Fresh Egg Mass Research Articles

Influence of Holding Conditions and Storage Duration ofHalyomorpha halys(Hemiptera: Pentatomidae) Eggs on Adventive and Quarantine Populations ofTrissolcus japonicus(Hymenoptera: Scelionidae) Behavior and Parasitism Success

Halyomorpha halys (Stål) is an invasive pest in the United States and other countries. In its native range, H. halys eggs are parasitized by a co-evolved parasitoid, Trissolcus japonicus (Ashmead). In the United States, T. japonicus, a classical biological control candidate, is being redistributed in many states where adventive populations exist. To establish if H. halys egg holding conditions affect T. japonicus foraging behavior or successful parasitism, naïve, female parasitoids from an adventive population were allowed to forage in laboratory bioassay arenas with either fresh or frozen (-20 or -80°C) egg masses, the latter held for five durations ranging from 1 h to 112 d. Parasitoid movements were recorded for 1 h. Thereafter, parasitoids were transferred with the same egg mass for 23 h. Additionally, female parasitoids from a quarantine colony were exposed to: 1) pairs of fresh egg masses and egg masses frozen at -40°C (>24 h) or 2) a single fresh egg mass or egg mass frozen at -40°C (<1 h). All exposed egg masses were held to assess progeny emergence. In the foraging bioassay, holding temperature and storage duration appeared to influence host-finding and host quality. Egg masses held at -80°C and fresh egg masses resulted in significantly greater levels of parasitism and progeny emergence compared with eggs held at -20°C. No differences were recorded between egg masses held at -40°C for ≤1 h and fresh egg masses. These results will help refine methods for preparation of egg masses for sentinel monitoring and parasitoid mass rearing protocols.

Laying sequence interacts with incubation temperature to influence rate of embryonic development and hatching synchrony in a precocial bird.

Incubation starts during egg laying for many bird species and causes developmental asynchrony within clutches. Faster development of late-laid eggs can help reduce developmental differences and synchronize hatching, which is important for precocial species whose young must leave the nest soon after hatching. In this study, we examined the effect of egg laying sequence on length of the incubation period in Wood Ducks (Aix sponsa). Because incubation temperature strongly influences embryonic development rates, we tested the interactive effects of laying sequence and incubation temperature on the ability of late-laid eggs to accelerate development and synchronize hatching. We also examined the potential cost of faster development on duckling body condition. Fresh eggs were collected and incubated at three biologically relevant temperatures (Low: 34.9°C, Medium: 35.8°C, and High: 37.6°C), and egg laying sequences from 1 to 12 were used. Length of the incubation period declined linearly as laying sequence advanced, but the relationship was strongest at medium temperatures followed by low temperatures and high temperatures. There was little support for including fresh egg mass in models of incubation period. Estimated differences in length of the incubation period between eggs 1 and 12 were 2.7 d, 1.2 d, and 0.7 d at medium, low and high temperatures, respectively. Only at intermediate incubation temperatures did development rates of late-laid eggs increase sufficiently to completely compensate for natural levels of developmental asynchrony that have been reported in Wood Duck clutches at the start of full incubation. Body condition of ducklings was strongly affected by fresh egg mass and incubation temperature but declined only slightly as laying sequence progressed. Our findings show that laying sequence and incubation temperature play important roles in helping to shape embryo development and hatching synchrony in a precocial bird.

Breeding biology of an endemic Bornean turdid, the Fruithunter (Chlamydochaera jefferyi), and life history comparisons withTurdusspecies of the world

ABSTRACT We present the first description of the breeding biology for the Fruithunter (Chlamydochaera jefferyi), a member of the cosmopolitan family Turdidae, and a montane endemic to the tropical Asian island of Borneo. We also compile breeding biology traits from the literature to make comparisons between the Fruithunter and the thrush genus Turdus. Our comparisons indicate that Fruithunters exhibit a slower life history strategy than both tropical and north temperate Turdus. We located and monitored 42 nests in 7 years in Kinabalu Park, Sabah, Malaysia. The mean clutch size was 1.89 ± 0.08 eggs, and the modal clutch size was 2 eggs. Mean fresh egg mass was 6.15 ± 0.13 g, representing 9.5% of adult female body mass. Average lengths of incubation and nestling periods were 14.56 ± 0.24 and 17.83 ± 0.31 days respectively. Only the female incubated and brooded the eggs and nestlings, but both the male and female fed nestlings. Female attentiveness during incubation was high throughout, reaching an asymptote...

It's what's inside that counts: egg contaminant concentrations are influenced by estimates of egg density, egg volume, and fresh egg mass.

In egg contaminant studies, it is necessary to calculate egg contaminant concentrations on a fresh wet weight basis and this requires accurate estimates of egg density and egg volume. We show that the inclusion or exclusion of the eggshell can influence egg contaminant concentrations, and we provide estimates of egg density (both with and without the eggshell) and egg-shape coefficients (used to estimate egg volume from egg morphometrics) for American avocet (Recurvirostra americana), black-necked stilt (Himantopus mexicanus), and Forster's tern (Sterna forsteri). Egg densities (g/cm(3)) estimated for whole eggs (1.056±0.003) were higher than egg densities estimated for egg contents (1.024±0.001), and were 1.059±0.001 and 1.025±0.001 for avocets, 1.056±0.001 and 1.023±0.001 for stilts, and 1.053±0.002 and 1.025±0.002 for terns. The egg-shape coefficients for egg volume (K v ) and egg mass (K w ) also differed depending on whether the eggshell was included (K v =0.491±0.001; K w =0.518±0.001) or excluded (K v =0.493±0.001; K w =0.505±0.001), and varied among species. Although egg contaminant concentrations are rarely meant to include the eggshell, we show that the typical inclusion of the eggshell in egg density and egg volume estimates results in egg contaminant concentrations being underestimated by 6-13%. Our results demonstrate that the inclusion of the eggshell significantly influences estimates of egg density, egg volume, and fresh egg mass, which leads to egg contaminant concentrations that are biased low. We suggest that egg contaminant concentrations be calculated on a fresh wet weight basis using only internal egg-content densities, volumes, and masses appropriate for the species. For the three waterbirds in our study, these corrected coefficients are 1.024±0.001 for egg density, 0.493±0.001 for K v , and 0.505±0.001 for K w .

Egg Mass in Glaucous-Winged Gulls (Larus Glaucescens) as a Function of Length and Width

Egg mass at laying is an important predictor of hatchling mass in birds (Deeming and Birchard 2007; Alabi and others 2012). Hatchling mass, in turn, affects reproductive success; smaller eggs produce smaller chicks, and smaller chicks are less likely to survive (Parsons 1975). Egg mass thus serves as an important measure of parental investment and fitness. For colonial seabirds, egg mass can be determined using a portable scale carried through the colony during nest surveys. In order to receive an accurate reading, however, the scale must rest on a level surface, remain sheltered from the wind, and be recalibrated at each new site. Furthermore, because eggs lose moisture over time and get progressively lighter, an egg should be weighed on the day that it is laid (Romanoff and Romanoff 1949). It is not always possible or convenient to fulfill these requirements for measuring egg mass. In contrast, egg length and width, which remain constant from laying to hatching, can be measured rapidly and accurately in the field with calipers. Several equations for estimating egg mass or volume from length and width have appeared in the literature. Hoyt (1979) estimated fresh egg mass M from length L and width W with the model M~kMLW , in which kM is a speciesspecific parameter. He provided kM values for 26 species, including Western Gulls (Larus occidentalis), for which kM was calculated to be 0.000531 g/mm (n 5 8). For chicken eggs, Narushin (2005) used geometric considerations to obtain the volume model V~ a{bW ð ÞLW, and Abanikannda and others (2007) used a model of the form M~azbLz cWzd(W=L). In this study, we tested these 3 alternative models as well as 3 allometric models for Glaucous-winged Gulls (L. glaucescens). In particular, we: (1) parameterized the models with data collected from a Glaucous-winged Gull colony; (2) selected the best model(s) using the Akaike Information Criterion (AIC); and (3) validated the selected model(s), without refitting, on a data set that was not used for parameter estimation. We collected data during the 2009 and 2010 breeding seasons at Protection Island National Wildlife Refuge (486079400 N, 122655900 W), Jefferson County, Washington, USA. Violet Point, a gravel spit extending to the southeast of the main island, contained a breeding colony of 3000 (in 2009) and 2469 (in 2010) pairs of Glaucous-winged Gulls (Cowles and others 2012, and unpubl. data). We selected 5 rectangular sample subareas of the Violet Point colony as shown in Figure 1 of Henson and others (2010; Plots A–E), with a combined sample area of 4205 m. Plot A bordered the beach on the north-central edge of the colony; Plot B was landlocked in the center of the colony; Plot C was at the west end of the colony and bordered the north beach of a small marina closed to the public; Plot D was in the center of the colony and also bordered the north beach of the marina; Plot E was in the center of the colony and bordered the south beach of the marina. Daily, throughout the 2009 and 2010 laying seasons (late May–early July), we monitored all nest cups in the 5 sample areas. When clutch initiation occurred in a nest, we placed a numbered wooden stake near the nest. Each staked nest was checked daily for new eggs. The mass of each egg was measured on the day it was laid using a 400-g capacity Ohaus Scout Pro SP401 portable electronic balance, and each egg was measured with vernier calipers at its widest and longest points. One egg, a ‘dwarf’ whose length (55.9 mm) and width (38.6 mm) were GENERAL NOTES

Fresh egg mass estimation using machine vision technique

Fresh egg mass estimation using machine vision technique In the present study a machine vision system was developed for estimating the mass of eggs arranged in a single array. A grabber frame equipped with a mirror was developed for positioning the eggs. Therefore, two images could be captured from each egg. Images were then processed by Matlab software. Six algorithms were developed to extract eggs features such as minimum, maximum and effective radii, perimeter and the frontal area from each image. The eggs were also weighed by a sensitive digital scale. Seventy percent of data after discarding the outliers were used to establish some models, and the remaining was used to verify the final model. The results showed that egg mass estimation can be accurate by using two perpendicular views of each egg. Amongst the models, one with predictors of area and effective radius was found to be the best. A high correlation coefficient was observed between eggs mass measured and predicted by the model, with an accuracy of about 95%.

Reaction of coffee genotypes to different populations of Meloidogyne spp.: detection of a naturally virulent M. exigua population

The reaction of seven genotypes of Coffea arabica to 10 Meloidogyne spp. populations collected mainly from coffee plantations in Brazil and Costa Rica was evaluated under greenhouse conditions. The inoculum consisted of 10,000 eggs per plant. Evaluations were done 8 months after inoculations considering the root fresh weight, gall and egg mass indices, number of eggs per gram of root and reproduction factor (RF). The cultivars Obata IAC 1669-20, Sarchimor IAC 4361 and Tupi Amarelo IAC 5111 exhibited susceptibility to the four Brazilian M. exigua populations tested. However, cv. Tupi Vermelho IAC 1669-33 revealed resistance (RF value of 0.7) to the M. exigua population from Lavras, Minas Gerais State, Brazil. A population of M. exigua from Bom Jesus de Itabapoana, Rio de Janeiro State, Brazil, was highly virulent on cv. IAPAR 59 (RF= 165.7), bearing resistance gene Mex-1, and was also virulent on genotype Paraiso (H 419-5-4-5-2) (RF=396.2). A Meloidogyne sp. population on coffee from Garca, Sao Paulo State, Brazil, reproduced at low rates (RF ranging from 0.1 to 3.9) on all genotypes. All tested cultivars were susceptible to M. incognita and M. paranaensis. M. mayaguensis of guava from Parana State, Brazil, reproduced at low rates in all coffee genotypes; however, another population of coffee, from Costa Rica, was more aggressive and showed RF value that ranged from 0.8 to 12.4. Results of this study point for the first time to the ability of a naturally occurring M. exigua population to overcome the resistance conferred by the Mex-1 gene.

Maternal resource variation across the laying sequence in Canada geese Branta canadensis maxima

Variation in maternal investments to offspring presumably reflects an optimization of resource allocation such that a female's fitness is maximized. In birds, both egg size and yolk constituents are examples of resources that can vary among offspring within a clutch. Egg size and maternally‐derived steroid hormone concentrations present in yolk have been characterized for many species that lay small clutches or have altricial young, but little information is available for species that lay moderate to large clutches of precocial young. In this study, we recorded laying position, measured fresh egg mass and determined maternally‐derived testosterone and estradiol concentrations present in yolks for whole clutches of free‐living Canada geese Branta canadensis maxima to assess variation in maternal resources within clutches. We found that egg size varied non‐linearly across the laying sequence such that first laid eggs were small, the largest eggs in the clutch occurred in the second and third positions, and size declined in eggs laid in subsequent positions. Concentration of testosterone in the yolk followed a pattern in which the first and second laid eggs have the highest concentrations within a clutch and declining concentrations in subsequently laid eggs. In contrast, maternally‐derived yolk estradiol concentrations (measured in a subset of clutches) did not change across the laying sequence.

Practical method of estimating fresh mass of Adélie penguin eggs

Fresh egg mass (FEM) is an important measure as it relates to many allometric relationships. Adelie penguin (Pygoscelis adeliae) eggs, as other bird eggs, begin to lose weight as soon as they are laid but their linear dimensions remain constant. The FEM of an Adelie penguin’s egg can be estimated within 1% from the relationship FEM = 0.564 × LW2, where L is the length and W is the width. The constant 0.564 was calculated by weighing the eggs after replacing the air cell with water. The calculated mean egg mass agrees well with that obtained by weighing eggs after replacement of the air cell with water (r2 = 0.996). This method of estimating FEM based on linear measurements is easily applicable in the field.

Breeding Biology of the Three-Striped Warbler in Venezuela: a Contrast between Tropical and Temperate Parulids

We document reproductive life history traits of the Three-striped Warbler (Basileuterus tristriatus) from 146 nests in Venezuela and compare our results to data from the literature for other tropical and temperate parulid species. Mean (± SE) clutch size was 1.96 ± 0.03 eggs (n = 96) and fresh egg mass was 2.09 ± 0.02 g. The incubation period was 15.8 ± 0.2 days (n = 23) and the nestling period was 10.5 ± 0.3 days (n = 12). Males did not incubate and rarely provided food for females during incubation. Females had 57 ± 2% (n = 49) nest attentiveness (% of time on the nest incubating), which caused egg temperature to commonly become cold relative to development. Both adults fed nestlings and feeding rates increased with nestling age. The growth rate constant for nestlings based on mass was K = 0.490, which is slower than for north temperate warblers. Predation was the primary source of nest failure and only 22% of nests were successful based on a Mayfield daily predation rate of 0.048 ± 0.006. Our literature review indicates parulids differ strongly in life histories between temperate and tropical/subtropical sites with species in the tropics having, on average, smaller clutches, longer incubation periods, lower nest attentiveness, longer off-bouts, and longer nestling periods.

Reproductive Biology of the Violet-Chested Hummingbird in Venezuela and Comparisons with Other Tropical and Temperate Hummingbirds

AbstractAbstract. We provide details on the breeding biology of the Violet-chested Hummingbird (Sternoclyta cyanopectus) based on 67 nests studied in Yacambú National Park, Venezuela, from 2002 through 2006. Clutch size was two white eggs, usually laid every other day. Fresh egg mass (0.95 ± 0.14 g) was 15% of female mass. Incubation and nestling periods were 20.4 ± 0.3 and 26.0 ± 0.4 days, respectively. Nest attentiveness increased from 60% in early incubation to 68% in late incubation. The female spent 50% of her time brooding young nestlings, but ceased brooding by 13 days of age. Only the female fed the young, with a low rate of nest visitation (3.3 trips per hour) that did not increase with age of the young. Growth rate based on nestling mass (K = 0.28) was slow. Daily predation rates decreased across stages and were 0.064 ± 0.044, 0.033 ± 0.008, and 0.020 ± 0.006 during the egg-laying, incubation, and nestling periods, respectively. Most, but not all, life history traits of the Violet-chested Hummingbird were similar to those reported for other tropical and temperate hummingbirds, providing further evidence that this family shows a relatively narrow range of life history variation.

Measuring egg size using digital photography: testing Hoyt's method using Florida Scrub-Jay eggs

Egg volumes are most often estimated using a mathematical model that incorporates length and width measurements and a species-specific shape variable. Although adequate in many respects, this technique does not account for intraspecific variation in egg shape. We developed a computer-automated technique that uses calibrated digital photographs to render precise measurements of several egg-size parameters including length, width, volume, and surface area. The system extracts egg outlines from photographs, and divides each egg into latitudinal slices that are subsequently regarded as simple geometric shapes (cylinders or cone frustra) with volumes and surface areas that can be summed to generate size parameters for the entire egg. We tested this technique using 491 eggs from Florida Scrub-Jay (Aphelocoma coerulescens) nests and compared the resulting egg volumes with volumes calculated using the preeminent method of estimating volume from linear measurements. Our method was highly accurate, and differences between the volumes from our method and the alternative method were strongly associated with variation in egg shape. Advantages of our technique include decreased handling of eggs and increased accuracy. Software resources and additional information regarding the technique are available at http://www.archbold-station.org/abs/data/birddata/Bridge-JFO-eggsize.htm. SINOPSIS. Medidas de huevos utilizando fotograf´ ia digital: poniendo a pruebas el m´ etodo

REPRODUCTIVE BIOLOGY OF THE VIOLET-CHESTED HUMMINGBIRD IN VENEZUELA AND COMPARISONS WITH OTHER TROPICAL AND TEMPERATE HUMMINGBIRDS

Abstract Abstract. We provide details on the breeding biology of the Violet-chested Hummingbird (Sternoclyta cyanopectus) based on 67 nests studied in Yacambu National Park, Venezuela, from 2002 through 2006. Clutch size was two white eggs, usually laid every other day. Fresh egg mass (0.95 ± 0.14 g) was 15% of female mass. Incubation and nestling periods were 20.4 ± 0.3 and 26.0 ± 0.4 days, respectively. Nest attentiveness increased from 60% in early incubation to 68% in late incubation. The female spent 50% of her time brooding young nestlings, but ceased brooding by 13 days of age. Only the female fed the young, with a low rate of nest visitation (3.3 trips per hour) that did not increase with age of the young. Growth rate based on nestling mass (K = 0.28) was slow. Daily predation rates decreased across stages and were 0.064 ± 0.044, 0.033 ± 0.008, and 0.020 ± 0.006 during the egg-laying, incubation, and nestling periods, respectively. Most, but not all, life history traits of the Violet-chested Hum...

VARIATION IN SIZE AND COMPOSITION OF BUFFLEHEAD (BUCEPHALA ALBEOLA) AND BARROW'S GOLDENEYE (BUCEPHALA ISLANDICA) EGGS

We investigated the relationships between egg nutrient constituents and fresh egg mass in Bufflehead (Bucephala albeola) and Barrow's Goldeneye (B. islandica). We found consistently positive relationships between egg mass and yolk, albumen, lipid, mineral, and water (absolute amounts); however, the proportions of nutrient components to fresh mass were highly variable in the eggs of both species (allometric relationships). In Bufflehead eggs, all components except mineral exhibited negative allometry with fresh egg mass. In Barrow's Goldeneye eggs, only mineral exhibited negative allometry, whereas yolk, lipid, and water all exhibited positive allometry with fresh egg mass. Overall, larger eggs of both species contained greater absolute amounts of nutrients; therefore, larger eggs were of better quality than smaller eggs. Nutrient content, however, was more highly correlated with mass in Barrow's Goldeneye eggs than in Bufflehead eggs. We propose that this may be due to the source of egg nutrients: because of their smaller body size, Buffleheads typically rely more on exogenous nutrients than Barrow's Goldeneyes.

Maternal effects in Wood Ducks: incubation temperature influences incubation period and neonate phenotype

SummaryMaternal effects often explain a significant amount of variation in offspring phenotype, and can be important in the evolution of life histories. Incubation of eggs is an important maternal effect, and optimal growth and development of avian embryos takes place within a narrow range of incubation temperatures, but the effect of incubation microclimate on neonate phenotype remains relatively unexplored in birds.In this study of Wood Ducks (Aix sponsaLinnaeus) we examined effects of incubation temperature on the length of incubation period and neonate quality. We monitored nest temperatures and incubation periods of naturally incubated Wood Duck nests and found a strong inverse relationship between incubation period and average nest temperature.Next, we collected three unincubated eggs from each of 48 nests, and randomly assigned eggs from each nest to one of three incubation temperatures (34·6, 36·0 and 37·4 °C). Experimental incubation temperatures overlapped average nest temperatures of naturally incubated Wood Duck nests.Hatching success varied with incubation temperature and was lowest for eggs incubated at the lowest temperature. Incubation period of experimental eggs decreased with increasing temperature but was not affected by fresh egg mass.Wood Duck embryos catabolized an estimated 34–38% of egg lipids and 25–33% of egg protein during incubation. Percentage change of lipids increased with decreasing incubation temperature, but not significantly. Embryos incubated at lower temperatures used a greater percentage of protein than embryos incubated at higher temperatures.In analyses using fresh egg mass as the covariate, we found that wet and dry mass of ducklings increased with increasing incubation temperature. Decreases in lipid content of Wood Duck neonates with decreasing incubation temperature were not significant, but eggs incubated at low temperatures produced ducklings that had reduced protein mass and that were structurally larger than ducklings from eggs incubated at high temperatures.Our study illustrates the importance of incubation temperature on the development of Wood Duck embryos. Decisions made by incubating parents that influence egg temperature can modify incubation period and offspring phenotype. Investigations of incubation as a reproductive cost should consider how parental decisions influence both parents and offspring.

Cardiac Rhythms in Avian Embryos and Hatchlings

Avian embryos develop within the confines of an eggshell independent of maternal physiological functions. The eggshell provides not only an airway for diffusive gas exchange of the embryo, but also a protective barrier between the embryo and the surroundings. The wide space outside the eggshell is available for measurements of embryonic physiological functions. Taking advantage of the hard eggshell, several methods have been developed to measure cardiogenic signals while maintaining an adequate gas exchange through the eggshell and cardiac rhythms of developing embryos have been determined. This review introduces the measuring methods for cardiogenic signals of embryos and shows daily changes (developmental pattern) of some cardiovascular variables. Daily determinations of heart rate (HR) from the cardiogenic signals exhibit developmental patterns of mean HR (MHR) in embryos of various species of birds. An allometric relationship is found between the fresh egg mass and embryonic MHR in 34 species of birds investigated so far. The developmental patterns of MHR are also determined by continuous measurements of HR to investigate a presence or absence of infradian, circadian and ultradian rhythms in developing embryos and also hatchlings. For investigation into beat-to-beat rhythms, instantaneous heart rate (IHR) is determined in prepipped and pipped embryos and hatchlings. In chickens, IHR baseline begins to fluctuate with appearance of transient decelerations with subsequent accelerations during the middle of incubation and distinctive patterns of IHR fluctuations develop in embryos and hatchlings. The patterns and baseline of IHR respond to exposure to altered environments and measurements of their responses have a possibility to elucidate development of some physiological functions.

Egg carotenoids in passerine birds introduced to New Zealand: relations to ecological factors, integument coloration and phylogeny

Summary Carotenoids are a diverse group of organic compounds that function as important antioxidants and immunostimulants and are of particular importance to developing embryos and young birds. In addition, they constitute the majority of yellow to red hues in the integumentary pigments of birds. We investigated the maternally derived carotenoid concentrations and balances in the yolks of eight European passerine species successfully introduced and abundant in New Zealand. Specifically, we addressed whether variation in maternally derived yolk carotenoids were related to phylogeny, integument coloration, native vs introduced distribution, breeding habitat and laying sequence. Across species, the concentration and balance of carotenoids deposited in yolks varied significantly. Egg carotenoid concentration was positively associated with the occurrence of male carotenoid pigmented body regions. Carotenoid concentrations differed between agricultural habitat types within New Zealand but not between samples from New Zealand and Europe. Controlling for the differences among species, and among clutches within species, increased egg carotenoid concentrations were significantly associated with decreasing fresh egg mass and eggs laid earlier in the laying sequence. We conclude that variability in the concentration and balance of carotenoids deposited in the egg yolk imply different relative roles for ecological and phylogenetic factors that warrant further investigation, both within and across species.

Nutritional quality of prebreeding diet influences breeding performance of the Florida scrub-jay.

Food supplementation studies of breeding birds have traditionally concentrated on energetic constraints on breeding performance. It is only recently that the nutritional quality of the prebreeding diet has also been considered influential. We examined the importance of specific nutrients in the prebreeding diet of the Florida scrub-jay ( Aphelocoma coerulescens). Birds were provided with one of two supplements (rich in protein and fat or rich in fat only) prior to breeding in 2000 and 2001 and their breeding performance, in relation to unsupplemented (control) birds, was examined. Birds receiving both supplements significantly advanced laying in both years, and increased clutch size in 2000 but not in 2001. Laying date explained variation in clutch size in birds on dietary supplements. Egg mass and volume declined with laying order, irrespective of dietary treatment, but birds on the high fat, high protein diet laid heavier third eggs than controls and this was independent of laying date. Laboratory analysis of 14 abandoned and unhatched eggs revealed that as egg mass increased so did the absolute amount of protein and water while fat content remained relatively fixed. Using these relationships between the masses of egg components and fresh egg mass, we calculated that heavier third eggs laid by birds on high fat and high protein, compared with those laid by controls, contained more water that may be fundamental to chick growth and survival. This is the first demonstration for an avian species that nutritional quality of prebreeding diet can simultaneously influence laying date, clutch size, and egg size and composition.

Respiration and energetics of embryonic development in a large altricial bird, the Australian pelican (Pelecanus conspicillatus).

We examined whether the previously reported low cost of embryonic development in pelicans could be attributed to a more efficient conversion of egg energy to hatchling tissues as a result of high initial egg water content, low embryonic metabolic rate and growth later in incubation than in more precocious species. We therefore determined egg and hatchling composition and the development of embryonic respiration in the Australian pelican Pelecanus conspicillatus, which lays one of the largest eggs (140-210 g) with an altricial developmental mode. The small yolk fraction (21%) is typical of all pelecaniforms; however, we found that intraspecific variability in fresh egg mass was related to water content (principally in the albumen), but independent of yolk mass (mean 13 g dry mass). P. conspicillatus eggs have, on average, 635 kJ of energy, irrespective of egg mass across the whole range of egg mass. The embryonic developmental pattern of O(2) consumption and CO(2) production showed clear plateaus lasting 2-3 days immediately prior to internal pipping, resembling the typical precocial pattern. However, the rate of pre-internal pipping O(2) consumption was low in comparison with that of precocial species of similar egg mass. There is no evidence to support the hypothesis that the observed plateau in rates of O(2) uptake is due to a diffusion limitation of the eggshell gas conductance in this species. Embryonic metabolic rate nearly doubled during the pipping period, but the mass-independent metabolic rate of the hatchling was low in comparison with that of the resting adult. The total O(2) consumed (11 063 ml) is equivalent to 217.3 kJ (or 34% of egg energy) based on indirect calorimetry and the observed respiratory exchange ratio of 0.71. Thus, the cost of development (direct calorimetry) was 0.29 kJ J(-1) in the egg (mean egg mass 168 g), which is one of lowest reported values. As a result, the production efficiency of pelican embryonic development was 61.6%, higher than the average for birds in general (56.9%) and, in particular, of seabirds that have prolonged incubation periods on the basis of egg mass. High efficiency in embryonic development in this species was attained as a result of rapid embryonic growth later in incubation, low hatchling energy density (23.6 kJ g(-1) dry matter) and dry matter content, low embryonic metabolic rate throughout incubation and a shorter than expected incubation period of 33 days (predicted 36 days).

VARIATION IN SIZE, COMPOSITION, AND QUALITY OF RUDDY DUCK EGGS AND DUCKLINGS

Abstract To evaluate why ducklings hatching from large eggs generally survive better than ducklings from small eggs, we quantified egg-size-related variation in composition and quality of eggs and ducklings of wild Ruddy Ducks (Oxyura jamaicensis). Fresh egg mass averaged 74.1 ± 4.3 g (SD), but ranged from 60.5 to 83.8 g. Despite remarkably large egg size relative to adult female body size, and a 1.4-fold difference in mass between the smallest and largest eggs, most egg constituents increased in direct proportion to fresh egg mass, with bigger eggs producing heavier and larger ducklings. However, large ducklings had proportionately larger yolk sac stores than did small ducklings. Thus, large ducklings also had greater total lipid reserves, an advantage that could enable them to survive better than small ducklings during the first few days after hatching. Variacion en el Tamano, Composicion y Calidad de los Huevos y Polluelos de Oxyura jamaicensis Resumen. Para evaluar por que los polluelos que eclosionan...