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Alan D Afton - One of the best experts on this subject based on the ideXlab platform.
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temporal variation in survival and recovery rates of Lesser Scaup a response
Journal of Wildlife Management, 2017Co-Authors: Todd W Arnold, David N Koons, Alan D Afton, Michael J. Anteau, Christopher A NicolaiAbstract:We recently analyzed long-term (1951–2011) continental band-recovery data from Lesser Scaup (Aythya affinis) and demonstrated that harvest rates declined through time, but annual survival rates exhibited no such trends; moreover, annual harvest and survival rates were uncorrelated for all age-sex classes. We therefore concluded that declining fecundity was most likely responsible for recent population declines, rather than changes in harvest or survival. Lindberg et al. (2017) critiqued our conclusions, arguing that we did little more than fail to reject a null hypothesis of compensatory mortality, postulated ecologically unrealistic changes in fecundity, and failed to give sufficient consideration to additive harvest mortality. Herein, we re-summarize our original evidence indicating that harvest has been compensatory, or at most weakly additive, and demonstrate that our analysis had sufficient power to detect strongly additive mortality if it occurred. We further demonstrate that our conclusions were not confounded by population size, band loss, or individual heterogeneity, as suggested by Lindberg et al. (2017), and we provide additional support for our conjecture that low fecundity played a major role in declining Scaup populations during 1983–2006. We therefore reiterate our original management recommendations: given low harvest rates and lack of demonstrable effect on Scaup survival, harvest regulations could return to more liberal frameworks, and waterfowl biologists should work together to continue banding Lesser Scaup and use these data to explore alternative hypotheses to identify the true ecological causes of population change, given that it is unlikely to be excessive harvest. © 2017 The Wildlife Society.
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environmental factors influence Lesser Scaup migration chronology and population monitoring
Journal of Wildlife Management, 2016Co-Authors: Taylor A Finger, Alan D Afton, Shannon S Badzinski, Scott A Petrie, Michael L Schummer, Michael A Johnson, Michael L Szymanski, Kevin J Jacobs, Glenn H Olsen, Mark A MitchellAbstract:Identifying environmental metrics specific to Lesser Scaup (Aythya affinis; Scaup) spring migration chronology may help inform development of conservation, management and population monitoring. Our objective was to determine how environmental conditions influence spring migration of Lesser Scaup to assess the effectiveness of the Waterfowl Breeding Population and Habitat Survey in accurately estimating Scaup populations. We first compared peak timing of mallard (Anas platyrhynchos) and Scaup migration from weekly ground surveys in North Dakota, USA because the Waterfowl Breeding Population and Habitat Survey is designed to capture annual mallard migration. As predicted, we detected that peak timing of Scaup and mallard migrations differed in 25 of 36 years investigated (1980–2010). We marked Scaup with satellite transmitters (n = 78; 7,403 locations) at Long Point, Lake Erie, Ontario, Canada; Pool 19 of the Mississippi River, Iowa and Illinois, USA; and Presque Isle Bay, Lake Erie, Pennsylvania, USA. We tested the assumption that our marked Scaup were representative of the continental population using the traditional survey area by comparing timing of migration of marked birds and Scaup counted in the North Dakota Game and Fish Department survey. We detected a strong positive correlation between marked Scaup and the survey data, which indicated that marked Scaup were representative of the population. We subsequently used our validated sample of marked Scaup to investigate the effects of annual variation in temperature, precipitation, and ice cover on spring migration chronology in the traditional and eastern survey areas of the Waterfowl Breeding Population and Habitat Survey, 2005–2010. We evaluated competing environmental models to explain variation in timing and rate of Scaup migration at large-scale and local levels. Spring migration of Scaup occurred earlier and faster during springs with warmer temperatures and greater precipitation, variables known to influence energy budgets and wetland availability. Our results suggest that surveys designed to index abundance of breeding mallards is imprecise for estimating Scaup abundance, and inaccurate at estimating breeding population size by survey stratum. © 2016 The Wildlife Society.
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temporal variation in survival and recovery rates of Lesser Scaup
Journal of Wildlife Management, 2016Co-Authors: Todd W Arnold, David N Koons, Alan D Afton, Michael J. Anteau, Christopher A NicolaiAbstract:Management of Lesser Scaup (Aythya affinis) has been hindered by access to reliable data on population trajectories and vital rates. We conducted a Bayesian analysis of historical (1951–2011) band-recovery data throughout North America to estimate annual survival and recovery rates for juvenile and adult male and female Lesser Scaup to determine if increasing harvest or declining survival rates have contributed to population changes and to determine if harvest has been primarily additive or compensatory. Annual recovery rates were low, ranging from 1% to 4% for adults and 2% to 10% for juveniles during most years, with trend models indicating that recovery rates have declined through time for all age–sex classes. Annual survival (mid-Aug to mid-Aug) averaged 0.402 ( 0.043) for juvenile males, 0.416 ( 0.067) for juvenile females, 0.689 ( 0.109) for adult males, and 0.602 ( 0.115) for adult females, where represents an estimate of annual process variation in each survival rate. Annual survival rates exhibited no evidence of long-term declines or negative correlations with annual recovery rates (i.e., an index of harvest intensity) for any age–sex class, suggesting that declining fecundity was the most likely explanation for population declines during 1975–2005. We conclude that hunting mortality played a minor role in affecting population dynamics of Lesser Scaup and waterfowl managers could take a less cautious approach in managing harvest, especially if recruiting or maintaining waterfowl hunters are viewed as important management objectives. © 2016 The Wildlife Society.
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hepatic element concentrations of Lesser Scaup aythya affinis during spring migration in the upper midwest
Archives of Environmental Contamination and Toxicology, 2011Co-Authors: Angela Pillatzki, Regg Neiger, Steven R Chipps, Kenneth F Higgins, Nancy Thiex, Alan D AftonAbstract:High concentrations of some hepatic elements might be contributing to the decline of the continental Lesser Scaup (Aythya affinis) population. We evaluated hepatic element concentrations of male and female Lesser Scaup collected from the upper Midwest (Iowa, Minnesota, North Dakota, and South Dakota) during the 2003 and 2004 spring migrations. We measured concentrations of 24 elements in livers of 117 Lesser Scaup. We found that only selenium concentrations were at levels (>3.0 μg/g wet weight [ww)]) proposed to adversely affect reproduction. Approximately 49% of females (n = 61) had individual hepatic concentrations >3.0 μg/g ww selenium (Se). Our observed hepatic concentration of Se was similar to that reported in Lesser Scaup collected from the mid-continental United States but less than Se concentrations reported from the Great Lakes region. We found that the liver cadmium (Cd) concentration for males was significantly higher than that for females. Gender differences in hepatic Cd concentrations have not been previously reported for Lesser Scaup, but Cd is known to have negative impacts on male reproduction. Our results indicate that Lesser Scaup migrating through the upper Midwest in spring have elevated Se levels and that males carry a significantly greater Cd burden than females. Moreover, elemental concentrations might be high enough to affect reproduction in both male and female Lesser Scaup, but controlled laboratory studies are needed to adequately assess the effects of Se and Cd on Lesser Scaup reproduction.
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testing competing hypotheses for chronology and intensity of Lesser Scaup molt during winter and spring migration
The Condor, 2011Co-Authors: Andrea C E Anteau, Michael J. Anteau, Alan D AftonAbstract:Abstract. We examined chronology and intensity of molt and their relationships to nutrient reserves (lipid and protein) of Lesser Scaup (Aythya affinis) to test predictions of two competing hypotheses. The “staggered cost” hypothesis states that contour-feather molt is nutritionally costly and should not occur during nutritionally costly periods of the annual cycle unless adequate nutrients are available. The “breeding plumage” hypothesis states that prealternate molt must be complete prior to nesting, regardless of nutrient availability. Males and females were completing prebasic molt during winter (Louisiana) and had similar molt intensities. Females underwent prealternate molt during spring migration (Illinois and Minnesota) and prebreeding (Manitoba) periods; 53% and 93% of females were in moderate to heavy molt in Minnesota and Manitoba, respectively, despite experiencing other substantial nutritional costs. Intensity of prealternate molt was not correlated with lipid reserves even though females, on...
Michael J. Anteau - One of the best experts on this subject based on the ideXlab platform.
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temporal variation in survival and recovery rates of Lesser Scaup a response
Journal of Wildlife Management, 2017Co-Authors: Todd W Arnold, David N Koons, Alan D Afton, Michael J. Anteau, Christopher A NicolaiAbstract:We recently analyzed long-term (1951–2011) continental band-recovery data from Lesser Scaup (Aythya affinis) and demonstrated that harvest rates declined through time, but annual survival rates exhibited no such trends; moreover, annual harvest and survival rates were uncorrelated for all age-sex classes. We therefore concluded that declining fecundity was most likely responsible for recent population declines, rather than changes in harvest or survival. Lindberg et al. (2017) critiqued our conclusions, arguing that we did little more than fail to reject a null hypothesis of compensatory mortality, postulated ecologically unrealistic changes in fecundity, and failed to give sufficient consideration to additive harvest mortality. Herein, we re-summarize our original evidence indicating that harvest has been compensatory, or at most weakly additive, and demonstrate that our analysis had sufficient power to detect strongly additive mortality if it occurred. We further demonstrate that our conclusions were not confounded by population size, band loss, or individual heterogeneity, as suggested by Lindberg et al. (2017), and we provide additional support for our conjecture that low fecundity played a major role in declining Scaup populations during 1983–2006. We therefore reiterate our original management recommendations: given low harvest rates and lack of demonstrable effect on Scaup survival, harvest regulations could return to more liberal frameworks, and waterfowl biologists should work together to continue banding Lesser Scaup and use these data to explore alternative hypotheses to identify the true ecological causes of population change, given that it is unlikely to be excessive harvest. © 2017 The Wildlife Society.
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temporal variation in survival and recovery rates of Lesser Scaup
Journal of Wildlife Management, 2016Co-Authors: Todd W Arnold, David N Koons, Alan D Afton, Michael J. Anteau, Christopher A NicolaiAbstract:Management of Lesser Scaup (Aythya affinis) has been hindered by access to reliable data on population trajectories and vital rates. We conducted a Bayesian analysis of historical (1951–2011) band-recovery data throughout North America to estimate annual survival and recovery rates for juvenile and adult male and female Lesser Scaup to determine if increasing harvest or declining survival rates have contributed to population changes and to determine if harvest has been primarily additive or compensatory. Annual recovery rates were low, ranging from 1% to 4% for adults and 2% to 10% for juveniles during most years, with trend models indicating that recovery rates have declined through time for all age–sex classes. Annual survival (mid-Aug to mid-Aug) averaged 0.402 ( 0.043) for juvenile males, 0.416 ( 0.067) for juvenile females, 0.689 ( 0.109) for adult males, and 0.602 ( 0.115) for adult females, where represents an estimate of annual process variation in each survival rate. Annual survival rates exhibited no evidence of long-term declines or negative correlations with annual recovery rates (i.e., an index of harvest intensity) for any age–sex class, suggesting that declining fecundity was the most likely explanation for population declines during 1975–2005. We conclude that hunting mortality played a minor role in affecting population dynamics of Lesser Scaup and waterfowl managers could take a less cautious approach in managing harvest, especially if recruiting or maintaining waterfowl hunters are viewed as important management objectives. © 2016 The Wildlife Society.
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testing competing hypotheses for chronology and intensity of Lesser Scaup molt during winter and spring migration
The Condor, 2011Co-Authors: Andrea C E Anteau, Michael J. Anteau, Alan D AftonAbstract:Abstract. We examined chronology and intensity of molt and their relationships to nutrient reserves (lipid and protein) of Lesser Scaup (Aythya affinis) to test predictions of two competing hypotheses. The “staggered cost” hypothesis states that contour-feather molt is nutritionally costly and should not occur during nutritionally costly periods of the annual cycle unless adequate nutrients are available. The “breeding plumage” hypothesis states that prealternate molt must be complete prior to nesting, regardless of nutrient availability. Males and females were completing prebasic molt during winter (Louisiana) and had similar molt intensities. Females underwent prealternate molt during spring migration (Illinois and Minnesota) and prebreeding (Manitoba) periods; 53% and 93% of females were in moderate to heavy molt in Minnesota and Manitoba, respectively, despite experiencing other substantial nutritional costs. Intensity of prealternate molt was not correlated with lipid reserves even though females, on...
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lipid reserves of Lesser Scaup aythya affinis migrating across a large landscape are consistent with the spring condition hypothesis
The Auk, 2009Co-Authors: Michael J. Anteau, Alan D AftonAbstract:ABSTRACT. The “spring condition” hypothesis (SCH) states that nutrition during spring migration affects survival, reproductive success, and, ultimately, population size of migratory birds. The North American population of Lesser Scaup (Aythya affinis) has experienced a marked decline, apparently because of poor recruitment. An important prediction of the SCH is that female Lesser Scaup have low lipid reserves during spring migration. We previously reported that lipid reserves and body mass of females collected on migratory stopover areas in northwestern Minnesota in springs 2000–2001 were lower than those on the same areas in the 1980s and markedly lower than those collected at Pool 19 of the Mississippi River in 2000–2001, an important preceding stopover area. However, it was unclear whether these findings represented a site-specific result or a landscape-scale phenomenon. Accordingly, we examined lipid and body mass of 641 female Lesser Scaup migrating across seven eco-physiographic regions of Iowa, Min...
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wetland use and feeding by Lesser Scaup during spring migration across the upper midwest usa
Wetlands, 2009Co-Authors: Michael J. Anteau, Alan D AftonAbstract:Low food availability and forage quality and concomitant decreased lipid reserves of Lesser Scaup (Aythya affinis; hereafter Scaup) during spring migration in the upper Midwest may partially explain reductions in the continental population of Scaup. In springs 2004–2005, we examined wetland use and feeding activity of Scaup on 356 randomly-selected wetlands within 6 regions in Iowa, Minnesota, and North Dakota. We examined wetland characteristics that favor high Scaup use in 286 of these wetlands. We found that probabilities of wetland use and feeding by Scaup increased with turbidity up to 45 and 30 NTU, respectively, but then declined at higher turbidity levels. Wetland use was positively correlated with size of open-water zone and amphipod densities, but was not correlated with chironomid densities. Feeding increased with amphipod density up to 26 m−3 and then declined at higher amphipod densities; Scaup seemingly forage most efficiently at amphipod densities above 26 m−3. Wetland use was higher in North Dakota than in southern Minnesota and Iowa. Our results indicate that effective wetland restoration efforts to benefit Scaup require maintaining abundant populations of amphipods (generally near 26 m−3 landscape geometric mean) in wetlands with large (> 500 m diameter) open-water zones throughout the upper Midwest, but especially within Iowa and southern Minnesota.
Robert G Clark - One of the best experts on this subject based on the ideXlab platform.
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Geographic variation in the isotopic (δD, δ13C, δ15N, δ34S) composition of feathers and claws from Lesser Scaup and northern pintail: implications for studies of migratory connectivity
Canadian Journal of Zoology, 2020Co-Authors: Robert G Clark, Keith A Hobson, Leonard I WassenaarAbstract:Stable hydrogen isotope (δD) measurements of bird feathers can reveal approximate North American latitudes where feathers were grown by linking feather δD values to well-defined geographic patterns in δD values in growing-season precipitation. In waterfowl, this approach may require caution because wetlands are potentially “disconnected” from predictable isotopic patterns in precipitation waters. Stable carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S) isotope values of avian tissues may show geographic structure but can be complicated by land use. We analyzed claws of wintering adult northern pintails (Anas acuta L., 1758) from California and Texas, and feathers and claws of Lesser Scaup ( Aythya affinis (Eyton, 1838)) ducklings from northwestern North America, to determine geographic variation in δD, δ13C, δ15N, and δ34S values. Wintering pintails from Texas and California were distinguished with claw δD and δ15N values. In Scaup, feather δD values differed among biomes and were positively associated with latitude; geographic variation in other isotopes was less pronounced. The δD values in feathers and claws of individual Scaup ducklings were correlated. A positive relationship between Scaup feather δD values and δD values in growing-season precipitation was similar to results reported for songbirds. Thus, δD values in waterfowl feathers can provide new knowledge about natal origins and moulting sites.
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Factors influencing mortality of Lesser Scaup (Aythya affinis) ducklings during a West Nile virus outbreak
Canadian Journal of Zoology, 2014Co-Authors: Kirsty Gurney, Robert G Clark, P.s. CurryAbstract:Temporal variation in exposure and (or) susceptibility to disease-causing agents may result in changing disease risks for offspring of seasonally reproducing organisms. Although increases in disease risk and disease-related mortality have been observed during the course of the breeding cycle in some systems, the extent to which this is a generalized ecological pattern remains uncertain. We obtained data during an outbreak of West Nile virus (WNV) associated mortality in 50 semicaptive Lesser Scaup (Aythya affinis (Eyton, 1838)) ducklings and used known-fate survival models to assess whether daily survival rate (DSR) was related to age, hatch date, immunogenic challenge, vector abundance, and risk of WNV infection. Ducklings produced late in the breeding cycle had lower survival probabilities, relative to earlier conspecifics, but the best predictor of DSR was relative risk, suggesting that reduced survival of late-hatched individuals may have been related to increasing exposure to WNV-infected vectors.
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seasonal variation in pre fledging survival of Lesser Scaup aythya affinis hatch date effects depend on maternal body mass
Journal of Avian Biology, 2012Co-Authors: Kirsty Gurney, Robert G Clark, Stuart M SlatteryAbstract:Among temperate-breeding birds, offspring survival and reproductive success are often inversely related to timing of breeding. The mechanisms that produce seasonal declines in offspring survival are not fully understood but may be related to temporal changes in parental quality, environmental quality, or both. We analyzed data for Lesser Scaup Aythya affinis to evaluate hypothesized effects of parental quality and date on pre-fledging survival. Maternal quality, as indexed by body mass, did not have an independent effect on offspring survival in this species. Maternal body mass did not decline seasonally and did not have an independent effect on duckling survival. Although we did not detect an independent effect of hatch date on duckling survival, duckling survival declined seasonally for broods raised by lightweight females, indicating an interactive effect of maternal mass and date. We hypothesize that this interaction may be driven by seasonally declining food resources coupled with the influence of female condition on the ability to monopolize food resources or remain attentive to the brood. We also tested morphological predictions of the date hypothesis by examining physical characteristics of ducklings. When corrected for age and size, late-hatched ducklings tended to have marginally larger digestive systems and smaller leg muscles than did early-hatched birds. Abundances of intestinal parasites acquired through diet decreased marginally in late-hatched ducklings. Results for digestive system and parasite infection patterns suggested that later-hatched broods may shift diets, consistent with a contribution of environmental factors to seasonal variation in offspring survival. Taken together, our results suggest that both female attributes and environmental conditions may influence seasonal patterns of offspring survival in this species.
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breeding season survival of female Lesser Scaup in the northern boreal forest
Arctic, 2010Co-Authors: Rodney K Brook, Robert G ClarkAbstract:One hypothesis advanced to explain the decline in Lesser Scaup ( Aythya affinis ) populations during the past 20 years is that adult female survival has decreased. However, no survival probability estimates exist for the boreal forest, the region where most Scaup breed. We captured and radio-marked female Lesser Scaup (n = 42) near Yellowknife, Northwest Territories, Canada, just before the breeding season in 1999 and 2000. Constant weekly survival probability was estimated using a Cormack-Jolly- Seber model (0.96). We extrapolate this rate to estimate survival probability for the nesting season (0.80, SE = 0.09), the period when females are at greatest risk of predation. Recent estimates of annual mortality (42%) suggest that about 50% of annual female mortality occurs during the breeding season, a result similar to recent conclusions from studies of prairie-nesting Lesser Scaup. Further, our survival estimate provides information required to produce preliminary models of population dynamics for boreal Lesser Scaup, a step that could greatly improve our understanding of decline in this species.
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a method for investigating population declines of migratory birds using stable isotopes origins of harvested Lesser Scaup in north america
PLOS ONE, 2009Co-Authors: Keith A Hobson, Robert G Clark, Michael B Wunder, Steven L Van Wilgenburg, Leonard I WassenaarAbstract:BACKGROUND: Elucidating geographic locations from where migratory birds are recruited into adult breeding populations is a fundamental but largely elusive goal in conservation biology. This is especially true for species that breed in remote northern areas where field-based demographic assessments are logistically challenging. METHODOLOGY/FINDINGS: Here we used hydrogen isotopes (deltaD) to determine natal origins of migrating hatch-year Lesser Scaup (Aythya affinis) harvested by hunters in the United States from all North American flyways during the hunting seasons of 1999-2000 (n = 412) and 2000-2001 (n = 455). We combined geospatial, observational, and analytical data sources, including known Scaup breeding range, deltaD values of feathers from juveniles at natal sites, models of deltaD for growing-season precipitation, and Scaup band-recovery data to generate probabilistic natal origin landscapes for individual Scaup. We then used Monte Carlo integration to model assignment uncertainty from among individual deltaD variance estimates from birds of known molt origin and also from band-return data summarized at the flyway level. We compared the distribution of Scaup natal origin with the distribution of breeding population counts obtained from systematic long-term surveys. CONCLUSIONS/SIGNIFICANCE: Our analysis revealed that the proportion of young Scaup produced in the northern (above 60 degrees N) versus the southern boreal and Prairie-Parkland region was inversely related to the proportions of breeding adults using these regions, suggesting that despite having a higher relative abundance of breeding adults, the northern boreal region was less productive for Scaup recruitment into the harvest than more southern biomes. Our approach for evaluating population declines of migratory birds (particularly game birds) synthesizes all available distributional data and exploits the advantages of intrinsic isotopic markers that link individuals to geography.
Heath M Hagy - One of the best experts on this subject based on the ideXlab platform.
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blood parasite infection linked to condition of spring migrating Lesser Scaup aythya affinis
Canadian Journal of Zoology, 2018Co-Authors: Loren Merrill, Jeffrey M Levengood, Joshua M Osborn, Conner J England, Heath M HagyAbstract:Numerous organisms exhibit carry-over effects, in which previous environmental conditions impact current performance. For example, reproductive output for many migratory birds can be impacted by events during the preceding migration. Lesser Scaup (Aythya affinis (Eyton, 1838); hereafter Scaup) declined dramatically during 1970s–2000s, and there is evidence linking reduced reproductive output to reduced body condition during spring migration. In addition to food availability and quality, haemosporidian parasites (Plasmodium spp., Haemoproteus spp.) may be associated with condition of spring-migrating birds. We examined whether haemosporidian parasite infection status was linked to measures of size (mass, wing length, tarsus length, and keel length) and condition (body fat, size-corrected mass, wing-loading) in female spring-migrating Scaup. Infection prevalence varied by year (21.7% in 2014; 47.1% in 2015) and percent body fat was negatively associated with the probability of infection. Body fat levels dec...
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associations of intestinal helminth infections with health parameters of spring migrating female Lesser Scaup aythya affinis in the upper midwest usa
Parasitology Research, 2018Co-Authors: Conner J England, Jeffrey M Levengood, Joshua M Osborn, Aaron P Yetter, Rebecca A Cole, Cory D Suski, Heath M HagyAbstract:Thousands of Lesser Scaup (Aythya affinis) die during spring and fall migrations through the upper Midwest, USA, from infections with Cyathocotyle bushiensis and Sphaeridiotrema spp. (Class: Trematoda) after ingesting infected intermediate hosts, such as non-native faucet snails (Bithynia tentaculata). The Lesser Scaup is a species of conservation concern and is highly susceptible to these infections. We collected female Lesser Scaup from spring migratory stopover locations throughout Illinois and Wisconsin and assessed biochemical and morphological indicators of health in relation to intestinal helminth loads. Helminth species diversity, total trematode abundance, and the infection intensities of the trematodes C. bushiensis and Sphaeridiotrema spp. were associated with percent body fat, blood metabolites, hematological measures, and an index of foraging habitat quality. Helminth diversity was negatively associated with percent body fat, albumin concentrations, and monocytes, whereas glucose concentrations displayed a slight, positive association. Total trematode abundance was negatively associated with blood concentrations of non-esterified fatty acids and albumin. Infections of C. bushiensis were positively related to basophil levels, whereas Sphaeridiotrema spp. infection intensity was negatively associated with packed cell volume and foraging habitat quality. Thus, commonly measured health metrics may indicate intestinal parasite infections and help waterfowl managers understand overall habitat quality. Intestinal parasitic loads offer another plausible mechanism underlying the spring condition hypothesis.
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spatiotemporal distributions of intestinal helminths in female Lesser Scaup aythya affinis during spring migration from the upper midwest usa
Journal of Helminthology, 2017Co-Authors: J C England, Jeffrey M Levengood, Joshua M Osborn, Aaron P Yetter, John M Kinsella, Rebecca A Cole, Cory D Suski, Heath M HagyAbstract:: We examined the associations between intestinal helminth infracommunity structure and infection parameters and the age, size, and year and region of collection of 130 female Lesser Scaup (Aythya affinis) during their 2014-2015 spring migrations through the upper Midwest, USA. We identified a total of 647,174 individual helminths from 40 taxa, including 20 trematodes, 14 cestodes, 4 nematodes and 2 acanthocephalans parasitizing Lesser Scaup within the study area. Lesser Scaup were each infected with 2-23 helminth taxa. One digenean, Plenosoma minimum, is reported for the first time in Lesser Scaup and in the Midwest. Mean trematode abundance and total helminth abundance was significantly less in 2015 than 2014, and we suspect that colder weather late in 2015 impacted the intermediate host fauna and caused the observed differences. Brillouin's species diversity of helminths was greatest in the northernmost region of the study area, which coincides with the range of a non-indigenous snail that indirectly causes annual mortality events of Lesser Scaup. While host age and size were not determined to be influential factors of helminth infracommunity structure, non-parametric ordination and permutational analysis of co-variance revealed that year and region of collection explained differences in helminth infracommunities. Our results suggest that spatiotemporal variations play an important role in the structure of intestinal helminth infracommunities found in migrating Lesser Scaup hosts, and may therefore impact host ability to build endogenous reserves at certain stopover locations in the Midwest.
Thomas W Custer - One of the best experts on this subject based on the ideXlab platform.
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Movement Patterns of Wintering Lesser Scaup in Grand Calumet River—Indiana Harbor Canal, Indiana
Journal of Great Lakes Research, 2009Co-Authors: Christine M Custer, Thomas W Custer, Daniel W Sparks, Randy K Hines, Christopher O KochannyAbstract:Lesser Scaup (Aythya affinis) winter in the Grand Calumet River—Indiana Harbor Canal (GCR-IHC) drainage into southern Lake Michigan, a polluted oasis in the highly urban and industrial corridor of northern Illinois and Indiana. The GCR-IHC is an important wintering area for Lesser Scaup in northwestern Indiana, especially after Lake Michigan freezes, because of the lack of other wildlife habitat in the area. We investigated the feeding and movement patterns of these wintering Lesser Scaup to better understand the ecological significance of this area to wintering waterfowl and to interpret contaminant levels in these Lesser Scaup. We implanted radio transmitters in 20 individuals in January 1994 and tracked them until early March 1994. Four Lesser Scaup disappeared and four died within the first 2 weeks after implantation; 12 Lesser Scaup remained in the GCR-IHC for the next 6–7 weeks. Individual radio-marked Scaup (n = 12) were located in the GCR-IHC on an average of 62.2% (extreme values = 25–87%) of the searches. No radio-marked Lesser Scaup were located outside the GCR-IHC. Lesser Scaup were feeding during 23% of the radio fixes.
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relationships of cadmium mercury and selenium with nutrient reserves of female Lesser Scaup aythya affinis during winter and spring migration
Environmental Toxicology and Chemistry, 2007Co-Authors: Michael J. Anteau, Christine M Custer, Alan D Afton, Thomas W CusterAbstract:: Trace elements may have important effects on body condition of ducks during spring migration, because individuals are experiencing energetically costly events (e.g., migration, nutrient reserve accumulation, pair formation, feather molt, and ovarian follicle development). We examined relationships among hepatic cadmium, mercury, and selenium concentrations (microg/g dry wt) and nutrient reserves (lipid, protein, and mineral) of female Lesser Scaup (Aythya affinis) during winter and spring migration at four locations within the Mississippi Flyway (LA, IL, and MN, USA, and MB, Canada). Selenium concentrations (range, 3.73-52.29 microg/g dry wt) were positively correlated with lipid reserves (F1,73 = 22.69, p < 0.001, type III partial r2 = 0.24), whereas cadmium was negatively correlated with lipid reserves (F1,73 = 6.92, p = 0.010, type III partial r2 = 0.09). The observed relationship between cadmium and lipid reserves may be cause for concern, because lipid reserves of females declined by 55 g (47%), on average, within the range of observed cadmium concentrations (0.23-7.24 microg/g dry wt), despite the relatively low cadmium concentrations detected. Mean cadmium concentrations were higher in Minnesota (1.23 microg/g dry wt) and Manitoba (1.11 microg/g dry wt) than in Louisiana (0.80 microg/g dry wt) and Illinois (0.69 microg/g dry wt). However, mean cadmium concentrations predict lipid reserves of females to be only 11 g lower, on average, in Minnesota than in Illinois. Previous research documented that lipid reserves were 100 g lower in Minnesota than in Illinois; consequently, cadmium is unlikely to be the sole cause for decreases in lipid reserves of females during late-spring migration.
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Trace Elements in Lesser Scaup (Aythya affinis) from the Mississippi Flyway
Ecotoxicology, 2003Co-Authors: Christine M Custer, Thomas W Custer, Alan D Afton, Michael J. Anteau, David E. WootenAbstract:Previous research reported that concentrations of selenium in the livers of 88–95% of Lesser Scaup from locations in Lake Erie, Lake St. Clair, and Lake Michigan, USA were either elevated (10–33 µg/g dry weight [dw]) or in the potentially harmful range (>33 µg/g dw). In order to determine the geographic extent of these high selenium concentrations, we collected Lesser Scaup in Louisiana, Arkansas, Illinois, Minnesota, Wisconsin, and Manitoba and analyzed the livers for 19 trace elements. We found that all trace element concentrations, except for selenium, generally were low. Arsenic, which usually is not detected in liver samples, was detected in Louisiana and may be related to past agricultural usages. Chromium, which also is not usually detected, was only present in Lesser Scaup from Arkansas and may be related to fertilizer applications. Cadmium and mercury concentrations did not differ among locations and concentrations were low. Selenium concentrations in Arkansas (geometric mean=4.2 µg/g dw) were significantly lower than those in Louisiana (10.7 µg/g dw), Illinois (10.5 µg/g dw), and Minnesota (8.0 µg/g dw); concentrations in Wisconsin and Manitoba were intermediate (6.6 and 6.5 µg/g dw). About 25% of Lesser Scaup livers contained elevated selenium concentrations; however, none were in the harmful range. We concluded that selenium concentrations in Lesser Scaup in the Mississippi Flyway are elevated in some individuals, but not to the extent that has been documented in the industrial portions of the Great Lakes.
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trace elements organochlorines polycyclic aromatic hydrocarbons dioxins and furans in Lesser Scaup wintering on the indiana harbor canal
Environmental Pollution, 2000Co-Authors: Thomas W Custer, Christine M Custer, Randy K Hines, Daniel W SparksAbstract:During the winter of 1993–94, male Lesser Scaup (Aythya affinis) were collected on the heavily polluted Indiana Harbor Canal (IHC), East Chicago, IN, USA, and examined for tissue contaminant levels. Lesser Scaup collected on the IHC had higher concentrations of cadmium (Cd), mercury (Hg), selenium (Se), polychlorinated biphenyls (PCBs), selected organchlorine pesticides, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polycyclic aromatic hydrocarbons, and aliphatic hydrocarbons than reference birds. Of the Scaup collected on the IHC, 44% had Cd concentrations in the liver considered above background for freshwater waterfowl (>3 μg/g dry wt.), 50% had Se concentrations in the liver above a level possibly harmful to the health of young and adult birds (>33 μg/g dry wt.), and 88% of the Scaup carcasses exceeded the PCB human consumption guidelines for edible poultry in the USA (>3.0 μg/g lipid wt.). The ratio of pristane:n-heptadecane concentrations in 47% of Lesser Scaup collected on IHC was elevated above 1.0, which is indicative of chronic exposure to petroleum hydrocarbons.
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mixed function oxygenases oxidative stress and chromosomal damage measured in Lesser Scaup wintering on the indiana harbor canal
Archives of Environmental Contamination and Toxicology, 2000Co-Authors: Thomas W Custer, Christine M Custer, Daniel W Sparks, Randy K Hines, M J Melancon, D J Hoffman, John W Bickham, J K WickliffeAbstract:During the winter of 1993–1994, male Lesser Scaup (Aythya affinis) were collected on the heavily polluted Indiana Harbor Canal, East Chicago, Indiana, and examined for several bioindicators of chemical exposure. Livers were analyzed for activities of three cytochrome P450–associated monooxygenases and four measures of oxidative stress. Blood and spleen were analyzed by flow cytometry for chromosomal damage. In a concurrent study, Scaup tissues were analyzed for organic and inorganic contaminants. Ethoxyresorufin-O-dealkylase (EROD) activity in livers of Scaup collected in January 1994 was significantly higher than in livers of Scaup collected in March 1994 or in livers of reference birds. Three hepatic monooxygenase activities were each significantly correlated with polycyclic aromatic hydrocarbon (PAH) concentrations in Scaup carcasses. Thiobarbituric acid (TBA) activity in Scaup livers was positively correlated with iron, boron, and lead concentrations in livers and polychlorinated biphenyl concentrations in carcasses. TBA activity was negatively correlated with protein-bound thiol activity and mercury concentrations in livers. The coefficient of variation of DNA content in Scaup blood cells was correlated with PAH concentrations in Scaup carcasses. This is the first field study with birds to demonstrate a correlation between liver monooxygenase activity and carcass PAH concentrations and to show a direct correlation between PAH concentrations in tissues and somatic chromosomal damage in blood.