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At least 109 records · Page 6Linked to original sources

USGS2011

Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient‐storage dynamics in the midcontinent population of greater white‐fronted geese ( Anser albifrons ; hereafter white‐fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February–April and in southern Saskatchewan during April–May, 1998 and 1999. In Nebraska, lipid content of white‐fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3‐week period. A study conducted during 1979–1980 in the Rainwater Basin reported that white‐fronted geese gained 8.8–17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high‐energy pulse crops in Saskatchewan. White‐fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape‐level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow spring‐staging waterfowl to disperse across the region and facilitate access to high‐energy foods over a larger cropland base.

Nebraska, Saskatchewan↗

USGS2018

Diet and condition of age‐0 Scaphirhynchus Sturgeon: Implications for shallow‐water habitat restoration

Insufficient food during early life could limit the population growth of endangered Pallid Sturgeon Scaphirhynchus albus in the lower Missouri River. Shallow‐water habitat restoration is intended to provide nursery benefits, including food, for young sturgeon, but the effect of shallow‐water habitat on their diet is unknown. Age‐0 Pallid Sturgeon are rare, providing little opportunity for direct evaluation; however, studying the closely related and abundant Shovelnose Sturgeon S. platorynchus may provide valuable information to guide habitat restoration efforts. We compared diet, body condition (lipid content), and change in body weight (24‐h bioenergetics simulation) for postdrift, age‐0 sturgeon among five reaches ranging widely in shallow‐water habitat availability. Lipid content of satiated and emaciated laboratory‐reared individuals were compared with that of wild‐caught fish. In general, shallow‐water habitat availability appeared to have little effect on the variables examined. Regardless of reach, wild‐caught fish primarily consumed chironomids, and empty stomachs were rare. Additionally, differences in prey weight, lipid content, or the modeled change in body weight did not usually correspond to differences in shallow‐water habitat availability. Instead, we found annual differences, as prey weight consumed and the percentage of fish with modeled weight gain was often higher in 2015 than 2014, while the opposite was true for the percentage of fish with lipid content values that were comparable with the emaciated laboratory standard. Overall, our findings complement recent suggestions that shallow‐water habitat restoration efforts, as previously implemented, may not benefit sturgeon populations. Our results coupled with previous research suggest that the lower Missouri River prey base can support a stable Shovelnose Sturgeon population; however, additional research is needed to determine whether this applies to Pallid Sturgeon.

Missouri↗

USGS2019

Energetic status of Alaskan Chinook Salmon: Interpopulation comparisons and predictive modeling using bioelectrical impedance analysis

Adult Pacific Salmon Oncorhynchus spp . undertake energetically demanding migrations wherein they must have adequate energy reserves to survive to spawning locations and reproduce. Proximate analysis provides insight into available energy stores (e.g., lipids), but the ability to non-lethally monitor energetic status may be useful for managers to better understand how energetic status affects salmon populations in light of population declines and threats from climate change and habitat alteration. Chinook Salmon Oncorhynchus tshawytscha (N = 129) were sampled for proximate analysis from four populations in Alaska to examine variation in energetic status pre- and post-spawning migration and to create predictive bioelectrical impedance analysis (BIA) models for this species. We also tested two BIA devices (Q2 and CQR), whether models were generalizable to a con-specific (Chum Salmon Oncorhynchus keta), and the feasibility of integrating BIA into field studies. Populations sampled pre- spawning migration had higher percent lipid (N = 77; mean = 42.57%) than those collected post spawning migration (N = 52; mean = 19.71%). Total percent lipid and water were more accurately predicted from the Q2 device based on BIA measurements (RMSE = 5.33; RMSE = 2.43, respectively), relative to CQR device measurements (RMSE = 6.27; RMSE = 2.66). Between-species (Chinook to Chum RMSE = 19.47; Chum to Chinook RMSE = 7.69) models were less accurate than species specific models created for Chinook and Chum Salmon, therefore single species models should be used. We field-tested the BIA model to predict Chinook Salmon %lipid and %water on a remote Southeast Alaska river. Techniques were quickly taught to field crews and predictions were similar to other pre-spawning migration estimates. Our results indicate that integration of BIA into population monitoring could be a valuable tool to assess spatial and temporal patterns of energetic status of Chinook Salmon.

Alaska↗

USGS2006

Polychlorinated biphenyls, mercury, and potential endocrine disruption in fish from the Hudson River, New York, USA

Tissue residues of total mercury (Hg), total polychlorinated biphenyls (PCBs), and lipid-based PCBs; plasma concentrations of endocrine biomarkers; and reproductive and histologic biomarkers were assessed in 460 carp (Cyprinus carpio), bass (Micropterus salmoides and Micropterus dolomieui), and bullhead (Ameiurus nebulosus) collected from eight sites across the Hudson River Basin in the spring of 1998 to determine if endocrine disruption was evident in resident fish species and to evaluate contaminant-biomarker interrelations. Total PCBs in bed sediments (maximum 2,500 ??g kg-1) could explain 64 to 90% of the variability in lipid-based PCB residues in tissues (maximum 1,250 ??g PCB g-lipid-1) of the four species. The 17??-estradiol to 11-ketotestosterone ratio, typically less than 1.0 in male fish and greater than 1.0 in females, exceeded 1.4 in all male largemouth bass and 35% of male carp and bullhead at one site 21 km downstream from a major PCB source. Endocrine biomarkers were significantly correlated with total Hg in female smallmouth bass and carp, and with lipid-based PCBs in males of all four species. Empirical evidence of endocrine modulation in blood plasma of male and female fish from sites with and without high PCB residues in bed sediments and fish tissues suggest that PCBs, Hg, or other contaminants may disrupt normal endocrine function in fish of the Hudson River. ?? Eawag, 2006.

Aquatic Sciences↗

USGS2001

Dietary restriction causes chronic elevation of corticosterone and enhances stress response in red-legged kittiwake chicks

Release of corticosterone in hungry kittiwake chicks facilitates begging and allows them to restore depleted energy reserves by increasing parental food provisioning. However, in order to avoid detrimental effects of chronic elevation of corticosterone, chicks might suppress adrenocortical activity in response to prolonged food shortages. In this study we examined temporal dynamics of corticosterone release in red-legged kittiwake (Rissa brevirostris) chicks exposed to prolonged restrictions in energy content and/or nutritional quality (low versus high lipid content) of their food. Starting at the age of 15 days, chicks were fed either high- or low-lipid fish at 40%, 65%, and 100% of ad libitum energy intake. Body mass measurements and baseline plasma samples were taken on a weekly basis after beginning of the treatment. After 3 weeks of treatment, chicks were exposed to a standardized acute handling and restraint stress protocol, where in addition to a baseline sample, three plasma samples were taken at intervals up to 50 min. We found that food-restricted chicks had lower body mass, chronically (during 2-3 weeks) elevated baseline and higher acute stress-induced levels of corticosterone compared to chicks fed ad libitum. Low lipid content of food further exacerbated these effects. An increase in baseline levels of corticosterone was observed within a week after energy requirements of food-restricted chicks exceeded their daily energy intake. A tendency for suppression of adrenocortical activity was observed in treatments fed low-lipid diets only at the end of the experiment. We suggest that nest-bound chicks, if food-stressed, might suffer deleterious effects of chronic elevation of corticosterone.

Journal of Comparative Physiology B: Biochemical, ↗

USGS2011

Individual condition and stream temperature influence early maturation of rainbow and steelhead trout, ncorhynchus mykiss

Alternative male phenotypes in salmonine fishes arise from individuals that mature as larger and older anadromous marine-migrants or as smaller and younger freshwater residents. To better understand the processes influencing the expression of these phenotypes we examined the influences of growth in length (fork length) and whole body lipid content in rainbow trout ( Oncorhynchus mykiss ). Fish were sampled from the John Day River basin in northeast Oregon where both anadromous ("steelhead") and freshwater resident rainbow trout coexist. Larger males with higher lipid levels had a greater probability of maturing as a resident at age-1+. Among males, 38% were maturing overall, and the odds ratios of the logistic model indicated that the probability of a male maturing early as a resident at age-1+ increased 49% (95% confidence interval (CI) = 23-81%) for every 5 mm increase in length and 33% (95% CI = 10-61%) for every 0.5% increase in whole body lipid content. There was an inverse association between individual condition and water temperature as growth was greater in warmer streams while whole body lipid content was higher in cooler streams. Our results support predictions from life history theory and further suggest that relationships between individual condition, maturation, and environmental variables (e.g., water temperature) are shaped by complex developmental and evolutionary influences.

Oregon↗

USGS1983

DDE in brown and white fat of hibernating bats

Samples of brown and white fat from hibernating bats (big brown bat, Eptesicus fuscus ; little brown bat, Myotis lucifugus ; and eastern pipistrelle, Pipistrellus subflavus ) collected in western Maryland, USA, were analysed to determine lipid and DDE content. Amounts of brown fat, expressed as percentages of total bat weight, were the same for all three species. Lipid content of brown fat was significantly less than that of white fat. Lipids of brown fat contained significantly higher (28%) concentrations of DDE than did lipids of white fat. In our mixed-species sample of 14 bats, concentrations of DDE increased exponentially in both brown and white fat as white fat reserves declined. Brown fat facilitates arousal from hibernation by producing heat through rapid metabolism of triglycerides. The question is raised whether organochlorine residues, such as DDE, may be concentrated and then liberated in lethal amounts by the processes of hibernation and arousal.

Maryland↗

USGS2020

Molecular indicators of methane metabolisms at cold seeps along the United States Atlantic margin

A lipid biomarker study was undertaken to determine the microbial composition and variability in authigenic carbonates and associated soft bottom habitats from the Norfolk and the Baltimore Canyon seep fields along the US mid-Atlantic margin. Results from this study capture a distinct molecular signal from methane oxidizing archaea, including archaeol (I), sn-2-hydroxyarchaeol, pentamethylicosane (PMI), and crocetane. These consortia of methane-oxidizing Archaea have been identified as carrying out anaerobic oxidation of methane (AOM), thereby favoring the precipitation of methane derived authigneic carbonates. The carbon isotope (δ13C) values of AOM-related lipids were strongly depleted in 13C, (i.e., archaeol: -91.64 ‰, sn-2-hydroxyarchaeol: -129.18 ‰, pentamethylicosane (PMI); -131.36 ‰, and crocetane: -70.94 ‰), confirming the dominance of methane as the dominant carbon source for the Archaea during AOM fractionation. The presence of terminally branched fatty acids such as the antesio- and iso-C15:0 components, diagnostic of sulfate-reducing bacteria (SRB), and their depleted δ13C signature (-107.6 ‰), supports syntrophy of SRB with methane-oxidizing archaea. While lipid biomarker profiles of authigenic carbonates biomarker are similar to those found in the seep sediment, suggesting a similar microbial assemblage within the seep-microbiome, a range in lipid composition, distribution, and isotopic signature between seep sites and matrix type suggests AOM is performed by multiple archaeal sources, instead of a single archaeal species.

Atlantic margin↗

USGS2021

Maternal transfer of polychlorinated biphenyls in Pacific sand lance (Ammodytes personatus), Puget Sound, Washington

We measured polychlorinated biphenyls (PCBs) in multiple age and size classes of Pacific sand lance ( Ammodytes personatus ), including eggs, young-of-the year, and adults to evaluate maternal transfer as a pathway for contaminant uptake and to add to the limited information on the occurrence of PCBs in sand lance in Puget Sound. Sampling was replicated at an urban embayment (Eagle Harbor) and a state park along an open shoreline (Clayton Beach), during spring and fall. Lipid-normalized concentrations of PCBs in sand lance at Eagle Harbor were 5–11 times higher than PCB concentrations in comparable samples at Clayton Beach. This was true for every life stage and size class of sand lance, including eggs removed from females. The same trend was observed in environmental samples. In Eagle Harbor, PCB concentrations in unfiltered water (0.19 ng/L), sieved (<63 μm) nearshore bed sediments (0.78 ng/g dw) and suspended particulate matter (1.69 ng/g dw) were 2–3 times higher than equivalent samples from near Clayton Beach. Sand lance collected in the fall (buried in sediment during presumed winter dormancy) had lower lipid content and up to four times higher PCB concentrations than comparably sized fish collected in the spring (by beach seine). Lipid content was 5–8% in spring fish and was reduced in fall fish (1–3%). Male sand lance had higher PCB concentrations than comparable females. All egg samples contained PCBs, and the lipid normalized egg/female concentration ratios were close to 1 (0.87–0.96), confirming that maternal transfer of PCBs occurred, resulting in sand lance eggs and early life stages being contaminated with PCBs even before they are exposed to exogenous sources. These life stages are prey for an even wider range of species than consume adult sand lance, creating additional exposure pathways for biota and increasing the challenges for mitigation of PCBs in the food web.

Washington↗

USGS1997

Proximate composition and energy density of some North Pacific forage fishes

Mature pelagic forage fish species (capelin, sand lance, squid) had greater lipid concentrations than juvenile age-classes of large demersal and pelagic fish species (walleye pollock, Pacific cod, Atka mackerel, greenling, prowfish, rockfish, sablefish). Myctophids preyed on by puffins have at least twice as much lipid per gram compared to mature capelin, sand lance and squid, and an order of magnitude greater lipid concentrations than juvenile forage fish. Energy density of forage fishes was positively correlated with lipid content, and negatively correlated with water, ash-free lean dry mass (mostly protein), and ash contents.

Comparative Biochemistry and Physiology, Part A: M↗

USGS1999

The effect of temperature and ration size on the growth, body composition, and energy content of juvenile coho salmon

Juvenile (postsmolt) coho salmon (Oncorhynchus kitsuch) were held in fresh water in the laboratory at 5, 10, 15, and 18A?C for 8 weeks and fed freshly thawed, juvenile alewives (Alosa pseudoharengus) at rates equal to 1 and 2 % of their wet body weight/day, and also at the ad libitum or unrestricted ration rate. Most rapid growth in weight (1.2% wet body weight/day) occurred among fish fed the ad libitum ration at 15A?C; growth was most rapid at about 10A?C for fish fed the 2% ration (0.7%/day), and the 1% ration (0.1%/day). Gross conversion efficiency was highest at 10A?C for all three ration levels. Gross body constituents and energy content of the test fish changed with temperature and ration during the study. Growth rate was positively related to lipid, energy content, and ration; lipid and energy content were positively related to water temperature; lipid, energy content, growth rate, ration, and water temperature were negatively related to water content; and protein was not related to any of the test variables. At the end of the study, water (68.7 to 76.4%) and lipid (3.5 to 10.4%) content were more variable than ash (1.8 to 3.1%), carbohydrate (0.1 to 1.9%), and protein (16.9 to 19.4%) content. Energy content of the fish increased with ration and was highest for each ration level at 15A?C.

Journal of Great Lakes Research↗

USGS2001

Differences in oxidative stress between young Canada geese and mallards exposed to lead-contaminated sediment

Lead (Pb) exposure results in an increase in tissue lipid peroxides and variation in glutathione (GSH) concentrations, which can be related to peroxidative damage of cell membranes in Pb-poisoned animals. Species and individual variation in sensitivity to Pb poisoning among animals may be due to differential resistance to oxidative stress. The effects of oxidative stress caused by Pb exposure (1.7, 414, and 828 µg/g of diet) were compared for the first 6 wk in growing young of two species of waterfowl, Canada geese ( Branta canadensis ) and mallards ( Anas platyrhynchos ), with the first species being possibly more sensitive to Pb poisoning based on previous field and laboratory observations. Blood and liver Pb concentrations increased more in mallards than in geese. This may be explained on the basis of body weight, being 3.2 times higher in geese, and by hepatic metabolism, where GSH S -transferase (GST) activity is 2.9-fold higher in geese and presumably has a role in the binding of Pb to GSH and subsequent biliary excretion. In contrast, mallards showed higher hepatic levels of GSH and activities of GSH peroxidase (GPX) and GSH reductase (GR). Although both species showed a rise in hepatic GSH concentration with Pb exposure, the relationship between increased lipid peroxidation and Pb exposure was only significant in geese. Within treatment groups, hepatic GSH concentrations were inversely related to liver Pb concentrations in both species, which may correspond to the role of GSH in Pb excretion. Hepatic GSH was also inversely related to hepatic lipid peroxidation, but only in mallards and in agreement with the species differences observed in GPX and GR activities. The lower resistance to lipid peroxidation of Canada geese may explain why geese can die in the field from Pb poisoning after ingesting fewer shot than found in the gizzards of mallards and with lower liver Pb concentrations than in mallards.

Journal of Toxicology and Environmental Health, Pa↗

USGS2023

Estimating fat content in barred owls (Strix varia) with predictive models developed from direct measures of proximate body composition

Body condition indices and related metrics can help assess habitat quality and other ecological processes, and ideally, these metrics are based on measures of lipids directly extracted from the species of interest. In recent decades, barred owls ( Strix varia ) have become a species of conservation concern as they invaded older forests of the US Pacific Northwest, and caused population declines of the closely related and federally threatened northern spotted owl ( Strix occidentalis caurina ). A simple and effective measure of barred owl body condition could help to understand how habitat quality varies within their new range, which in turn can inform their management and other aspects of their ecology. Using 77 barred owl carcasses collected during experimental removals in Washington and Oregon, USA, we measured the amount of lipid in each specimen with proximate body composition analysis. We then fit and compared (with adjusted R 2 values) alternative linear regression models to estimate the percent lipids in dry mass of the owls based on morphometric body condition indices, a qualitative fat score of subcutaneous breast fat, sex and the time of year females were collected (relative to egg production). Adjusted R 2 values for all models ranged from 0.49 to 0.87, with the best model including mass divided by foot-pad length, fat score, sex and the time of year a female was collected. Most models generated comparable estimates of percent lipids at a population level and we provided correction factors to apply these models when used with live barred owls, allowing for site-specific comparisons of body condition among individuals inhabiting a diversity of environmental conditions.

Conservation Physiology↗

USGS2004

Constraints of body size and swimming velocity on the ability of juvenile rainbow trout to endure periods without food

The hypothesis that body size and swimming velocity affect proximate body composition, wet mass and size-selective mortality of fasted fish was evaluated using small (107 mm mean total length, LT) and medium (168 mm mean LT) juvenile rainbow trout Oncorhynchus mykiss that were sedentary or swimming (c. 1 or 2 body lengths-1) and fasted for 147 days. The initial amount of energy reserves in the bodies of fish varied with L T. Initially having less lipid mass and relatively higher mass-specific metabolic rates caused small rainbow trout that were sedentary to die of starvation sooner and more frequently than medium-length fish that were sedentary. Swimming at 2 body length s-1 slightly increased the rate of lipid catabolism relative to 1 body length s-1, but did not increase the occurrence of mortality among medium fish. Death from starvation occurred when fish had <3.2% lipid remaining in their bodies. Juvenile rainbow trout endured long periods without food, but their ability to resist death from starvation was limited by their length and initial lipid reserves. ?? 2004 The Fisheries Society of the British Isles.

Journal of Fish Biology↗

USGS2008

Characterizing the nutritional strategy of incubating king eiders Somateria spectabilis in northern Alaska

We measured plasma concentrations of variables associated with lipid metabolism (free fatty acids, glycerol, triglyceride, and ??- hydroxybutyrate), protein metabolism (uric acid), and baseline corticosterone to characterize the nutritional state of incubating king eiders Somateria spectabilis and relate this to incubation constancy at two sites, Kuparuk and Teshekpuk, in northern Alaska. King eiders at both sites appeared to employ a partial-income incubation strategy, relying on both endogenous and exogenous energy resources. Females maintained high invariant levels of free fatty acids, ??-hydroxybutyrate, and glycerol throughout incubation, indicating that fat reserves were a major energy source, and not completely depleted during incubation. Similarly, uric acid did not increase, suggesting effective protein sparing or protein ingestion and adequate lipid reserves throughout incubation. Baseline corticosterone and triglyceride levels increased during incubation, indicative of an increase in foraging during late stages of incubation. Incubating females at Kuparuk had higher triglyceride concentrations but also had higher ??-hydroxybutyrate concentrations than females at Teshekpuk. This dichotomy may reflect a short-term signal of feeding overlaying the longer-term signal of reliance on endogenous lipid reserves due to higher food intake yet higher metabolic costs at Kuparuk because of its colder environment. Incubation constancy was not correlated with plasma concentrations of lipid or protein metabolites. ?? 2008 The Authors.

Journal of Avian Biology↗

USGS2015

Association of anatase (TiO2) and microbes: unusual fossilization effect or a potential biosignature?

We combined microbial paleontology and molecular biology methods to study the Eyreville B drill core from the 35.3-Ma-old Chesapeake Bay impact structure,Virginia, USA. The investigated sample is a pyrite vein collected from the 1353.81-1353.89 m depth interval, located within a section of biotite granite. The granite is a pre-impact rock that was disrupted by the impact event. A search for inorganic (mineral) biosignatures revealed the presence of micron-size rod morphologies of anatase (TiO2) embedded in chlorite coatings on pyrite grains. Neither the Acridine Orange microbial probe nor deoxyribonucleic acid (DNA) extraction followed by polymerase chain reaction (PCR) amplifi cation showed the presence of DNA or ribonucleic acid (RNA) at the location of anatase rods, implying the absence of viable cells in the investigated area. A Nile Red microbial probe revealed the presence of lipids in the rods. Because most of the lipids are resistant over geologic time spans, they are good biomarkers, and they are an indicator of biogenicity for these possibly 35-Ma-old microbial fossils. The mineral assemblage suggests that rod morphologies are associated with low-temperature (<100 °C) hydrothermal alteration that involved aqueous fl uids. The temporal constraints on the anatase fossils are still uncertain because pre-impact alteration of the granite and postimpact heating may have provided identical conditions for anatase precipitation and microbial preservation.

Geological Society of America Bulletin↗

USGS2013

Maturation characteristics and life history strategies of the Pacific Lamprey, Entosphenus tridentatus

Lampreys (Petromyzontiformes) have persisted over millennia and now suffer a recent decline in abundance. Complex life histories may have factored in their persistence; anthropogenic perturbations in their demise. The complexity of life histories of lampreys is not understood, particularly for the anadromous Pacific lamprey, Entosphenus tridentatus Gairdner, 1836. Our goals were to describe the maturation timing and associated characteristics of adult Pacific lamprey, and to test the null hypothesis that different life histories do not exist. Females exhibited early vitellogenesis – early maturation stages; males exhibited spermatogonia – spermatozoa. Cluster analyses revealed an “immature” group and a “maturing–mature” group for each sex. We found statistically significant differences between these groups in the relationships between (i) body mass and total length in males; (ii) Fulton’s condition factor and liver lipids in males; (iii) the gonadosomatic index (GSI) and liver lipids in females; (iv) GSI and total length in females; (v) mean oocyte diameter and liver lipids; and (vi) mean oocyte diameter and GSI. We found no significant difference between the groups in the relationship of muscle lipids and body mass. Our analyses support rejection of the hypothesis of a single life history. We found evidence for an “ocean-maturing” life history that would likely spawn within several weeks of entering fresh water, in addition to the formerly recognized life history of spending 1 year in fresh water prior to spawning—the “stream-maturing” life history. Late maturity, semelparity, and high fecundity suggest that Pacific lamprey capitalize on infrequent opportunities for reproduction in highly variable environments.

Canadian Journal of Zoology↗

USGS2011

Testing competing hypotheses for chronology and intensity of lesser scaup molt during winter and spring migration

We examined chronology and intensity of molt and their relationships to nutrient reserves (lipid and protein) of Lesser Scaup ( Aythya affinisK/i>) 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 average, were nutritionally stressed. Molt intensity was not negatively correlated with protein reserves at any location. Chronology and intensity of prealternate molt varied little and were not temporally staggered from other nutritionally costly events. Prealternate molt did not influence nutrient reserves, and nutrient reserves likely were not the ultimate factor influencing chronology or intensity of prealternate molt of females. We surmise that nutrients required for prealternate molt come from exogenous sources and that the "staggered cost" hypothesis does not explain chronology of prealternate molt in female Lesser Scaup; rather, it appears that molt must be complete prior to nesting, consistent with the "breeding plumage" hypothesis.

The Condor↗