Cygnus Columbianus Research Articles

A review of lead poisoning in swans

Nearly 10,000 swans of six species or subspecies from 14 countries have died from poisoning caused by lead that originated from ingestion of fishing weights, shotgun pellets (shot), or contaminated vegetation or sediments associated with mining and smelting wastes. Lead contamination in mute swans in England caused local population declines during the late 1970s and 1980s. More tundra swans died from lead poisoning than any other species. The extreme record involved an estimated 7200 tundra swans that died over five winters at one locality in North Carolina. The recent legislation to ban lead fishing weights in most of England and Wales and recent replacement of lead shot with steel shot for waterfowl hunting in the United States and a few areas of Europe, including Denmark, are expected to reduce the incidence of lead poisoning in swans.

A review of lead poisoning in swans

Nearly 10,000 swans of six species or subspecies from 14 countries have died from poisoning caused by lead that originated from ingestion of fishing weights, shotgun pellets (shot), or contaminated vegetation or sediments associated with mining and smelting wastes. Lead contamination in mute swans in England caused local population declines during the late 1970s and 1980s. More tundra swans died from lead poisoning than any other species. The extreme record involved an estimated 7200 tundra swans that died over five winters at one locality in North Carolina. The recent legislation to ban lead fishing weights in most of England and Wales and recent replacement of lead shot with steel shot for waterfowl hunting in the United States and a few areas of Europe, including Denmark, are expected to reduce the incidence of lead poisoning in swans.

Lead poisoning and other causes of mortality in trumpeter (Cygnus buccinator) and tundra (C. columbianus) swans in western Washington.

Lead poisoning and other causes of mortality of 115 trumpeter (Cygnus buccinator) and 21 tundra (C. columbianus) swans from northwestern Washington (USA) from 1986 to 1992 are reported. Necropsies were performed on all 136 swans, liver lead analysis conducted on 110, and differentiation between lead and steel shot pellets recovered from gizzards in 97 swans. Shot pellets were detected in 44 (32%) of 136 gizzards. Lead shot was recovered from 32 (33%) of 97 gizzards and steel shot from 16 (16%). Mean intensity of lead shot in gizzards was nearly five times greater than steel shot. Thirty-nine (35%) of 110 livers had lead concentrations diagnostic of lead poisoning (> 6 ppm, wet weight). Mean (+/- SE) weight for 61 non-lead poisoned trumpeter swans was 9.8 (+/- 0.30) kg, significantly heavier (P < 0.05) than 30 lead poisoned trumpeters (mean = 6.8 +/- 0.23 kg). There was no significant difference (P > 0.05) in weights between lead poisoned (n = 9) and non-lead poisoned (n = 12) tundra swans. Lead poisoning was the primary cause of death, accounting for 29% of the mortalities. Other causes of mortality identified were aspergillosis (17%), illegally shot (11%), and other traumatic factors (12%). The cause of death for 43 swans was not determined. Lead poisoning from the ingestion of lead shot continues to be a principal cause of mortality in swans overwintering in northwestern Washington.

Tundra Swan Habitat Preferences during Migration in North Dakota

I studied tundra swan (Cygnus columbianus columbianus) habitat preference in North Dakota during autumn migration, 1988-89. Many thousand tundra swans stop in the Prairie Pothole region during autumn migration, but swan resource use has not been quantified. I examined habitat preference in relation to an index of sago pondweed (Potamogeton pectinatus) presence, extent of open water, and wetland size. I compared habitat preference derived from counts of all swans to those derived from foraging swans only and cygnets only. Foraging swans preferred wetlands with sago pondweed (P = 0.03); the number of foraging swans per wetland was >4 times higher on wetlands with sago pondweed than on wetlands without sago

Changes in the wildfowl populations wintering on the Severn Estuary

Monthly winter counts of seven major wildfowl species show that, since 1960, Bewick's swan, shelduck, wigeon, teal and pintail have significantly increased in both the Severn and Britain as a whole; European White-fronted geese have shown no trend on the Severn but have significantly declined in Britain; mallard show no trend on the Severn but have increased in Britain. All except shelduck show a correlation between the trends in Britain and the Severn Estuary, while all but mallard and pintail rank as internationally important on the Severn. In recent years the Severn has assumed a considerable importance for pochard and tufted ducks. The status of many species in the Severn Estuary is dependent on the management of key areas.

Changes in the wildfowl populations wintering on the Severn Estuary

Monthly winter counts of seven major wildfowl species show that, since 1960, Bewick's swan, shelduck, wigeon, teal and pintail have significantly increased in both the Severn and Britain as a whole; European White-fronted geese have shown no trend on the Severn but have significantly declined in Britain; mallard show no trend on the Severn but have increased in Britain. All except shelduck show a correlation between the trends in Britain and the Severn Estuary, while all but mallard and pintail rank as internationally important on the Severn. In recent years the Severn has assumed a considerable importance for pochard and tufted ducks. The status of many species in the Severn Estuary is dependent on the management of key areas.

Reproductive Ecology of Tundra Swans on the Arctic National Wildlife Refuge, Alaska

Management of tundra swans (Cygnus columbianus) is hampered by a lack of information on their nesting and brood-rearing ecology. We studied tundra swan nesting and brood-rearing ecology on the Arctic National Wildlife Refuge (ANWR), Alaska, 1988-90. Nest success was 58% (n = 31) in 1988, 83% (n = 36) in 1989, 84% (n = 43) in 1990, and 76% (n = 110) for the 3 years. Nests were located predominately in marshes dominated by sheathed pondweed (Potamogeton vaginatus), mare's tail (Hippuris vulgaris), and Hoppner sedge (Carex subspathacea), or by pendent grass (Arctophila fulva), water sedge (C. aquatilis), and tall cotton grass (Eriophorum angustifolium). Nests were seldom located in upland or partially vegetated habitats and were near coastal lagoons or large coastal lakes. Incubating swans were easily disturbed by ground observers and left their nests when we were 500-2,000 m from the nest. Swans did not cover eggs with nest material prior to departure; thus, eggs were vulnerable to avian predation and thermal stress. Broodforaging sites on the Kongakut Delta (n = 41) were frequently in aquatic-marsh (59%) and saline graminoidshrub (29%) habitats, occasionally in graminoid-marsh (7%) and partially vegetated (5%) habitats, and absent from upland, graminoid-shrub-water sedge, and graminoid-shrub-cotton grass habitats. Brood-foraging sites on the Canning Delta (n = 35) were frequently in graminoid-marsh (46%), graminoid-shrub-water sedge (26%), and aquatic-marsh (23%) habitats, occasionally in graminoid-shrub-cotton grass (3%) and upland habitats (3%), and absent from saline graminoid-shrub and partially vegetated habitats. Young cygnets grazed in terrestrial habitats more frequently than older broods on the Kongakut (P = 0.003) and Canning (P = 0.053) deltas. Wetlands with sheathed pondweed were uncommon but preferred by broods (P = 0.001). Using field experiments, we evaluated effects of swan grazing and fertilization from feces on aboveground biomass production and plant-species composition. Fertilization from swan feces did not have an overall effect (P = 0.991) or interact with clipping (simulated grazing with hand shears) (P = 0.881) for any response variable investigated. Clipping increased total vegetational biomass the year of clipping (P = 0.001), decreased biomass the year after clipping (P = 0.001), and increased total shoot densities (P = 0.017). Shoot densities after clipping increased for Hoppner sedge (P = 0.010), did not change for tundra grass (Dupontia fischeri) (P = 0.296), and decreased for chickweed (Stellaria humifusa) (P = 0.006). Traditional use of foraging sites may enhance grazing areas by increasing plant production the year of grazing and densities of plant species that tolerate grazing. Protection of aquatic-marsh, graminoid-marsh, and saline graminoid-shrub habitats, particularly those supporting sheathed pondweed and traditionally used nesting areas, is important for maintaining current swan populations on ANWR. J. WILDL. MANAGE. 58(4):757-773

Interspecific Aggression by Tundra Swans toward Snow Geese on the Sagavanirktok River Delta, Alaska

Interspecific Aggression by Tundra Swans toward Snow Geese on the Sagavanirktok River Delta, Alaska

Harvest management of tundra swans Cygnus columbianus in North America : J. R. Serie & J. C. Bartonek, Wildfowl, Suppl.1, 1991, pp 359–367

Sport hunting of Tundra Swans in the U.S. is regulated under provisions of the Migratory Bird Treaty Act of 1918. Management plans cooperatively developed and agreed to between Flyway Councils and Federal wildlife agencies in Canada and the U.S. prescribe allowable harvest levels and provisions for regulating it. Harvests are managed by Eastern and Western Populations. Presently, hunts are authorized in specific locations during fall migration in the States of Alaska, Montana, Nevada, North and South Dakota, and Utah and on wintering areas in the States of New Jersey, North Carolina, and Virginia. A specified number of permits are approved by the USFW to participating states allowing each applicant to take one Tundra Swan per season. During 1979-88, the number of permits to harvest Western Population swans has averaged 3,552 per year. Of these, 1,075 swans are retrieved and 215 unretrieved. During 1986-88, an average of6,467permits have been issued to harvest Eastern Population swans. Of these, an average of 2,617 swans are retrieved and 302 unretrieved. In recent years, about 10,000permits are issued and account for a total kill of about 4,200 annually, including retrieved and unretrieved. Of this amount, 70% are derivedfrom the Eastern Population and 30% results from the Western Population. These harvest estimates account for less than 3% of the pre-season winter population estimate and are below the 10% harvest rate guideline specified in the management plans. Both Eastern and Western Populations of Tundra Swans have increased in numbers and expanded their distributions over the years since special hunting seasons were first established. Presently, these numbers exceed the populations goals prescribed by various management plans. To better assess the effects of hunting on Tundra Swans, special studies are needed to validate population estimates, identify subpopulations, determine seasonal movements and measure changes in recovery and survival rates.

Post-fire recovery of riparian resources on the Idaho batholith: a geographic information system analysis: S. H. Scher, in: GIS application in natural resources, ed M. Heit & A. Shortreid, (GIS World Inc.), 1991, pp 343–347

Many birds feed on submerged macrophytes during a temporally discrete period every year, for instance during migratory stopover or at the wintering grounds. Hence, seasonal herbivory is a common feature of the life cycle in many aquatic macrophytes. We are interested in the effect of Bewick's swans (Cygnus columbianus bewickii) feeding on the tubers of fennel pondweed (Potamogeton pectinatus) in the Netherlands every autumn. For that purpose, we developed a sequential macrophyte population model, including seasons of tuber production, herbivory and winter mortality as distinct and unambiguously defined events. The model is characterised and parameterised with both field and laboratory data. Tuber consumption inevitably decreases the density of ramets sprouting next spring, but it may actually increase the density of tubers produced in the following autumn. Hence, we can only understand the effect of grazing on the fennel pondweed population by recognising the seasonal structure of density-dependence. The mean density of fennel pondweed and the yield taken by swans are dependent on the foraging threshold below which no grazing takes place. Furthermore, the consumption has a stabilising effect for a wide range of parameter values.

Observations on sympatric Tundra, Cygnus columbianus, and Trumpeter swans, C. buccinator, in north-central Alaska, 1989-1991

Observations on sympatric Tundra, Cygnus columbianus, and Trumpeter swans, C. buccinator, in north-central Alaska, 1989-1991

Annual Survival Rates of Adult and Immature Eastern Population Tundra Swans

Tundra swans (Cygnus columbianus) of the eastern population were neckbanded in Maryland, North Carolina, and Alaska from 1966 through 1990. These swans were resighted and recaptured during autumn, winter, and spring, 1966-90. Although the original motivation for this study involved swan movements, we wanted to use the resulting data to test hypotheses about sources of variation in swan survival rates. Recaptures of legbanded and neckbanded swans permitted us to estimate neckband loss rates, which were found to vary with age and sex of swans, and number of years since initial application

The Timing of Wing Molt in Tundra Swans: Energetic and Non-Energetic Constraints

Date of wing molt initiation, based on the regression of tenth primary length on capture date, was calculated for breeding and nonbreeding Tundra Swans (Cygnus columbianus columbianus) on the Colville River Delta, Alaska. Breeding females initiated wing molt significantly later than breeding males and nonbreeding males and females; the molt of breeding females was correlated with the date on which their eggs hatched. Breeding males did not differ significantly from nonbreeding males and females in the date of molt initiation. Timing of molt in breeding males and females was consistent with the views that females delay molt while replenishing energy spent on reproduction, but was also consistent with the breeding pair's need for primaries to defend territories and to defend and brood young. Other results, including an increase in an index of female body condition throughout most of the molt period, and a positive correlation between clutch size and female hatchto-molt interval, were not predicted by the hypothesis that past energy expenditures constrain the timing of molt. Patterns of wing molt within and among other Northern Hemisphere geese and swans are also difficult to explain on the basis of energetics alone. For example, breeding females initiate molt before breeding males in many species. Also, there is extreme asynchrony between mates in two swan species; one of those species also exhibits variation in which sex initiates wing molt first. Both patterns suggest that asynchrony, per se, is important, probably to facilitate brood protection or territory defense. In Tundra Swans and other northern breeding geese and swans, the non-energetic demands of territory defense, brood defense, and brooding are probably important constraints on the timing of wing molt.

Lead toxicosis in tundra swans near a mining and smelting complex in northern Idaho

Die-offs of waterfowl have occurred in the Coeur d'Alene River system in northern Idaho since at least the early 1900's. We investigated causes of mortality and lead and cadmium contamination of 46 tundra swans (Cygnus columbianus) from 1987 to 1989; an additional 22 swans found dead in 1990 were not examined. We necropsied 43 of the 46 birds found from 1987 to 1989; 38 of these were from the Coeur d'Alene River system, which has been contaminated with mining and smelting wastes for a century, and the other 5 were from a nearby, relatively uncontaminated area. Of the 36 livers of swans from the contaminated area that were analyzed, 32 contained lethal levels of lead (6 to 40 micrograms/g, wet weight) and all birds exhibited several symptoms of lead poisoning, notably enlarged gall bladders containing viscous, dark-green bile. Only 13% of the lead-poisoned birds (10% when data were included from other studies of swans in the area) contained shot, compared to 95% of lead-poisoning swans in studies outside northern Idaho. Lead concentrations in blood samples from 16 apparently healthy swans (0.5 to 2.3 micrograms/g, and 4 lead-poisoned birds found moribund (1.3 to 9.6 micrograms/g) indicating that tundra swans accumulated high levels of lead from ingestion of sediment that contained up to 8,700 micrograms/g of lead and plants that contained up to 400 micrograms/g. The swans spend only a few weeks in the area staging during the spring migration. The five tundra swans from the uncontaminated area had low levels of lead and essentially no symptoms of lead poisoning.(ABSTRACT TRUNCATED AT 250 WORDS)

CORRELATIONS OF DAILY ACTIVITY WITH AVIAN CHOLERA MORTALITY AMONG WILDFOWL

We tested the hypothesis that wildfowl activities can influence the risk of avian cholera (Pasteurella multocida infection) for susceptible birds at Centerville, Humboldt County, California (USA). Avian cholera mortality characteristics from past epizootics were correlated with variations in flock size, habitat use and 11 feeding and nonfeeding behaviors among six empirically defined groups of wildfowl: American coots (Fulica americana), tundra swans (Cygnus columbianus), American wigeon (Anas americana), northern pintails (A. acuta), northern shovelers (A. clypeata)/mallards (A. platyrhynchos), and teal (A. discors, A. crecca, A. cyanoptera). The position of these wildfowl groups in past mortality sequences was directly correlated with mean flock size, time spent on land, and time spent grazing on land or in shallow water. We propose that variations in bird density, habitat use and frequency of grazing may serve as predisposing factors to avian cholera among wildfowl.

Tundra swans near Skeidarnarjökull, Iceland. (Photo by D. A. Walker, September 1986.)

Tundra swans near Skeidarnarjökull, Iceland. (Photo by D. A. Walker, September 1986.)

鉛中毒に罹患したハクチョウとマガンの治療

During the period from April to May 1990, 18 swans (Cygnus spp.) and 80 wild geese (Anser albifrons) were found emaciated or dead because of lead-poisoning caused by ingestion of lead shots at Lake Miyajima in Hokkaido. Twenty-seven wild geese, four Whooper Swans (C. cygnus cygnus), and two Bewick's swans (C. cygnus bewickii) were treated using disodium calcium ethylenediaminetetraacetate (CaEDTA). The concentration of blood lead at the time of admission averaged 4.6, ranging from 3.2 to 8.0μg/ml in swans, and averaged 5.6, ranging from 0.4 to 23.0μg/ml in wildgeese. In all of the swans 4 to 40 lead pellets, with an average of 17 were seen on radiographs of their gizzards. In 22 of the geese 1 to 48 lead pellets, with an average of 10.5 per bird, were seen. The blood lead levels decreased to about 1/2 to 1/5 of the initial values one week after the institution of the therapy in all the bird treated. Eleven of 27 birds recovered 3 to 8 weeks after the therapy. These lead shots were rapidly eroded as the birds recovered their appetite in re-sponse to the treatment and disappeared no radiographs during treatment days 17 to 52. Sixteen geese and all the swans failed to recover their apPetite and died within 4 weeks in spite of a decrease in the concentra-tion of blood lead.

Bewick's Swans: Their Feeding Ecology and Coexistence with Other Grazing Anatidae

Bewick's Swans: Their Feeding Ecology and Coexistence with Other Grazing Anatidae

Satellite tracking of migrating Bewick's swans

Satellite tracking of migrating Bewick's swans

The variability of DNA fingerprints in three species of swan

The genetic variation in three species of swans was examined by DNA fingerprinting. Human minisatellite probes detected a number of highly variable fragments in the restriction digests of total nuclear DNA. Assuming bands to be independent, the average allele frequency for minisatellite loci was 0·154, 0·154 and 0·109 for Mute, Whooper and Bewick's Swans, respectively. The pattern of band-distribution showed a certain degree of species-specificity, so that the fingerprints may reflect taxonomic affinities of the species. Pedigree analysis of a single family of Mute Swans showed that most of the variable fragments were inherited in a simple Mendelian fashion, allowing the relatedness of the individuals to be determined. DNA fingerprinting potentially provides a large number of genetic markers for studying the behavioural ecology, population genetics and evolution of swans.