investigate the distribution and abundance of marbled cats we conducted intensive, felid-focused camera trap surveys of eight forest areas and two oil palm plantations in Sabah, Malaysian Borneo. Study sites were broadly representative of the range of habitat types and the gradient of anthropogenic disturbance and fragmentation present in contemporary Sabah. We recorded marbled cats from all forest study areas apart from a small, relatively isolated forest patch, although photographic detection frequency varied greatly between areas. No marbled cats were recorded within the plantations, but a single individual was recorded walking along the forest/plantation boundary. We collected sufficient numbers of marbled cat photographic captures at three study areas to permit density estimation based on spatially explicit capture-recapture analyses. Estimates of population density from the primary, lowland Danum Valley Conservation Area and primary upland, Tawau Hills Park, were 19.57 (SD: 8.36) and 7.10 (SD: 1.90) individuals per 100 km², respectively, and the selectively logged, lowland Tabin Wildlife Reserve yielded an estimated density of 10.45 (SD: 3.38) individuals per 100 km². The low detection frequencies recorded in our other survey sites and from published studies elsewhere in its range, and the absence of previous density estimates for this felid suggest that our density estimates may be from the higher end of their abundance spectrum. We provide recommendations for future marbled cat survey approaches.     

Identifying habitat conservation priorities and gaps for migratory shorebirds and waterfowl in California

Conservation of migratory shorebirds and waterfowl presents unique challenges due to extensive historic loss of wetland habitats, and current reliance on managed landscapes for wintering and migratory passage. We developed a spatially-explicit approach to estimate potential shorebird and waterfowl densities in California by integrating mapped habitat layers and statewide bird survey data with expert-based habitat rankings. Using these density estimates as inputs, we used the Marxan site-selection program to identify priority shorebird and waterfowl areas at the ecoregional level. We identified 3.7 million ha of habitat for shorebirds and waterfowl, of which 1.4 million ha would be required to conserve 50% of wintering populations. To achieve a conservation goal of 75%, more than twice as much habitat (3.1 million ha) would be necessary. Agricultural habitats comprised a substantial portion of priority areas, especially at the 75% level, suggesting that under current management conditions, large areas of agricultural land, much of it formerly wetland, are needed to provide the habitat availability and landscape connectivity required by shorebird and waterfowl populations. These habitats were found to be largely lacking recognized conservation status in California (96% un-conserved), with only slightly higher levels of conservation for priority shorebird and waterfowl areas. Freshwater habitats, including wetlands and ponds, were also found to have low levels of conservation (67% un-conserved), although priority shorebird and waterfowl areas had somewhat higher levels of conservation than the state as a whole. Conserving migratory waterfowl and shorebirds will require a diversity of conservation strategies executed at a variety of scales. Our modeled results are complementary with other approaches and can help prioritize areas for protection, restoration and other actions. Traditional habitat protection strategies such as conservation easements and fee acquisitions may be of limited utility for protecting and managing significant areas of agricultural lands. Instead, conservation strategies focused on incentive-based programs to support wildlife friendly management practices in agricultural settings may have greater utility and conservation effectiveness.