| susceptibility of the knot (calidris canutus) to plasmodium hermani. | | 1981 | 7299594 |
| impacts of man-made landscape features on numbers of estuarine waterbirds at low tide. | the potential impact of human disturbance on wintering waterbirds using intertidal mudflats was considered by relating their numbers to the presence of nearby footpaths, roads, railroads, and towns. data were obtained for six english estuaries from the wetland bird survey low tide count scheme. counts were undertaken monthly from november to february, and data were available for an average of 2.8 years per estuary for the period 1992-1993 to 1999-2000. count sections and the positions of man-mad ... | 2002 | 12402099 |
| mechanisms promoting higher growth rate in arctic than in temperate shorebirds. | we compared prefledging growth, energy expenditure, and time budgets in the arctic-breeding red knot (calidris canutus) to those in temperate shorebirds, to investigate how arctic chicks achieve a high growth rate despite energetic difficulties associated with precocial development in a cold climate. growth rate of knot chicks was very high compared to other, mainly temperate, shorebirds of their size, but strongly correlated with weather-induced and seasonal variation in availability of inverte ... | 2003 | 12647140 |
| cost-benefit analysis of mollusc eating in a shorebird. i. foraging and processing costs estimated by the doubly labelled water method. | although the energy costs of foraging and food processing in vertebrates may be considerable, they have rarely been quantified separately. here we present estimates for both cost factors based on a series of trials with a shorebird, the red knot calidris canutus, fed natural and artificial prey types under naturalistic but fully controlled indoor aviary conditions. during eight 1-day trials we successfully manipulated the extent to which the five red knots were (1) actively probing and walking ( ... | 2003 | 12939368 |
| cost-benefit analysis of mollusc-eating in a shorebird. ii. optimizing gizzard size in the face of seasonal demands. | aiming to interpret functionally the large variation in gizzard masses of red knots calidris canutus, we experimentally studied how the digestive processing rate is influenced by the size of the gizzard. during their non-breeding season, red knots feed on hard-shelled molluscs, which they ingest whole and crush in their gizzard. in three experiments with captive birds we tested predictions of the hypothesis that gizzard size, via the rate of shell crushing and processing, constrains intake rate ... | 2003 | 12939369 |
| foraging in a tidally structured environment by red knots (calidris canutus): ideal, but not free. | besides the "normal" challenge of obtaining adequate intake rates in a patchy and dangerous world, shorebirds foraging in intertidal habitats face additional environmental hurdles. the tide forces them to commute between a roosting site and feeding grounds, twice a day. moreover, because intertidal food patches are not all available at the same time, shorebirds should follow itineraries along the best patches available at a given time. finally, shorebirds need additional energy stores in order t ... | 2006 | 16761598 |
| shellfish dredging pushes a flexible avian top predator out of a marine protected area. | there is a widespread concern about the direct and indirect effects of industrial fisheries; this concern is particularly pertinent for so-called "marine protected areas" (mpas), which should be safeguarded by national and international law. the intertidal flats of the dutch wadden sea are a state nature monument and are protected under the ramsar convention and the european union's habitat and birds directives. until 2004, the dutch government granted permission for ~75% of the intertidal flats ... | 2006 | 17105350 |
| long flights do not influence immune responses of a long-distance migrant bird: a wind-tunnel experiment. | heavy physical work can result in physiological stress and suppressed immune function. accordingly, long-distance migrant birds that fly for thousands of km within days can be expected to show immunosuppression, and hence be more vulnerable to infections en route. the red knot calidris canutus linnaeus is a long-distance migrant shorebird. we flew red knots the equivalent of 1500 km over 6 days in a wind tunnel. the humoral and cell-mediated immune responses of the flyers were compared to those ... | 2007 | 17371911 |
| exposure of red knots (calidris canutus rufa) to select avian pathogens; patagonia, argentina. | as part of the shorebird surveillance, red knots (calidris canutus rufa) were sampled in two patagonian sites in argentina, río grande and san antonio oeste, during 2005-2006. cloacal swabs and serum samples were collected from 156 birds and tested by virus isolation (newcastle disease virus), polymerase chain reaction (pcr; avian influenza virus and plasmodium/hemoproteus), and for antibodies to st. louis encephalitis virus. all test results were negative. | 2007 | 17984283 |
| constitutive immune function responds more slowly to handling stress than corticosterone in a shorebird. | ecological immunologists are interested in how immune function changes during different seasons and under different environmental conditions. however, an obstacle to answering such questions is discerning the effects of biological factors of interest and investigation artifacts such as handling stress. here we examined handling stress and its effects on constitutive (noninduced) immune function via two protocols on captive red knots (calidris canutus). we investigated how constitutive immunity r ... | 2008 | 18752420 |
| seasonal redistribution of immune function in a migrant shorebird: annual-cycle effects override adjustments to thermal regime. | throughout the annual cycle, demands on competing physiological systems change, and animals must allocate resources to maximize fitness. immune function is one such system and is important for survival. yet detailed empirical data tracking immune function over the entire annual cycle are lacking for most wild animals. we measured constitutive immune indices once a month for a year on captive red knots (calidris canutus). we also examined temperature as an environmental contributor to immune vari ... | 2008 | 18999941 |
| hormonal correlates and thermoregulatory consequences of molting on metabolic rate in a northerly wintering shorebird. | even though molt involves both endocrine and energetic changes in bird bodies, this study is among the first to combine assessments of energy costs together with thyroid hormone variations in molting birds. individual shorebirds (red knots calidris canutus islandica) were measured while in full summer and winter plumage as well as during peak of molt. molt was associated with a 9.8% increase in average mass-independent basal metabolic rate (bmr) above nonmolting levels. individual plasma levels ... | 2009 | 19199554 |
| no evidence for melatonin-linked immunoenhancement over the annual cycle of an avian species. | the winter immunoenhancement hypothesis associates long nights and increased exposure to melatonin with enhanced immune function in winter when resource availability is low and the chances of becoming ill are high. thus, increased exposure to melatonin in the winter could be adaptive for species facing difficult winter conditions. this idea has found some support in studies of resident mammals. in birds, the link between day length and melatonin over the annual cycle is weaker, and contributions ... | 2009 | 19234709 |
| landscape-scale experiment demonstrates that wadden sea intertidal flats are used to capacity by molluscivore migrant shorebirds. | 1. whether intertidal areas are used to capacity by shorebirds can best be answered by large-scale manipulation of foraging areas. the recent overexploitation of benthic resources in the western dutch wadden sea offers such an 'experimental' setting. 2. we review the effects of declining food abundances on red knot calidris canutus islandica numbers, based on a yearly large-scale benthic mapping effort, long-term colour-ringing and regular bird-counts from 1996 to 2005. we focus on the three-way ... | 2009 | 19490380 |
| surveillance for highly pathogenic avian influenza in migratory shorebirds at the terminus of the east asian-australasian flyway. | to determine if migratory birds arriving in new zealand in the southern hemisphere spring of 2004 were infected with the highly pathogenic avian influenza (ai) virus, h5n1. | 2009 | 19521465 |
| how well do food distributions predict spatial distributions of shorebirds with different degrees of self-organization? | 1. habitat selection models usually assume that the spatial distributions of animals depend positively on the distributions of resources and negatively on interference. however, the presence of conspecifics at a given location also signals safety and the availability of resources. this may induce followers to select contiguous patches and causes animals to cluster. resource availability, interference and attraction therefore jointly lead to self-organized patterns in foraging animals. 2. we anal ... | 2010 | 20337758 |
| 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 kn ... | 2011 | 22132150 |
| intestinal microbiota and species diversity of campylobacter and helicobacter spp. in migrating shorebirds in delaware bay. | using 16s rrna gene sequencing analysis, we examined the bacterial diversity and the presence of opportunistic bacterial pathogens (i.e., campylobacter and helicobacter) in red knot (calidris canutus; n = 40), ruddy turnstone (arenaria interpres; n = 35), and semipalmated sandpiper (calidris pusilla; n = 22) fecal samples collected during a migratory stopover in delaware bay. additionally, we studied the occurrence of campylobacter spp., enterococci, and waterfowl fecal source markers using quan ... | 2014 | 24413599 |
| enterococcus species diversity in fecal samples of wild marine species as determined by real-time pcr. | analyses using culture-independent molecular techniques have improved our understanding of microbial composition. the aim of this work was to identify and quantify enterococci in fecal samples of wild marine species using real-time quantitative pcr. seven enterococcus species were examined in fecal dna of south american fur seals (arctocephalus australis), subantarctic fur seals (arctocephalus tropicalis), green turtles (chelonia mydas), magellanic penguins (spheniscus magellanicus), snowy-crown ... | 2017 | 27991828 |
| declines in migrant shorebird populations from a winter-quarter perspective. | many long-distance migrating shorebird (i.e., sandpipers, plovers, flamingos, oystercatchers) populations are declining. although regular shorebird monitoring programs exist worldwide, most estimates of shorebird population trends and sizes are poor or nonexistent. we built a state-space model to estimate shorebird population trends. compared with more commonly used methods of trend estimation, state-space models are more mechanistic, allow for the separation of observation and state process, an ... | 2015 | 25858334 |
| surveillance of charadriiformes in northern australia shows species variations in exposure to avian influenza virus and suggests negligible virus prevalence. | the virologic surveillance of 4248 charadriiformes since 1992 primarily from coastal northwest australia did not detect any evidence of avian influenza virus (aiv) excretion (test prevalence = 0%; 95% confidence interval [ci]: 0%-0.09%). past exposure to aiv was evident from serologic testing using nucleoprotein (np) competitive-elisa (c-elisa) with an overall seroprevalence of 8.8% (95% ci: 8%-9.7%). the c-elisa seroprevalence of family scolopacidae and genus numenius was significantly higher w ... | 2014 | 25055621 |
| 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 ... | 2012 | 22493108 |
| variation in the innate and acquired arms of the immune system among five shorebird species. | to contribute to an understanding of the evolutionary processes that shape variation in immune responses, we compared several components of the innate and acquired arms of the immune system in five related, but ecologically diverse, migratory shorebirds (ruff philomachus pugnax l., ruddy turnstone arenaria interpres l., bar-tailed godwit limosa lapponica l., sanderling calidris alba pallas and red knot c. canutus l.). we used a hemolysis-hemagglutination assay in free-living shorebirds to assess ... | 2006 | 16391350 |
| shorebird community variations indicative of a general perturbation in the mont-saint-michel bay (france). | the mont-saint-michel bay located on the east atlantic flyway is the first site in france for wintering shorebirds, with, on average, 53,000 individuals in january. seven species represent 96% of that community: dunlin (calidris alpina), knot (calidris canutus), oystercatcher (haematopus ostralegus), curlew (numenius arquata), grey plover (pluvialis squatarola), bar-tailed godwit (limosa lapponica) and black-tailed godwit (limosa limosa). the international bird census organised by wetlands inter ... | 2003 | 14558463 |
| short-term effects of reclamation of part of seal sands, teesmouth, on wintering waders and shelduck : i. shorebird diets, invertebrate densities, and the impact of predation on the invertebrates. | the invertebrate macrofauna of seal sands, teesmouth, is very limited in species composition. nereis diversicolor has a two-year life cycle; the larger size-class provides the main prey of the birds pluvialis squatarola, numenius arquata and limosa lapponica. hydrobia ulvae is an important food of p. squatarola and calidris canutus. small carcinus maenas occur in late autumn and are taken by the larger shorebirds. small macoma balthica are also taken, but are scarce and not an important bird foo ... | 1979 | 28308862 |
| stakeholder contributions to assessment, monitoring, and conservation of threatened species: black skimmer and red knot as case studies. | stakeholder contributions to conservation projects often occur during the problem formulation stage, yet the role of stakeholders throughout the process is seldom considered. we examine the diversity of state and federal agencies, conservation organizations, other non-governmental organizations, environmental justice communities, consultants, industry, and the general public in the conservation of red knot (calidris canutus rufa) and black skimmer (rynchops niger) in new jersey. we suggest that ... | 2017 | 28097613 |
| diversity of mhc class i alleles in spheniscus humboldti. | the major histocompatibility complex locus (mhc) is a gene region related to immune response and exhibits a remarkably great diversity. we deduced that polymorphisms in mhc genes would help to solve several issues on penguins, including classification, phylogenetic relationship, and conservation. this study aimed to elucidate the structure and diversity of the so far unknown mhc class i gene in a penguin species. the structure of an mhc class i gene from the humboldt penguin (spheniscus humboldt ... | 2017 | 27654451 |
| seasonal time keeping in a long-distance migrating shorebird. | because of the complications in achieving the necessary long-term observations and experiments, the nature and adaptive value of seasonal time-keeping mechanisms in long-lived organisms remain understudied. here we present the results of a 20-year-long study of the repeated seasonal changes in body mass, plumage state, and primary molt of 45 captive red knots calidris canutus islandica, a high arctic breeding shorebird that spends the nonbreeding season in temperate coastal areas. birds kept out ... | 2016 | 27466352 |
| diet preferences as the cause of individual differences rather than the consequence. | behavioural variation within a species is usually explained as the consequence of individual variation in physiology. however, new evidence suggests that the arrow of causality may well be in the reverse direction: behaviours such as diet preferences cause the differences in physiological and morphological traits. recently, diet preferences were proposed to underlie consistent differences in digestive organ mass and movement patterns (patch residence times) in red knots (calidris canutus islandi ... | 2016 | 27306138 |
| body shrinkage due to arctic warming reduces red knot fitness in tropical wintering range. | reductions in body size are increasingly being identified as a response to climate warming. here we present evidence for a case of such body shrinkage, potentially due to malnutrition in early life. we show that an avian long-distance migrant (red knot, calidris canutus canutus), which is experiencing globally unrivaled warming rates at its high-arctic breeding grounds, produces smaller offspring with shorter bills during summers with early snowmelt. this has consequences half a world away at th ... | 2016 | 27174985 |
| understanding spatial distributions: negative density-dependence in prey causes predators to trade-off prey quantity with quality. | negative density-dependence is generally studied within a single trophic level, thereby neglecting its effect on higher trophic levels. the 'functional response' couples a predator's intake rate to prey density. most widespread is a type ii functional response, where intake rate increases asymptotically with prey density; this predicts the highest predator densities at the highest prey densities. in one of the most stringent tests of this generality to date, we measured density and quality of bi ... | 2016 | 27053747 |
| validating the incorporation of 13c and 15n in a shorebird that consumes an isotopically distinct chemosymbiotic bivalve. | the wealth of field studies using stable isotopes to make inferences about animal diets require controlled validation experiments to make proper interpretations. despite several pleas in the literature for such experiments, validation studies are still lagging behind, notably in consumers dwelling in chemosynthesis-based ecosystems. in this paper we present such a validation experiment for the incorporation of 13c and 15n in the blood plasma of a medium-sized shorebird, the red knot (calidris ca ... | 2015 | 26458005 |
| natural selection by pulsed predation: survival of the thickest. | selective predation can lead to natural selection in prey populations and may alleviate competition among surviving individuals. the processes of selection and competition can have substantial effects on prey population dynamics, but are rarely studied simultaneously. moreover, field studies of predator-induced short-term selection pressures on prey populations are scarce. here we report measurements of density dependence in body composition in a bivalve prey (edible cockle, cerastoderma edule) ... | 2015 | 26378316 |
| the effect of digestive capacity on the intake rate of toxic and non-toxic prey in an ecological context. | digestive capacity often limits food intake rate in animals. many species can flexibly adjust digestive organ mass, enabling them to increase intake rate in times of increased energy requirement and/or scarcity of high-quality prey. however, some prey species are defended by secondary compounds, thereby forcing a toxin limitation on the forager's intake rate, a constraint that potentially cannot be alleviated by enlarging digestive capacity. hence, physiological flexibility may have a differenti ... | 2015 | 26287951 |
| how salinity and temperature combine to affect physiological state and performance in red knots with contrasting non-breeding environments. | migratory shorebirds inhabit environments that may yield contrasting salinity-temperature regimes-with widely varying osmoregulatory demands, even within a given species-and the question is: by which physiological means and at which organisational level do they show adjustments with respect to these demands? red knots calidris canutus winter in coastal areas over a range of latitudes. the nominal subspecies winters in salty areas in the tropics, whereas the subspecies calidris canutus islandica ... | 2015 | 25851406 |
| complexity of bioindicator selection for ecological, human, and cultural health: chinook salmon and red knot as case studies. | there is considerable interest in developing bioindicators of ecological health that are also useful indicators for human health. yet, human health assessment usually encompasses physical/chemical exposures and not cultural well-being. in this paper, we propose that bioindicators can be selected for all three purposes. we use chinook or king salmon (oncorhynchus tshawytscha) and red knot (calidris canutus rufa, a sandpiper) as examples of indicators that can be used to assess human, ecological, ... | 2015 | 25666646 |
| moving on with foraging theory: incorporating movement decisions into the functional response of a gregarious shorebird. | models relating intake rate to food abundance and competitor density (generalized functional response models) can predict forager distributions and movements between patches, but we lack understanding of how distributions and small-scale movements by the foragers themselves affect intake rates. using a state-of-the-art approach based on continuous-time markov chain dynamics, we add realism to classic functional response models by acknowledging that the chances to encounter food and competitors a ... | 2015 | 25283546 |
| benefits of foraging in small groups: an experimental study on public information use in red knots calidris canutus. | social foraging is common and may provide benefits of safety and public information. public information permits faster and more accurate estimates of patch resource densities, thus allowing more effective foraging. in this paper we report on two experiments with red knots calidris canutus, socially foraging shorebirds that eat bivalves on intertidal mudflats. the first experiment was designed to show that red knots are capable of using public information, and whether dominance status or sex affe ... | 2015 | 25218106 |
| avian influenza virus antibodies in pacific coast red knots (calidris canutus roselaari). | prevalence of avian influenza virus (aiv) antibodies in the western atlantic subspecies of red knot (calidris canutus rufa) is among the highest for any shorebird. to assess whether the frequency of detection of aiv antibodies is high for the species in general or restricted only to c. c. rufa, we sampled the northeastern pacific coast subspecies of red knot (calidris canutus roselaari) breeding in northwestern alaska. antibodies were detected in 90% of adults and none of the chicks sampled. vir ... | 2014 | 24807362 |
| digestive capacity and toxicity cause mixed diets in red knots that maximize energy intake rate. | among energy-maximizing animals, preferences for different prey can be explained by ranking the prey according to their energetic content. however, diet choice also depends on characteristics of the predator, such as the need to ingest necessary nutrients and the constraints imposed by digestion and toxins in food. in combination, these factors can lead to mixed diets in which the energetically most profitable food is not eaten exclusively even when it is abundant. we studied diet choice in red ... | 2014 | 24739197 |
| personality drives physiological adjustments and is not related to survival. | the evolutionary function and maintenance of variation in animal personality is still under debate. variation in the size of metabolic organs has recently been suggested to cause and maintain variation in personality. here, we examine two main underlying notions: (i) that organ sizes vary consistently between individuals and cause consistent behavioural patterns, and (ii) that a more exploratory personality is associated with reduced survival. exploratory behaviour of captive red knots (calidris ... | 2014 | 24671971 |
| domesticating nature? surveillance and conservation of migratory shorebirds in the "atlantic flyway". | using a recent environmental controversy on the u.s. east coast over the conservation of red knots (calidris canutus rufa) as a lens, i present a history of north american efforts to understand and conserve migratory shorebirds. focusing on a few signal pieces of american legislation and their associated bureaucracies, i show the ways in which migratory wildlife have been thoroughly enrolled in efforts to quantify and protect their populations. interactions between wildlife biologists and endang ... | 2014 | 24268929 |
| economic design in a long-distance migrating molluscivore: how fast-fuelling red knots in bohai bay, china, get away with small gizzards. | we carried out an observational and experimental study to decipher how resource characteristics, in interaction with the predator's phenotype, constrain a fitness-determining performance measure, i.e. refuelling in a migrant bird. two subspecies of red knot (calidris canutus rogersi and c. c. piersmai) use northern bohai bay, yellow sea, china, for the final prebreeding stopover, during their 10,000-15,000 km long migrations between wintering and breeding areas. here, they feed on small bivalves ... | 2013 | 24006345 |
| [temporal and spatial distribution of shorebirds (charadriiformes) at san ignacio lagoon, baja california sur, mexico]. | baja california peninsula has several wetlands that represent important ecosystems for shorebirds. san ignacio lagoon is one of these sites, and supports 10% of the total abundance of shorebirds reported in this peninsula. since there is few information about this group in this area, we studied spatial and temporal changes in abundance and distribution of shorebirds in san ignacio lagoon. for this, we conducted twelve monthly censuses (october 2007-september 2008) on the entire internal perimete ... | 2013 | 23894976 |
| toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird. | recent insights suggest that predators should include (mildly) toxic prey when non-toxic food is scarce. however, the assumption that toxic prey is energetically as profitable as non-toxic prey misses the possibility that non-toxic prey have other ways to avoid being eaten, such as the formation of an indigestible armature. in that case, predators face a trade-off between avoiding toxins and minimizing indigestible ballast intake. here, we report on the trophic interactions between a shorebird ( ... | 2013 | 23740782 |
| unusual patterns in ¹⁵n blood values after a diet switch in red knot shorebirds. | when a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. this change is generally best described by an exponential decay curve. indeed, after a diet switch in captive red knot shorebirds (calidris canutus islandica), the depletion of (13)c in both blood cells and plasma followed an exponential decay curve. surprisingly, the diet switch with a dietary (15)n/(14)n ratio (δ(15)n) change from 11.4 to 8 ... | 2013 | 23656233 |
| three-phase fuel deposition in a long-distance migrant, the red knot (calidris canutus piersmai), before the flight to high arctic breeding grounds. | refuelling by migratory birds before take-off on long flights is generally considered a two-phase process, with protein accumulation preceding rapid fat deposition. the first phase expresses the demands for a large digestive system for nutrient storage after shrinkage during previous flights, the second phase the demands for fat stores to fuel the subsequent flight. at the last staging site in northward migration, this process may include expression of selection pressures both en route to and af ... | 2013 | 23638114 |
| when the seasons don't fit: speedy molt as a routine carry-over cost of reproduction. | the failure of animals to fit all life-cycle stages into an annual cycle could reduce the chances of successful breeding. in some cases, non-optimal strategies will be adopted in order to maintain the life-cycle within the scope of one year. we studied trade-offs made by a high arctic migrant shorebird, the red knot calidris canutus islandica, between reproduction and wing feather molt carried out in the non-breeding period in the dutch wadden sea. we compared primary molt duration between birds ... | 2013 | 23349758 |
| characterization of mhc class i in a long-distance migrant shorebird suggests multiple transcribed genes and intergenic recombination. | the major histocompatibility complex (mhc) includes highly polymorphic gene families encoding proteins crucial to the vertebrate acquired immune system. classical mhc class i (mhci) genes code for molecules expressed on the surfaces of most nucleated cells and are associated with defense against intracellular pathogens, such as viruses. these genes have been studied in a few wild bird species, but have not been studied in long-distance migrating shorebirds. red knots calidris canutus are medium- ... | 2013 | 23239370 |
| 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 carb ... | 2012 | 23001427 |
| health status of seabirds and coastal birds found at the german north sea coast. | systematic 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. | 2012 | 22812640 |
| 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 exclosure ... | 2012 | 22764500 |
| 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 ma ... | 2012 | 22686517 |
| disentangling the roles of frequency-vs. state-dependence in generating individual differences in behavioural plasticity. | theoretical work suggests that both negative frequency-dependent payoffs and state-dependent payoffs can lead to individual variation in behavioural plasticity. we investigated the roles of both frequency- and state-dependence on the occurrence of individual variation in behavioural plasticity in a series of experiments where we manipulated perceived predation danger for red knots (calidris canutus islandica). we found individual variation in plasticity in a trait with negative frequency-depende ... | 2011 | 21978266 |
| shorebirds' seasonal adjustments in thermogenic capacity are reflected by changes in body mass: how preprogrammed and instantaneous acclimation work together. | phenotypic flexibility in shorebirds has been studied mainly in the context of adjustments to migration and to quality of food; little is known on how birds adjust their phenotype to harsh winter conditions. we showed earlier that red knot (calidris canutus islandica) can acclimate to cold by elevating body mass. this goes together with larger pectoral muscles, i.e., greater shivering machinery, and thus, better thermogenic capacity. here, we present results of a yearlong experiment with indoor ... | 2011 | 21700573 |
| how do migratory species stay healthy over the annual cycle? a conceptual model for immune function and for resistance to disease. | migration has fascinated researchers for years and many active areas of study exist. however, the question of how migratory species stay healthy within the context of their annual cycle remains relatively unexplored. this article addresses this question using red knots (calidris canutus) as a model migrant species. we review recent research on immune function in red knots and integrate this work with the broader eco-immunological literature to introduce a conceptual model. this model synthesizes ... | 2010 | 21558209 |
| scaling up ideals to freedom: are densities of red knots across western europe consistent with ideal free distribution? | local studies have shown that the distribution of red knots calidris canutus across intertidal mudflats is consistent with the predictions of an ideal distribution, but not a free distribution. here, we scale up the study of feeding distributions to their entire wintering area in western europe. densities of red knots were compared among seven wintering sites in the netherlands, uk and france, where the available mollusc food stocks were also measured and from where diets were known. we tested b ... | 2011 | 21325322 |
| hematologic and plasma biochemistry values for endangered red knots (calidris canutus rufa) at wintering and migratory sites in argentina. | we obtained hematologic and plasma biochemistry values for adult, long-distance migrant red knots at their southernmost wintering site in río grande (tierra del fuego, argentina) and at the first stopover site in san antonio oeste (río negro, argentina). lymphocytes (l) followed by heterophils (h) were the most abundant leukocytes. h/l ratio and glucose levels were significantly higher at río grande, possibly because of the stress of migration and molting. packed cell volume results ranged widel ... | 2010 | 20688666 |
| many routes lead to rome: potential causes for the multi-route migration system of red knots, calidris canutus islandica. | migrants, such as birds or representatives of other taxa, usually make use of several stopover sites to cover the distance between their site of origin and destination. potentially, multiple routes exist, but often little is known about the causes and consequences of alternative migration routes. apart from their geographical distribution, the suitability of potential sites might play an important role in the animals' decisions for a particular itinerary. we used an optimal-migration model to te ... | 2010 | 20583722 |
| ambient temperature does not affect fuelling rate in absence of digestive constraints in long-distance migrant shorebird fuelling up in captivity. | pre-flight fuelling rates in free-living red knots calidris canutus, a specialized long-distance migrating shorebird species, are positively correlated with latitude and negatively with temperature. the single published hypothesis to explain these relationships is the heat load hypothesis that states that in warm climates red knots may overheat during fuelling. to limit endogenous heat production (measurable as basal metabolic rate bmr), birds would minimize the growth of digestive organs at a t ... | 2010 | 20339851 |
| stochastic atmospheric assistance and the use of emergency staging sites by migrants. | numerous animals move vast distances through media with stochastic dynamic properties. avian migrants must cope with variable wind speeds and directions en route, which potentially jeopardize fine-tuned migration routes and itineraries. we show how unpredictable winds affect flight times and the use of an intermediate staging site by red knots (calidris canutus canutus) migrating from west africa to the central north siberian breeding areas via the german wadden sea. a dynamic migration model in ... | 2010 | 20071381 |
| diet selection in a molluscivore shorebird across western europe: does it show short- or long-term intake rate-maximization? | 1. studies of diet choice usually assume maximization of energy intake. the well-known 'contingency model' (cm) additionally assumes that foraging animals only spend time searching or handling prey. despite considerable empirical support, there are many foraging contexts in which the cm fails, but such cases were considered exceptions rather than the rule. 2. for animals constrained by the rate at which food is digested, cm does not necessarily lead to maximal energy intake rates because the tim ... | 2010 | 19674177 |
| limited access to food and physiological trade-offs in a long-distance migrant shorebird. i. energy metabolism, behavior, and body-mass regulation. | previous experiments showed reduction of basal metabolic rate (bmr) in birds facing energetic challenges. we alternately exposed two groups of red knots (calidris canutus) to either 6 h or 22 h of food availability for periods of 22 d. six h of access to food led to a 6%-10% loss of body mass over the first 8 d, with nearly all of the birds' daily energy expenditures supported by body nutrient stores during the first 2 d. birds responded by increasing feeding behavior and food intake, but the re ... | 2009 | 19663606 |
| are birds stressed during long-term flights? a wind-tunnel study on circulating corticosterone in the red knot. | during endurance flight most birds do not feed and have to rely on their body reserves. fat and protein is catabolised to meet the high energetic demands. even though the hormonal regulation of migration is complex and not yet fully understood, the adrenocortical hormone corticosterone crystallizes to play a major role in controlling physiological traits in migratory birds during flight. however, results from field studies are partially equivocal, not least because data from birds during enduran ... | 2013 | 19481083 |
| vision and touch in relation to foraging and predator detection: insightful contrasts between a plover and a sandpiper. | visual fields were determined in two species of shorebirds (charadriiformes) whose foraging is guided primarily by different sources of information: red knots (calidris canutus, tactile foragers) and european golden plovers (pluvialis apricaria, visual foragers). the visual fields of both species showed features that are found in a wide range of birds whose foraging involves precision pecking or lunging at food items. surprisingly, red knots did not show comprehensive panoramic vision as found i ... | 2009 | 18842546 |
| travelling on a budget: predictions and ecological evidence for bottlenecks in the annual cycle of long-distance migrants. | long-distance migration, and the study of the migrants who undertake these journeys, has fascinated generations of biologists. however, many aspects of the annual cycles of these migrants remain a mystery as do many of the driving forces behind the evolution and maintenance of the migrations themselves. in this article we discuss nutritional, energetic, temporal and disease-risk bottlenecks in the annual cycle of long-distance migrants, taking a sandpiper, the red knot calidris canutus, as a foc ... | 2008 | 17638692 |
| expression of annual cycles in preen wax composition in red knots: constraints on the changing phenotype. | birds living in seasonal environments change physiology and behavior in correspondence to temporally changing environmental supplies, demands and opportunities. we recently reported that the chemical composition of uropygial gland secretions of sandpipers (scolopacidae, order charadriformes) changes during the breeding season from mixtures of monoesters to diesters, which fulfill specific functions related to incubation. a proper temporal match between the expression of diester preen waxes and i ... | 2007 | 17397066 |
| alterations in tissue aerobic capacity may play a role in premigratory fattening in shorebirds. | migratory shorebirds show regulated seasonal increases in body mass (bm) even in captivity, consisting primarily, but not exclusively, of fat. we examined whether captive red knot (calidris canutus) exhibited seasonal alterations in mitochondrial volume (liver, pectoral muscle) and/or succinate dehydrogenase (sdh) activity (liver, pectoral muscle, heart, small intestine) during three distinct life-cycle stages: stable bm, spring peak in bm, and as bm rapidly declined after the spring peak. mitoc ... | 2005 | 17148139 |
| thermogenic side effects to migratory predisposition in shorebirds. | in the calidrine sandpiper red knot (calidris canutus), the weeks preceding takeoff for long-distance migration are characterized by a rapid increase in body mass, largely made up of fat but also including a significant proportion of lean tissue. before takeoff, the pectoral muscles are known to hypertrophy in preparation for endurance flight without any specific training. because birds facing cold environments counterbalance heat loss through shivering thermogenesis, and since pectoral muscles ... | 2007 | 17138724 |
| acclimation to different thermal conditions in a northerly wintering shorebird is driven by body mass-related changes in organ size. | seasonal acclimatization and experimental acclimation to cold in birds typically results from increased shivering endurance and elevated thermogenic capacity leading to improved resistance to cold. a wide array of physiological adjustments, ranging from biochemical transformations to organ mass variations, are involved in this process. several studies have shown that improved cold endurance is accompanied by increases in summit metabolic rate (m(sum)), a measure of maximal heat production and an ... | 2006 | 16888062 |
| assessment of the amount of body water in the red knot (calidris canutus): an evaluation of the principle of isotope dilution with 2h, (17)o, and (18)o as measured with laser spectrometry and isotope ratio mass spectrometry. | we have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (red knot, calidris canutus) through an assessment of the amount of body water in it. birds were quantitatively injected with a dose of water with elevated concentrations of 2h, (17)o, and (18)o. thereafter, blood samples were taken and distilled. the resulting water samples were analysed using an isotope ratio mass spectrometry (for 2h and (18)o only) and a stable isotope ratio ... | 2006 | 16500750 |
| plasma metabolites reflect seasonally changing metabolic processes in a long-distance migrant shorebird (calidris canutus). | migrant birds have tightly scheduled annual cycles consisting of several distinct life cycle (sub-)stages such as reproduction, migration, moult and overwintering, each of which have specific metabolic requirements (e.g., fattening during migration, protein build-up during moult). this study examines changes in fat and protein metabolism during the annual cycle of body mass and moult over 1.5 years in a captive flock of an arctic-breeding shorebird, the red knot calidris canutus islandica. 2-5 h ... | 2002 | 16351872 |
| reinterpretation of gizzard sizes of red knots world-wide emphasises overriding importance of prey quality at migratory stopover sites. | the size of digestive organs can be rapidly and reversibly adjusted to ecological circumstances, but such phenotypic flexibility comes at a cost. here, we test how the gizzard mass of a long-distance migrant, the red knot (calidris canutus), is adjusted to (i) local climate, (ii) prey quality and (iii) migratory fuelling demands. for eight sites around the world (both wintering and stopover sites), we assembled data on gizzard masses of free-living red knots, the quality of their prey and the lo ... | 2005 | 16321783 |
| adults and larvae of skrjabinocerca canutus n. sp. (nematoda: acuariidae) from calidris canutus rufa (aves: scolopacidae) on the southern southwest atlantic coast of south america. | adults and larvae of a new species of skrjabinocerca shikhobalova, 1930 (nematoda: acuarioidea) are described on the basis of light and scanning electron microscope studies. specimens were recovered from calidris canutus rufa wilson (aves: scolopacidae) from the southwest atlantic coast of uruguay. data on the hosts, localities and main features of the four previously described species of the genus are provided. s. canutus n. sp. can be distinguished its congeners by a combination of the followi ... | 2005 | 15841348 |
| role of the low-affinity glucocorticoid receptor in the regulation of behavior and energy metabolism in the migratory red knot calidris canutus islandica. | plasma corticosterone increases in association with migratory flight in the red knot calidris canutus islandica, suggesting that corticosterone may promote migratory activity and/or energy mobilization in this species. this hypothesis is supported by general effects of glucocorticoids, which include stimulation of locomotion and the mobilization of energy depots. we experimentally examined the role of elevated corticosterone levels in the migratory red knot by comparing foraging behavior, flight ... | 2013 | 15449237 |
| rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in delaware bay. | most populations of migrant shorebirds around the world are in serious decline, suggesting that vital condition-dependent rates such as fecundity and annual survival are being affected globally. a striking example is the red knot (calidris canutus rufa) population wintering in tierra del fuego, which undertakes marathon 30,000 km hemispheric migrations annually. in spring, migrant birds forage voraciously on horseshoe crab eggs in delaware bay in the eastern usa before departing to breed in arct ... | 2004 | 15255108 |
| characterization of the red knot (calidris canutus) mitochondrial control region. | we sequenced the complete mitochondrial control regions of 11 red knots (calidris canutus). the control region is 1168 bp in length and is flanked by trna glutamate (glu) and the gene nd6 at its 5' end and trna phenylalanine (phe) and the gene 12s on its 3' end. the sequence possesses conserved sequence blocks f, e, d, c, csb-1, and the bird similarity box (bsb), as expected for a mitochondrial copy. flanking trna regions show correct secondary structure, and a relative rate test indicated no si ... | 2003 | 12897864 |
| incompletely informed shorebirds that face a digestive constraint maximize net energy gain when exploiting patches. | foragers that feed on hidden prey are uncertain about the intake rate they can achieve as they enter a patch. however, foraging success can inform them, especially if they have prior knowledge about the patch quality distribution in their environment. we experimentally tested whether and how red knots (calidris canutus) use such information and whether their patch-leaving decisions maximized their long-term net energy intake rate. the results suggest that the birds combined patch sample informat ... | 2003 | 12858284 |
| sandpipers (scolopacidae) switch from monoester to diester preen waxes during courtship and incubation, but why? | recently, a shift in preen wax composition, from lower molecular weight monoesters to higher molecular weight diesters, was described for individuals of a sandpiper species (red knot, calidris canutus) that were about to leave for the tundra breeding grounds. the timing of the shift indicated that diester waxes served as a quality signal during mate choice. here, this hypothesis is evaluated on the basis of a survey of preen wax composition in 19 sandpiper species. all of these species showed th ... | 2002 | 12396488 |
| when a year takes 18 months: evidence for a strong circannual clock in a shorebird. | during the last three of 20 years kept as a pet, a red knot (calidris canutus) went through two complete 'circannual' cycles of body mass and plumage. with a record cycle length of 18 months, this individual shorebird provides evidence for an exceptionally strong circannual clock system. the absence of synchronisation to outdoor but visible periodic cues suggests that the constant, socially-induced, day-night environment was of overriding importance. so far, only for songbirds is there firm expe ... | 2002 | 12146795 |
| fuel use and metabolic response to endurance exercise: a wind tunnel study of a long-distance migrant shorebird. | this study examines fuel use and metabolism in a group of long-distance migrating birds, red knots calidris canutus (scolopacidae), flying under controlled conditions in a wind tunnel for up to 10 h. data are compared with values for resting birds fasting for the same time. plasma levels of free fatty acids, glycerol and uric acid were elevated during flight, irrespective of flight duration (1-10 h). triglyceride levels, the estimated concentration of very-low-density lipoproteins (vldls) and be ... | 2002 | 12124368 |
| an experimental test of the relationship between temporal variability of feeding opportunities and baseline levels of corticosterone in a shorebird. | in this study, we tested the hypothesis that baseline corticosterone levels increase with a change from constant to variable feeding schedules. captive red knots, calidris canutus, were presented with food that was either available during the same time each day (constant) or starting at variable times during the day. food intake rates, frequency of aggressive interactions, and baseline levels of corticosterone were measured. in the majority of cases, red knots showed higher plasma corticosterone ... | 2002 | 12115922 |
| baseline and stress-induced levels of corticosterone during different life cycle substages in a shorebird on the high arctic breeding grounds. | after a migratory flight of several thousand kilometers to their high arctic breeding grounds, red knots (calidris canutus islandica, scolopacidae) showed high baseline concentrations of plasma corticosterone (58 ng/ml). such high baseline corticosterone levels may be conditional for the right behavioral and metabolic adjustments to environmental and social stresses that shorebirds experience on arrival in an unpredictable tundra breeding environment. despite the high baseline levels of corticos ... | 2013 | 12024295 |
| energetic bottlenecks and other design constraints in avian annual cycles. | the flexible phenotypes of birds and mammals often appear to represent adjustments to alleviate some energetic bottleneck or another. by increasing the size of the organs involved in digestion and assimilation of nutrients (gut and liver), an individual bird can increase its ability to process nutrients, for example to quickly store fuel for onward flight. similarly, an increase in the exercise organs (pectoral muscles and heart) enables a bird to increase its metabolic power for sustained fligh ... | 2002 | 21708694 |
| carrying large fuel loads during sustained bird flight is cheaper than expected. | birds on migration alternate between consuming fuel stores during flights and accumulating fuel stores during stopovers. the optimal timing and length of flights and stopovers for successful migration depend heavily on the extra metabolic power input (fuel use) required to carry the fuel stores during flight. the effect of large fuel loads on metabolic power input has never been empirically determined. we measured the total metabolic power input of a long-distance migrant, the red knot (calidris ... | 2001 | 11607031 |
| time course and reversibility of changes in the gizzards of red knots alternately eating hard and soft food. | the ability to change organ size reversibly can be advantageous to birds that perform long migrations. during winter, red knots (calidris canutus) feed on shellfish and carry a muscular gizzard that weighs 10% of their body mass. gizzard size decreases when these birds eat soft foods, e.g. while breeding in the tundra. we studied the reversibility and time course of such changes using ultrasonography. two groups of shellfish-adapted knots (n=9 and n=10) were fed alternately a hard and a soft foo ... | 2001 | 11441058 |
| mercury in bar-tailed godwit (limosa lapponica) and lesser knot (calidris canutus): spatially explicit information from non-breeding birds in new zealand. | | 2001 | 11353371 |
| ingested water equilibrates isotopically with the body water pool of a shorebird with unrivaled water fluxes. | we investigated the applicability of (2)h to measure the amount of body water (tbw) and water fluxes in relation to diet type and level of food intake in a mollusk-eating shorebird, the red knot (calidris canutus). six birds were exposed to eight experimental indoor conditions. average fractional (2)h turnover rates ranged between 0. 182 day(-1) (sd = 0.0219) for fasting birds and 7.759 day(-1) (sd = 0.4535) for birds feeding on cockles (cerastoderma edule). average tbw estimates obtained with t ... | 2000 | 11049863 |
| baseline corticosterone peaks in shorebirds with maximal energy stores for migration: a general preparatory mechanism for rapid behavioral and metabolic transitions? | in captive red knots (calidris canutus, scolopacidae) showing a regulated body mass increase of 50% related to their migration from temperate staging sites to tundra breeding grounds, plasma corticosterone concentrations increased from less than 10 ng. ml(-1) to levels as high as 30 ng. ml(-1) when the energy storage for migration was complete. these birds did not fly, but concentrations dropped to very low levels (<5 ng. ml(-1)) as soon as the birds started their voluntary fasts to the low body ... | 2000 | 11042017 |
| molecular analysis of intact preen waxes of calidris canutus (aves: scolopacidae) by gas chromatography/mass spectrometry. | the intact preen wax esters of the red knot calidris canutus were studied with gas chromatography/mass spectrometry (gc/ms) and gc/ms/ms. in this latter technique, transitions from the molecular ion to fragment ions representing the fatty acid moiety of the wax esters were measured, providing additional resolution to the analysis of wax esters. the c21-c32 wax esters are composed of complex mixtures of hundreds of individual isomers. the odd carbon-numbered wax esters are predominantly composed ... | 2000 | 10907788 |
| structural identification of the diester preen-gland waxes of the red knot (calidris canutus). | the intact c(32)-c(48) diester wax esters of the preen gland of the migrating bird calidris canutus are shown, using synthesized standards, to comprise predominantly c(12)-c(16) alkane-1,2-diols esterified with octanoic, decanoic, and dodecanoic acid at one position, and with predominantly even-numbered carbon fatty acids at the other position. | 2000 | 10757724 |
| avian pectoral muscle size rapidly tracks body mass changes during flight, fasting and fuelling. | we used ultrasonic imaging to monitor short-term changes in the pectoral muscle size of captive red knots calidris canutus. pectoral muscle thickness changed rapidly and consistently in parallel with body mass changes caused by flight, fasting and fuelling. four knots flew repeatedly for 10 h periods in a wind tunnel. over this period, pectoral muscle thickness decreased in parallel with the decrease in body mass. the change in pectoral muscle thickness during flight was indistinguishable from t ... | 2000 | 10667974 |
| body-building without power training: endogenously regulated pectoral muscle hypertrophy in confined shorebirds | shorebirds such as red knots calidris canutus routinely make migratory flights of 3000 km or more. previous studies on this species, based on compositional analyses, suggest extensive pectoral muscle hypertrophy in addition to fat storage before take-off. such hypertrophy could be due to power training and/or be effected by an endogenous circannual rhythm. red knots of two subspecies with contrasting migration patterns were placed in a climate-controlled aviary (12 h:12 h l:d photoperiod) where ... | 1999 | 10504319 |
| rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird. | the adaptive value of size changes in different organ and muscle groups was studied in red knots (calidris canutus islandica) in relation to their migration. birds were sampled on five occasions: at arrival in iceland in may 1994, two times during subsequent refueling, at departure toward, and on return from, the high arctic breeding grounds. during their 24-d stopover in may, body mass increased from 144.3 to 214.5 g. mass gains were lowest over the first week (0.85 g/d, only fat-free tissue de ... | 2008 | 10438678 |
| estimating organ size in small migrating shorebirds with ultrasonography: an intercalibration exercise. | organs, even of fully grown adult birds, mammals, and reptiles, may show substantial size changes in relation to specific performances. these changes are difficult to study, because measurements usually can only be obtained following the death of the animal. we explored the use of ultrasonographic imaging, a relatively simple noninvasive technique, to measure size of pectoral muscles and stomach in two small shorebird species (red knots calidris canutus and golden plovers pluvialis apricaria). a ... | 2016 | 9882600 |
| computer simulation of fat and muscle burn in long-distance bird migration | the mechanical power required from a bird's flight muscles was recalculated at regular intervals (default 6 min), and the energy consumed in the interval was accounted for by reducing fuel reserves, which also reduced the all-up mass and the body cross-sectional area. part of the energy requirement was met by consuming flight muscle tissue, according to one of three alternative "muscle burn criteria". these were (1) specific work held constant, (2) power density held constant and (3) muscle mass ... | 1998 | 9593656 |
| heavy metals and selenium in feathers of three shorebird species from delaware bay. | concentrations of lead, cadmium, mercury, selenium, chromium and manganese were examined in breast feathers of shorebirds migrating north through cape may, new jersey in 1991 and 1992. although we predicted that metal levels would be positively correlated with weight, this was only true for mercury in red knots (calidris canutus). selenium was negatively correlated with weight in red knots. no other significant correlation of metal concentrations with weight were found. lead and mercury were hig ... | 1993 | 24221132 |
| an epizootic among knots (calidris canutus) in florida. i. disease syndrome, histology and transmission studies. | about 150 knots found sick or dead had distention of serosal blood vessels, and small, raised hemorrhagic foci on the serosal surface of the jejunum and ileum. the principal finding was endaortitis with large intimal multinucleated cysts that contained a protozoan parasite within a cytoplasmic vacuole. there was endarteritis of mesenteric arteries and muscular arteries of the external layers of the intestinal tract. single or multiple schizont-like stages containing zoites were in the wall of th ... | 1977 | 883096 |
| an epizootic among knots (calidris canutus) in florida. ii. ultrastructure of the causative agent, a besnoitia-like organism. | multinucleated cysts near the luminal surface of the thoracic aortas of diseased knots (calidris canutus) were similar to besnoitia cysts. ultrastructurally, the cyst had four distinct layers. the central area included a vacuole that contained a sporozoan with a conoid, polar ring, micronemes, rhoptries, nucleus, mitochondria, dense bodies, a lipid-like vacuole and endoplasmic reticulum. external to the vacuole was a layer with organelles typical of vertebrate cells. the wall of the cyst was irr ... | 1977 | 407700 |
| indirect effects of lemming cycles on sandpiper dynamics: 50 years of counts from southern sweden. | the bird-lemming hypothesis postulates that breeding success of tundra-nesting geese and waders in siberia follows the cyclic pattern of lemming populations, as a result of predators switching from lemmings to birds when the lemming population crashes. we present 50 years of data on constant-effort catches of red knot calidris canutus and curlew sandpiper c. ferruginea at an autumn migratory stopover site (ottenby) at the baltic sea, supplemented with literature data on winter censuses of dark-b ... | 2002 | 28547301 |