The Experts below are selected from a list of 90768 Experts worldwide ranked by ideXlab platform
Bart A. Nolet - One of the best experts on this subject based on the ideXlab platform.
-
the exception to the rule retreating ice front makes bewick s Swans cygnus columbianus bewickii migrate slower in spring than in autumn
Journal of Avian Biology, 2014Co-Authors: Rascha J M Nuijten, Andrea Kolzsch, J A Van Gils, Bethany J Hoye, Kees Oosterbeek, P P De Vries, M L Klaassen, Bart A. NoletAbstract:In the vast majority of migratory bird species studied so far, spring migration has been found to proceed faster than autumn migration. In spring, selection pressures for rapid migration are purportedly higher, and migratory conditions such as food supply, daylength, and/or wind support may be better than in autumn. In Swans, however, spring migration appears to be slower than autumn migration. Based on a comparison of tundra swan Cygnus columbianus tracking data with long-term temperature data from wheather stations, it has previously been suggested that this was due to a capital breeding strategy (gathering resources for breeding during spring migration) and/or to ice cover constraining spring but not autumn migration. Here we directly test the hypothesis that Bewick's Swans Cygnus columbianus bewickii follow the ice front in spring, but not in autumn, by comparing three years of GPS tracking data from individual Swans with concurrent ice cover data at five important migratory stop-over sites. In general, ice constrained the Swans in the middle part of spring migration, but not in the first (no ice cover was present in the first part) nor in the last part. In autumn, the Swans migrated far ahead of ice formation, possibly in order to prevent being trapped by an early onset of winter. We conclude that spring migration in Swans is slower than autumn migration because spring migration speed is constrained by ice cover. This restriction to spring migration speed may be more common in northerly migrating birds that rely on freshwater resources.
-
Commensal foraging with Bewick’s Swans Cygnus bewickii doubles instantaneous intake rate of Common Pochards Aythya ferina
Ardea, 2012Co-Authors: Abel Gyimesi, Bart Van Lith, Bart A. NoletAbstract:Aquatically foraging Bewick's Swans Cygnus bewickii have been repeatedly reported to be accompanied by diving ducks, but the exact nature of this relationship is unclear. Based on field observations, we found a strong correlation between the number of foraging Swans and the number of foraging Common Pochards Aythya ferina and Tufted Ducks Aythya fuligula at our study site (Lauwersmeer, the Netherlands), with the median ratio being close to one diving duck per swan. To determine whether the association was kleptoparasitic or commensal, we measured in a series of experimental trials the instantaneous intake rates of Bewick's Swans and Common Pochards when foraging alone and when foraging together. On average, pochards in company with a swan attained twice the instantaneous intake rate as compared with foraging alone. This was mainly due to gleaning food items that floated away as a result of the swan's trampling activity, and was not due to stealing: in fact, food intake rates of Swans were not affected by ...
-
commensal foraging with bewick s Swans cygnus bewickii doubles instantaneous intake rate of common pochards aythya ferina
Ardea, 2012Co-Authors: Abel Gyimesi, B Van Lith, Bart A. NoletAbstract:Aquatically foraging Bewick's Swans Cygnus bewickii have been repeatedly reported to be accompanied by diving ducks, but the exact nature of this relationship is unclear. Based on field observations, we found a strong correlation between the number of foraging Swans and the number of foraging Common Pochards Aythya ferina and Tufted Ducks Aythya fuligula at our study site (Lauwersmeer, the Netherlands), with the median ratio being close to one diving duck per swan. To determine whether the association was kleptoparasitic or commensal, we measured in a series of experimental trials the instantaneous intake rates of Bewick's Swans and Common Pochards when foraging alone and when foraging together. On average, pochards in company with a swan attained twice the instantaneous intake rate as compared with foraging alone. This was mainly due to gleaning food items that floated away as a result of the swan's trampling activity, and was not due to stealing: in fact, food intake rates of Swans were not affected by ...
-
search paths of Swans foraging on spatially autocorrelated tubers
Journal of Animal Ecology, 2002Co-Authors: Bart A. Nolet, Wolf M MooijAbstract:1. Tundra Swans forage on below-ground pondweed tubers that are heterogeneously distributed in space. The Swans have no visual cues to delineate patches. It was tested whether Swans employ an area-restricted search tactic. Theory predicts that Swans should alternate between an intensive (low-speed, sinuous) search mode in high tuber density areas and an extensive (high-speed, directed) search mode between these areas. 2. A quantitative analysis of movement paths recorded over short time frames (15 min) revealed that the sequential step lengths were strongly autocorrelated. After partitioning the data in low-speed paths and high-speed paths, this autocorrelation was very much reduced. 3. Movement paths with low speed were non-directional and could well be described as random walks. In contrast, high-speed paths were directed forward, and were better described as correlated (i.e. directional) random walks. 4. Movement paths recorded over longer time frames (1-4 h) provided empirical evidence that an alternation of low-speed, sinuous and high-speed, directed searches occurred. 5. There was a spatial autocorrelation in tuber biomass density, being significantly positively correlated until c. 10 m distance. The scale of the food clump size and step length of high-speed paths matched, suggesting that they were causally linked. 6. Computer simulations confirmed that Swans using the observed search tactic achieved a higher energy gain than Swans using only an intensive search mode, provided that the tuber biomass density occurred in clumps. They also achieved a higher gain than Swans that alternated between intensive and extensive search mode, but always moved in a random direction.
-
skipping Swans fuelling rates and wind conditions determine differential use of migratory stopover sites of bewick s Swans cygnus bewickii
Ardea, 2002Co-Authors: Jan H Beekman, Bart A. Nolet, Marcel KlaassenAbstract:Some migratory birds refuel at stopover sites that they by-pass on the return trip. In theory, this skipping behaviour is only expected in time-selected migrants when the overflown site is of a lower quality than the departure site. We provide empirical evidence that quality differences in stopover sites are the cause for skipping in Bewick's Swans Cygnus bewickii tracked by satellite telemetry. Two and five complete tracks were recorded in spring and autumn, respectively, showing that the White Sea was visited for c. 2 weeks in spring, but by-passed (or visited for a few days at the most) in autumn. Skipping of the White Sea in autumn was predicted by a dynamic programming model which was based on calculated gain rates during stopover in the Pechora Delta and the White Sea. This prediction was not sensitive to plausible variations in gain rates. Relative to the Pechora Delta the White Sea is a poor site because a large tidal amplitude precludes foraging on the beds of the submerged macrophyte Fennel Pondweed Potamogeton pectinatus during high tide. The dynamic programming model predicted a fast autumn migration. However, the phenology of autumn arrival dates of Bewick's Swans on the wintering grounds revealed that only in three out of ten years a significant number of birds was able to reach the wintering grounds without refuelling. In the other years, unfavourable wind conditions along the Russian/Baltic part of the route prevented such non-stop migration.
Eileen C. Rees - One of the best experts on this subject based on the ideXlab platform.
-
Incidence of embedded shotgun pellets in Bewick's Swans Cygnus columbianus bewickii and whooper Swans Cygnus cygnus wintering in the UK
Biological Conservation, 2011Co-Authors: Julia L. Newth, Martin J. Brown, Eileen C. ReesAbstract:Abstract The migratory whooper Swans (Cygnus cygnus) and Bewick’s Swans (Cygnus columbianus bewickii) have been protected by national and international legislation throughout their migratory ranges since the mid 20th century, yet illegal shooting of both species still occurs. X-rays taken of wild caught Swans at several sites in the UK were inspected to determine: (1) the incidence of embedded pellets in live birds, (2) inter-specific differences in the level of illegal shooting, and (3) trends in the prevalence of shot-in pellets between the 1970s and the 2000s. A significantly higher proportion of Bewick’s Swans (31.2%) contained shot-in pellets than whooper Swans (13.6%). The likelihood of a bird having been shot increased with its age for both species. The proportion of Bewick’s Swans with embedded shot was higher during the 1970s and 1980s than in the 1990s and 2000s but the incidence remains high, with 22.7% of Bewick’s Swans X-rayed in the 21st century containing shot. The prevalence of whooper Swans with embedded shot did not change significantly over time (14.9% with pellets in the 1980s compared with 13.2% with pellets in the 2000s). As the Swans follow different migration routes, the results not only have implications for consistent and effective implementation of legislation, but show that illegal shooting must be addressed at both national and international levels.
-
Diseases of Swans in captivity
1992Co-Authors: Martin J. Brown, Emma Linton, Eileen C. ReesAbstract:The results of post mortem data from 373 Swans that died within Wildfowl and Wetlands Trust collections between 1951 and 1989 inclusive were analyzed. The most common causes of death were tuberculosis and visceral gout in adult Swans, acuaria in juveniles, and pneumonia, omphalitis and trauma in downies. Differences between the species in their levels of susceptibility to the different diseases are described and further improvements in husbandry technique are propounded.
Ya A Kondratiev - One of the best experts on this subject based on the ideXlab platform.
-
the distribution and status of bewick s Swans cygnus bewickii tundra Swans c columbianus and whooper Swans c cygnus in the extreme northeast of the ussr
Wildfowl, 2013Co-Authors: Ya A KondratievAbstract:The distribution, numbers and status of three swan species: Bewick’s, Tundra and Whooper Swans, in the ‘Extreme Northeast of Asia ’ are described. The breeding grounds of Bewick’s Swans cover the maritime tundra of the Arctic basin eastwards as far as Kolyuchin Bay in the Chukotka Sea. A total of 1,200 Bewick’s Swans live in the region of which at least 90% are concentrated in the Kolyma Lowlands (over 700 birds) and Chaun Lowlands (over 300 birds). Breeding birds comprise about 23 % of the total number of Bewick's Swans in the breeding grounds each year. It has been established that some pairs of Tundra Swans are breeding in a number of low-lying sections of the sea-coast of eastern Chukotka. The region of supposed sporadic breeding extends from the Vankarem Lowland to Krest Bay. There are no data concerning the status of the Tundra Swan but intensive economic development of the breeding sites causes concern for the fate of this species. The Whooper Swan is widely distributed in the taiga zone of the Extreme Northeast, but data on its breeding status and population size are very limited. According to preliminary estimates about 2,200 Whooper Swans are in the region. Two main migration routes have been monitored. Birds which settle in the Anadyr-Penzhina Lowland fly across Kamchatka and the Kurile Islands. The remaining birds follow the western Sea of Okhotsk.
Hongliang Chai - One of the best experts on this subject based on the ideXlab platform.
-
migratory whooper Swans cygnus cygnus transmit h5n1 virus between china and mongolia combination evidence from satellite tracking and phylogenetics analysis
Scientific Reports, 2018Co-Authors: Weiyue Meng, Dongping Liu, Qiqi Yang, Lixia Chen, Qiang Dai, Ruyi Gao, Guogang Zhang, Huaiyu Tian, Hongliang ChaiAbstract:In late 2014, a highly pathogenic avian influenza (hereafter HPAI) H5N1 outbreak infected whooper Swans Cygnus cygnus wintering at the Sanmenxia Reservoir area, China, and raised concerns about migratory linkages between wintering and breeding grounds of whooper Swans. In this study, 61 Swans were satellite tracked from 2013 to 2016 to determine the spatial association of their migration routes and H5N1 outbreaks, and 3596 fecal samples were collected along the migration routes for virology testing. Swans departed the wintering grounds and migrated along the Yellow River, and flew over the Yin Mountains in China. The Brownian bridge movement model showed there was a high degree of spatiotemporal overlap between the core use area along the spring migration pathway and historical H5N1 events in China and Mongolia from 2005 to 2015. The H5N1 strain was isolated and phylogenetic analyses confirmed that the HA gene sequence generated is genetically similar to that of the epidemic strain at a previous wintering site (the Sanmenxia Reservoir area) along its flyway. Our results identified a previously unknown migratory link of whooper Swans in central China with Mongolia and confirmed that the Swans could carry the HPAI H5N1 virus during migration, resulting in long-distance transmission.
Julia L. Newth - One of the best experts on this subject based on the ideXlab platform.
-
Incidence of embedded shotgun pellets in Bewick's Swans Cygnus columbianus bewickii and whooper Swans Cygnus cygnus wintering in the UK
Biological Conservation, 2011Co-Authors: Julia L. Newth, Martin J. Brown, Eileen C. ReesAbstract:Abstract The migratory whooper Swans (Cygnus cygnus) and Bewick’s Swans (Cygnus columbianus bewickii) have been protected by national and international legislation throughout their migratory ranges since the mid 20th century, yet illegal shooting of both species still occurs. X-rays taken of wild caught Swans at several sites in the UK were inspected to determine: (1) the incidence of embedded pellets in live birds, (2) inter-specific differences in the level of illegal shooting, and (3) trends in the prevalence of shot-in pellets between the 1970s and the 2000s. A significantly higher proportion of Bewick’s Swans (31.2%) contained shot-in pellets than whooper Swans (13.6%). The likelihood of a bird having been shot increased with its age for both species. The proportion of Bewick’s Swans with embedded shot was higher during the 1970s and 1980s than in the 1990s and 2000s but the incidence remains high, with 22.7% of Bewick’s Swans X-rayed in the 21st century containing shot. The prevalence of whooper Swans with embedded shot did not change significantly over time (14.9% with pellets in the 1980s compared with 13.2% with pellets in the 2000s). As the Swans follow different migration routes, the results not only have implications for consistent and effective implementation of legislation, but show that illegal shooting must be addressed at both national and international levels.
