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At least 73 records · Page 4Linked to original sources
USGS2016

Retrospective: Adjusting contaminant concentrations in bird eggs to account for moisture and lipid Loss during their incubation

By the 1960s, research and monitoring efforts on chlorinated pesticide residues in tissues of wildlife were well underway in North America and Europe. Conservationists and natural resource managers were attempting to resolve whether pesticide exposure and accumulated residues were related to population declines in several species of predatory and scavenging birds (e.g., bald eagle Haliaeetus leucocephalus , peregrine falcon Falco peregrinus , brown pelican Pelecanus occidentalis and osprey Pandion haliaetus ). The avian egg was a favored sampling matrix even before the realization that eggshell thinning was linked to population declines (Ratcliffe 1967 ; Hickey and Anderson 1968 ) and that the concentration of p,p ’-DDE in an egg was associated with the shell thinning phenomenon (e.g., Blus et al. 1972 ; Wiemeyer et al. 1988 ). The necessity for making wet-weight concentration adjustments to account for natural moisture loss during incubation of viable eggs was realized. Correction for the more dramatic moisture loss in non-viable decaying eggs was recognized as being paramount. For example, the ∑DDT residues in osprey eggs were reported to vary by as much as eightfold without accounting for moisture loss adjustments (Stickel et al. 1965 ). In the absence of adjusting concentrations to the fresh wet-weight that was present at the time of egg laying, the uncorrected values exaggerated contaminant concentrations, yielding artifactual results and ultimately incorrect conclusions. The adjustment to fresh wet-weight concentration is equally important for many other persistent contaminants including PCBs, dioxins, furans, and brominated diphenyl ethers.

Bulletin of Environmental Contamination and Toxico↗
USGS1999

Accumulation of butyltins in sediments and lipid tissues of the Asian clam, Potamocorbula amurensis, near Mare Island Naval Shipyard, San Francisco Bay

Studies of butyltin compounds in soil, benthic sediments and the Asian clam Potamocorbula amurensis were conducted at the former Mare Island Naval Shipyard, and nearby Mare Island and Carquinez Straits in San Francisco Bay, California. Soils from a sandblast abrasives dump site at the shipyard contained low concentrations of mono-, di- and tributyltin (0.3-52 ng/g, total butyltin). Similarly, concentrations of total butyltin in benthic sediments from nearby Mare Island and Carquinez Straits ranged from 1.3 to 8.1 ng/g. In contrast, clams accumulated much greater concentrations (152-307 ng/g, total butyltin). Tributyltin (TBT) and dibutyltin (DBT) made up from 54-85% to 15-46%, respectively, of the total butyltin body burden of the clams. Biota Sediment Accumulation Factors (BSAFs) for butyltins in Potamocorbula were in reasonable agreement with literature values; they are greater than those of neutral hydrophobic compounds, suggesting that partitioning and binding processes may be involved in bioaccumulation. Tributyltin is a potent endocrine disrupting chemical. There is potential for long-term chronic effects of TBT in San Francisco Bay.

Marine Pollution Bulletin↗
USGS1994

The role of nutrient reserves for clutch formation by Northern Pintails in Alaska

We analyzed carcass composition of female Northern Pintails ( Anas acuta ) in Alaska to assess the importance of nutrient reserves for formation of first clutches (n = 85) and renests (n = 39). Habitat (tundra vs. boreal forest), hen age (yearling vs. adult), and year (1990 vs. 1991) did not affect nutrient reserve use. During formation of first clutches, Northern Pintail hens relied on lipid reserves more than any other duck species that has been studied. For much of the nesting season, lipid reserves were used to meet costs beyond those incurred by clutch formation. Date of initiation of rapid follicle growth was related to lipid reserve dynamics; lipid reserves at initiation and the rate of lipid use both declined through the season. Protein reserves declined slightly with commitment of protein to the clutch and with date of initiation of rapid follicle growth. Use of mineral reserves for first nests was negligible. Renesting females did not use nutrient reserves. Lipid reserve levels were positively related to the amount of lipid reserves needed to complete the clutch and clutch sizes predicted from a lipid dynamics model were consistent with known clutch sizes. Similar relationships did not exist for protein. We suggest that lipid reserve levels affect timing of nesting and proximately limit clutch size of Northern Pintails.

Alaska↗
USGS1981

The role of nutrient reserves in mallard reproduction

Mallard ( Anas platyrhynchos ) populations breeding in temperate North America obtain a significant part of the energy and lipid requirements of reproduction at sites occupied prior to arrival on the breeding grounds. Protein for egg formation, however, is obtained principally from the diet during the nesting period. Both sexes arrive heavy and fat in North Dakota but experience substantial weight loss and lipid depletion during the nesting cycle. Weight loss is most pronounced among females and averages 25% from prelaying to late incubation. Body weights of both sexes are positively correlated with carcass lipid content. The paired male draws upon lipids early in the nesting season when an activity center is being established and defended and when females are preparing to nest. The female's lipid reserves are utilized primarily during laying and early incubation. The significance of lipid reserves diminishes as the nesting season progresses, and females do not acquire substantial lipid stores prior to renesting when the initial clutch is destroyed. The magnitude of lipid reserves carried in female carcasses is positively correlated with clutch size from mid-April to early June. Protein transfer for egg formation from flight and leg muscle and body organs can account for only a small part of the protein requirement for the clutch. By utilizing lipid reserves to meet energy requirements, the female can acquire sufficient protein from the diet to produce a large initial clutch even when foods are relatively scarce, whereas the renesting female must rely entirely upon food resources available at the breeding site for its nutrient and energy requirements.

The Auk↗
USGS2004

Nutrient reserves of Lesser Scaup ( Aythya affinis ) during spring migration in the Mississippi Flyway: A test of the spring condition hypothesis

The continental scaup population (Lesser [ Aythya affinis ] and Greater [ A. marila ] combined) has declined markedly since 1978. One hypothesis for the population decline states that reproductive success has decreased because female scaup are arriving on breeding areas in poorer body condition than they did historically (i.e. spring condition hypothesis). We tested one aspect of that hypothesis by comparing body mass and nutrient reserves (lipid, protein, and mineral) of Lesser Scaup at four locations (Louisiana, Illinois, Minnesota, and Manitoba) between the 1980s and 2000s. We found that mean body mass and lipid and mineral reserves of females were 80.0, 52.5, and 3.0 g higher, respectively, in the 2000s than in the 1980s in Louisiana; similarly, body mass and lipid and mineral reserves of males were 108.8, 72.5, and 2.5 g higher, respectively. In Illinois, mean body mass and lipid reserves of females were 88.6 and 56.5 g higher, respectively, in the 2000s than in the 1980s; similarly, body mass and lipid and mineral reserves of males were 80.6, 76.0, and 2.7 g higher, respectively. Mean body mass of females were 58.5 and 58.9 g lower in the 2000s than in the 1980s in Minnesota and Manitoba, respectively; mean body mass of males, similarly, were 40.7 g lower in Minnesota. Mean lipid reserves of females in the 2000s were 28.8 and 27.8 g lower than those in the 1980s in Minnesota and Manitoba, respectively. Mean mineral reserves of females in the 2000s were 3.2 g lower than those in the 1980s in Manitoba. Consequently, females arriving to breed in Manitoba in the 2000s had accumulated lipid reserves for 4.1 fewer eggs and mineral reserves for 0.8 fewer eggs than those arriving to breed there in the 1980s. Accordingly, our results are consistent with the spring condition hypothesis and suggest that female body condition has declined, as reflected by decreases in body mass, lipids, and mineral reserves that could cause reductions in reproductive success and ultimately a population decline.

The Auk↗
USGS2001

Intraspecific variation in nutrient reserve use during clutch formation by Lesser Scaup

We studied nutrient reserve dynamics of female Lesser Scaup ( Aythya affinis ) to identify sources of intraspecific variation in strategies of nutrient acquisition for meeting the high nutritional and energetic costs of egg formation. We collected data from interior Alaska and combined these with data for Lesser Scaup from midcontinent breeding areas ( Afton and Ankney 1991 ), allowing a rangewide analysis for the species. We found little evidence that nutrient reserve use differed between Alaskan and midcontinent Lesser Scaup, except that subarctic birds used a small amount of protein reserves when forming eggs, whereas midcontinent birds did not. Mineral reserves contributed relatively little to the clutch, but endogenous lipid accounted for approximately two-thirds of the lipid in the clutch. Levels of endogenous lipid and protein at initiation of clutch formation declined with date of initiation. Also, absolute amounts of lipid and protein reserves used declined through the season, corresponding to smaller clutch sizes. Our data are consistent with a seasonally variable threshold of lipid reserves for initiation of clutch formation and considerable reliance on lipid reserves, suggestive of lipid control of productivity via effects on clutch size and initiation dates. However, our data cannot refute the hypothesis that clutch size or initiation dates are set by other factors that in turn dictate the amount of lipid reserves that are stored and used. Despite uncertainty regarding the role of nutrient limitations on productivity, maintenance of adequate food resources on winter, migration, and breeding areas should be a management concern, given the high costs of clutch formation by Lesser Scaup, evidence of recent population declines, and potential links between nutrition and productivity.

Alaska↗
USGS2007

Relationships of cadmium, mercury, and selenium with nutrient reserves of female lesser scaup (Aythya affinis) during winter and spring migration

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.

Environmental Toxicology and Chemistry↗
USGS1995

Comparison of condition indices in migratory passerines at a stopover site in coastal Louisiana

We evaluated the utility of four nondestructive condition indices—body mass, body mass scaled by wing chord length, fat scoring, and total body electrical conductivity method (TOBEC)—as predictors of lipid levels in migrating Wood Thrushes ( Hylocichla mustelina ), Swainson's Thrushes ( Catharus ustulatus ), and Summer Tanagers ( Piranga rubra ). The Red-winged Blackbird ( Agelaius phoeniceus ), a winter resident, was examined for comparative purposes. In addition, we examined differences among species in relationships of total body lipids and condition indices. Body mass was the best index of lipid levels, explaining 36%-82% of the variation in total body lipids in all four species. The relative contributions of the other indices to the prediction of lipid mass varied among species although TOBEC was selected for inclusion in each regression equation. For two species, equations including TOBEC measurements had lower errors in lipid prediction than equations only using the other nondestructive indices. Errors in lipid prediction were large for all the regression equations based on condition indices. In many cases it will be necessary to develop species-specific equations to predict lipid levels with condition indices.

Louisiana↗
USGS1982

Proximate composition and caloric content of eight Lake Michigan fishes

We measured the proximate composition (percentage lipid, water, fat-free dry material, ash) and caloric content of eight species of Lake Michigan fish: lake trout (Salvelinus namaycush), coho salmon (Oncorhynchus kisutch), lake whitefish (Coregonus clupeaformis), bloater (Coregonus hoyi), alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), deepwater sculpin (Myoxocephalus quadricornis), and slimy sculpin (Cottus cognatus). Except for alewives, proximate composition and caloric content did not differ significantly between males and females. And, for coho salmon, there was no significant difference in composition between fish collected in different years. Lipid and caloric content of lake trout increased directly with age. In all species examined, lipids and caloric contents were significantly lower in small, presumably immature, fish than in larger, older fish. Lipid content of lake trout, lake whitefish, and bloaters (range of means, 16-22%) was nearly 3 times higher than that of coho salmon, sculpins, rainbow smelt, and alewives (range of means, 5.2-7.0%). The mean caloric content ranged from 6.9 to 7.1 kcal/g for species high in lipids and from 5.8 to 6.3 kcal/g for species low in lipids. Although the caloric content of all species varied directly with lipid content and inversely with water content, an increase in lipid content did not always coincide with a proportional increase in caloric content when other components of fish composition were essentially unchanged. This observation suggests that the energy content of fish estimated from the proximate composition by using universal conversion factors may not necessarily be accurate.

Technical Paper↗
USGS2021

Plasma metabolite indices are robust to extrinsic variation and useful indicators of foraging habitat quality in Lesser Scaup

Energy acquisition and storage are important for survival and fecundity of birds during resource-limited periods such as spring migration. Plasma-lipid metabolites (i.e. triglyceride [TRIG], β-hydroxybutyrate [BOHB]) have been used to index changes in lipid stores and, thus, have utility for assessing foraging habitat quality during migration. However, such an index may be affected by energetic maintenance costs, diet, and other factors, and further validation under experimental conditions is needed to understand potential sources of variation and verify existing indices. We evaluated a plasma-lipid metabolite index using 30 female and 28 male wild Lesser Scaup ( Aythya affinis ; hereafter scaup) held in short-term captivity (~24 hr) during spring migration. Similar to previous observational studies, BOHB was negatively associated and TRIG was positively associated with mass change ( R 2 = 0.68). BOHB estimates were nearly identical to those published on free-living scaup, but TRIG estimates differed from free-living scaup and varied by sex, with females having a greater rate of predicted mass change than captive and free-living males. Our results suggest TRIG may be a better measure of energy income than deposition because lipid deposition likely varies with energetic maintenance costs, stress, and underlying physiological processes while TRIG relates primarily to energy income. In contrast, BOHB was a reliable predictor of negative mass change across sexes. The sex-based differences in apparent lipid deposition rates warrant further research before a generalizable model is advisable for comparing mass change predictions across studies. However, if predictions are standardized, this technique is generally robust to variations in energy income vs. lipid deposition across sexes. Accordingly, our evaluation provides verification for the utility of plasma-lipid metabolites as an indicator of foraging habitat quality during migration.

Illinois↗
USGS2019

Extreme climatic variability during migration invokes physiological and dietary plasticity among spring migrating ducks

Environmental stochasticity encountered during migration can have negative consequences for individuals and population demographics through direct reductions in survival or cross-seasonal impacts. We took advantage of substantial interannual variation in spring migration conditions over a 4 year field study to examine physiological and dietary variation among two species of migrant ducks. We collected female Lesser Scaup ( Aythya affinis (Eyton, 1838)) and Blue-winged Teal ( Spatula discors (Linnaeus, 1766)) during spring migration and measured lipid and protein reserves, an index of recent lipid metabolism based on concentrations of lipid metabolites in plasma, and diets. We documented systematic interannual variation among these metrics in both species, contrasting primarily the warmest, earliest spring and the coldest, latest spring. Lesser Scaup had reduced lipid and protein reserves and consumed less energy-rich prey during the coldest and latest spring but showed no interannual variation in the index of lipid metabolism. Blue-winged Teal similarly had reduced protein reserves in the cold, late spring but maintained constant lipid reserves among years, likely facilitated by increased consumption of energy-rich seeds reflected in diets and lipid metabolism. Our results reveal impacts of environmental stochasticity on migrants and suggest that recruitment may be impacted by variable conditions encountered during migration during extreme weather events.

South Dakota↗
USGS2003

Physiological responses of juvenile rainbow trout to fasting and swimming activity: Effects on body composition and condition indices

The physiological traits that allow fish to survive periods of limited food resources are poorly understood. We assessed changes in proximate body composition, relative organ mass, blood metabolites, and relative weight (Wr) of sedentary and actively swimming (15 cm/s) juvenile rainbow trout (154-182 mm total length) over 147 d of fasting. Fasting caused measurable responses that were augmented when fish were swimming. Lipids and plasma triacylglycerides declined over time. Proteins were catabolized simultaneously with lipid reserves, but ammonia concentrations in plasma did not increase. The liver somatic index (LSI) did not change substantially over 105 d, suggesting that gluconeogenesis maintained blood glucose concentrations and hepatic glycogen reserves for a substantial period of fasting. The gut somatic index (GSI) and Wr declined linearly during fasting, but the LSI did not decline until after 105 d of fasting. Consequently, the use of different body condition indices could lead to different conclusions about the condition of juvenile rainbow trout. Swimming activity caused fish to have lower lipid and protein reserves than those of sedentary fish. No mortalities were observed among sedentary fish, but mortalities occurred among actively swimming fish after 97 d of fasting when 3.2% or less lipid remained in their bodies. Body condition indices did not account for differences in proximate body composition between sedentary and actively swimming fish and were relatively poor predictors of lipid content and risk of mortality. The probability of mortality was most accurately predicted by percent lipid content. Therefore, we suggest that fisheries scientists consider using percent lipid content when evaluating the physiological status and risk of mortality due to starvation among juvenile rainbow trout.

Transactions of the American Fisheries Society↗
USGS2026

Seasonal and decadal changes in winter body condition of four sympatric diving ducks

Winter body condition is an important driver of survival, reproductive output, and overall population health in waterfowl. Diving duck species use distinct habitats, exploit unique resources, and can collectively provide an integrated index of winter habitat quality. The San Francisco Bay (SFB) is the largest estuary on the west coast of North America, serving as critical wintering habitat for diving ducks in the Pacific Flyway. To evaluate the body condition of diving ducks after multiple decades of tidal habitat restoration in SFB, we compared structurally corrected measurements (annual and decadal) of total carcass lipid among canvasback ( Aythya valisineria ), greater scaup ( Aythya marila ), lesser scaup ( Aythya affinis ), and ruddy duck ( Oxyura jamaicensis ). We found greater and lesser scaup gained lipid reserves within the estuary prior to spring migration; however, canvasback and ruddy duck lipid levels declined throughout the winter and into the spring. Lipid loss over the wintering period could indicate a reduction in foraging resource availability, dietary shifts, or metabolic changes. These deficiencies could have negative cross-seasonal implications, as these species must accumulate resources outside of their wintering areas to fuel migration and reproduction. Lipid levels were elevated in lesser scaup collected in 2017-2019 compared to 1998-2000, while we found no decadal differences in lipid levels for canvasback or greater scaup. Our findings suggest tidal restoration in SFB, among other factors, may benefit some diving duck species.

California↗
USGS2007

Fatty acid signatures of stomach oil and adipose tissue of northern fulmars (Fulmarus glacialis) in Alaska: Implications for diet analysis of Procellariiform birds

Procellariiforms are unique among seabirds in storing dietary lipids in both adipose tissue and stomach oil. Thus, both lipid sources are potentially useful for trophic studies using fatty acid (FA) signatures. However, little is known about the relationship between FA signatures in stomach oil and adipose tissue of individuals or whether these signatures provide similar information about diet and physiology. We compared the FA composition of stomach oil and adipose tissue biopsies of individual northern fulmars ( N = 101) breeding at three major colonies in Alaska. Fatty acid signatures differed significantly between the two lipid sources, reflecting differences in dietary time scales, metabolic processing, or both. However, these signatures exhibited a relatively consistent relationship between individuals, such that the two lipid sources provided a similar ability to distinguish foraging differences among individuals and colonies. Our results, including the exclusive presence of dietary wax esters in stomach oil but not adipose tissue, are consistent with the notion that stomach oil FA signatures represent lipids retained from prey consumed during recent foraging and reflect little metabolic processing, whereas adipose tissue FA signatures represent a longer-term integration of dietary intake. Our study illustrates the potential for elucidating short- versus longer-term diet information in Procellariiform birds using different lipid sources.

Alaska↗
USGS2022

Summer/fall diet and macronutrient assimilation in an Arctic predator

Free-ranging predator diet estimation is commonly achieved by applying molecular-based tracers because direct observation is not logistically feasible or robust. However, tracers typically do not represent all dietary macronutrients, which likely obscures resource use as prey proximate composition varies and tissue consumption can be specific. For example, polar bears ( Ursus maritimus ) preferentially consume blubber, yet diets have been estimated using fatty acids based on prey blubber or stable isotopes of lipid-extracted prey muscle, neither of which represent both protein and lipid macronutrient contributions. Further, additional bias can be introduced because dietary fat is known to be flexibly routed beyond short-term energy production and storage. We address this problem by simultaneously accounting for protein and lipid assimilation using carbon and nitrogen isotope compositions of lipid-containing prey muscle and blubber to infer summer/fall diet composition and macronutrient proportions from Chukchi Sea polar bear guard hair ( n = 229) sampled each spring between 2008 and 2017. Inclusion of blubber (85–95% lipid by dry mass) expanded the isotope mixing space and improved separation among prey species. Ice-associated seals, including nutritionally dependent pups, were the primary prey in summer/fall diets with lower contributions by Pacific walruses ( Odobenus rosmarus ) and whales. Percent blubber estimates confirmed preferential selection of this tissue and represented the highest documented lipid assimilation for any animal species. Our results offer an improved understanding of summer/fall prey macronutrient usage by Chukchi Sea polar bears which likely coincides with a nutritional bottleneck as the sea ice minimum is approached.

Alaska↗