Calidris Canutus Research Articles

Shorebirds and stakeholders: Effects of beach closure and human activities on shorebirds at a New Jersey coastal beach

Coastal habitats are critical for conservation of migrant shorebirds. We examined the effect of beach closure on recreationists and on shorebirds, at an important southbound stopover area for shorebirds at Brigantine, New Jersey. The study had three prongs: 1) involve stakeholders during all phases, 2) assess public use of the beach and responses to closure, and 3) assess shorebird use of the beach and response to closure. Stakeholders were involved in the design, implementation and evaluation of the project. The beach was used for fishing, walking, dog-walking, and other recreational activities. Sixty percent of recreationists were positive about the study and beach closure to protect shorebirds. The data indicate that: 1) involving a wide range of stakeholders early and often was important to our ability to conduct, design, and implement the study, 2) the beach was used by different types of recreationists 3) beach users were supportive of the closure, 4) spatial use by shorebirds depended upon whether the beach was open or closed, especially for red knot, and 5) all species of shorebirds used a small beach area behind a protective fence whether the beach was open or closed. Red knot behavior was most affected by beach closure; they spread out over the entire beach when it was closed, and concentrated at the tip when it was open. Conservation measures should take into account stakeholders views, human uses, beach physiognomy, and potential closure of refuge areas during critical migration times for shorebirds.

Shorebird patches as fingerprints of fractal coastline fluctuations due to climate change

The Florida coast is one of the most species-rich ecosystems in the world. This paper focuses on the sensitivity of the habitat of threatened and endangered shorebirds to sea level rise induced by climate change, and on the relationship of the habitat with the coastline evolution. We consider the resident Snowy Plover (Charadrius alexandrinus nivosus), and the migrant Piping Plover (Charadrius melodus) and Red Knot (Calidris canutus) along the Gulf Coast of Mexico in Florida. We analyze and model the coupled dynamics of habitat patches of these imperiled shorebirds and of the shoreline geomorphology dictated by land cover change with consideration of the coastal wetlands. The land cover is modeled from 2006 to 2100 as a function of the A1B sea level rise scenario rescaled to 2 m. Using a maximum-entropy habitat suitability model and a set of macroecological criteria we delineate breeding and wintering patches for each year simulated. Evidence of coupled ecogeomorphological dynamics was found by considering the fractal dimension of shorebird occurrence patterns and of the coastline. A scaling relationship between the fractal dimensions of the species patches and of the coastline was detected. The predicted power law of the patch size emerged from scale-free habitat patterns and was validated against 9 years of observations. We predict an overall 16% loss of the coastal landforms from inundation. Despite the changes in the coastline that cause habitat loss, fragmentation, and variations of patch connectivity, shorebirds self-organize by preserving a power-law distribution of the patch size in time. Yet, the probability of finding large patches is predicted to be smaller in 2100 than in 2006. The Piping Plover showed the highest fluctuation in the patch fractal dimension; thus, it is the species at greatest risk of decline. We propose a parsimonious modeling framework to capture macroscale ecogeomorphological patterns of coastal ecosystems. Our results suggest the potential use of the fractal dimension of a coastline as a fingerprint of climatic change effects on shoreline-dependent species. Thus, the fractal dimension is a potential metric to aid decision-makers in conservation interventions of species subjected to sea level rise or other anthropic stressors that affect their coastline habitat.

The contributions of resource availability and social forces to foraging distributions: a spatial lag modelling approach

The spatial distribution of foraging animals at a given time simultaneously depends on (1) exogenous environmental variables such as resource availability and abiotic habitat characteristics, and (2) the endogenous variable social aggregation made up of the opposing mechanisms of conspecific attraction and repulsion. We developed an exogenous environment–social aggregation model to analyse the spatial distributions of six abundant shorebird species in the Dutch Wadden Sea at resolutions of 150 × 150, 200 × 200 and 250 × 250 m. We used these resolutions to check the robustness of the estimates to the modifiable areal unit problem. We estimated the model parameters by spatial autoregression. This approach enables, among others, estimation of the direct and indirect effects of an exogenous environmental variable on animal density. The former is given by the regression coefficient and the latter, which is due to the amplification of the direct effect by social aggregation, by the spatial multiplier. At all resolution levels and for all species, the explanatory power of social aggregation, measured by Nagelkerke R2, was larger than the combined contribution of the exogenous environmental variables food availability, silt content and mudflat elevation. Social aggregation was stronger for dunlin, Calidris alpina, red knot, Calidris canutus, and curlew, Numenius arquata, than for oystercatcher, Haematopus ostralegus, grey plover, Pluvialis squatarola, and bar-tailed godwit, Limosa lapponica. The total impacts (that is, direct effect plus all indirect impacts) of the exogenous environmental predictors tended to exceed substantially the direct effects (which tend to be the only ones examined in studies on foraging distributions).

Annual survival of Red Knots (Calidris canutus rufa) wintering in Florida

ABSTRACT. Populations of Red Knots (Calidris canutus rufa) have declined an estimated 80% in the past 25 years. Declines are primarily attributed to dwindling food resources in Delaware Bay, their last migratory stopover before the breeding grounds. Red Knots wintering in Florida also decreased in numbers, prompting the need to estimate local vital rates to determine whether local factors contribute to declining trends. We estimated age-specific annual survival rates and compared them with estimates from populations of Red Knots wintering in South America using the Barker model. Adult annual survival rates between 2005 and 2010 averaged 0.89 ± 0.02 [SD]; range: 0.86–0.94) and were similar to estimates reported for Delaware Bay (0.87–0.92). Juvenile survival (0.95 ± 0.06 [SE]) and adult fidelity (0.81 ± 0.05 [SE]) were also high. However, juvenile survival did not include the period between fledging and arrival in Florida, a period of potentially high mortality. Similar adult survival rates suggested that ...

Evidence of species-specific detoxification processes for trace elements in shorebirds

This study investigated sub-lethal effects and detoxification processes activated in free-ranging Red Knots (RKs) (Calidris canutus) from the Pertuis Charentais on the Atlantic coast of France, and compared the results with previous data obtained on another shorebird species, the Black-tailed Godwit (Limosa limosa). The concentrations of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were assessed in the liver, kidneys, muscle and feathers. Stable isotope analyses of carbon and nitrogen were carried out to determine whether differences in diet explained variations in elemental uptake. The mRNA expression of relevant genes (cytochrome c oxidase 1, acetyl-CoA carboxylase, Cu/Zn and Mn superoxide dismutase, catalase, metallothionein, malic enzyme), antioxidant enzyme activities (catalase, glutathione peroxidase (GPx), superoxide dismutase), and metallothionein (MT) levels were investigated to shed light on trace element detoxification and toxic effects. Although Red Knots were characterized by elevated As and Se concentrations which were potentially toxic, most elements were usually below toxicity threshold levels. The results strongly suggested a dietary specialization of Red Knots, with individuals feeding on higher trophic status prey experiencing higher As, Hg and Se burdens. Red Knots and Godwits also showed discrepancies in elemental accumulation and detoxification processes. Higher As and Se concentrations in Red Knots enhanced catalase gene expression and enzyme activity, while Godwits had higher Ag, Cu, Fe and Zn levels and showed higher MT production and GPx activity. The results strongly suggest that detoxification pathways are essentially trace element- and species-specific.

Among-year site fidelity of Red Knots during migration in Washington

Many shorebirds exhibit within- and among-year site fidelity during their annual cycle. Little is known, however, about the migration ecology of Red Knots (Calidris canutus) that migrate along the Pacific Flyway and occur in Washington in numbers that exceed counts elsewhere on the flyway. At two large estuaries in coastal Washington, Grays Harbor and Willapa Bay, we searched for and recorded the locations of Red Knots (N= 547) that had been individually marked with leg flags at their wintering grounds in Baja California Sur, Mexico, during the period from October 2006 to April 2009. In 2010, we resighted 43 Red Knots at Grays Harbor and Willapa Bay that had been observed at these sites in previous years, primarily in 2009. We found a high degree of site fidelity between years, with birds observed in 2010 more likely to return to the same stopover site used in 2009 than to switch stopover sites. For knots that did not switch estuaries between years, the median nearest distance between locations where individuals were observed between years was 1.4 km at Grays Harbor and 0.6 km at Willapa Bay. Our results provide the first evidence of stopover site fidelity by Red Knots of the roselaari subspecies. Fidelity occurred at three spatial scales: coastal Washington, the two estuaries where we conducted our study, and specific mudflat areas within the estuaries. Because our study sites support high populations of bivalves, Red Knots may be returning to the same areas in subsequent years to exploit what we suspect is a predictable food resource. The abundance of Red Knots and high degree of site fidelity suggest that our study sites in Grays Harbor and Willapa Bay are important for the conservation of this species on the Pacific Flyway. RESUMEN No hay informacion sobre la fidelidad de los playeros rojizos del Pacifico (Calidris canutus roselaari) a las costas de Washington, pese a que en ellas sus numeros superan los de otras partes de la ruta migratoria. Investigaciones de fidelidad al sitio permitiran contextualizar la importancia de los estuarios de Washington para esta subespecie en su migracion al norte. En las primaveras de 2009 y 2010 registramos, en Grays Harbor y Bahia Willapa, playeros rojizos marcados individualmente con banderas en las patas (N= 547). Las aves se marcaron en Baja California Sur, Mexico, su principal zona de invernacion, entre octubre de 2006 y abril de 2009. En 2010 observamos 43 playeros rojizos previamente registrados, sobre todo en 2009. Encontramos una fidelidad interanual alta al sitio, con mayor probabilidad de reobservar a las aves en el mismo sitio en ambos anos. Ademas la distancia entre las localidades donde registramos a los individuos en los dos anos, sugiere una fidelidad alta a zonas especificas dentro de los sitios de escala. La distancia media entre las localidades de observacion (diferentes anos), fue de 1.4 km para Grays Harbor y 0.6 km para Bahia Willapa. Nuestros resultados proporcionan la primera evidencia de fidelidad a un sitio de paso de esta subespecie. Asi la fidelidad ocurre a tres escalas espaciales: la costa de Washington, los dos estuarios y areas especificas dentro de los humedales. Esta fidelidad se relaciona probablemente con las grandes poblaciones de bivalvos que existen en el area, los cuales, presumimos, representan un recurso predecible para las aves. La abundancia de playeros rojizos y el alto grado de fidelidad al lugar sugieren que nuestros sitios de estudio (Grays Harbor y Bahia Willapa) son importantes para la conservacion de estas aves.

Health status of seabirds and coastal birds found at the German North Sea coast

BackgroundSystematic pathological investigations to assess the health status of seabirds and coastal birds in Germany were performed. The investigation was conducted to obtain data on possible causes of decline in seabird and coastal bird populations.Methods48 individuals of 11 different species of seabirds and coastal birds were collected by the stranding network along the entire German North Sea coast from 1997 to 2008, including mainly waders such as Eurasian oystercatchers (Haematopus ostralegus) and red knots (Calidris canutus) as well as seabirds such as northern fulmars (Fulmaris glacialis) and common scoters (Melanitta nigra).For most birds (n = 31) found dead along the shore no obvious cause of death was evident, while 17 individuals were killed by collisions with lighthouses.ResultsOverall, the nutritional status of the investigated birds was very poor, and the body mass in most cases was significantly lower compared to masses of living birds caught during the same periods of the year. This is partly linked to chronic parasitic or bacterial infections in different organs or to septicaemia. In some cases infections with zoonotic tuberculosis caused by Mycobacterium spp. were found. Avian influenza was not found in any of the collected birds.ConclusionThe presented data contribute to the evaluation of the health status of birds in the German North Sea. Moreover, they present an important tool for the assessment of potential pathogens with an impact on the health status of seabirds and coastal birds.

Independence among physiological traits suggests flexibility in the face of ecological demands on phenotypes

Phenotypic flexibility allows animals to adjust their physiology to diverse environmental conditions encountered over the year. Examining how these varying traits covary gives insights into potential constraints or freedoms that may shape evolutionary trajectories. In this study, we examined relationships among haematocrit, baseline corticosterone concentration, constitutive immune function and basal metabolic rate in red knot Calidris canutus islandica individuals subjected to experimentally manipulated temperature treatments over an entire annual cycle. If covariation among traits is constrained, we predict consistent covariation within and among individuals. We further predict consistent correlations between physiological and metabolic traits if constraints underlie species-level patterns found along the slow-fast pace-of-life continuum. We found no consistent correlations among haematocrit, baseline corticosterone concentration, immune function and basal metabolic rate either within or among individuals. This provides no evidence for constraints limiting relationships among these measures of the cardiovascular, endocrine, immune and metabolic systems in individual red knots. Rather, our data suggest that knots are free to adjust individual parts of their physiology independently. This makes good sense if one places the animal within its ecological context where different aspects of the environment might put different pressures on different aspects of physiology.

Constraints on fast ejecta in the Crab supernova remnant from optical spectral lines

Studies of young remnants offer an opportunity to test theoretical models of stellar evolution, explosion models and nucleosynthesis, as well as our understanding of the compact objects in the centre of the exploded stars.The first part of the thesis involves observations of the Crab nebula. We have used photometric and spectroscopic observations to search for a faint halo around the visible nebula, that could carry the missing mass and kinetic energy of the nebula. No halo was found. In the photometric data due to psf contamination, and in the spectroscopic no fast velocity components were present. We have also used optical and IR photometry to check for variation in the emissivity and dynamic structure of the Crab pulsar wind nebula (PWN), to try to understand the nature of plerionic PWNe. There, we measured flux variations up to 20% in the IR and also shifting of the wisps with velocities up to 0.2c. We also showed that the nearby red knot moves in tandem with the Crab pulsar.The second part of the thesis, deals with photometric & spectroscopic observations of SN 1987A in the LMC. The aim of the project was to monitor the evolution of the outer rings (ORs) of SN 1987A. The fading of the ORs is consistent with recombination and cooling after the initial flash ionization by the supernova. From the spectroscopic data we measured the density and temperature in the ORs where we found temperatures of ~ 12,000 K for the [N II] gas, and ~ 25,000 K for the [O III]. Finally, from the [O II], and [S II] ratios we estimated electron densities of ~ 1,000 cm-3 and ~ 2,500 cm-3, respectively. From the evolution of Hα, we argue that the highest density in the ORs could be 5,000 cm-3.

Migration and Over-Wintering of Red Knots (Calidris canutus rufa) along the Atlantic Coast of the United States

Abstract. Surveys and banding records of Calidris canutus rufa indicate that Red Knots migrate mainly north and south through Massachusetts, Delaware Bay, and Virginia, and winter in Florida and South America. We fitted 40 adult Red Knots with geolocators at Monomoy National Wildlife Refuge, Massachusetts, during fall migration (2009), and in this paper report on the locations of migration and wintering along the Atlantic coast of the United States of eight recaptured knots. The knots' migration patterns varied: four birds wintered along the U.S. Atlantic coast, and the rest went to the Caribbean islands or the northern edge of South America. Knots spent 58 to 75 days in Monomoy Refuge before migrating south in November. Seven of the eight stopped along the U.S. Atlantic coast for relatively long periods. For the six with complete yearly cycles, the total time spent along the Atlantic coast averaged 218 days (range 121–269 days). All eight knots crossed the Atlantic outer continental shelf from two to six...

Trophic cascade induced by molluscivore predator alters pore‐water biogeochemistry via competitive release of prey

Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a tropical intertidal ecosystem, providing evidence for a three-level trophic cascade induced by predation by molluscivore Red Knots (Calidris canutus) that affects pore water biogeochemistry. In the exclosures the knots' favorite prey (Dosinia isocardia) became dominant and reduced the individual growth rate in an alternative prey (Loripes lucinalis). Dosinia, a suspension feeder, consumes suspended particulate organic matter (POM), whereas Loripes is a facultative mixotroph, partly living on metabolites produced by sulfur-oxidizing chemoautotrophic bacteria, but also consuming suspended POM. Reduced sulfide concentrations in the exclosures suggest that, without predation on Dosinia, stronger competition for suspended POM forces Loripes to rely on energy produced by endosymbiotic bacteria, thus leading to an enhanced uptake of sulfide from the surrounding pore water. As sulfide is toxic to most organisms, this competition-induced diet shift by Loripes may detoxify the environment, which in turn may facilitate other species. The inference that predators affect the toxicity of their environment via a multi-level trophic cascade is novel, but we believe it may be a general phenomenon in detritus-based ecosystems.

Experimental evidence for cryptic interference among socially foraging shorebirds

Foraging rate and the distribution of foragers depend on prey distribution in conjunction with interindividual interactions. Generalized functional response models predict intake rates and spatial distributions of foragers on the basis of resource distribution and interference competition. The adequacy of these models depends on how well they capture the foragers' essential behavior. In this paper, we report on the results of a foraging experiment designed to examine the mechanisms of interference competition using red knots Calidris canutus that feed on buried bivalves. Red knots are rarely observed to interfere in the field, but this does not imply absence of interference. Our experimental setup minimized resource depletion, which allowed us to quantify interference competition as the decline in intake rate as a function of group size, with prey density and social status as additional treatments. We found that intake rate and searching efficiency decreased with group size and that dominant birds had higher intake rates than subordinates. Additionally, time spent searching for prey increased with group size. The decrease in intake rate was not due to conventional interference mechanisms (such as kleptoparasitism and time spent interacting with conspecifics) but to cryptic interference, that is, avoidance of physical encounters with conspecifics. To accurately predict intake rates and foraging distributions, theory and models need to account for the possibility that animals anticipate and try to avoid, at some costs, physical encounters with conspecifics (i.e., conflicts that would make conventional interference behavior visible).

Avian influenza virus infection dynamics in shorebird hosts.

To gain insight into avian influenza virus (AIV) transmission, exposure, and maintenance patterns in shorebirds at Delaware Bay during spring migration, we examined temporal AIV prevalence trends in four Charadriiformes species with the use of serial cross-sectional data from 2000 through 2008 and generalized linear and additive models. Prevalence of AIV in Ruddy Turnstones (Arenaria interpres morinella) increased after arrival, peaked in mid-late May, and decreased prior to departure. Antibody prevalence also increased over this period; together, these results suggested local infection and recovery prior to departure. Red Knots (Calidris canutus rufa), Sanderlings (Calidris alba), and Laughing Gulls (Leucophaeus atricilla) were rarely infected, but dynamic changes in antibody prevalence differed among species. In Red Knots, declining antibody prevalence over the stopover period suggested AIV exposure prior to arrival at Delaware Bay with limited infection at this site. Antibody prevalence was consistently high in Laughing Gulls and low in Sanderlings. Both viral prevalence and antibody prevalence in Sanderlings varied directly with those in turnstones, suggesting virus spillover to Sanderlings. Results indicate that, although hundreds of thousands of birds concentrate at Delaware Bay during spring, dynamics of AIV infection differ among species, perhaps due to differences in susceptibility, potential for contact with AIV at this site, or prior exposure. Additionally, Ruddy Turnstones possibly act as a local AIV amplifying host rather than a reservoir.

Seasonal Variation In Shorebird Abundance In The State of Rio Grande Do Sul, Southern Brazil

We describe the frequency of occurrence and seasonal variations of shorebirds (Charadriidae and Scolopacidae) along a 120-km transect of beach between Balneário Pinhal and Mostardas north of Lagoa do Peixe National Park, Rio Grande do Sul State over a 2-year period (Oct 2007 to Sep 2009). A total of 96,889 shorebirds was recorded. The greatest abundance occurred between October and April and the lowest occurred between May and September. The most abundant of the 17 species recorded were Sanderlings (Calidris alba), White-rumped Sandpipers (C. fuscicollis), and Red Knots (C. canutus). The least abundant were Semipalmated Sandpipers (C. pusilla), Rufous-chested Plovers (Charadrius modestus), and Hudsonian Godwits (Limosa haemastica). Fourteen species were migrants from the Northern Hemisphere, one was a migrant from the Southern Hemisphere, and two were residents. Nine species were recorded regularly, two were recorded sporadically, and six were recorded occasionally. Six Nearctic species were recorded in June and July most likely indicating the presence of non-breeding immatures. The beaches of Rio Grande do Sul are important migration stopover and wintering sites for many shorebirds in southern Brazil and should be a focus of conservation efforts, especially given the increasing development pressure that threatens these areas.

Phenotypic compromises in a long‐distance migrant during the transition from migration to reproduction in the High Arctic

Summary1. Seasonal carry‐over effects may be important structuring components of avian life‐history cycles. However, little is known on physiological transitions between stages and on phenotypic compromises that may be made at such time to improve fitness.2. We studied postmigratory body remodelling in red knots (Calidris canutus islandica) arriving on the Arctic breeding grounds. Our objectives were to determine the effects of body reconstruction and preparation for breeding on maintenance energy costs and to determine whether weather conditions can force compromises between functions required for postmigration recovery of body composition, thermoregulation and breeding.3. During two consecutive springs at the northernmost land on Earth (Alert, Ellesmere Island, Canada, 82°30′N), we monitored changes in knots post‐arrival body stores. Using ultrasonography, we also tracked changes in gizzard size, an indicator of gut size, and pectoral muscle thickness, not only an endogenous protein source but also a thermogenic organ. We measured basal metabolic rate (BMR) throughout reconstruction and compared it with BMR of nonbreeding red knots wintering in the Dutch Wadden Sea.4. Arriving knots faced temperatures up to 13 °C lower than during midwinter. Birds arrived with large body stores and pectoral muscles, which declined in size while they grew their gizzard and prepared for breeding. BMR at arrival was indistinguishable from winter BMR and increased linearly throughout reconstruction. BMR increased up to 69% faster in females than males, likely due to the development of their reproductive organs.5. Birds had lower body stores but larger muscles in the colder year, and muscle loss was correlated with the warming of spring temperatures. Therefore, muscles would not only serve as a nutrient source, but their thermogenic function could also provide the flexibility to cope with high thermostatic costs in the spring. However, retaining muscles for shivering may limit protein recirculation and delay the onset of breeding.6. Postmigratory recovery therefore involves significant energy costs and arriving birds likely have to make physiological compromises, depending on spring conditions, which may impact on fitness. Although this period is clearly critical in the life cycle of red knots, it is one of the least understood life‐history stages in Arctic‐breeding shorebirds.

Small-scale demographic structure suggests preemptive behavior in a flocking shorebird

Under the ideal-free distribution, omniscient individuals with similar habitat requirements that are free to move should be distributed such that no individual can improve fitness by changing sites; deviations would indicate trade-offs and constraints on ranging behavior. We studied site occupancy and annual survival in red knots Calidris c. canutus at their main wintering area Banc d’Arguin, Mauritania. We collected mark-resighting data at 2 high-tide roosts (A and B) that were only 3 km apart and within sight. Birds were faithful to their roosts and foraged in nearby intertidal areas, with no overlap between birds from A and B. Shellfish-rich seagrass beds were of greater abundance for birds roosting at A than at B. During 8 winters, we found different sex ratios (48% and 58% males at A and B, respectively) and different proportion of juveniles (22% and 45%) at the 2 roosts. Adult annual survival was higher at A (0.83±0.01 standard error [SE]) than at B (0.81±0.03). Though rare, between winter season movements were 3 times more frequent from B to A than vice versa, indicating that knots can assess the differences in site quality: birds behaved as if they were “ideal”. As larger females and older birds occurred more at A, differences in competitive ability might maintain the site occupancy pattern. As females return from the high Arctic breeding grounds first, and adults return before juveniles, priority of occupancy may also play a role. Such an advantage of arriving earlier would represent a seasonal carryover effect.

Using a shore bird (red knot) fitted with geolocators to evaluate a conceptual risk model focusing on offshore wind

With a worldwide increase in energy needs, many countries are increasing their development of renewable sources, such as wind and solar. We examined possible risk to a migrating and wintering shorebird (red knots Calidris canutus rufa) along the Atlantic Coast of the United States by developing a conceptual model of assessment endpoints, stressors, exposure, and effects characterization, and testing the applicability of knots fitted with geolocators to provide data for salient aspects of exposure and risk for coastal and offshore development. Birds were fitted with geolocators in Delaware Bay (New Jersey) and Monomoy Refuge (Massachusetts) in 2009, and recaptured at the same locations in 2010. The knots recaptured in Delaware Bay were long-distance migrants that spent less time along the Atlantic Coast (<7%, N=3), while the knots recaptured in Monomoy spent over half of the year migrating, at stopovers, and wintering along the Atlantic Coast (>60%, N=6 with one-year cycle). The continuous record of geolocators provides useful data for a risk evaluation about: (1) high use areas for this shorebird (2) migration, staging and wintering areas, (3) possible foraging times while at stopovers, (4) synchrony of arrival and departure times, (5) weight or condition following a yearly cycle, and (6) direction of movements over the Atlantic Outer Continental Shelf (AOCS), a potential risk consideration with respect to offshore wind development. All knots crossed the AOCS at least twice during long-distance flights, and more often on shorter flights. The knots captured at Monomoy spent over 60% of their cycle while migrating, at stopovers, and while wintering along the Atlantic coast, suggesting the importance of this region to conservation of knots.

Highly pathogenic avian influenza virus H5N1 infection in a long-distance migrant shorebird under migratory and non-migratory states.

Corticosterone regulates physiological changes preparing wild birds for migration. It also modulates the immune system and may lead to increased susceptibility to infection, with implications for the spread of pathogens, including highly pathogenic avian influenza virus (HPAIV) H5N1. The red knot (Calidris canutus islandica) displays migratory changes in captivity and was used as a model to assess the effect of high plasma concentration of corticosterone on HPAIV H5N1 infection. We inoculated knots during pre-migration (N = 6), fueling (N = 5), migration (N = 9) and post-migration periods (N = 6). Knots from all groups shed similar viral titers for up to 5 days post-inoculation (dpi), peaking at 1 to 3 dpi. Lesions of acute encephalitis, associated with virus replication in neurons, were seen in 1 to 2 knots per group, leading to neurological disease and death at 5 to 11 dpi. Therefore, the risk of HPAIV H5N1 infection in wild birds and of potential transmission between wild birds and poultry may be similar at different times of the year, irrespective of wild birds' migratory status. However, in knots inoculated during the migration period, viral shedding levels positively correlated with pre-inoculation plasma concentration of corticosterone. Of these, knots that did not become productively infected had lower plasma concentration of corticosterone. Conversely, elevated plasma concentration of corticosterone did not result in an increased probability to develop clinical disease. These results suggest that birds with elevated plasma concentration of corticosterone at the time of migration (ready to migrate) may be more susceptible to acquisition of infection and shed higher viral titers—before the onset of clinical disease—than birds with low concentration of corticosterone (not ready for take-off). Yet, they may not be more prone to the development of clinical disease. Therefore, assuming no effect of sub-clinical infection on the likelihood of migratory take-off, this may favor the spread of HPAIV H5N1 by migratory birds over long distances.

Tangled up in knots: An emotional ecology of field science

Over the past 20 years, wildlife biologists, birders (bird watchers), and environmental activists have converged on the Delaware Bay, New Jersey USA every spring to study a migratory shorebird called the red knot (Calidris canutus rufa). Linked intimately with the spring-time landscape of the Bay and dependent on another species, the horseshoe crab (Limulus polyphemus), for survival, the population of this bird has declined precipitously with the advent of a horseshoe crab fishery in the eastern U.S. – a situation studied extensively by state biologists. Following the work of Lorraine Daston and Kay Milton on moral economies and ecologies of emotion, respectively, this article takes these studies as its central concern, showing the constitutive role of emotion in the generation of environmental knowledge. I describe field sites on the Delaware Bay as spaces where human and nonhuman actors create an "ecology of emotion" that serves to cohere social groups and motivate actions. These actions, however, move scientists from research sites on the bay into public decision-making fora, requiring the translation and obfuscation of the values underpinning their work into forms socially acceptable in bureaucratic contexts. I suggest, therefore, that the selective filtering of emotion and value in such contextual shifts impoverishes the quality of public environmental discourse and policy.

Functional ecology of saltglands in shorebirds: flexible responses to variable environmental conditions

Summary1. Birds of marine environments have specialized glands to excrete salt, the saltglands. Located on the skull between the eyes, the size of these organs is expected to reflect their demand, which will vary with water turnover rates as a function of environmental (heat load, salinity of prey and drinking water) and organismal (energy demand, physiological state) factors. On the basis of inter‐ and intraspecific comparisons of saltgland mass (msg) in 29 species of shorebird (suborder Charadrii) from saline, fresh and mixed water habitats, we assessed the relative roles of organism and environment in determining measured msg species.2. The allometric exponent, scaling dry msg to shorebird total body mass (mb), was significantly higher for coastal marine species (0·88, N = 19) than for nonmarine species (0·43, N = 14). Within the marine species, those ingesting bivalves intact had significantly higher msg than species eating soft‐bodied invertebrates, indicating that seawater contained within the shells added to the salt load.3. In red knots (Calidris canutus), dry msg varied with monthly averaged ambient temperature in a U‐shaped way, with the lowest mass at 12·5 °C. This probably reflects increased energy demand for thermoregulation at low temperatures and elevated respiratory water loss at high temperatures. In fuelling bar‐tailed godwits (Limosa lapponica), dry msg was positively correlated with intestine mass, an indicator of relative food intake rates. These findings suggest once more that saltgland masses vary within species (and presumably individuals) in relation to salt load, that is a function of energy turnover (thermoregulation and fuelling) and evaporative water needs.4. Our results support the notion that msg is strongly influenced by habitat salinity, and also by factors influencing salt load and demand for osmotically free water including ambient temperature, prey type and energy intake rates. Saltglands are evidently highly flexible organs. The small size of saltglands when demands are low suggests that any time costs of adjustment are lower than the costs of maintaining a larger size in this small but essential piece of metabolic machinery.