| lead and pcb's in canvasback ducks: relationship between enzyme levels and residues in blood. | blood samples were taken for two successive years from canvasback ducks trapped in the chesapeake bay. the first winter (1972-1973) five plasma enzymes known to respond to organochlorine poisoning were examined. abnormal enzyme elevations suggested that 20% of the population sampled (23/115 ducks) might contain organochlorine contaminants, but no residue analyses were performed. the second winter (1974) two of the same enzymes, aspartate aminotransferase and lactate dehydrogenase, and a third en ... | 1976 | 827981 |
| infection and mortality in captive wild-trapped canvasback ducks. | fungal, bacterial and malarial infections, as well as malnutrition caused heavy mortality in a group of wild-trapped canvasbacks (aythya valisineria) held in 10 x 3 x 2 m open-water pens. deaths occurred between 21 and 158 days after confinement and were associated with infections of aspergillus fumigatus, escherichia coli, staphylococcus sp., streptococcus sp., klebsiella sp., enterobacter sp., and plasmodium sp. infection and mortality was believed to result from reduced resistance associated ... | 1976 | 1255909 |
| vernal increases in prolactin levels of nonbreeding male and female canvasbacks (aythya valisineria). | serum levels of prolactin were determined in nonbreeding male and female canvasbacks (aythya valisineria) from mid-april to late june to evaluate the temporal changes occurring during spring. during this time interval, serum prolactin levels increased 1.5- to 2-fold in both males and nonlaying females (p less than 0.01). serum prolactin levels of males and females exposed to natural lighting and temperature at delta, manitoba (50 degrees 11'n, 98 degrees 19'w), steadily increased from mid-april ... | 1989 | 2591720 |
| seasonal variation in pituitary responsiveness to luteinizing hormone-releasing hormone of mallards and canvasbacks. | endocrine profiles of wild mallards (anas platyrhynchos) and canvasbacks (aythya valisineria) were determined during the spring and the summer. males and females of each species were treated with a single intravenous injection of 12 micrograms of synthetic luteinizing hormone-releasing hormone (lhrh). preinjection and postinjection blood samples were collected and lh levels were determined by radioimmunoassay. lhrh evoked a brisk and significant elevation in serum lh in all ducks indicating the ... | 1985 | 3891506 |
| the canvasback duck (aythya valisineria); a new host record for plasmodium. | | 1968 | 5691433 |
| serum levels of luteinizing hormone (lh), prolactin, estradiol, and progesterone in laying and nonlaying canvasback ducks (aythya valisineria). | temporal changes in the levels of serum luteinizing hormone (lh), prolactin, estradiol, and progesterone associated with the reproductive patterns of 53 wild captive canvasback ducks were measured. the reproductive endocrinology of both laying and nonlaying females was compared in this 3-year study. females that remained sexually inactive had ovaries with small, undeveloped follicles. nonlaying ducks also had lower serum levels of lh (p less than 0.01), prolactin (p less than 0.05), estradiol, a ... | 1983 | 6354837 |
| diagnostic exercise. amyloidosis secondary to chronic infection in a canvasback duck. | | 1983 | 6834771 |
| comparative migration, growth and development of typhlocoelum cucumerinum sisowi in dabbling ducks and typhlocoelum cucumerinum cucumerinum in diving ducks. | experimental infections of mallards (anas platyrhynchos l.) with typhlocoelum cucumerinum sisowi (skrjabin, 1913) and of canvasbacks (aythya valisineria (wilson)) with typhlocoelum cucumerinum cucumerinum (rudolphi, 1809) revealed significant differences in various parameters of the life-cycle in the definitive host. both t. c. sisowi and t. c. cucumerinum migrate to the trachea via the abdominal cavity, air sacs and lungs, although t. c. cucumerinum migrate more quickly and more synchronously t ... | 1982 | 7070844 |
| prevalence and intensity of typhlocoelum cucumerinum (digenea) in wild anatids of quebec, canada. | the upper respiratory tracts of 534 wild anatids representing 20 species, shot during the 1976, 1977 and 1978 hunting seasons, were examined for typhlocoelum cucumerinum (rudolphi, 1809). typhlocoelum cucumerinum cymbium (diesing, 1850) were recovered from anas platyrhynchos, anas rubripes, anas acuta, anas discors and anas crecca. the maximum prevalence (16.7%) and intensity of infection (1.6) occurred in mallards (a. platyrhynchos). aythya valisineria and aythya marila harboured typhlocoelum c ... | 1980 | 7373728 |
| the occurrence of mycoplasmas in selected wild north american waterfowl. | we determined the prevalence of mycoplasma infection in breeding mallard (anas platyrhynchos) and canvasback (aythya valisineria) hens and their broods from the central united states (1988 to 1990); and wintering american black duck (anas rubripes) and mallard hens from the eastern united states (1990 to 1993). mycoplasmas were isolated by culturing tracheal swabs from 656 live birds and tissue samples from 112 dead waterfowl. nine (18%) of 51 mycoplasma isolates were identified as mycoplasma an ... | 1995 | 8592358 |
| exposure of wild waterfowl to mycoplasma anatis. | we developed an elisa procedure to assess the presence of m. anatis-specific serum antibody in ducks. sera from exposed and unexposed pekin ducks (anas platyrhynchos) were used to standardize the elisa and to establish reference ranges to classify elisa results as exposed or not exposed. we conducted serological surveys of female waterfowl in the central and eastern united states between 1988 and 1992 to assess the frequency of exposure in wild waterfowl. adult breeding mallards (anas platyrhync ... | 1996 | 8722273 |
| male-driven evolution among eoaves? a test of the replicative division hypothesis in a heterogametic female (zw) system. | because avian females are heterogametic, the reverse of mammals, avian sex chromosomes undergo significantly different patterns and numbers of dna replications than do those in mammals. this makes the w (female-specific) and the z chromosomes an excellent model system for the study of the replicative division hypothesis, which purports that dna substitution rate is determined by the number of germline replications. the sex-specific chromosome in birds (the w) is predicted to change at the slowes ... | 1999 | 10594176 |
| relating body condition to inorganic contaminant concentrations of diving ducks wintering in coastal california. | in wild waterfowl, poor winter body condition may negatively affect migration, survival, and reproduction. environmental contaminants have been shown to adversely affect the body condition of captive birds, but few field studies have examined body condition and contaminants in wild birds during the winter. we assessed the body condition of carcasses from a collection of canvasbacks (aythya valisineria) and lesser (a. affinis) and greater scaup (a. marila) wintering in coastal california. we used ... | 2002 | 11706369 |
| comparison of renal and salt gland function in three species of wild ducks. | three processes central to osmoregulation of marine birds were compared in three species of ducks that differ in habitat affinity, diet and saline tolerance. these processes are filtration of na+ and water from the plasma by the kidneys, their reabsorption along the renal tubules, and secretion by the salt glands. barrow's goldeneyes bucephala islandica, the most marine species, have the highest rates for all three processes and only this species can secrete all the infused salt via the salt gla ... | 2003 | 12909708 |
| redistribution of extracellular water and sodium may contribute to saline tolerance in wild ducks. | the compartmentalization of body fluids was measured in three species of ducks that differ in saline tolerance. half of the birds of each species drank freshwater, while the other half drank saline (300 mm nacl). among ducks that drank freshwater, total body water (tbw) was similar among all species, but barrow's goldeneyes (bucephala islandica), the most marine species, had larger extracellular fluid volume (ecfv) than freshwater mallards (anas platyrhynchos) or estuarine canvasbacks (aythya va ... | 2005 | 15887091 |
| blood values of the canvasback duck by age, sex and season. | blood samples were obtained from canvasback ducklings from manitoba and saskatchewan and from immature and adult canvasbacks on the mississippi river near lacrosse, wisconsin and the chesapeake bay. these samples were used to determine baseline data on red cell counts, hematocrit, total protein, glucose, cholesterol, hemaglobin and distribution of plasma proteins. calculations were also made to determine mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concent ... | 1976 | 16498873 |
| incidence of malaria in a wintering population of canvasbacks (aythya valisineria) on chesapeake bay. | canvasback ducks wintering on chesapeake bay had a 6% incidence of leucocytozoon simondi and 2% incidence of haemoproteus. subinoculation of whole blood into pekin ducklings produced a plasmodium infection rate of 31%. females were more frequently infected (12/22) than males (15/68). the parasite was identified as p. circumflexum. | 1970 | 16512153 |
| geographical gradients in the population dynamics of north american prairie ducks. | 1. geographic gradients in population dynamics may occur because of spatial variation in resources that affect the deterministic components of the dynamics (i.e. carrying capacity, the specific growth rate at small densities or the strength of density regulation) or because of spatial variation in the effects of environmental stochasticity. to evaluate these, we used a hierarchical bayesian approach to estimate parameters characterizing deterministic components and stochastic influences on popul ... | 2008 | 18631261 |
| the efficacy of protoporphyrin as a predictive biomarker for lead exposure in canvasback ducks: effect of sample storage time. | we used 363 blood samples collected from wild canvasback dueks (aythya valisineria) at catahoula lake, louisiana, u.s.a. to evaluate the effect of sample storage time on the efficacy of erythrocytic protoporphyrin as an indicator of lead exposure. the protoporphyrin concentration of each sample was determined by hematofluorometry within 5 min of blood collection and after refrigeration at 4 °c for 24 and 48 h. all samples were analyzed for lead by atomic absorption spectrophotometry. based on a ... | 1996 | 24193824 |
| rapid increase in contaminant burdens following loss of body condition in canvasbacks (aythya valisineria) overwintering on the lake st. clair region of the great lakes. | overwintering canvasbacks were collected in the lake st. clair region of the great lakes in the winter of 2008/09 and livers were analyzed for organochlorines, mercury (hg), and selenium (se). we found dramatic increases in hepatic concentrations of hg, se, sum pcbs, p,p'-dde, and other organochlorines in canvasbacks in which concentrations in february were greater than concentrations in november when overwintering ducks arrived in the study area. increases in contaminant burdens were generally ... | 2019 | 31654909 |
| integrated modeling of communities: parasitism, competition, and demographic synchrony in sympatric ducks. | functionally similar species often co-occur within an ecosystem, and they can compete for or facilitate each other's access to resources. the coupled dynamics of such species play an important role in shaping biodiversity and an ecosystem's resilience to perturbations. here we study two congeneric north american ducks: redhead aythya americana and canvasback a. vaselineria. both are largely sympatric during the breeding season, and in addition to competition, facultative parasitic egg-laying can ... | 2012 | 23236916 |
| intra-guild interactions and projected impact of climate and land use changes on north american pochard ducks. | the co-occurrence of functionally similar species is very common in nature, and is often put forward as a basis for ecosystem resilience to disturbance. at the same time, competition between similar species is also considered a strong driver of community composition. however, environmental stochasticity can alter this prediction, either because competitive abilities depend on time-varying factors or because covariance in species' responses to environmental conditions masks the effect of competit ... | 2013 | 23322386 |
| sexual imprinting misguides species recognition in a facultative interspecific brood parasite. | sexual reproduction relies on the recognition of conspecifics for breeding. most experiments in birds have implicated a critical role for early social learning in directing subsequent courtship behaviours and mating decisions. this classical view of avian sexual imprinting is challenged, however, by studies of megapodes and obligate brood parasites, species in which reliable recognition is achieved despite the lack of early experience with conspecifics. by rearing males with either conspecific o ... | 2010 | 20484239 |
| sediment ingestion rates in waterfowl (anatidae) and their use in environmental risk assessment. | when waterfowl (anatidae) ingest sediment as they feed, they are exposed to the environmental contaminants in those sediments. the rate of ingestion may be key to assessing environmental risk. rates of sediment ingestion were estimated as from <2% to 22% in 16 species of waterfowl collected in the northeastern united states. the piscivorous red-breasted merganser (mergus serrator) ingested sediment at the lowest rate and the benthos-feeding canvasback (aythya valisineria) at the highest rate. se ... | 2008 | 18237229 |
| trace elements in canvasbacks (aythya valisineria) wintering in louisiana, usa, 1987-1988. | we determined trace element concentrations in livers of canvasbacks (aythya valisineria) collected at catahoula lake and the mississippi river delta, louisiana during, the winter of 1987-1988. forty percent of canvasbacks wintering at lake catahoula had elevated concentrations of lead (>6.7 microg g(-1) dry weight) in the liver; 33% had concentrations consistent with lead intoxication (>26.7 microg g(-1)). based on the number of canvasbacks that winter at lake catahoula and the frequency of lead ... | 1994 | 15091696 |
| combining band recovery data and pollock's robust design to model temporary and permanent emigration. | capture-recapture models are widely used to estimate demographic parameters of marked populations. recently, this statistical theory has been extended to modeling dispersal of open populations. multistate models can be used to estimate movement probabilities among subdivided populations if multiple sites are sampled. frequently, however, sampling is limited to a single site. models described by burnham (1993, in marked individuals in the study of bird populations, 199-213), which combined open p ... | 2001 | 11252610 |
| evaluation of isoflurane and propofol anesthesia for intraabdominal transmitter placement in nesting female canvasback ducks. | heart rate, occurrence of apnea, body temperature, quality of anesthesia and nest abandonment were compared during either propofol or isoflurane anesthesia of nesting female canvasback ducks (aythya valisineria) at 15 to 18 days of incubation. one hundred eighteen canvasbacks were assigned randomly to three treatments so that nest abandonment could be compared among treatments from may to july 1995 and 1996. sterile dummy silicone implants were placed during an abdominal laparotomy while ducks w ... | 2000 | 10813615 |
| circadian rhythms in diving behavior and ventilatory response to asphyxia in canvasback ducks. | underwater feeding behavior was measured in 10 captive canvasback ducks (aythya valisineria) for 12 days under a 12:12-h light-dark photoperiod. feeding activity exhibited a daily rhythm, with 76% of dives occurring at night. in separate experiments on six of these ducks, a circadian rhythm was observed in the duration of voluntary dives. dives at night (14.7 +/- 0.7 s) were significantly longer than those during the day (10.7 +/- 0.7 s). these day-night differences in diving behavior were accom ... | 1998 | 9530234 |