| prediction of bird-day carrying capacity on a staging site: a test of depletion models. | 1. the carrying capacity of a site for migratory water birds, expressed in bird-days, can be of particular conservation value. several attempts have been made to model this carrying capacity using ideal free distribution models such as, for instance, depletion models, in which the distribution is fully determined by exploitative competition. 2. in the tests of depletion models carried out so far, no alternative models were compared; rather, one specific model was tested. we tested whether bird-d ... | 2006 | 17032360 |
| hampered performance of migratory swans: intra- and inter-seasonal effects of avian influenza virus. | the extent to which animal migrations shape parasite transmission networks is critically dependent on a migrant's ability to tolerate infection and migrate successfully. yet, sub-lethal effects of parasites can be intensified through periods of increased physiological stress. long-distance migrants may, therefore, be especially susceptible to negative effects of parasitic infection. although a handful of studies have investigated the short-term, transmission-relevant behaviors of wild birds infe ... | 2016 | 27252210 |
| host behaviour and physiology underpin individual variation in avian influenza virus infection in migratory bewick's swans. | individual variation in infection modulates both the dynamics of pathogens and their impact on host populations. it is therefore crucial to identify differential patterns of infection and understand the mechanisms responsible. yet our understanding of infection heterogeneity in wildlife is limited, even for important zoonotic host-pathogen systems, owing to the intractability of host status prior to infection. using novel applications of stable isotope ecology and eco-immunology, we distinguish ... | 2011 | 21733894 |
| above- and below-ground vertebrate herbivory may each favour a different subordinate species in an aquatic plant community. | at least two distinct trade-offs are thought to facilitate higher diversity in productive plant communities under herbivory. higher investment in defence and enhanced colonization potential may both correlate with decreased competitive ability in plants. herbivory may thus promote coexistence of plant species exhibiting divergent life history strategies. how different seasonally tied herbivore assemblages simultaneously affect plant community composition and diversity is, however, largely unknow ... | 2010 | 19756762 |
| compensatory growth in an aquatic plant mediates exploitative competition between seasonally tied herbivores. | the degree to which vertebrate herbivores exploitatively compete for the same food plant may depend on the level of compensatory plant growth. such compensation is higher when there is reduced density-dependent competition in plants after herbivore damage. whether there is relief from competition may largely be determined by the life-history stage of plants under herbivory. such stage-specific compensation may apply to seasonal herbivory on the clonal aquatic plant sago pondweed (potamogeton pec ... | 2009 | 19694137 |
| effects of influenza a virus infection on migrating mallard ducks. | the natural reservoir of influenza a virus is waterfowl, particularly dabbling ducks (genus anas). although it has long been assumed that waterfowl are asymptomatic carriers of the virus, a recent study found that low-pathogenic avian influenza (lpai) infection in bewick's swans (cygnus columbianus bewickii) negatively affected stopover time, body mass and feeding behaviour. in the present study, we investigated whether lpai infection incurred ecological or physiological costs to migratory malla ... | 2009 | 19129127 |
| spatial, temporal, and species variation in prevalence of influenza a viruses in wild migratory birds. | although extensive data exist on avian influenza in wild birds in north america, limited information is available from elsewhere, including europe. here, molecular diagnostic tools were employed for high-throughput surveillance of migratory birds, as an alternative to classical labor-intensive methods of virus isolation in eggs. this study included 36,809 samples from 323 bird species belonging to 18 orders, of which only 25 species of three orders were positive for influenza a virus. informatio ... | 2007 | 17500589 |
| hampered foraging and migratory performance in swans infected with low-pathogenic avian influenza a virus. | it is increasingly acknowledged that migratory birds, notably waterfowl, play a critical role in the maintenance and spread of influenza a viruses. in order to elucidate the epidemiology of influenza a viruses in their natural hosts, a better understanding of the pathological effects in these hosts is required. here we report on the feeding and migratory performance of wild migratory bewick's swans (cygnus columbianus bewickii yarrell) naturally infected with low-pathogenic avian influenza (lpai ... | 2007 | 17264886 |
| animal-plant-microbe interactions: direct and indirect effects of swan foraging behaviour modulate methane cycling in temperate shallow wetlands. | wetlands are among the most important ecosystems on earth both in terms of productivity and biodiversity, but also as a source of the greenhouse gas ch(4). microbial processes catalyzing nutrient recycling and ch(4) production are controlled by sediment physico-chemistry, which is in turn affected by plant activity and the foraging behaviour of herbivores. we performed field and laboratory experiments to evaluate the direct effect of herbivores on soil microbial activity and their indirect effec ... | 2006 | 16736186 |
| clonal diversity and structure within a population of the pondweed potamogeton pectinatus foraged by bewick's swans. | clonal diversity within plant populations is affected by factors that influence genet (clone) survival and seed recruitment, such as resource availability, disturbance, seed dispersal mechanism, propagule predation and the age of the population. here we studied a population of potamogeton pectinatus, a pseudo-annual aquatic macrophyte. within populations reproduction appears to be mainly asexually through subterranean propagules (tubers), while recruitment via seeds is believed to be relatively ... | 2002 | 12296955 |
| lead poisoning in swans in japan. | we investigated the occurrence, source and exposure time of lead poisoning in whooper swans (cygnus cygnus cygnus) and bewick's swans (cygnus columbianus bewickii) in japan during the winters of 1984-1987. concentrations of lead in various tissues and physiological evidence of lead shot in some birds indicated that lead shotgun pellets were the source of lead, and exposure occurred after the birds arrived in japan. mortality probably occurred within 30 days after exposure to, and retention of, l ... | 1990 | 15092262 |
| short-term foraging costs and long-term fueling rates in central-place foraging swans revealed by giving-up exploitation times. | foragers tend to exploit patches to a lesser extent farther away from their central place. this has been interpreted as a response to increased risk of predation or increased metabolic costs of prey delivery. here we show that migratory bewick's swans (cygnus columbianus bewickii), though not incurring greater predation risks farther out or delivering food to a central place, also feed for shorter periods at patches farther away from their roost. predictions from an energy budget model suggest t ... | 2007 | 17427132 |
| avian herbivory: an experiment, a field test, and an allometric comparison with mammals. | mechanistic studies on herbivore functional responses have largely taken place in mammals; very little has been done in herbivorous birds so far. here we aim to fill that gap by experimentally quantifying the (short-term) functional response of a large avian herbivore, the bewick's swan (cygnus columbianus bewickii). we explicitly distinguish between encounter-limited and handling-limited foraging by analyzing the results in the framework of the models of d. e. spalinger and n. t. hobbs, origina ... | 2007 | 18051661 |
| longer guts and higher food quality increase energy intake in migratory swans. | 1. within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. this therefore calls for a formalization of how animals could optimize food absorption rates. 2. here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constr ... | 2008 | 18662243 |
| habitat use throughout migration: linking individual consistency, prior breeding success and future breeding potential. | 1. habitat use can influence individual performance in a wide range of animals, either immediately or through carry-over effects in subsequent seasons. given that many animal species also show consistent individual differences in reproductive success, it seems plausible that individuals may have consistent patterns of habitat use representing individual specializations, with concomitant fitness consequences. 2. stable-carbon isotope ratios from a range of tissues were used to discern individual ... | 2012 | 22272688 |
| complete mitochondrial genome of the bewick's swan cygnus columbianus bewickii (aves, anseriformes, anatidae). | the mitochondrial genome of bewick's swan cygnus columbianus bewickii was completely sequenced and then the resultant data were compared with those of the whistling swan cygnus columbianus columbianus. the complete mitochondrial genome sequence of c. c. bewickii was 16,727 bp in length and its gene arrangement pattern, gene content, and genome organization were identical to those of cygnus species. the similarities of nucleotide and amino acid sequences between the two swans were 99.1% and 99.6% ... | 2012 | 22409756 |
| predicting effects of water regime changes on waterbirds: insights from staging swans. | predicting the environmental impact of a proposed development is notoriously difficult, especially when future conditions fall outside the current range of conditions. individual-based approaches have been developed and applied to predict the impact of environmental changes on wintering and staging coastal bird populations. how many birds make use of staging sites is mostly determined by food availability and accessibility, which in the case of many waterbirds in turn is affected by water level. ... | 2016 | 26862895 |