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Theunis Piersma - One of the best experts on this subject based on the ideXlab platform.
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red knots Calidris canutus islandica manage body mass with dieting and activity
The Journal of Experimental Biology, 2020Co-Authors: Theunis Piersma, Kimberley J Mathot, Anne Dekinga, Eva M A Kok, Piet J Van Den HoutAbstract:ABSTRACT Mass regulation in birds is well documented. For example, birds can increase body mass in response to lower availability and/or predictability of food and decrease body mass in response to increased predation danger. Birds also demonstrate an ability to maintain body mass across a range of food qualities. Although the adaptive significance of mass regulation has received a great deal of theoretical and empirical attention, the mechanisms by which birds achieve this have not. Several non-exclusive mechanisms could facilitate mass regulation in birds. Birds could regulate body mass by adjusting food intake (dieting), activity, baseline energetic requirements (basal metabolic rate), mitochondrial efficiency or assimilation efficiency. Here, we present the results of two experiments in captive red knots (Calidris canutus islandica) that assess three of these proposed mechanisms: dieting, activity and up- and down-regulation of metabolic rate. In the first experiment, knots were exposed to cues of predation risk that led them to exhibit presumably adaptive mass loss. In the second experiment, knots maintained constant body mass despite being fed alternating high- and low-quality diets. In both experiments, regulation of body mass was achieved through a combination of changes in food intake and activity. Both experiments also provide some evidence for a role of metabolic adjustments. Taken together, these two experiments demonstrate that fine-scale management of body mass in knots is achieved through multiple mechanisms acting simultaneously.
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benefits of foraging in small groups an experimental study on public information use in red knots Calidris canutus
Behavioural Processes, 2015Co-Authors: Allert I Bijleveld, Jan A Van Gils, Jeltje Jouta, Theunis PiersmaAbstract: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 affected its use. We showed that knots can detect the foraging success of conspecifics and choose a patch accordingly. Neither dominance status nor sex influenced public information use. In the second experiment, by manipulating group size, we investigated whether public information use affected food-patch discovery rates and patch residence times. We showed that the time needed before locating a food patch decreased in proportion to group size. Also, an individual's number of patch visits before locating the food declined with group size, and, to our surprise, their average patch residence time did as well. Moreover, knots differed in their search strategy in that some birds consistently exploited the searching efforts of others. We conclude that socially foraging knots have the potential to greatly increase their food-finding rate by using public information. This article is part of a Special Issue entitled: In Honor of Jerry Hogan.
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mortality within the annual cycle seasonal survival patterns in afro siberian red knots Calidris canutus canutus
Journal of Ornithology, 2013Co-Authors: Bernard Spaans, Jutta Leyrer, Tamar Lok, Maarten Brugge, Brett K Sandercock, Theunis PiersmaAbstract:Estimates of seasonal mortality for long-distance migrant birds are extremely challenging to collect and consequently reports are scarce. Determining when and where mortality occurs within the annual cycle is important for an understanding of population dynamics and the evolutionary drivers of long-distance migration. We collected data on seasonal survival in a mark–recapture study of colour-marked Red Knots Calidris canutus canutus in their main wintering area at tropical Banc d’Arguin, Mauritania, West Africa. Our study population breeds 9,000 km to the northeast on Taymyr Peninsula, central northern Siberia. Our results show that annual apparent survival decreased from 0.87 ± 0.01 (SE) in 2002–2005 to 0.78 ± 0.02 in 2006–2009. During the 3-year time-window between 2006 and 2009, additional resightings just before migration and after return to the wintering grounds allowed us to partition the year into two periods: the non-breeding period on the Banc d’Arguin, and the migration and breeding period away from it. We estimated that, on the Banc d’Arguin, the 2-month apparent survival rate was 0.94 ± 0.01, whereas 2-month survival approached unity during the rest of year. Hence, most mortality occurred on the tropical wintering grounds. We review the possible physiological and ecological stressors involved and discuss the generality of these results.
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three phase fuel deposition in a long distance migrant the red knot Calidris canutus piersmai before the flight to high arctic breeding grounds
PLOS ONE, 2013Co-Authors: Theunis PiersmaAbstract: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 after arrival at the breeding grounds, which remains unascertained. Here we investigated changes in body composition during refuelling of High Arctic breeding red knots (Calidris canutus piersmai) in the northern Yellow Sea, before their flight to the tundra. These red knots followed a three-phase fuel deposition pattern, with protein being stored in the first and last phases, and fat being deposited mainly in the second phase. Thus, they did not shrink nutritional organs before take-off, and even showed hypertrophy of the nutritional organs. These suggest the build up of strategic protein stores before departure to cope with a protein shortage upon arrival on the breeding grounds. Further comparative studies are warranted to examine the degree to which the deposition of stores by migrant birds generally reflects a balance between concurrent and upcoming environmental selection pressures.
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red knots Calidris canutus piersmai and c c rogersi depend on a small threatened staging area in bohai bay china
Emu, 2010Co-Authors: Danny I Rogers, Hongyan Yang, Chris J Hassell, Adrian Boyle, Ken G Rogers, Bing Chen, Zhengwang Zhang, Theunis PiersmaAbstract:We monitored numbers of Red Knots (Calidris canutus) staging in Bohai Bay, China (39°02′N, 118°15′E) on northward migration. Knots were identified to subspecies, and we systematically searched for colour-banded birds from the non-breeding grounds. We modelled migratory turnover, and revised estimates of flyway population using recently published counts from the non-breeding grounds. Two Russian-breeding subspecies occurred at our study site: C. c. rogersi (migrating to Chukotka), and C. c. piersmai (migrating to the New Siberian Islands); they co-occur on non-breeding grounds in Australia and New Zealand, but differ markedly in timing of migration. We conservatively estimate that our study site, comprising only 20 km of coastline, was used by over 45% of the combined world population of adult C. c. rogersi and C. c. piersmai – a conclusion supported by the independent data on frequency of resighting of colour-banded birds from north-western Australia and New Zealand. Much of this vital staging area is now being destroyed through construction of the Caofedian Industrial Zone and more westerly developments, which comprise only some of the many tidal flat ‘reclamation’ projects in the region. Preservation of the remaining tidal flats of Bohai Bay is essential to the conservation of Red Knots in the East Asian–Australasian Flyway.
Anne Dekinga - One of the best experts on this subject based on the ideXlab platform.
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red knots Calidris canutus islandica manage body mass with dieting and activity
The Journal of Experimental Biology, 2020Co-Authors: Theunis Piersma, Kimberley J Mathot, Anne Dekinga, Eva M A Kok, Piet J Van Den HoutAbstract:ABSTRACT Mass regulation in birds is well documented. For example, birds can increase body mass in response to lower availability and/or predictability of food and decrease body mass in response to increased predation danger. Birds also demonstrate an ability to maintain body mass across a range of food qualities. Although the adaptive significance of mass regulation has received a great deal of theoretical and empirical attention, the mechanisms by which birds achieve this have not. Several non-exclusive mechanisms could facilitate mass regulation in birds. Birds could regulate body mass by adjusting food intake (dieting), activity, baseline energetic requirements (basal metabolic rate), mitochondrial efficiency or assimilation efficiency. Here, we present the results of two experiments in captive red knots (Calidris canutus islandica) that assess three of these proposed mechanisms: dieting, activity and up- and down-regulation of metabolic rate. In the first experiment, knots were exposed to cues of predation risk that led them to exhibit presumably adaptive mass loss. In the second experiment, knots maintained constant body mass despite being fed alternating high- and low-quality diets. In both experiments, regulation of body mass was achieved through a combination of changes in food intake and activity. Both experiments also provide some evidence for a role of metabolic adjustments. Taken together, these two experiments demonstrate that fine-scale management of body mass in knots is achieved through multiple mechanisms acting simultaneously.
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why afro siberian red knots Calidris canutus canutus have stopped staging in the western dutch wadden sea during southward migration
Ardea, 2010Co-Authors: Casper Kraan, Jan A Van Gils, Bernard Spaans, Anne Dekinga, Theunis PiersmaAbstract:Afro-Siberian Red Knots Calidris canutus canutus use the western Dutch Wadden Sea as a refuelling area during southward migration from Taimyr to West Africa. Here we document the decline of their food stocks in this area, based on a yearly large-scale benthic mapping effort, from 1996 to 2005. For each benthic sampling position, intake rate (mg/s, ash-free dry mass) was predicted by an optimal diet model based on digestive rate maximization. Over the ten years, when accounting for a threshold value to meet energetic fuelling demands, subspecies canutus lost 86% of its suitable foraging area. Over this period, the proportion of probable canutus in mist-net catches in July—August declined relative to overwintering islandica Knots. This suggests that canutus dropped even more in numbers than islandica, for which we showed earlier a food-explained decline in numbers. We discuss the possible causality between a decline in the quality of intertidal mudflats in the Dutch Wadden Sea and population declines of Kno...
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do red knots Calidris canutus islandica routinely skip iceland during southward migration
The Condor, 2010Co-Authors: Maurine W Dietz, Bernard Spaans, Marcel Klaassen, Anne Dekinga, Harry Korthals, Casper H A Van Leeuwen, Theunis PiersmaAbstract:Abstract. Subspecies Calidris canutus islandica of the Red Knot breeds on the arctic tundra of northeastern Canada and northern Greenland and winters along the coasts of northwestern Europe. During northward migration, it stops over in either Iceland or northern Norway. It has been assumed that it does the same during southward migration. Using ratios of stable carbon isotopes (δ13C) in whole blood, blood cells, and plasma, we investigated evidence for a stopover in Iceland en route from the breeding grounds to the Dutch Wadden Sea. With the expected diet (shellfish) and stopover duration at Iceland (12–15 days, maximum 17 days) and the turnover rates of blood cells (15.1 days) and plasma (6.0 days), Red Knots that stopped in Iceland should arrive with a blood (cell) δ13C midway between a tundra (-24.7‰) and a marine value (-14.0‰) and a plasma δ13C approaching the marine value (-15.3‰). However, many adults arriving at the Wadden Sea had δ13C ratios in blood (cells) and plasma below these levels, and som...
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phenotypic compromise in the face of conflicting ecological demands an example in red knots Calidris canutus
Journal of Avian Biology, 2010Co-Authors: Francois Vezina, Anne Dekinga, Theunis PiersmaAbstract:Phenotypic flexibility is a phenomenon where physiological functions in animals are reversibly adjusted in response to ecological constraints. Research usually focuses on effects of single constraints, but under natural conditions animals face a multitude of restrictions acting simultaneously, and potentially generating conflicting demands on the phenotype. We investigated the conflicting demands of low temperatures and a low quality diet on the phenotype of a shorebird, the red knot Calidris canutus. We tested the effects of switching diet from a high quality trout food to low quality hard-shelled bivalves in captive birds acclimated to temperatures reflecting natural winter conditions. Feeding on bivalves generated a digestive constraint forcing the birds to increase the height and width of their gizzard by 66% and 71%, respectively, over 30 days. The change in gizzard size was associated with an initial 15% loss of body mass and a reduction in size of the pectoral muscles by 11%. Because pectoral muscle size determines summit metabolic rate (Msum, an indicator of cold endurance), measured Msum declined by 9%. Therefore, although the birds were acclimated to cold, gizzard growth led to a loss of cold endurance. We propose that cold-acclimated knots facing a digestive constraint made a phenotypic compromise by giving-up cold hardiness for digestive capacity. Field studies suggest that phenotypic compromises occur in free-living red knots as well and help improve survival.
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limited access to food and physiological trade offs in a long distance migrant shorebird i energy metabolism behavior and body mass regulation
Physiological and Biochemical Zoology, 2009Co-Authors: Francois Vezina, Anne Dekinga, Deborah M Buehler, Magali Petit, Theunis PiersmaAbstract:Abstract 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 response was slow. There were no gains of mass before day 15, which suggests a digestive bottleneck and a period of physiological adjustment. Food‐restricted birds exhibited decreases in pectoral‐muscle thickness and BMR in association with a loss of body mass. Although a decrease in BMR saves energy, savings represented only 2%–7% of the daily energy spent in excess of that acquired during the deficit period. Red knots did not downregulate mass‐independent BMR. On the bases of recent independent findings an...
Jan A Van Gils - One of the best experts on this subject based on the ideXlab platform.
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benefits of foraging in small groups an experimental study on public information use in red knots Calidris canutus
Behavioural Processes, 2015Co-Authors: Allert I Bijleveld, Jan A Van Gils, Jeltje Jouta, Theunis PiersmaAbstract: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 affected its use. We showed that knots can detect the foraging success of conspecifics and choose a patch accordingly. Neither dominance status nor sex influenced public information use. In the second experiment, by manipulating group size, we investigated whether public information use affected food-patch discovery rates and patch residence times. We showed that the time needed before locating a food patch decreased in proportion to group size. Also, an individual's number of patch visits before locating the food declined with group size, and, to our surprise, their average patch residence time did as well. Moreover, knots differed in their search strategy in that some birds consistently exploited the searching efforts of others. We conclude that socially foraging knots have the potential to greatly increase their food-finding rate by using public information. This article is part of a Special Issue entitled: In Honor of Jerry Hogan.
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why afro siberian red knots Calidris canutus canutus have stopped staging in the western dutch wadden sea during southward migration
Ardea, 2010Co-Authors: Casper Kraan, Jan A Van Gils, Bernard Spaans, Anne Dekinga, Theunis PiersmaAbstract:Afro-Siberian Red Knots Calidris canutus canutus use the western Dutch Wadden Sea as a refuelling area during southward migration from Taimyr to West Africa. Here we document the decline of their food stocks in this area, based on a yearly large-scale benthic mapping effort, from 1996 to 2005. For each benthic sampling position, intake rate (mg/s, ash-free dry mass) was predicted by an optimal diet model based on digestive rate maximization. Over the ten years, when accounting for a threshold value to meet energetic fuelling demands, subspecies canutus lost 86% of its suitable foraging area. Over this period, the proportion of probable canutus in mist-net catches in July—August declined relative to overwintering islandica Knots. This suggests that canutus dropped even more in numbers than islandica, for which we showed earlier a food-explained decline in numbers. We discuss the possible causality between a decline in the quality of intertidal mudflats in the Dutch Wadden Sea and population declines of Kno...
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digestive organ size and behavior of red knots Calidris canutus indicate the quality of their benthic food stocks
Israel Journal of Ecology & Evolution, 2007Co-Authors: Jan A Van Gils, Bernard Spaans, Anne Dekinga, Piet J Van Den Hout, Theunis PiersmaAbstract:Assuming that animals respond optimally to environmental changes, both behavior and physiology should be useful indicators of the way that animals perceive the quality of their environment. For verification, we examined foraging time and gizzard size of the red knot (Calidris canutus), a long-distance migrant shorebird that ingests hard-shelled mollusk prey whole and therefore readily faces digestive constraints. Nevertheless, even when digestively bottlenecked, knots can still enhance their daily energy intake by flexibly increasing the size of their digestive system, notably the gizzard, and/or by feeding longer per day. Whether such adjustments are actually necessary depends on the quality (condition) of their food, i.e., the ratio of flesh to shell mass. Hence, gizzard mass and daily foraging time in knots may be reliable indicators of the quality of their invertebrate prey. This idea is explored by using field data on radio-marked knots during late summer in the Dutch Wadden Sea. Their gizzards were measured using ultrasonography and the knots' movements and working hours were monitored using handheld receivers and automated radio-tracking systems. Indeed, gizzard mass alone predicted annual variation in food quality satisfactorily; however, adding estimates for daily foraging time significantly improved the predictions. We discuss and conceptualize how knots may trade off digestive organ size against foraging time upon arrival in the Wadden Sea, given the quality and quantity of the food on offer, and why these findings are relevant in the context of conservation of migration systems.
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foraging in a tidally structured environment by red knots Calidris canutus ideal but not free
Ecology, 2006Co-Authors: Jan A Van Gils, Bernard Spaans, Anne Dekinga, Theunis PiersmaAbstract: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 to survive unpredictable periods of bad weather, during which food patches are covered by extreme tides. In order to model such tide-specific decisions, we applied stochastic dynamic programming in a spatially explicit context. Two assumptions were varied, leading to four models. First, birds had either perfect (ideal) or no (non-ideal) information about the intake rate at each site. Second, traveling between sites was either for free or incurred time and energy costs (non-free). Predictions were generated for three aspects of foraging: area use, foraging routines, and energy stores. In general, non-ideal foragers should feed most intensely and should maintain low energy stores. If traveling for such birds is free, they should feed at a random site; otherwise, they should feed close to their roost. Ideal foragers should concentrate their feeding around low tide (especially when free) and should maintain larger energy stores (especially when non-free). If traveling for such birds is free, they should feed at the site offering the highest intake rate; otherwise, they should trade off travel costs and intake rate. Models were parameterized for Red Knots (Calidris canutus) living in the Dutch Wadden Sea in late summer, an area for which detailed, spatially explicit data on prey densities and tidal heights are available. Observations of radio-marked knots (area use) and unmarked knots (foraging routines, energy stores) showed the closest match with the ideal/non-free model. We conclude that knots make state-dependent decisions by trading off starvation against foraging-associated risks, including predation. Presumably, knots share public information about resource quality that enables them to behave in a more or less ideal manner. We suggest that our modeling approach may be applicable in other systems where resources fluctuate in space and time.
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modelling phenotypic flexibility an optimality analysis of gizzard size in red knots Calidris canutus
Ardea, 2006Co-Authors: Jan A Van Gils, Theunis Piersma, Anne Dekinga, Phil F BattleyAbstract:Reversible phenotypic changes, such as those observed in nutritional organs of long-distance migrants, increasingly receive the attention of ornithologists. In this paper we review the cost-benefit studies that have been performed on the flexible gizzard of Red Knots Calidris canutus. By varying the hardness of the diet on offer gizzard mass could experimentally be manipulated, which allowed quantification of the energetic costs and benefits as a function of gizzard size. These functions were used to construct an optimality model of gizzard mass for Red Knots on migration and during winter. Two possible currencies were assumed, one in which Knots aim to balance their energy budget on a daily basis (satisficers), and one in which Knots aim to maximise their daily energy budget (net rate maximisers). The model accurately predicted variation in gizzard mass that we observed (1) between years, (2) within years, and (3) between sites. Knots maintained satisficing gizzards during winter and rate-maximising gizzards when fuelling for migration. The model-exercise revealed the importance of digestive constraints and quality of prey in the life of Knots.
Rudi Drent - One of the best experts on this subject based on the ideXlab platform.
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digestive bottleneck affects foraging decisions in red knots Calidris canutus i prey choice
Journal of Animal Ecology, 2005Co-Authors: Jan A Van Gils, Theunis Piersma, Anne Dekinga, Sem R De Rooij, Jelmer Van Belle, Jaap Van Der Meer, Rudi DrentAbstract:Summary 1. Rate-maximizing foragers that only divide their time between searching and handling prey should, according to the classical contingency model (CM), only select those prey whose energy content per unit handling time (i.e. profitability) exceeds or equals long-term average energy intake rate. 2. However, if digestively constrained foragers were to follow this so-called ‘zero-one rule’, they would need to take digestive breaks and their energy intake over total time would not be maximized. They should, according to the digestive rate model (DRM), also consider the rate at which a prey type is digested (i.e. digestive quality), such that time lost to digestive breaks is minimized. 3. In three different contexts, we tested these competing models in a mollusc-eating shorebird, the red knot ( Calidris canutus ), that is often digestively constrained due to its habit of ingesting its bulky prey whole. Measurements on gizzard size (using ultrasonography) and prey-characteristics confirmed that in each test the birds were digestively bottlenecked and should thus follow the DRM in order to maximize long-term energy intake. 4. In the first experiment, knots were offered a choice between two fully exposed prey, and tended to select prey by the criterion of digestive quality rather than profitability. 5. In the second experiment, knots were offered two buried prey types and preferred the highest quality prey to the most profitable prey. 6. In the wild, knots mainly fed on high quality Mya and largely ignored poor quality, but equally profitable, Cerastoderma . 7. Thus, each test verified the predictions of the DRM and rejected those of the CM. Given that many species face digestion constraints, we expect that the DRM is likely to explain diet composition in many more studies.
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variability in basal metabolic rate of a long distance migrant shorebird red knot Calidris canutus reflects shifts in organ sizes
Physiological and Biochemical Zoology, 1996Co-Authors: Theunis Piersma, Leo W Bruinzeel, M Kersten, J.w. Van Der Meer, Rudi Drent, Petra WiersmaAbstract:We studied differences in body composition and basal metabolic rate (BMR, measured in postabsorptive birds under thermoneutral conditions at night) in two subspecies of red knots, Calidris canutus: one that spends the nonbreeding season under energetically costly climatic conditions at temperate latitudes (subspecies islandica in western Europe) and one that winters in the hot and humid tropics (subspecies canutus in West and South Africa). To examine whether the possible differences would be upheld under identical conditions, we kept both groups in captivity as well Body composition was quantified with respect to the fat and lean components of 10 "organs" (breast muscles, leg muscles, stomach, intestine, liver, kidneys, lungs, heart, and the skin, and skeleton and attached muscle). Captive birds had lighter lean tissues than wild birds, especially those of the stomach, intestine, kidneys, and liver (the nutritional organs). During the northern winter wild islandica knots had higher lean masses than canut...
Allan J Baker - One of the best experts on this subject based on the ideXlab platform.
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multi year surveillance of selected avian pathogens in the migrant shorebird red knot Calidris canutus rufa at its main stopover site in patagonia argentina
Journal of Ornithology, 2014Co-Authors: Veronica L Damico, Allan J Baker, Patricia M. González, Deborah M Buehler, Marcelo BertellottiAbstract:To investigate possible reasons for recent declines in Red Knot (Calidris canutus rufa) populations we surveyed for selected pathogens in Red Knots captured in San Antonio Bay, Argentina, on their northward migration during the period 2006–2011. Blood, cloacal swabs and faeces were analysed for bacteria [Salmonella sp., Shigella sp., enteropathogenic Escherichia coli (N = 42) and other coliforms (N = 35)], viral agents [responsible for avian influenza (N = 239), St. Louis encephalitis (N = 51) and Newcastle disease (N = 239)] and avian malaria parasites [Plasmodium sp. and Haemoproteus sp. (N = 284)]. All 698 samples taken from 303 individuals were negative, providing no evidence that Red Knots sampled at this stopover site were infected with these pathogens at the time of sampling.
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Reverse Movements of Red Knots Calidris canutus During Northward Migration in Argentina
Ardeola, 2014Co-Authors: Verónica L. D’amico, Patricia M. González, R. I. Guy Morrison, Allan J BakerAbstract:SUMMARY. Migratory birds are sometimes known to make reverse movements to seek better fuelling sites before undertaking long-distance migratory flights across ecological barriers. Red knots Calidris canutus rufa regularly make prodigious migratory flights of ∼ 8,000 km from southern South America to North America; these flights depend critically on the birds being able to store adequate fuel at southern staging sites. Knots staging at San Antonio Oeste (SAO) in northern Patagonia in Argentina could potentially backtrack ∼200 km southwards to complete refuelling at Peninsula Valdes (PV). We therefore analysed resightings of birds individually marked in SAO or the flyway at these two staging sites in 2006, 2007, 2009 and 2010 to investigate whether reverse movements occurred between them. In the four-year period, 63 detected individuals backtracked south from SAO to PV in one or more years. These movements occurred in all years of the study thus demonstrating the annual occurrence of flights of ∼200 km in t...
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a rare case of plasmodium haemamoeba relictum infection in a free living red knot Calidris canutus rufa scolopacidae
Journal of Ornithology, 2010Co-Authors: Veronica L Damico, Allan J BakerAbstract:The Red Knot (Calidris canutus rufa) is a Nearctic migrant shorebird that breeds in the Canadian Arctic and spends the winter season in coastal sites in South America. A rare case of a blood protozoan was found by molecular analyses from an adult bird captured during spring migration at the last refuelling stopover in Delaware Bay USA in 2006. The parasite was identified as Plasmodiumrelictum belonging to subgenus Haemamoeba based on the shape of meronts, roundish gametocytes, and its position in the erythrocytes from the blood smears examination. A partial cytochrome b sequence was a 100% match to a sequence of Plasmodium relictum, sequence Genbank accession number: id DQ659543.1 (lineage code haplotype P5). This is the first report of avian malaria in a wild individual of C. c. rufa.
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staging behavior in red knot Calidris canutus in delaware bay implications for monitoring mass and population size
The Auk, 2009Co-Authors: Simon Gillings, Allan J Baker, Philip W. Atkinson, Karen A. Bennett, Nigel A. Clark, Patricia M. González, Kimberly B Cole, Kevin S Kalasz, Clive MintonAbstract:Abstract.— Many migratory birds use staging sites to gain essential resources to fuel their ongoing migration. Understanding staging strategies reveals much about migration systems and is essential if one is concerned with monitoring population trends and mass gains, two of the principal methods for assessing the “health” of a migratory population. In spring 2004, we investigated the staging behavior in Delaware Bay of Red Knot (Calidris canutus) using mark-recapture techniques and resightings of birds marked in the preceding spring. Individuals staged for 11–12 days, which declined to 8–10 days late in the season. Arrivals were asynchronous, but departures tended to be synchronized. A simple sensitivity analysis showed that the mark-recapture analysis estimated length of stay to within +10% and confirmed biases in monitoring trends and mass gains using peak counts and mass-on-date regressions. Alternative methods using staging duration to estimate passage population size and mass gains were shown to be u...
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using stable isotope ratios to unravel shorebird migration and population mixing a case study with red knot Calidris canutus
2007Co-Authors: Philip W. Atkinson, Allan J Baker, Amanda Dey, Karen A. Bennett, Nigel A. Clark, Simon Gillings, Kimberly B Cole, Jacquie A Clark, A G Duiven, Patricia M. GonzálezAbstract:Identifying demographic mechanisms is fundamental to understanding the causes of population change in waterbirds. This may be relatively easy for static breeding and wintering populations, but populations of mixed breeding or wintering origin often occur in stopover sites in spring and autumn, and thus estimates of survival and recruitment from these areas are inevitably representative of all the birds marked, rather than individual populations. We used stable isotope analysis of flight feathers to identify the different wintering populations of Red Knot Calidris canutus rufa that passed through Delaware Bay, north-eastern USA, in the springs of 2004 and 2005. Here, they feed and fatten on an abundance of Horseshoe Crab Limulus polyphemus eggs before flying to their Arctic breeding areas. δ13N values separated birds from wintering areas in southern South America (“southern” birds) and Brazil/south-eastern USA (“northern” birds). Northern birds were further separated using δ13C values. Approximately 55% of the birds caught within Delaware Bay were from the southern population, 22.5% from Brazil, and 12.5% from the south-eastern USA, while 10% were of unknown (although most likely “northern”) origin. At a site on the Atlantic coast of Delaware Bay, where only Mussel Mytilus spp. spat were available, the proportion of short-distance migrants from the south-eastern USA was much higher, and is most likely related to their shorter-hop migration strategy that allows them to take advantage of this hard-shelled prey resource.
