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First Egg (first + egg)
Selected AbstractsMothers reduce egg provisioning with ageECOLOGY LETTERS, Issue 4 2003David Giron Abstract Precise and comprehensive data on resource allocation into individual eggs are rare and this empirical void in the literature of life history strategies contrasts with the large number of theoretical studies. We show a marked decrease in reproductive investment in eggs with mother's age for egg size, sugar, protein, lipid and energy contents of eggs for a parasitic wasp. Egg size is a good predictor of offspring fitness, measured as survival of starving neonate larvae, but does not reveal possible biochemical changes. Lipids stabilize quickly at a minimal threshold while proteins and sugars decrease smoothly down to about 30% of the amount invested in the first egg. Because proteins have the highest correlation with egg size, we predict that they should be better predictors of larval fitness than lipids and sugars. Assessing the adaptive value of the observed patterns will require a multidimensional approach to egg provisioning. [source] The effects of low dietary calcium during egg-laying on eggshell formation and skeletal calcium reserves in the Zebra Finch Taeniopygia guttataIBIS, Issue 2 2001S. JAMES REYNOLDS Many small passerines forage intensively for calcium-rich foods during laying. Increased incidences of shell defects in eggs of small passerines have been reported, particularly in western Europe, and these have been explained in terms of declining calcium availability in soils, resulting from prolonged anthropogenic acid deposition. Studies in the field have provided laying birds, nesting in areas of low calcium availability, with calcium supplements. An alternative approach was adopted in this study by allowing captive Zebra Finches Taeniopygia guttata to lay first clutches on ad libitum calcium, switching them to a low calcium diet for 72 hours for the formation of all but the first egg of the second clutch and reinstating ad libitum calcium for the final clutch. Control females had access to ad libitumcalcium for all three clutches. Clutch sizes did not vary significantly between birds on low calcium and controls. The former took over three days longer to lay clutch 3 than did controls but the difference was not statistically significant. Birds on low calcium laid eggs that declined in shell ash mass with laying sequence, indicating that birds may have been calcium-limited. Although not statistically significant, eggshell thickness also declined with laying sequence in clutches laid by females on low calcium. The remaining egg measurements (shell mass, shell surface area and volume] of clutches laid by birds on low calcium did not differ significantly from those of controls. Furthermore, females on low calcium did not resort to skeletal reserves to provide sufficient calcium for egg formation. Dietary calcium appears to be of paramount importance in providing sufficient calcium for clutch formation. [source] Food limitation explains most clutch size variation in the Nazca boobyJOURNAL OF ANIMAL ECOLOGY, Issue 4 2001L. D. Clifford Summary 1,Natural selection is expected to optimize clutch size, but intrapopulation variation is maintained in many bird species. The Nazca booby provides a simple system in which to investigate clutch size evolution because clutch size and brood size are decoupled due to obligate siblicide. The indirect effect of brood size on clutch size evolution can therefore be eliminated. 2,In Nazca boobies, second eggs provide insurance against the failure of the first egg or early death of the first hatchling, but approximately half of all females lay only one egg. We tested the hypothesis that one-egg clutches result from food limitation by providing female Nazca boobies with supplemental food. 3,A higher proportion of supplemented females produced two-egg clutches than did control females. Supplemented females produced larger second-laid eggs than did control females, but not first-laid eggs. Laying date and laying interval were not affected. 4,Comparisons of clutch size and egg volume between years indicated that the supplemental feeding experiment was not conducted in a year with a poor natural food supply. Thus supplemented females produced larger clutch sizes despite apparently normal natural food levels. 5,This experiment nearly completes our understanding of clutch size variation in the Nazca booby, and indicates that food limitation and the costs of egg-laying should be considered carefully in studies of clutch size evolution. [source] Experimental addition of greenery reduces flea loads in nests of a non-greenery using species, the tree swallow Tachycineta bicolorJOURNAL OF AVIAN BIOLOGY, Issue 1 2007Dave Shutler Several bird species, including cavity-nesters such as European starlings Sturnus vulgaris, add to their nests green sprigs of plants such as yarrow Achillea millefolium that are rich in volatile compounds. In this field study on another cavity-nester, tree swallows Tachycineta bicolor, we tested whether yarrow reduced ectoparasite loads (the nest protection hypothesis), stimulated nestling immune systems (the drug hypothesis), or had other consequences for nestling growth or parental reproductive success (predicted by both preceding hypotheses). Tree swallows do not naturally add greenery to their nests, and thus offer several advantages in testing for effects of greenery independent of other potentially confounding explanations for the behaviour. We placed fresh yarrow in 23 swallow nests on the day the first egg was laid, replenishing every two days until clutch completion (=three times), and at 44 control nests, nesting material was simply touched. At 12 days of age, we measured nestling body size and mass, and took blood smears to do differential white blood cell counts. We subsequently determined the number and proportion of young fledging from nests and the number of fleas remaining after fledging. Higher humidity was associated with higher flea numbers whereas number of feathers in the nest was not. Our most significant finding was that an average of 773 fleas Ceratophyllus idius was found in control nests, versus 419 in yarrow nests. Possibly, parents compensate for blood that nestlings lose to ectoparasites by increasing food delivery, because we detected no differences between treatments in nestling mass, nestling leukocyte profiles, or proportion of young fledging, or relative to flea numbers. Our results provide no support for the drug hypothesis and strong support for the nest protection hypothesis. [source] Pre-breeding energy requirements: thyroid hormone, metabolism and the timing of reproduction in house sparrows Passer domesticusJOURNAL OF AVIAN BIOLOGY, Issue 3 2003Olivier Chastel We measured thyroid hormone (T3) levels and energy expenditure of pre-breeding house sparrows Passer domesticus in relation to the timing of breeding and reproductive success. The onset of reproduction was synchronised in two waves, separated by a three-week interval. On an annual basis, early breeders (birds that bred for the first time during the first wave) made significantly more breeding attempts, laid significantly more egg and raised 2.3 times more chicks to fledging than late breeders (birds that bred for the first time during the second wave). By the end of March, about one month before the first egg was laid in the population, plasma titres of testosterone in males and estradiol in females were still low and did not differ between early and late breeders. However, birds that subsequently bred early had higher titres of plasma triiodothyronine (T3) than birds that started to breed late. We show for the first time in a free-living bird population that Basal Metabolic Rate (BMR) is positively correlated with the plasma titre of T3. Differences in plasma T3 accounted for 48% of the inter-individual variation in BMR. Elevated T3 levels indicate that energy requirements increase prior to breeding. Although early breeding appears to be advantageous in terms of the number of offspring raised on an annual basis, the increased energy requirements prior to breeding are thought to delay the onset of reproduction in those birds that cannot afford the additional energy expenditure early in the season. [source] Sex-biased hatching sequences in the cooperatively breeding Noisy MinerJOURNAL OF AVIAN BIOLOGY, Issue 3 2001Kathryn E. Arnold The Noisy Miner Manorina melanocephala (Meliphagidae) is a cooperatively breeding bird species in which sons often remain on their natal home ranges and help one or both of their parents. In a population of Noisy Miners in SE Queensland, Australia, a molecular technique was used to explore adult and offspring sex ratios, and also hatching sequences. Among the adult population, there were 2.31 males for every female, and roughly 99% of helping was performed by males. At hatching and fledging, the population sex ratio was even, with exactly 57 males and 57 females. However, in 17 out of 18 broods the first egg to hatch was male. First-hatched males were significantly larger and heavier than their sisters just prior to fledging. Through their helping behaviour, large healthy sons could clearly enhance the future reproductive success of parents, and benefit the entire group. Sex-biased hatching sequences could potentially provide cooperatively breeding birds with a subtle and precise way of varying investment in the helping sex. [source] Direct and correlated responses to selection on age at physiological maturity in Drosophila simulansJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2000D. E. L. Promislow Biologists who study the timing of development in insects have focused on variation in duration of pre-adult stages almost without exception. However, development is not complete until adults are not only morphologically mature, but also reproductively mature. Here we describe an experiment in the fruit fly, Drosophila simulans, in which we used artificial selection to create lines with shortened and lengthened duration from eclosion to the age when the first egg was laid. We found significant genetic variation for this trait. The response to selection on age when the first egg was laid was due to variation among females. Delayed adult development was correlated with rapid pre-adult development and longer life span in females. The approach we use here resolves some difficulties with previous approaches used to study the genetics of senescence, and provides an opportunity to study the hitherto unexamined predictions derived from classic models for the evolution of senescence. [source] Breeding biology of White-rumped Tanagers in central BrazilJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2010Luane R. Dos Santos ABSTRACT White-rumped Tanagers (Cypsnagra hirundinacea) are widely distributed in northern Brazil, Bolivia, and Paraguay, and are classified as vulnerable in the state of Paraná and as endangered in the state of São Paulo, Brazil. Little is currently known about their breeding biology. We studied the breeding behavior of White-rumped Tanagers in the Cerrado (Neotropical savanna) in central Brazil from 2002 to 2007. The breeding period extended from mid-August to mid-December. Nests were cup-shaped and located mainly in trees of the genus Kielmeyera at a mean height of 3.7 ± 0.3 m (SE). Clutch sizes varied from one to three eggs and the incubation period lasted an average of 16.0 ± 0.3 d. Incubation was by females only and started with the laying of the first egg. Mean nest attentiveness (percent time on nests by females) was 64 ± 0.08%. Nestlings were fed by males, females, and, when present, helpers. The mean rate of food delivery rate to nests was 5.2 ± 0.4 items/h, with rates similar for males (mean = 2.7 ± 0.3 items/h) and females (mean = 2.4 ± 0.3 items/h). The mean duration of the nestling period was 12.1 ± 0.5 d. Compared to many temperate species of tanagers, White-rumped Tanagers in our study had relatively small clutches, low nest attentiveness, and long incubation periods. As with other tropical species, such characteristics might be due to food limitation or high rates of nest predation. RESUMEN Cypsnagra hirundinacea está ampliamente distribuida desde el norte de Brasil, Bolivia y Paraguay, y está clasificada como vulnerable en el estado de Paraná y en peligro en el estado de São Paulo, Brasil. Actualmente poco es conocido sobre su biología reproductiva. Estudiamos el comportamiento reproductivo de C. hirundinacea en el cerrado (Sabana Neotropical) en la región central de Brasil desde el 2002 hasta el 2007. El periodo reproductivo se extiende desde mediados de agosto hasta mediados de diciembre. Los nidos en forma de copa estaban localizados principalmente en arboles del genero Kielmeyera a una altura promedio de 3.7 ± 0.3 (ES) m. El tamaño de la nidada vario entre uno y tres huevos y el periodo de incubación duro en promedio 16 ± 0.3 días. La incubación fue realizada exclusivamente por la hembra y comenzó después de la puesta del primer huevo. El promedio de atención al nido (porcentaje del tiempo en el nido por parte de la hembra) fue de 64 ± 0.08%. Los polluelos fueron alimentados por el macho, la hembra y, cuando estaban presentes, ayudantes. El promedio de la tasa de alimentación al nido fue de 5.2 ± 0.4 viajes/hr, con tasas similares entre el macho (promedio = 2.7 ± 0.3 viajes/hr) y la hembra (promedio = 2.4 ± 0.3 viajes/hr). El promedio de duración del periodo de polluelos fue de 12.1 ± 0.5 días. Comparado con muchas especies de tangaras de la zona temperada, C. hirundinacea tiene una nidada relativamente pequeña, baja atención al nido y un periodo largo de incubación. Pero las diferencias con otras especies tropicales en estas variables se pueden deber a variación en la disponibilidad de alimento o altas tasa de depredación. [source] What limits insect fecundity?FUNCTIONAL ECOLOGY, Issue 3 2008Body size-, oviposition in a butterfly, temperature-dependent egg maturation Summary 1Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting. 2Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother's condition and her egg production might be expected. 3In the temperate butterfly Pararge aegeria, the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes. 4The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size. 5This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects. [source] Differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs of Snares Penguins Eudyptes robustus and their influence on hatching asynchronyIBIS, Issue 2 2005MELANIE MASSARO Brood reduction in birds is frequently induced by hatching asynchrony. Crested penguins (genus Eudyptes) are obligate brood reducers, but in contrast to most other birds, first-laid eggs are considerably smaller in size than second-laid eggs; furthermore, first-laid eggs hatch after their siblings. The mechanisms underlying this reversal in size and hatching order remain unclear. In this study, we tested whether the second-laid eggs of Snares Penguins Eudyptes robustus have a higher eggshell porosity allowing them to maintain a higher metabolic rate throughout incubation and to hatch before their first-laid siblings. We investigated differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs within clutches and examined the influence of these shell characteristics on hatching asynchrony. First-laid eggs of Snares Penguins were approximately 78% of the size of the larger second eggs. Second-laid eggs had considerably thicker shells and more pores per cm2 than first eggs, whereas pore diameter did not differ between eggs. Water vapour conductance was greater in second- (16.8 mg/day/torr) than in first-laid eggs (14.9 mg/day/torr). The difference in water vapour conductance between first- and second-laid eggs within clutches was related to hatching patterns. In nests where second eggs hatched before first-laid eggs, second eggs had a considerably greater water conductance than their sibling, whereas in nests where both eggs hatched on the same day, the difference in water conductance between eggs was very small, and in a few nests where small first eggs hatched before their larger sibling, they had a greater water conductance than their larger second-laid nestmate. Surprisingly few studies have investigated differences in shell characteristics between eggs within clutches and associated effects on hatching asynchrony. This study has demonstrated that such differences exist between eggs within clutches and that they can influence hatching patterns. [source] Effects of heat shock on ovary development and hsp83 expression in Tribolium castaneum (Coleoptera: Tenebrionidae)ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009Jingjing Xu Abstract Heat shock affects reproductive performance in insects including Tribolium castaneum. In this study, the effects of heat shock on ovary development and hsp83 expression in T. castaneum were investigated. Two lines of T. castaneum, H line and C line, from the same base population were established and maintained for five successive generations. In each generation, the newly hatched beetles (within 3,h after eclosion) in the H line were treated with a heat shock at 40°C for 1,h, and those in the C line were raised at normal temperature (30°C) as control treatment. Four traits related to ovary development were measured for the beetles of the fifth generation: days from eclosion to laying the first eggs (To), days from eclosion to laying the first hatchable eggs (Th), ovariole size on the third day after eclosion, and pupal mass of their offspring. The results showed that the beetles of the H line had a significantly longer pre-oviposition period (0.6 more days) and smaller ovariole size than those of the C line. No significant difference in pupal mass was observed. Applying heat shock to the offspring of the fifth generation of both lines led to significantly higher hsp83 expression in offspring of the C line than in offspring of the H line. Within each line, the hsp83 expression level in offspring with heat shock was significantly higher than that of offspring without heat shock, but the difference in the C line was much larger than that in the H line. We infer from these results that a tradeoff between heat resistance, registered as hsp83 expression, and ovarian development operates under heat stress in T. castaneum. 2009 Wiley Periodicals, Inc. [source] | ||||||||||||||||||||||