202 research outputs found
History, Status, and Taxonomic Identity of Caribou (Rangifer tarandus) in Northwest Greenland
Historical references indicate that caribou (Rangifer tarandus L.) numbers drastically declined throughout the Thule District during the early part of this century, and that the primary causes were: (1) the influx of polar explorers and their distribution of firearms to the Thule Eskimos which initiated extensive hunting pressure on caribou; and (2) a series of relatively mild, wet winters resulting in snow conditions which restricted access to forage and caused several catastrophic die-offs. No live caribou were seen during six hours of aerial surveys over Inglefield Land, Thule District, Northwest Greenland, during July 1978. No fresh caribou sign was found during five days of searching in the Rensselaer Bay area of Inglefield Land. Unless some individuals were not detected or subsequent emigration from Ellesmere Island has occurred, the Inglefield Land caribou population has been extirpated. The Thule District caribou population apparently originated from barren-ground caribou (R. t. groenlandicus Gmlin) which emigrated from Southwest Greenland, rather than from Peary caribou (R. t. pearyi Allen) from Ellesmere Island.Key words: caribou, Rangifer, Greenland, Thule District, Inglefield Land, High ArcticMots clés: caribou, Rangifer, Groenland, district de Thule, terre d'Inglefield, nord de l'Arctiqu
Measurements, Chick Meals and Breeding Distribution of Dovekies (Alle alle) in Northwest Greenland
This paper reports the results of an investigation of Dovekies (Alle alle L.) breeding near Cape Atholl and Siorapaluk in the Thule District, Northwest Greenland during July and August 1978. Mean values for body measurements of breeding birds were: total length = 218.2 mm (n = 265), wing length = 122.9 mm (n - 266), tail length - 40.8 mm (n = 266) and body weight = 150.5 g (n = 209). Most measurements between the sexes were not significantly different, but mean body weight of males (153.8 g) was significantly greater than that of females (147.2 g). Body weight was highly correlated with wing length and total length in males, but not in females. Food delivered to nestlings consisted primarily of copepods (Calanus hyperboreas and C. glacialis) and amphipods (Parathemisto libellula and Apherusa glacialis). Size of chick meals delivered by male and female parents did not differ significantly and average meal weight was 3.48 g (sd = 1.24, n = 204) with mean weight of meals increasing through the chick-rearing period. General information is presented on measurements of subadults, timing of breeding, feeding areas, population size and colony attendance, and predation and disturbance. The distribution of Dovekie colonies in the Thule District is reviewed and compared with earlier information.Key words: Dovekie, morphometrics, chick diet, seabirds, NW GreenlandMots clés: Dovekie, morphométrie, régime des oisillons, oiseaux marins, nord-ouest du Groenlan
Factors Influencing Nest Attendance and Time-activity Budgets of Peregrine Falcons in Interior Alaska
An essential prerequisite to examining the impacts of anthropogenic disturbance on avian nesting activities is understanding the intrinsic and extrinsic factors that influence the birds' allocation of time to breeding behaviors. We examined factors influencing nest attendance and time-activity budgets of peregrine falcons (Falco peregrinus anatum) breeding along the Tanana River in Alaska in 1995, 1996, and 1997. First, as is typical of most bird species with nidicolous young and biparental care, females attended the nest more than males and, as the nesting cycle progressed, female attendance decreased to levels similar to those of males. Second, nest area attendance followed a circadian rhythm; parents attended the nest area less during early morning and late evening, which are prime hunting periods, than during late morning. Finally, although females typically performed most of the incubating, the division of labor between males and females during incubation differed among pairs. Higher attendance in the nest area by females during incubation appeared to be associated with more young fledged among successful pairs.Une condition indispensable pour examiner les retombées de la perturbation anthropique sur la nidification aviaire est reproducteurs. On a étudié les facteurs qui ont influencé la présence au nid et les budgets temps-activités des faucons pèlerins (Falco peregrinus anatum) nichant le long de la rivière Tanana en Alaska en 1995, 1996 et 1997. Tout d'abord, comme on doit s'y attendre de la plupart des espèces aviaires dont les petits sont nidicoles et où les soins sont biparentaux, les femelles étaient présentes au nid plus que les mâles et, à mesure que le cycle de nidification avançait, la présence des femelles diminuait à des niveaux semblables à ceux de la présence des mâles. Deuxièmement, la présence aux environs du nid suivait un rythme circadien, les parents passant moins de temps près du nid au début de la matinée et en fin de soirée - temps forts de la chasse - qu'en fin de et femelles durant l'incubation différait selon les paires. Durant l'incubation, la présence plus affirmée des femelles dans la zone du nid semblait être associée à un nombre supérieur de petits qui prenaient leur envol chez les paires qui avaient réussi à se reproduire
Defense responses of Hevea brasiliensis to elicitors from root rot fungi
L'élicitation de quelques réactions de défense du système racinaire de l'Hévéa (#Hevea brasiliensis) aux attaques du #Rigidoporus lignosus$ a été réalisée en injectant des extraits des parois fongiques dans les racines de jeunes plantes âgées de 1 mois. Une étude de la cinétique a révélé, au microscope optique, une induction de la lignification 3, 8, 15 et 45 jours après l'injection d'éliciteurs. Les résultats obtenus montrent que certaines réactions de défense des racines des plantes ligneuses peuvent être stimulées par des éliciteurs fongiques dans le but de renforcer les barrières structurales des tissus hôtes. (D'après résumé d'auteur
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Research, Monitoring, and Evaluation of Avian Predation on Salmonid Smolts in the Lower and Mid-Columbia River, 2006 Final Season Summary.
This study investigates predation by piscivorous waterbirds on juvenile salmonids (Oncorhynchus spp.) from throughout the Columbia River Basin. During 2006, study objectives in the Columbia River estuary, work funded by the Bonneville Power Administration, were to (1) monitor and evaluate previous management initiatives to reduce Caspian tern (Hydroprogne caspia) predation on juvenile salmonids (smolts); (2) measure the impact of double-crested cormorant (Phalacrocorax auritus) predation on smolt survival, and assess potential management options to reduce cormorant predation; and (3) monitor large colonies of other piscivorous waterbirds in the estuary (i.e., glaucous-winged/western gulls [Larus glaucescens/occidentalis]) to determine the potential impacts on smolt survival. Study objectives on the mid-Columbia River, work funded by the Walla Walla District of the U.S. Army Corps of Engineers, were to (1) measure the impact of predation by Caspian terns and double-crested cormorants on smolt survival; and (2) monitor large nesting colonies of other piscivorous waterbirds (i.e., California gulls [L. californicus], ring-billed gulls [L. delawarensis], American white pelicans [Pelecanus erythrorhynchos]) on the mid-Columbia River to determine the potential for significant impacts on smolt survival. Our efforts to evaluate system-wide losses of juvenile salmonids to avian predation indicated that Caspian terns and double-crested cormorants were responsible for the vast majority of smolt losses to avian predators in the Columbia Basin, with most losses occurring in the Columbia River estuary. In 2006, East Sand Island in the Columbia River estuary supported the largest known breeding colonies of Caspian terns and double-crested cormorants in the world. The Caspian tern colony on East Sand Island consisted of about 9,200 breeding pairs in 2006, up slightly (but not significantly so) from the estimate of colony size in 2005 (8,820 pairs). There has not been a statistically significant change in the size of the Caspian tern colony on East Sand Island since 2000. Tern nesting success averaged 0.72 fledglings per breeding pair in 2006, significantly higher than in 2005 (0.37 fledglings per breeding pair), a year of poor ocean conditions. Despite the presumably higher availability of marine forage fishes in 2006, the proportion of juvenile salmonids in diets of Caspian terns (32% of prey items) averaged higher than in 2005 (23% of prey items) and 2004 (18% of prey items). Steelhead smolts were particular vulnerable to predation by East Sand Island terns in 2006, with predation rates as high as 20% on particular groups of PIT-tagged fish reaching the estuary. Consumption of juvenile salmonids by terns nesting at the East Sand Island colony in 2006 was approximately 5.3 million smolts (95% c.i. = 4.4-6.2 million), significantly higher than the estimated 3.6 million smolts consumed in 2005, but still roughly 7 million fewer smolts consumed compared to 1998 (when all terns nested on Rice Island in the upper estuary). Caspian terns nesting on East Sand Island continue to rely primarily on marine forage fishes as a food supply, even in 2005 when availability of marine forage fishes declined due to poor ocean conditions. Further management of Caspian terns to reduce losses of juvenile salmonids would be implemented under the Caspian Tern Management Plan for the Columbia River Estuary; the Records of Decision (RODs) authorizing implementation of the plan were signed in November 2006. The ROD lists as the management goal the redistribution of approximately half of the East Sand Island Caspian tern colony to alternative colony sites in interior Oregon and San Francisco Bay, California (USFWS 2006). Implementation of the management plan is stalled, however, because of the lack of appropriated funds
Use of Fatty Acid Analysis to Determine Dispersal of Caspian Terns in the Columbia River Basin, U.S.A.
Lethal control, which has been used to reduce local abundances of animals in conflict with humans or with endangered species, may not achieve management goals if animal movement is not considered. In populations with emigration and immigration, lethal control may induce compensatory immigration, if the source of attraction remains unchanged. Within the Columbia River Basin (Washington, U.S.A.), avian predators forage at dams because dams tend to reduce rates of emigration of juvenile salmonids (Oncorhynchus spp.), artificially concentrating these prey. We used differences in fatty acid profiles between Caspian Terns (Hydroprogne caspia) at coastal and inland breeding colonies and terns culled by a lethal control program at a mid-Columbia River dam to infer dispersal patterns. We modeled the rate of loss of fatty acid biomarkers, which are fatty acids that can be traced to a single prey species or groups of species, to infer whether and when terns foraging at dams had emigrated from the coast. Nonmetric multidimensional scaling showed that coastal terns had high levels of C20 and C22 monounsaturated fatty acids, whereas fatty acids of inland breeders were high in C18:3n3, C20:4n6, and C22:5n3. Models of the rate of loss of fatty acid showed that approximately 60% of the terns collected at Rock Island Dam were unlikely to have bred successfully at local (inland) sites, suggesting that terns foraging at dams come from an extensive area. Fatty acid biomarkers may provide accurate information about patterns of dispersal in animal populations and may be extremely valuable in cases where populations differ demonstrably in prey base
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Susceptibility of Juvenile Steelhead to Avian Predation: the Influence of Individual Fish Characteristics and River Conditions
Identification of the factors that influence susceptibility to predation can aid in developing management strategies to recover fish populations of conservation concern. Predator-prey relationships can be influenced by numerous factors, including prey condition, prey size, and environmental conditions. We investigated these factors by using juvenile steelhead Oncorhynchus mykiss from the Snake River (Pacific Northwest, USA), a distinct population segment that is listed as threatened under the U. S. Endangered Species Act. During 2007-2009, steelhead smolts (n = 25,909) were captured, examined for external condition characteristics (e. g., body injuries, descaling, external signs of disease, fin damage, and ectoparasite infestations), marked with passive integrated transponder (PIT) tags, and released to continue their out-migration. Recoveries of PIT tags on a downstream colony of Caspian terns Hydroprogne caspia (n = 913 tags) indicated that steelhead susceptibility to Caspian tern predation increased significantly with decreases in steelhead external condition, decreased water discharge, and decreased water clarity. Susceptibility to Caspian tern predation also increased with increasing steelhead fork length up to 202 mm but then decreased for longer steelhead. Recoveries of PIT tags on a downstream colony of double-crested cormorants Phalacrocorax auritus (n = 493 tags) indicated that steelhead susceptibility to double-crested cormorant predation increased significantly with declining external condition of steelhead, and that steelhead of hatchery origin were more susceptible than their wild counterparts. Results indicate that steelhead susceptibility to avian predation is dependent on fish condition and length and is influenced by river conditions and rearing environment.Keywords: Snake River, Avoidance behavior, Relative vulnerability, Double crested cormorants, Foraging patterns, Chinook salmon, Passive integrated transponders, Caspian terns, Lower Columbia River, Salmon Oncorhynchus tshawytsch
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Nutritional stress affects corticosterone deposition in feathers of Caspian tern chicks
Stressful environmental conditions affect the adrenocortical function of developing animals, which can have consequences
for their fitness. Discovery of the avian stress hormone corticosterone (CORT) in feathers has the potential to broaden the
application of endocrine research in ecological and evolutionary studies of wild birds by providing a long-term measure
of CORT secretion. Mechanisms of CORT deposition in feathers are not well known and few studies have related feather
CORT to circulating plasma CORT during feather growth. Our objective was to experimentally test the validity of
using feather CORT as a measure of CORT secretion in developing birds experiencing nutritional stress. Caspian tern
Hydroprogne caspia chicks were fed ad libitum or restricted (35% less than ad libitum) diets for four weeks. We measured
CORT in feathers from these chicks to examine the relationship between feather CORT concentrations and nutritional
limitation, circulating plasma CORT, and feather development. We found that feather CORT was higher in controls fed
ad libitum than in restricted individuals, despite higher levels of plasma CORT in restricted chicks compared to controls.
Feather mass and growth rates were strongly and positively related to feather CORT concentrations in both treatments.
This is the first experimental study to show that feather CORT concentrations can be lower in response to nutritional
stress, even when plasma CORT concentrations are elevated. Our results indicate that CORT deposition in feathers may be
confounded when feather mass and growth rates are compromised by nutritional stress. We conclude that feather CORT
can be used for assessing nutritional stress in growing birds, but the direction of response depends on how strongly stress
affects feather development
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Developing Nondestructive Techniques for Managing Conflicts Between Fisheries and Double-Crested Cormorant Colonies
Double-crested cormorants (Phalacrocorax auritus) have been identified as the source of significant mortality to juvenile salmonids (Oncorhynchus spp.) in the Columbia River Basin. Management plans for reducing the size of a large colony on East Sand Island (OR, USA) in the Columbia River estuary are currently being developed. We evaluated habitat enhancement and social attraction as nondestructive techniques for managing cormorant nesting colonies during 2004–2007. We tested these techniques on unoccupied plots adjacent to the East Sand Island cormorant colony. Cormorants quickly colonized these plots and successfully raised young. Cormorants also were attracted to nest and raised young on similar plots at 2 islands approximately 25 km from East Sand Island; 1 island had a history of successful cormorant nesting whereas the other was a site where cormorants had previously nested unsuccessfully. On a third island with no history of cormorant nesting or nesting attempts, these techniques were unsuccessful at attracting cormorants to nest. Our results suggest that some important factors influencing attraction of nesting cormorants using these techniques include history of cormorant nesting, disturbance, and presence of breeding cormorants nearby. These techniques may be effective in redistributing nesting cormorants away from areas where fish stocks of conservation concern are susceptible to predation, especially if sites with a recent history of cormorant nesting are available within their foraging or dispersal range.Keywords: salmonids, social attraction, Phalacrocorax auritus, predation, habitat enhancement, cormoran
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Quantifying Avian Predation on Fish Populations: Integrating Predator-Specific Deposition Probabilities in Tag Recovery Studies
Accurate assessment of specific mortality factors is vital to prioritize recovery actions for threatened and endangered species. For decades, tag recovery methods have been used to estimate fish mortality due to avian predation. Predation probabilities derived from fish tag recoveries on piscivorous waterbird colonies typically reflect minimum estimates of predation due to an unknown and unaccounted-for fraction of tags that are consumed but not deposited on-colony (i.e., deposition probability). We applied an integrated tag recovery modeling approach in a Bayesian context to estimate predation probabilities that accounted for predator-specific tag detection and deposition probabilities in a multiple-predator system. Studies of PIT tag deposition were conducted across three bird species nesting at seven different colonies in the Columbia River basin, USA. Tag deposition probabilities differed significantly among predator species (Caspian terns Hydroprogne caspia: deposition probability = 0.71, 95% credible interval [CRI] = 0.51–0.89; double-crested cormorants Phalacrocorax auritus: 0.51, 95% CRI = 0.34–0.70; California gulls Larus californicus: 0.15, 95% CRI = 0.11–0.21) but showed little variation across trials within a species or across years. Data from a 6-year study (2008–2013) of PIT-tagged juvenile Snake River steelhead Oncorhynchus mykiss (listed as threatened under the Endangered Species Act) indicated that colony-specific predation probabilities ranged from less than 0.01 to 0.17 and varied by predator species, colony location, and year. Integrating the predator-specific deposition probabilities increased the predation probabilities by a factor of approximately 1.4 for Caspian terns, 2.0 for double-crested cormorants, and 6.7 for California gulls compared with traditional minimum predation rate methods, which do not account for deposition probabilities. Results supported previous findings on the high predation impacts from strictly piscivorous waterbirds nesting in the Columbia River estuary (i.e., terns and cormorants), but our findings also revealed greater impacts of a generalist predator species (i.e., California gulls) than were previously documented. Approaches used in this study allow for direct comparisons among multiple fish mortality factors and considerably improve the reliability of tag recovery models for estimating predation probabilities in multiple-predator systems
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