Do purely capital layers exist among flying birds? Evidence of exogenous contribution to arctic-nesting common eider eggs

The strategy of relying extensively on stored resources for reproduction has been termed capital breeding and is in contrast to income breeding, where needs of reproduction are satisfied by exogenous (dietary) resources. Most species likely fall somewhere between these two extremes, and the position of an organism along this gradient can influence several key life-history traits. Common eiders (Somateria mollissima) are the only flying birds that are still typically considered pure capital breeders, suggesting that they depend exclusively on endogenous reserves to form their eggs and incubate. We investigated the annual and seasonal variation in contributions of endogenous and exogenous resources to egg formation in eiders breeding at the East Bay colony in the Canadian Arctic. We collected prey items along with females and their eggs during various stages of breeding and used two complementary analytical approaches: body reserve dynamics and stable isotope [δ(13)C, δ(15)N] mixing models. Indices of protein reserves remained stable from pre-laying to post-laying stages, while lipid reserves declined significantly during laying. Similarly, stable isotope analyses indicated that (1) exogenous nutrients derived from marine invertebrates strongly contributed to the formation of lipid-free egg constituents, and (2) yolk lipids were constituted mostly from endogenous lipids. We also found evidence of seasonal variation in the use of body reserves, with early breeders using proportionally more exogenous proteins to form each egg than late breeders. Based on these results, we reject the hypothesis that eiders are pure capital layers. In these flying birds, the fitness costs of a strict capital breeding strategy, such as temporary loss of flight capability and limitation of clutch and egg size, may outweigh benefits such as a reduction in egg predation rate.     

International importance of the eastern Chukchi Sea as a staging area for migrating king eiders

The evaluation of habitats used by arctic birds on migration is crucial for their conservation. We explored the importance of the eastern Chukchi Sea (ECS) as a staging area for king eiders (Somateria spectabilis) migrating between breeding areas in Siberia and western North America and wintering areas in the Bering Sea. We tracked 190 king eiders with satellite transmitters between 1997 and 2007. In late summer, 74% of satellite-tracked king eiders migrating south staged in the ECS for 13 ± 13 (SD) days between late June and early November. During spring migration, king eiders staged in the ECS between mid-April and early June for 21 ± 10 days. All instrumented birds migrating to breeding grounds in western North America (n = 62), and 6 of 11 males migrating to breeding grounds in Siberia, used this area for at least 1 week during spring migration. The importance of this staging area renders it possible that industrial development could adversely affect king eider populations in both Siberia and North America.     

Using eggshell membranes as a non-invasive tool to investigate the source of nutrients in avian eggs

Development of minimally invasive techniques to collect nutritional information from free-living birds is desirable for both ethical and conservation reasons. Here, we explore the utility of waterfowl eggshell membranes to determine the nutrient source of egg formation by using stable isotope ratios. We compared δ¹³C and δ¹⁵N of membranes from complete king eider (Somateria spectabilis) eggs to membranes of hatched or depredated eggs of the same clutch remaining after incubation. Despite large variation among membranes (δ¹³C: −26 to −14‰) we found a highly predictable relationship between δ¹³C of complete egg membranes and remaining (hatched or depredated) membranes from the same clutch. We did not find a consistent change in either δ¹³C or δ¹⁵N of eggshell membranes during incubation. We suggest that isotope ratios of membranes can be used to determine the source of exogenous nutrients for egg production in income breeders, and that membranes may offer a clutch-specific reference point for dietary nutrients (‘income endpoint’) in isotopic mixing models quantifying nutrient allocation in capital or mixed-strategy breeders.     

Diet: tissue stable isotope fractionation of carbon and nitrogen in blood plasma and whole blood of male reindeer Rangifer tarandus

Estimates of diet derived from stable isotope analyses are sensitive to the accuracy of corrections made for diet-tissue fractionation. In particular, diet-tissue fractionation in reindeer Rangifer tarandus may be expected to differ significantly from the generic values often used in stable isotope dietary calculations, given the known values obtained from other ungulates and the complex digestive system and nutrient recycling characteristic of the species. We fed domestic reindeer a homogenous artificial diet of known isotopic value in order to directly determine diet-tissue isotopic fractionation of carbon and nitrogen, the main elements used in stable isotope dietary analyses. Diet-tissue fractionation values for blood plasma were +3.5 ± 0.1‰ (δ¹³C) and +4.2 ± 0.3‰ (δ¹⁵N). Diet-tissue fractionation values for whole blood were +3.7 ± 0.2‰ (δ¹³C) and +2.5 ± 0.3‰ (δ¹⁵N). Metabolic turnover rates were clearly sufficient for complete tissue replacement over the period of artificial feeding for blood plasma, but may not have been so for whole blood, especially for δ¹⁵N. Our values, except for whole blood δ¹⁵N, differ considerably from the generic values often used in dietary studies and interspecific comparisons of trophic niche. The results underline the importance of obtaining as specific as possible fractionation values for the species, tissue, and in some cases sex and physiological status of animals under examination, and the potential problems associated with assuming ‘generic’ fractionation values when comparing species, especially where digestive processes are dissimilar.     

Capital breeding and allocation to life-history demands are highly plastic in lizards

The use of stored resources to fuel reproduction, growth, and self-maintenance in the face of uncertain nutrient availability is a tactic common to many organisms. The degree to which organisms rely on stored resources in response to varied nutrients, however, is not well quantified. In this study, we used stable isotope methods to quantify the use of stored versus incoming nutrients to fuel growth and egg and fat body development in lizards under differing nutrient regimes. We found that the degree of capital breeding is a function of an individual's body condition. Furthermore, given sufficient income, lizards in poor condition can allocate simultaneously to storage, growth, and reproduction and "catch up" in body size and reproductive allocation to better-conditioned animals. Using natural variation in the δ(13)C of environmental nutrient pulses, we also found a high degree of variation in capital breeding in a lizard community. These findings demonstrate that capital breeding in lizards is not simply a one-way flow of endogenous stores to eggs but is a function of the condition state of individuals and seasonal nutrient availability. We use our findings to comment on capital breeding in lizards and the utility of the capital-income concept in general.     

Does winter region affect spring arrival time and body mass of king eiders in northern Alaska?

Events during the non-breeding season may affect the body condition of migratory birds and influence performance during the following breeding season. Migratory birds nesting in the Arctic often rely on endogenous nutrients for reproductive efforts, and are thus potentially subject to such carry-over effects. We tested whether king eider (Somateria spectabilis) arrival time and body mass upon arrival at breeding grounds in northern Alaska were affected by their choice of a winter region in the Bering Sea. We captured birds shortly after arrival on breeding grounds in early June 2002–2006 at two sites in northern Alaska and determined the region in which individuals wintered using satellite telemetry or stable isotope ratios of head feathers. We used generalized linear models to assess whether winter region explained variation in arrival body mass among individuals by accounting for sex, site, annual variation, and the date a bird was captured. We found no support for our hypothesis that either arrival time or arrival body mass of king eiders differed among winter regions. We conclude that wintering in different regions in the Bering Sea is unlikely to have reproductive consequences for king eiders in our study areas.     

Habitat used by common and king eiders in spring in the southeast Beaufort Sea and overlap with resource exploration

The southeast Beaufort Sea is a critical spring staging area for common and king eiders (Somateria mollissima v-nigrum, S. spectabilis), and is for many the final stop before they reach their breeding grounds throughout the western Canadian Arctic. The region also has significant oil and gas potential, and the recent approval of a pipeline through the Mackenzie Valley may make development of these resources economically viable. We used satellite telemetry to determine the distribution and habitat use of eiders staging in the southeast Beaufort Sea in spring, and the overlap of eiders with oil and gas exploration. From 2004 to 2009, we monitored 51 eiders equipped with platform terminal transmitters (PTTs) throughout spring migration (May–June). We compared the marine habitats used by each species, and evaluated habitat preferences using resource selection functions. The location and extent of the flaw lead (open water along the interface between mobile pack ice and stationary landfast ice) at the time when eiders were staging varied among years, but both species showed a strong preference for use of flaw lead habitats. This preference was stronger for common eiders than for king eiders, which also used pack ice extensively. Common eiders generally occurred near the landfast ice edge, whereas king eiders were just as often nearer to the pack ice edge of the flaw lead. Average water depth (±SE) for common eiders was 22 ± 2 m compared to 30 ± 1 m for king eiders. Kernel density estimators showed that eiders generally occurred in lower densities in areas of otherwise suitable habitat off the Mackenzie River delta. We suggest that this is a result of the highly turbid water discharged by the Mackenzie River, which limits visibility. Oil and gas exploration overlapped significantly with the areas used by eiders. The high density of birds using the restricted and ice-rich flaw lead habitats indicates that an accidental spill in the region could be catastrophic for Canada's western Arctic eider populations. © 2013 The Wildlife Society.     

The diet of king eiders wintering in Nuuk,Southwest Greenland,with reference to sympatric wintering common eiders

Coastal and offshore waters of Southwest Greenland are internationally important wintering areas for king eiders (Somateria spectabilis) breeding in eastern Canadian Arctic and in northwestern Greenland. This paper presents the first assessment of their winter diet. Based on esophageal-proventricular samples from 26 females (13 juveniles and 13 older birds) and 15 males (11 juveniles and four older birds) collected in 2000–2002 (November–May) in coastal waters of Nuuk, we identified 28 prey species. The diet consisted of almost equal proportions (aggregate fresh mass) of polychaetes, echinoderms, crustaceans and molluscs. The dominant prey species were Pectinaria spp. (26.8%), Strongylocentrotus droebachiensis (18.4%), Mya eideri (11.2%) and Hyas araneus (9.7%). The polychaetes have previously been identified as important prey for eiders in Greenland, but apparently not outside Greenland. Compared with a diet study of common eiders Somateria mollissima from the same wintering area, the king eiders consumed significantly less bivalves and significantly more echinoderms. This difference corresponded with observations that common eiders were feeding in shallow waters, while king eiders were feeding in deeper waters farther from the shore. Benthic surveys are needed to confirm that diet corresponds with prey availability.     

The protective effect of egg yolk from different avian species during the cryopreservation of Karayaka ram semen

Egg yolk is one of the most widely used cryoprotective components for sperm preservation and a wide range of factors affect its action on sperm motility, viability and fertilizing ability. The aim of this experiment was to determine the effect of different species egg yolk, namely the domestic chicken (Gallus gallus domesticus), the goose (Anatidae anser), turkey (Meleagris gallopavo), duck (Anatidae anas platyrhynchos), Japanase quail (Coturmix japonica) and chucker (Alectoris chukar) on sperm quality following cryopreservation of ram semen. Ejaculates were collected using the artificial vagina from three Karayaka rams and spermatological characteristics assessed for the pooled semen. Semen samples were evaluated as split ejaculates in the trial and samples extended with a Tris-citric acid-glucose extender containing the different avian egg yolk (15%) and glycerol (5%). The semen straws were equilibrated at 4 °C for 2 h, frozen in liquid nitrogen vapour (for 15 min at ?120 °C) and stored in liquid nitrogen (?196 °C). After thawing (37 °C for 30 s), sperm motility, viability, abnormal acrosome and membrane integrity (HOST) were evaluated. Results showed chucker egg yolk to have the best cryoprotective effect in terms of the highest sperm motility (54.0%), compared to the other five avian egg yolks (p < 0.05) evaluated. Sperm frozen in chucker egg yolk also showed a higher percentage viability (59%), than sperm stored in quail and turkey egg yolk (p < 0.05). The percentage of acrosomal abnormalities after thawing was lower in the chucker egg yolk, than the other species (p < 0.05). There was no significant difference in sperm membrane integrity between the egg yolks, except for the quail (p < 0.05). Results suggest that chucker egg yolk could be used as an alternative for chicken egg yolk, in a semen extender in cryopreservation, but it warrants further evaluation in fertility trials.     

Egg lipid and thiamine vary between early and late spawning lake sturgeon

Nutritional deficiency associated with reduced thiamine (vitamin B1) and reduced natural reproduction of salmonid species in the Great Lake Region is well established. The negative relationship between egg thiamine and lipid concentration to post-hatch larval growth and survival in teleost species, coupled with the limited research of egg thiamine in Acipenseriform species of conservation concern, including lake sturgeon, indicates that study of thiamine concentrations lake sturgeon eggs is warranted. Eggs were collected from females (N = 12) during the early and late portion of the spawning run in 2007 in a wild population from Black Lake, MI. Concentrations of thiamine, lipid and fatty acid concentration were measured along with female biological information (body size and egg size) and characteristics of larvae at hatch. Significant differences in egg thiamine concentrations were observed between early- and late-spawning females (mean ± SD: 2.36 nmol·g⁻¹ ± 1.09 vs. 0.73 ± 0.25 nmol·g⁻¹, W = 0.05, p < .01). No significant relationships were observed between female body size or egg size and egg lipid or thiamine concentration. Differences in lipid and thiamine concentrations were not predictive of larval body size or yolk sac volume at hatch. Total and phosphorylated thiamine were correlated with n-3 polyunsaturated fatty acids, suggesting that dietary items were likely partially responsible for provisioning of essential compounds. Given the negative effects of low egg thiamine concentration on larval survival in other fish species globally, results indicate that further research in areas of nutrient acquisition and thiamine effects on larval survival, natural recruitment, and hatchery feeding strategies is warranted for lake sturgeon.     

Carbon and nitrogen isotope composition of vegetation on King George Island,maritime Antarctic

We report abundance of ¹³C and ¹⁵N contents in terrestrial plants (mosses, lichens, liverworts, algae and grasses) from the area of Barton Peninsula (King George Island, maritime Antarctic). The investigated plants show a wide range of δ¹³C and δ¹⁵N values between −29.0 and −20.0‰ and between −15.3 and 22.8‰, respectively. The King George Island terrestrial plants show species specificity of both carbon and nitrogen isotope compositions, probably due to differences in plant physiology and biochemistry, related to their sources and in part to water availability. Carbon isotope compositions of Antarctic terrestrial plants are typical of the C₃ photosynthetic pathway. Lichens are characterized by the widest carbon isotope range, from −29.0 to −20.0‰. However, the average δ¹³C value of lichens is the highest (−23.6 ± 2.8‰) among King George Island plants, followed by grasses (−25.6 ± 1.7‰), mosses (−25.9 ± 1.6‰), liverworts (−26.3 ± 0.5‰) and algae (−26.3 ± 1.2‰), partly related to habitats controlled by water availability. The δ¹⁵N values of moss samples range widest (−9.0 to 22.8‰, with an average of 4.6 ± 6.6‰). Lichens are on the average most depleted in ¹⁵N (mean = −7.4 ± 6.4‰), whereas algae are most enriched in ¹⁵N (10.0 ± 3.3‰). The broad range of nitrogen isotope compositions suggest that the N source for these Antarctic terrestrial plants is spatially much variable, with the local presence of seabird colonies being particularly significant.     

Use of the Beaufort Sea by King Eiders Breeding on the North Slope of Alaska

Abstract: We estimated areas used by king eiders (Somateria spectabilis) in the Alaskan Beaufort Sea, how distributions of used areas varied, and characteristics that explained variation in the number of days spent at sea, to provide regulatory agencies with baseline data needed to minimize impacts of potential offshore oil development. We implanted sixty king eiders with satellite transmitters at nesting areas on the North Slope of Alaska, USA, in 2002-2004. More than 80% of marked eiders spent >2 weeks staging offshore prior to beginning a postbreeding molt migration. During postbreeding staging and migration, male king eiders had much broader distributions in the Alaskan Beaufort Sea than female eiders, which were concentrated in Harrison and Smith Bays. Distribution did not vary by sex during spring migration in the year after marking. Shorter residence times of eiders and deeper water at locations used during spring migration suggest the Alaskan Beaufort Sea might not be as critical a staging area for king eiders during prebreeding as it is postbreeding. Residence time in the Beaufort Sea varied by sex, with female king eiders spending more days at sea than males in spring and during postbreeding. We conclude the Alaskan Beaufort Sea is an important staging area for king eiders during postbreeding, and eider distribution should be considered by managers when mitigating for future offshore development. We recommend future studies examine the importance of spring staging areas outside the Alaskan Beaufort Sea.     

Incubation behavior of king eiders on the coastal plain of northern Alaska

Incubating birds balance their energetic demands during incubation with the needs of the developing embryos. Incubation behavior is correlated with body size; larger birds can accumulate more endogenous reserves and maintain higher incubation constancy. King eiders (Somateria spectabilis) contend with variable and cold spring weather, little nesting cover, and low food availability, and thus are likely to rely heavily on endogenous reserves to maintain high incubation constancy. We examined the patterns of nest attendance of king eiders at Teshekpuk and Kuparuk, Alaska (2002–2005) in relation to clutch size, daily temperature, and endogenous reserves to explore factors controlling incubation behavior. Females at Kuparuk had higher constancy (98.5 ± 0.2%, n = 30) than at Teshekpuk (96.9 ± 0.8%, n = 26), largely due to length of recesses. Mean recess length ranged from 21.5 to 23.7 min at Kuparuk, and from 28.5 to 51.2 min at Teshekpuk. Mean body mass on arrival at breeding grounds (range; Teshekpuk 1,541–1,805, Kuparuk 1,616–1,760), and at the end of incubation (Teshekpuk 1,113–1,174, Kuparuk 1,173–1,183), did not vary between sites or among years (F < 1.1, P > 0.3). Daily constancy increased 1% with every 5°C increase in minimum daily temperature (β _min = 0.005, 95% CI 0.002, 0.009). Higher constancy combined with similar mass loss at Kuparuk implies that females there met foraging requirements with shorter recesses. Additionally, females took more recesses at low temperatures, suggesting increased maintenance needs which were potentially ameliorated by feeding during these recesses, indicating that metabolic costs and local foraging conditions drove incubation behavior.     

Invasion by an exotic tree alters above and belowground ecosystem components

With the widespread introduction and invasion of exotic plants there is a need for studies that quantify alterations of basic ecosystem structure and function. Ecosystem invasion by Melaleuca quinquenervia significantly altered both above- and belowground ecosystem components in this study. We measured the quantity and nutrient concentration of the litterfall, litter layer, and soil; microbial biomass pools; and rates of potentially mineralizable nitrogen and soil oxygen demand. Annual litterfall was 4.9 times higher in the non-invaded sites and contained 1.9 times more phosphorus than invaded sites. Non-invaded plots contained a larger litter layer compared to invaded plots: 2.4 ± 1.2 kg m⁻² and 0.62 ± 0.3 kg m⁻² , respectively. Lower nutrient concentration and quantity of the litter layer in the invaded plots led to changes in the aboveground storage of nutrients. In the invaded plots there was four times less carbon, seven times less nitrogen, and ten times less phosphorus stored in the organic litter layer compared to the non-invaded plots. Microbial biomass nutrient pools were consistently lower at both the 0–5 cm and 5–15 cm depth in the invaded soils compared to non-invaded soils, indicating a plant mediated change. Although M. quinquenervia altered microbial community structure, microbial activities were not different between invaded and non-invaded plots at either depth as measured by rates of soil oxygen demand and potentially mineralizable nitrogen. These changes may affect both native plant growth and water quality, and may act to promote and maintain site dominance by M. quinquenervia.     

Abundance and energy requirements of eiders (Somateria spp.) suggest high predation pressure on macrobenthic fauna in a key wintering habitat in SW Greenland

The number of common eiders (Somateria mollissima borealis) in west Greenland declined dramatically during the twentieth century, supposedly because of human activities. However, their sensitivity to alternative drivers of variation, such as climate conditions, diseases or food availability, remains unstudied. In this study, we describe prey availability and assess the trophic coupling between eiders and their macrobenthic prey in a shallow inlet, Nipisat Sound; a key wintering habitat in the south-west Greenland Open Water Area. Macrobenthic species abundance and biomass were studied, and annual production was estimated by an empirical model, including environmental characteristics, fauna composition and individual biomass. In spring 2008, average macrozoobenthic abundance and biomass were 6,912 ind m⁻² and 28.4 g ash-free dry mass (AFDM) m⁻² (647 kJ m⁻²), respectively. Annual production was estimated at 13.9 g AFDM m⁻² year⁻¹ (317 kJ m⁻² year⁻¹). During the winters of 2008–2010, we monitored the number of common eiders (S. mollissima borealis) and king eiders (Somateria spectabilis) and observed a distinct peak in abundance during winter with up to 15.000 birds in Nipisat Sound. Based on physiological costs of different activities in combination with the observed behavioural pattern, we obtained an estimate of the energy required for eiders to balance their costs of living, which amounted to 58% of the estimated total annual production of macrobenthos in Nipisat Sound. This result suggests that eider predation affects macrobenthic species composition and biomass and demonstrates the potential importance of variations in prey availability for the population dynamics of eiders in Greenland.     

Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies

 The isotope enrichment ɛ* of ¹³C between tooth enamel of large ruminant mammals and their diet is 14.1 ± 0.5‰. This value was obtained by analyzing both the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment, although our data cannot determine if it is significantly different. We also found a ¹³C isotope enrichment ɛ* of 3.1 ± 0.7‰ for horn relative to diet, and 11.1 ± 0.8‰ for enamel relative to horn for ruminant mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic composition of the atmosphere, determine the fraction of C₃ or C₄ biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C₄ photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats. Received: 1 July 1998 / Accepted: 9 February 1999     

Effects of ambient temperature and methionine supplementation of a low protein diet on the performance of laying hens

The effects of ambient temperature and the supplementation of methionine to a low protein diet on egg production, egg quality, blood constituents and nitrogen excretion of laying hens were studied. The objective was to derive an environmental friendly feed formulation for warm climate. Seventy-two 29-week-old commercial White Leghorn hens of Babcock ISA white strain were used in this trial. The design is a completely randomized design with a 2×3 factors arrangement of treatments. Two constant ambient temperatures were 24±1°C and 34±1°C with 85% relative humidity. The three dietary treatments were 170 g kg⁻¹ crude protein, 140 g kg⁻¹ crude protein and 140 g kg⁻¹ crude protein supplemented with methionine 1.4 g kg⁻¹. Hens were allotted into six groups according to egg production and body weight. Birds were raised in individual wire cages for the experimental feeding period of five weeks. At the end of the feeding trial, one replicate of laying hens (four birds) from each treatment were selected for a four-day metabolic study for the daily collection of the excreta. The blood samples were withdrawn from the wing vein for analysis of hematocrit, blood glucose, sodium, potassium, magnesium, calcium, phosphorus and uric acid. Experimental results indicate that increases in ambient temperature significantly depress feed intake, egg production, egg weight and live weight of laying hens. High ambient temperature also caused inferior egg quality, including shell weight, shell thickness, shell breaking strength and specific gravity. Ambient temperature also changes the egg components with heavier egg albumin and yolk in the low-temperature group. Increasing ambient temperature also caused an increase in pH value in the plasma. This increase revealed a trend of depressed glucose (P<0.05) in the plasma of the laying hens. The dietary treatments, however, did not significantly influence feed intakes. Except egg weight, laying hens that were fed with the low protein (140 g kg⁻¹) with methionine supplemented diet produced similar numbers of egg and feed conversion as the layers fed with the high protein diet. The low protein with methionine supplemented diet produced significantly lighter eggs than the high dietary protein diet under the high ambient temperature, but produced heavier egg under the low ambient temperature. The concentration of uric acid in the plasma and nitrogen in the excreta of the high protein group was significantly higher than the other two low protein dietary groups (P<0.05).     

Resource use for reproduction depends on spring arrival time and wintering area in an arctic breeding shorebird

Resources for egg production may come from body reserves stored before breeding (“capital breeders”) or from food acquired at the breeding site (“income breeders”). Arctic migrants were long thought to be capital breeders, because they often arrive at a time when local food availability is still limited. However, later evidence suggested that arctic breeding shorebirds are primarily income breeders, or that they use a mixed strategy depending on laying date. We explored the relationship between laying date and resource use for reproduction in the pectoral sandpiper Calidris melanotos breeding in the Alaskan arctic by contrasting carbon isotope (δ¹³C) values of the local diet and of maternal plasma, cellular blood, feather and claw with those of the eggs produced. Our results revealed that early breeding females utilize resources for egg production that were acquired recently at staging areas, whereas later breeding females mostly relied on nutrients derived from local food sources. These findings suggest that the resource allocation strategy used for reproduction differs among females, and varies depending on the timing of arrival and the start of reproduction. The arrival date at the breeding ground and laying date may critically depend on non‐breeding season events such as winter habitat choice, staging areas or migration routes. By comparing maternal feather δ¹³C, claw δ¹³C and feather δD, we examined whether non‐breeding season events influenced the use of resources for egg production through variation in capture date or clutch initiation date. Female pectoral sandpipers originating from moulting areas characterized by higher (more positive) δD signatures were caught earlier and started laying earlier, and they used stored resources for reproduction. Using regional maps of δD values for precipitation in the wintering sites in South America, we compared the spatial variation in the observed feather δD signatures. This analysis indicated that female pectoral sandpipers with higher δD signatures, presumably coming from more north‐easterly wintering sites in southern America, started laying earlier and used mostly stored resources for egg production, compared to females that wintered (or at least moulted) further south. Our results thus show that winter moulting habitat is linked to breeding resource allocation strategy in this high‐arctic breeding shorebird.     

Arctic waders and the capital‐income continuum: Further tests using isotopic contrasts of egg components

Birds migrating annually to high‐latitude breeding grounds may benefit from the transport of endogenous nutrient reserves that ultimately contribute to reproduction. Shorebirds represent a diverse group of Arctic breeders that typically arrive on the breeding grounds with body reserves enriched in ¹³C and ¹⁵N due to wintering and staging in marine or estuarine habitats. Such isotopic differences between endogenous macronutrient reserves and local foodwebs allow the use of stable isotopes to test for the source of nutrient allocations to eggs. We examined δ¹³C and δ¹⁵N values in lipid‐free yolk and albumen and δ¹³C values in yolk lipid of first clutches of ten species of sandpiper and plover breeding near Churchill, Manitoba, Canada in 2003. Most birds had egg isotope values indicating a C3 terrestrial biome, which fits primarily an income (exogenous) breeding strategy. Two exceptions were single sandpiper and plover with strong marine isotope values. Among species, strong positive relationships for each isotope between egg tissue components suggest that egg proteins and lipids tended to be derived from the same isotopic source. Correlations of egg δ¹³C values for lipids and proteins approached theoretical relationships expected for exogenous breeding strategies, based on captive studies. Significant positive correlations between clutch initiation date and δ¹³C values of egg lipids and albumen suggest some endogenous nutrient contributions to later laid eggs but the circumstances under which this may occur are unstudied. Where possible, we recommend that researchers use blood and fat biopsies from laying females as a means of anchoring endogenous and exogenous endpoints for modeling of each reproductive event. We encourage the isotopic analysis of egg albumen, yolk and yolk lipids among individuals and species and tests of correlations among these components as a means of inferring origins of nutrients to eggs.     

Effects of Dietary Selenium Source,Storage Time,and Temperature on the Quality of Quail Eggs

We report the effects of time of storage, temperature, and supplementation with sodium selenite- and selenium-enriched yeast on the quality of quail eggs. For this study, 90 10-week-old female Japanese quails (Coturnix coturnix japonica) with similar body size were caged individually and randomly divided into five groups of 18 quails each. One group was fed a normal diet and served as control. A second group was supplemented with 0.2 mg/kg sodium selenite (In-Se) and three groups supplemented with 0.1, 0.2, and 0.3 mg/kg of a commercially available selenium-enriched yeast (O-Se1, O-Se2, and O-Se3, respectively). The eggs were collected at third and fourth weeks of the experiment and were stored at 4°C and 20°C for 0, 15, 30, and 45 days. Extension of the storage time to 45 days at 20°C resulted in significant deterioration of egg quality. The albumen Haugh unit (HU), pH, albumen index, yolk index, and egg weight loss were the most important parameters influenced by the nature of the selenium sources, storage time, and temperature. Storage time and temperature were also significant for egg weight loss, HU, and albumen and yolk indexes. The results show that supplementation with selenium yeast significantly affected shell weight, shell thickness, HU, albumen index, yolk index, and pH. The HU decreased with increased storage time and temperature. Higher levels of Se-yeast administration resulted in greater HU compared to the selenite and control groups.