Replacement Clutches Research Articles

Reproduction of varanid lizards (Reptilia: Squamata: Varanidae) at the Bronx Zoo

Captivity provides many opportunities for studying the reproductive biology of varanid lizards (Family: Varanidae; genus: Varanus). This article presents reproductive data for 12 varanid species maintained in captivity at the Bronx Zoo between 1977 and 2010. Five species, V. prasinus, V. beccarii, V. melinus, V. mertensi, and V. ornatus have successfully reproduced at the zoo, for which clutch, incubation, and hatchling data are presented, and compared with previously published values. Clutch, incubation, and hatchling measurements typically fell within the known ranges for each species, or represent minor range extensions. V. mertensi was the only species that reproduced seasonally (χ(2) = 9.061, P = 0.029). Five species multiclutched; individual V. mertensi and V. prasinus females produced as many as four clutches per year. The shortest intervals between successive clutches observed for V. kordensis (61 days), V. melinus (77 days), V. mertensi (51 days), and V. prasinus (68 days) represent the shortest known values for each species. Relative clutch mass (RCM) ranged from 0.187 to 0.437. A mean RCM of 0.370 ± 0.092 for V. prasinus is substantially higher than previously published values for the species. These results illustrate that when maintained under favorable conditions in captivity, some varanids are capable of remarkably high fecundities, rapid reproductive turnover rates, and sizeable maternal investments. Periodicals, Inc.

Paternal genotype reconstruction reveals multiple paternity and sex ratios in a breeding population of leatherback turtles (Dermochelys coriacea)

When animals are difficult to observe while breeding, insights into the mating system may be gained by using molecular techniques. Patterns of extra-pair copulation, multiple paternity and parental genotype analysis may elucidate population characteristics that help improve knowledge of life history while informing management decisions. During the course of a long-term study of leatherback turtles, we assessed the level of multiple paternity in successive clutches for 12 known females nesting at Sandy Point National Wildlife Refuge (St. Croix, U.S. Virgin Islands). We used seven polymorphic microsatellite markers to genotype the females and 1,019 hatchlings representing 38 nests (3–4 clutches from each female). Using deductive genotype reconstruction and GERUD1.0, we identified the 12 mothers and 17 different fathers that were responsible for 38 nests. We found that seven females (58.3%) showed no evidence of multiple paternity in their clutches, while five females (41.7%) had mated with two males each. There was evidence of two fathers (polyandry) in successive clutches for these five females. Multiple fathers didn’t contribute to clutches equally. For clutches laid by an individual female, the primary father was responsible for 53.7 to 85.9% of the hatchlings. We demonstrate the feasibility of using male genotype reconstruction to characterize the male component of this breeding population and to assess operational sex ratios for breeding sea turtles.

Rate of egg maturation in marine turtles exhibits ‘universal temperature dependence’

1. The metabolic theory of ecology (MTE) predicts that, after correcting for body mass variation among organisms, the rates of most biological processes will vary as a universal function of temperature. However, empirical support for 'universal temperature dependence' (UTD) is currently equivocal and based on studies of a limited number of traits. 2. In many ectothermic animals, the rate at which females produce mature eggs is temperature dependent and may be an important factor in determining the costs of reproduction. 3. We tested whether the rate of egg maturation in marine turtles varies with environmental temperature as predicted by MTE, using the time separating successive clutches of individual females to estimate the rate at which eggs are formed. We also assessed the phenotypic contribution to this rate, by using radio telemetry to make repeated measurements of interclutch intervals for individual green turtles (Chelonia mydas). 4. Rates of egg maturation increased with seasonally increasing water temperatures in radio-tracked green turtles, but were not repeatable for individual females, and did not vary according to maternal body size or reproductive investment (number and size of eggs produced). 5. Using a collated data set from several different populations and species of marine turtles, we then show that a single relationship with water temperature explains most of the variation in egg maturation rates, with a slope that is statistically indistinguishable from the UTD predicted by MTE. However, several alternative statistical models also described the relationship between temperature and egg maturation rates equally parsimoniously. 6. Our results offer novel support for the MTE's predicted UTD of biological rates, although the underlying mechanisms require further study. The strong temperature dependence of egg maturation combined with the apparently weak phenotypic contribution to this rate has interesting behavioural implications in ectothermic animals. We suggest that maternal thermoregulatory behaviour in marine turtles, and many other reptiles, is consistent with a strategy of adaptively increasing body temperatures to accelerate egg maturation.

Talgoxens Parus major antal och häckningsbiologi – resultat av 25 års holkstudier

A nest-box population of Great Tits Parus major was followed in 1986–2010. Maximum number of breeding attempts was three times higher than the minimum number but there was no significant trend through 2005. The number of nest-boxes declined from 94 to 55 during the last five years making it difficult to interpret the recent trend but most likely there was an increase. 17% of the first breeding attempts failed and resulted in replacement clutches. The number of second clutches was 13% of the number of first clutches. There was no correlation between population size and winter temperature. There was no significant advancement of laying date in spite of the fact laying date was correlated with April temperature and that local April temperature showed a significant positive trend during the study period. Mean clutch size was 9.2 eggs. The number of fledglings was 4.65, which is low compared to other studies. Replacement and second clutches produced 4.37 fledglings. Both clutch size and number of fledglings declined during the study period.

Male‐skewed adult sex ratio, survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.

Sex allocation from an owl perspective: clutch order could determine brood sex to reduce sibling aggression in the Eagle Owl Bubo bubo

Hatching asynchrony in altricial bird species occurs if incubation starts before clutch completion. It determines differential within-brood growth, which may result in a competitive and developmental hierarchy among siblings.As a consequence, asymmetric sibling competition frequently results in post-hatching mortality of the last-hatched offspring. Because nestling hierarchy is not necessarily adaptive, species that are able to raise large broods should have evolvedmechanisms to reducewithin-broodmortality due to sibling competition. One mechanism to reduce offspring mortality could be to favour the occurrence of the larger sex among late-laid chicks. We explored this possibility by studying the sex allocation of 349 Eagle Owl (Bubo bubo) chicks from 137 broods, as a function of clutch size and order. In broods of four chicks, parents seemed to invest in the less energetically expensive sex (male) at the third position, and females (the larger sex) as the last, and therefore smallest, chick in the brood. This strategy should reduce asymmetric sibling competition: the relative position of chicks of each sex within the brood is likely to be crucial for maximizing the success of clutches.

Renesting of Common Terns Sterna hirundo in the life history perspective

Replacement clutches may increase the annual reproductive output of individuals and the population, but cause additional effort and may have fitness consequences. Whether longevity and lifetime reproductive success are affected by renesting is unknown. In an individual-based long-term study (1992–2009) we investigated Common Terns Sterna hirundo breeding at the colony site “Banter See” on the German North Sea coast and marked with transponders. This approach allowed us to study short-term as well as long-term consequences of relaying for both the population and individuals. In 5 of 7 years characterized by higher relaying activity, breeding success of replacement clutches was similar or even higher than that of first clutches, but in the total study period only 4.5% of all fledglings (4.4% of natal recruits) stemmed from replacement clutches. Demographic effects of relaying were minor. In most years, relaying birds were able to increase their annual reproductive output through the replacement clutch. Relaying Common Terns were high quality individuals, arriving and laying earlier, and characterized by higher age and body condition than non-relaying conspecifics. Relaying probability decreased with delayed arrival and laying date of first clutch. Survival to the next year did not differ between breeders with or without a replacement clutch. In the lifetime perspective, individuals with at least one renesting event had higher survival, longevity, lifetime reproductive success and fitness compared to birds without a replacement clutch. The higher lifetime reproductive success of the renesting individuals was achieved by a longer lifespan as well as by the reproductive output due to relaying. The positive links between survival, additional effort for replacement clutches and their success are obviously due to the fact that only those individuals relay that can cope with the additional effort required for production and care of the replacement clutch. In this way, renesting is an indicator of high individual quality and a benefit for fitness.

The Effect of Maternal State on the Steroid and Macronutrient Content of Lesser Black-Backed Gull Eggs

It has been proposed that female birds can influence the phenotype of their offspring by provisioning eggs with variable amounts of nutrients and maternal hormones. Egg quality is strongly influenced by maternal body reserves and the amount of food available at the time of egg formation. This study investigated the effects of maternal state and food availability on the capacity of female lesser black-backed gulls Larus fuscus to provision their eggs with macronutrients and steroid hormones. Maternal state was reduced by increasing egg-production effort, whereas extra food was provided to reverse this effect. Compared with eggs of first clutches, eggs of experimentally induced replacement clutches exhibited a lower yolk/albumen ratio and contained more yolk testosterone. During one of the three years in which the study was performed, replacement eggs also contained more 17β-estradiol. Food provisioning during the relaying interval did not affect changes in yolk/albumen ratio or steroid concentrations, but fed females produced bigger eggs in their replacement clutch. This study demonstrates significant within-female consistency in egg size, macronutrient content, and yolk steroid concentration, and it shows that these egg characteristics are influenced by maternal state, food availability, and the timing of breeding.

Increased reproductive performance of Red-backed Shrikes Lanius collurio in forest clear-cuts

In Sweden, the centre of distribution of the nationally red-listed Red-backed Shrike Lanius collurio has shifted from farmland landscapes to forest landscapes from the 1960s until today. In this study, reproductive performance of Red-backed Shrikes breeding in grasslands in a 75-km2 farmland landscape and clear-cuts in a 75-km2 forest landscape was compared during 1994–1995. During 2003, order of settlement and reproductive performance as well as food abundance and nest predator abundance were assessed in a 3-km2 area in each landscape type. The average number of fledglings was significantly higher in clear-cuts than in grasslands. Furthermore, post-fledgling survival and the probability of replacement clutches following nest failure were likely to be higher in clear-cuts than in grasslands due to the significantly earlier arrival date to clear-cuts. These differences are likely explained by a lower nest predation in clear-cuts compared to grasslands. Today, forest clear-cuts represent the primary habitat of the Red-backed Shrike in Sweden, and probably also elsewhere in the boreal parts of northern Europe.

Breeding Biology of Brown NoddiesAnous stolidusat Their Southern-Most Breeding Site, Gough Island, in Comparison to Other Sites

We investigated the breeding biology of the Brown Noddy Anous stolidus at its southern-most breeding locality, cold-temperate Gough Island (40°S) in the South Atlantic Ocean. We monitored 19 nests over three seasons for breeding schedules, and measured the growth of eight chicks and six fledglings during the 2005/06 breeding season. Across all seasons, egg-laying occurred between 2–12 December, mean incubation was 37 days and median hatch date was 15 January. Three late hatch dates suggest that replacement clutches can be laid if failure occurs early in the season. Chicks fledged after a mean of 46 days, but remained in the vicinity of the nest and were provisioned by adults for up to 11 days. Hatching success was 88%, fledging success 92% and breeding success 81%, which is higher than at most other sites. The size, chick growth-rates and pre-fledging fast displayed by Gough's Brown Noddies are similar to that of Brown Noddies breeding at other mid-latitude Atlantic locations. These similarities of these migratory noddy populations, as well as mirrored breeding schedules suggest a single mid-latitude Atlantic meta-population.

Response of parasitically laying goldeneyes to experimental nest predation

Conspecific brood parasitism (CBP) has been identified as an integral life history component in birds. Recent empirical and theoretical studies suggest that nest predation is an important ecological factor affecting the occurrence and evolution of CBP; however, behavioural responses of parasites to nest predation remain unexplored. Here we report on a field experiment addressing the ability of parasitically laying common goldeneye, Bucephala clangula, females to respond to nest predation, based either on their own experience or on public information. Females that started parasitic laying in a nest and afterwards experienced partial clutch predation stopped laying in the nest. However, nests that faced partial clutch predation earlier in the season were not avoided by other parasitically laying females later in the season; these later-laying females had not themselves experienced the partial clutch predation in the nest. Hence, considering within-season responses to nest predation, a parasite uses its own experience, rather than public information, in laying decisions and nest choice. The rate of parasitic laying in the experimental nests decreased from the first to the last year of the experiment. Because the experimental nests never produced a successful clutch, this finding suggests that parasites used information on the ever-failing nature of the nests and avoided laying in them. Our results offer new experimental evidence to support the hypothesis that safety and success of nest sites play important roles in CBP.

Physiological actions of corticosterone and its modulation by an immune challenge in reptiles

Hormones are an important interface between genome and environment, because of their ability to modulate the animal’s phenotype. In particular, corticosterone, the stress hormone in lizards, is known to reallocate energy from non-essential functions to affect morphological, physiological and behavioral traits that help the organism to deal with acute or chronic stressors. However, the effects of corticosterone on life history stages are still unclear primarily because of the dependence of life history stages on both internal and external factors. Using a cross-design, we tested the effect of elevated levels of exogenous corticosterone on the physiology of pregnant females in different immune contexts in a wild population of common lizards ( Lacerta vivipara). Immune challenge was induced by the injection of sheep red blood cells (SRBC) and corticosterone levels were increased using a transdermal administration of corticosterone. Thereafter, reproductive traits, metabolism and cellular immune responses were measured. The elevation of corticosterone in pregnant females significantly altered reproductive and physiological performance. The corticosterone treatment decreased clutch success, juvenile size and body condition, but enhanced measures of physiological performance, such as metabolism and catalase activity. These first results reinforce the understanding of the physiological actions of corticosterone in reptiles. The data also demonstrated different direct impacts of immune challenge by SRBC on inflammatory response and antioxidant activity. The injection of SRBC stimulated the SOD activity in larger females. Finally, we demonstrated experimentally the modulation of the corticosterone action by the immune challenge on stamina and hatching date.

Natural History and Flash Repertoire of the Synchronous FireflyPhotinus carolinus(Coleoptera: Lampyridae) in the Great Smoky Mountains National Park

The synchronous firefly Photinus carolinus (Green) of the moist cove hardwood forests of the Great Smoky Mountains National Park attracts much public attention during its spectacular month-long mating display known as The Light Show. In previous studies flash synchrony among P. carolinus males has been investigated, but little is known about its natural history and mating behavior. This study provides additional information on the habits, flash signal variation, mating strategies, predation and historical records of P. carolinus. The polyandrous females remate throughout their approximately 3-week adult lifespan, laying successive clutches of eggs. While stationary females generally respond to male courtship signals with a receptive doublet flash signal, they also produce a rhythmic flash while walking, and can revert back to the receptive state. In this protandrous species, the average number of flashes per flash train in male courtship signals increases after females have emerged. I describe pseudo-female male flashes and group chaos flashing associated with mating clusters as well as conditions causing distress flashing in both sexes. With a backdrop of changing habitat and increasing human pressure, observations taken from the past 18 years and over 1000 h spent in the field additionally describe male guarding of a female pupa, mate guarding via prolonged copulation, common predator and phorid infestation challenges for this firefly.

Maternal transfer of chlorinated contaminants in the leatherback turtles, Dermochelys coriacea, nesting in French Guiana

We examined the maternal transfer of organochlorine contaminants (OCs), pesticides (DDTS and HCHs) and polychlorinated biphenyls (PCBs), and the temporal variation of blood and eggs concentrations from 38 leatherback turtles ( Dermochelys coriacea) nesting in French Guiana. PCBs were found to be the dominant OCs with respective mean concentrations of 55.14 ng g −1 lipid-mass for egg and 1.26 ng mL −1 wet-mass for blood. OC concentrations were lower than concentrations measured in other marine turtles which might be due to the lower trophic position (diet based on gelatinous zooplankton) and to the location of their foraging and nesting grounds. All OCs detected in leatherback blood were detected in eggs, suggesting a maternal transfer of OCs. This transfer was shown to depend on female blood concentration for ΣDDTs and for the most prevalent PCB congeners, since significant relationships were found between paired blood–egg concentrations. During the nesting season, OC concentrations in eggs and the percentage of lipid in eggs were found to decline in successive clutches, highlighting a process of offloading from females to their eggs and a decreasing investment of lipid from females into their clutches. OCs in eggs tended to be higher in females spending 3 years in the foraging grounds between two nesting seasons than in those spending 2 years, suggesting an impact of time spacing two breeding seasons, called remigration interval, and of location of the foraging grounds.

Energy crop cultivations of reed canary grass — An inferior breeding habitat for the skylark, a characteristic farmland bird species

Abstract Here, I present the first comparison of the abundance of farmland birds in energy grass fields and in cereal-dominated conventionally cultivated fields (CCFs). I demonstrate that in boreal farmland, skylark (Alauda arvensis) densities were significantly lower in reed canary grass (RCG) (Phalaris arundinacea) fields than in CCFs. I found that during the early breeding season RCG fields and CCFs are equally good habitats, but over the ensuing couple of weeks RCG rapidly grows too tall and dense for field-nesting species. Consequently, RCG is an inferior habitat for skylark for laying replacement clutches (after failure of first nesting) or for a second clutch after one successful nesting. The results imply that if RCG cultivation is to be expanded, the establishment of large monocultures should be avoided in farmland landscapes; otherwise the novel habitat may affect detrimentally the seriously depleted skylark population, and probably also other field-nesting bird species with similar breeding habitats.

Variation in multiple paternity and sperm utilization patterns in natural populations of a simultaneous hermaphrodite land snail

Mating frequency has important implications for patterns of sexual selection and sexual conflict, and hence for issues such as the maintenance of genetic diversity and speciation. We assessed the level of multiple paternity and sperm utilization patterns in four natural populations of the simultaneous hermaphrodite land snail Arianta arbustorum using four polymorphic microsatellite loci. A total of 1088 offspring from 26 wild-caught snails were genotyped to determine the number of fathers siring each brood and paternity skew in succeeding clutches. Multiple paternity was detected in the offspring of all 26 mother snails examined with the contribution of two to six fathers. The four populations examined differed in the level of multiple paternity. Snails in the population with the highest density of adults showed the highest level of multiple paternity, whereas snails in the population with the lowest density exhibited the lowest value of multiple paternity. Highly skewed paternity patterns were found in the progeny of 15 (57.7%) of the 26 mother snails. The number and identity of fathers siring the offspring of single mothers also varied among successive clutches. Furthermore, genetic analyses indicate a low level of self-fertilization in one of the four populations.

Female Zebra Finches (Taeniopygia guttata) Are Chronically but Not Cumulatively “Anemic” during Repeated Egg Laying in Response to Experimental Nest Predation

Recently it has been recognized that reproduction itself, or the regulatory processes controlling reproduction, might contribute to physiological costs of reproduction. Reproductive anemia, a decrease in hematocrit and hemoglobin concentration, might provide one such mechanism underlying the costs of egg production in birds. In this study, we investigated the effect of repeated cycles of egg production in response to experimental nest predation (egg removal) on hematological traits in female zebra finches (Taeniopygia guttata). We predicted that if the negative effect of egg production on hematocrit and hemoglobin concentration was cumulative, with anemia being proportional to reproductive effort, then females laying more clutches, or laying successive clutches without recovery during incubation, would show greater reproductive anemia. In contrast, if females maintain hematocrit and hemoglobin concentration at some minimum functional level independent of reproductive effort, then there should be no difference in hematological traits among females laying two or more successive clutches. Our results supported the second of these hypotheses: egg-laying females had reduced hematocrit (-7.5%) and hemoglobin concentrations (-10%), but the extent of reproductive anemia did not differ among females laying either two or three successive clutches, with or without recovery during incubation, or in females laying 7-21 eggs. Females maintained low hematocrit and hemoglobin for 20-35 d, and we suggest that prolonged periods of anemia might be common and functionally important in free-living birds, for example, where females produce multiple successive clutches in response to high levels of nest predation or where they initiate a second clutch while still rearing first brood chicks.

Factors That Affect Renesting in Mallards (Anas platyrhynchos)

ABSTRACT. Renesting is an important strategy for coping with nest loss in many species of birds. We investigated renesting behavior of radiomarked Mallards (Anas platyrhynchos) breeding in the Canadian Prairie Parklands and found that females were persistent renesters, replacing >57% of 4,112 destroyed nests. Renesting propensity was most affected by nest initiation date, with ∼90% of unsuccessful females renesting if destroyed clutches had been initiated in April but <10% renesting for clutches initiated after 20 June. Probability of renesting declined with successive number of nesting attempts, but this was primarily an effect of initiation date. Renesting propensity increased with female age and body condition and declined for birds that had invested more time tending their previous clutch, but the latter effect was pronounced only among late-nesting females. The amount of time required to produce a replacement clutch was primarily a function of whether females were engaged in rapid follicle growth whe...

SEVERE COSTS OF REPRODUCTION PERSIST INANOLISLIZARDS DESPITE THE EVOLUTION OF A SINGLE-EGG CLUTCH

A central tenet of life-history theory is that investment in reproduction compromises survival. We tested for costs of reproduction in wild brown anoles (Anolis sagrei) by eliminating reproductive investment via surgical ovariectomy and/or removal of oviductal eggs. Anoles are unusual among lizards in that females lay single-egg clutches at frequent intervals throughout a lengthy reproductive season. This evolutionary reduction in clutch size is thought to decrease the physical burden of reproduction, but our results show that even a single egg significantly impairs stamina and sprint speed. Reproductive females also suffered a reduction in growth, suggesting that the cumulative energetic cost of successive clutches constrains the allocation of energy to other important functions. Finally, in each of two separate years, elimination of reproductive investment increased breeding-season survival by 56%, overwinter survival by 96%, and interannual survival by 200% relative to reproductive controls. This extreme fitness cost of reproduction may reflect a combination of intrinsic (i.e., reduced allocation of energy to maintenance) and extrinsic (i.e., increased susceptibility to predators) sources of mortality. Our results provide clear experimental support for a central tenet of life-history theory and show that costs of reproduction persist in anoles despite the evolution of a single-egg clutch.

Sperm release and use at fertilization by yellow dung fly females (Scathophaga stercoraria)

Females of many species mate multiple times and store transferred sperm in storage organs. The mechanisms underlying sperm release from the stores at fertilization remain poorly understood, although they are central to an understanding of the female influence on post-copulatory male competition. Using double-mated females of the yellow dung fly, we counted the sperm sticking to the surface of deposited eggs of two successive clutches to obtain insight into the physiological processes associated with fertilization. The number of sperm released to fertilize an egg decreased between the first and second clutches, as well as within clutches from early to late eggs. These results indicate that: (1) sperm are lost from the stores over time independent of egg laying and (2) the number of sperm released depends on the amount of sperm stored. The lower number of sperm on eggs of the second clutches was accompanied by a strong increase of the proportion of sperm adhering to the micropyle region, suggesting that sperm use is more efficient and sperm release better controlled when sperm supply is substantially reduced. Finally, our approach indicates that sperm storage capacity of the female is higher than assumed from counts of spermathecal sperm.