Smaller Clutches Research Articles

Review on Production and Reproduction Performance of Indigenous Chicken in Ethiopia

The review summarizes the production and reproductive performance of indigenous chicken in Ethiopia. Even though the total population of indigenous chicken is high enough (98%) than other exotic and crossbreeds, the gain from the poultry sector is still low. Thus, production was encountered under free-range systems with low input for the sector, which limits the profit due to low egg production, small egg size, slow growth rate, late maturity, small clutch size, intensive inclination to broodiness, and high mortality of chickens. The reproductive performance of indigenous chickens includes hatchability and fertility of eggs in addition to the above, which depended on health, nutrition, genetics, storage, incubation condition, and seasonal fluctuation, as well as the number of eggs given to broody hens, was also another factor that causes variability. The hatchability of broody hen reaches up to 85.69%, which was higher than reports from a modern incubator in governmental poultry breed and multiplication centre in Ethiopia (69%) under standard breeding conditions. In terms of the egg and meat production, minimum values were recorded than other exotic and cross breeds because there was no identified productive breed in the country and still in classifications based on ecotypes/location/ and feather plumages of the chicken, even if they have good quality in terms of test for their products. They are also good scavenging as well as foragers and have a high level of disease tolerance, good maternal quality, adapt to harsh conditions and poor-quality feeds. However, there is a lack of knowledge about poultry production, limitation of feed resources, the prevalence of disease as well as institutional and socio-economic conditions are faced

Tibetan birds lay larger but fewer eggs in a clutch.

How do offspring size and number vary along elevational gradients? This is a striking but rarely addressed question in life-history evolution. Here we comparatively explore it using phylogenetically paired passerine birds of lowland China vs. the Tibetan plateau spanning an elevational range of 18-4500m. Toward the Tibetan plateau, egg size increased, clutch size decreased and total clutch volume (= clutch size × egg size) did not change, when accounting for major confounding factors. Larger eggs and smaller clutches can be a response to harsh abiotic conditions at higher elevations and the corresponding reduction in food resources required for raising young, respectively. There was a negative correlation between egg size and clutch size after controlling for elevation effect on either trait, suggesting that the trade-off contributed to the expression of these two traits across elevations, given the lack of an elevational trend in total clutch volume. Tibetan birds had a shorter breeding season, prolonged incubation and nestling period than their lowland counterparts. While fewer clutches over the short breeding season may facilitate the increase in egg size, the concentration of annual reproductive investment did not seem to act on clutch size; despite the smaller clutches, hard environments may impose greater costs of parental care on Tibetan birds. The current research provides insight into the evolution of avian life histories across elevations.

The evolution of reproductive strategies in turtles.

Optimal egg size theory assumes that changes in the egg and clutch are driven by selection, resulting in adjustments for the largest possible production of offspring with the highest fitness. Evidence supports the idea that large-bodied turtles tend to produce larger clutches with small and round eggs, while smaller species produce small clutches with large and elongated eggs. Our goals were to investigate whether egg and clutch size follow the predictions of egg size theory, if there are convergent reproductive strategies, and identify ecological factors that influence clutch and egg traits across all clades of living turtles. Using phylogenetic methods, we tested the covariance among reproductive traits, if they are convergent among different turtle lineages, and which ecological factors influence these traits. We found that both egg shape and size inversely correlate with clutch size, although with different evolutionary rates, following the predictions of the egg size theory. We also present compelling evidence for convergence among different turtle clades, over at least two reproductive strategies. Furthermore, climatic zone is the only ecological predictor to influence both egg size and fecundity, while diet only influences egg size. We conclude that egg and clutch traits in Testudines evolved independently several times across non-directly related clades that converged to similar reproductive strategies. Egg and clutch characteristics follow the trade-offs predicted by egg size theory and are influenced by ecological factors. Climatic zone and diet play an important role in the distribution of reproductive characteristics among turtles.

Breeding Ecology of the Snow Partridge (Lerwa lerwa) in High-Altitude Regions, Tibet

To explore the environmental adaptation strategies of high-altitude breeding birds to alpine regions, we studied the breeding ecology of the Snow Partridge (Lerwa lerwa) in the Qinghai-Tibet Plateau. Incubation behavior was determined using data loggers in Basu County (2018) and Cuona County (2019), in the Tibet Autonomous Region, China. We monitored seven Snow Partridge nests; clutch sizes ranged from 4–5 eggs per nest (mean=4.71±0.45 eggs, N=7), egg mass ranged from 28.1–37.7 g (mean=31.1±2.5 g, N=28), and the hatching success rate was 87.9% (N=33 eggs, six nests hatched successfully, and one nest suffered a predator attack). Nesting females typically took 1–4 recesses each day (mean=1.8±0.7, N=39 days). In five females, the first daily recess occurred at 0601 to 0709 (mean=0626±16 min, N=39 days) and the duration ranged from 60 min to 615 min (mean=179±102 min, N=39 days). The average nest attendance was 85.6±5.9% (75.9–92.8%, N=6 nests). Compared with other Galliformes, Snow Partridges lay larger eggs and smaller clutches, leave their nests fewer times per day but with a lower nest attendance, and a bimodal pattern of recess timing. Additionally, Snow Partridges build cave nest structures. These characteristics are highly adapted to the alpine region of the Tibetan Plateau and balance the thermal needs of the developing embryos and the self-maintenance needs of the incubating females.

Temperature-Dependent Reproductive Success of Stickleback Lateral Plate Morphs: Implications for Population Polymorphism and Range Shifts Under Ocean Warming

Changing environments associated with rapid climate change can shape direct measures of fitness such as reproductive success by altering mating behavior, fecundity and offspring development. Using a polymorphic oceanic population of threespine stickleback (Gasterosteus aculeatus), we investigated whether a 4°C increase in sea surface temperature influenced clutch siring success, reproductive output, and offspring growth among lateral plate morphs. Since low plated morphs are thought to have a selective advantage in warmer environments, we predicted that low plated males should have higher clutch siring success in +4°C environments, and that thermal plasticity of traits (e.g., egg size, offspring growth) should reflect different trait optima in different environments among plate morphs. Parentage analysis of egg clutches revealed temperature-specific clutch siring success, in that low plated males sired more clutches in +4°C environments and completely plated males sired more clutches at ambient (seasonal) temperature. Both completely and low plated females laid larger eggs when acclimated to +4°C, but only completely plated females had smaller clutches at +4°C. Offspring of low and partially plated females grew much less at +4°C compared to those of completely plated females. Taken together, our results demonstrate that ocean warming could impact reproductive success at various levels, with differential effects depending on phenotype, in this case, lateral plate morph. Some traits (clutch siring success, egg size) showed better performance for low plated fish at +4°C, whereas others (e.g., growth) did not. Higher clutch siring success of low plated males at elevated temperature might indicate a future shift in plate morph composition for polymorphic stickleback populations, with potential implications for colonization ability during range shifts under climate change.

Terrestrial reproduction and parental care drive rapid evolution in the trade-off between offspring size and number across amphibians

The trade-off between offspring size and number is central to life history strategies. Both the evolutionary gain of parental care or more favorable habitats for offspring development are predicted to result in fewer, larger offspring. However, despite much research, it remains unclear whether and how different forms of care and habitats drive the evolution of the trade-off. Using data for over 800 amphibian species, we demonstrate that, after controlling for allometry, amphibians with direct development and those that lay eggs in terrestrial environments have larger eggs and smaller clutches, while different care behaviors and adaptations vary in their effects on the trade-off. Specifically, among the 11 care forms we considered at the egg, tadpole and juvenile stage, egg brooding, male egg attendance, and female egg attendance increase egg size; female tadpole attendance and tadpole feeding decrease egg size, while egg brooding, tadpole feeding, male tadpole attendance, and male tadpole transport decrease clutch size. Unlike egg size that shows exceptionally high rates of phenotypic change in just 19 branches of the amphibian phylogeny, clutch size has evolved at exceptionally high rates in 135 branches, indicating episodes of strong selection; egg and tadpole environment, direct development, egg brooding, tadpole feeding, male tadpole attendance, and tadpole transport explain 80% of these events. By explicitly considering diversity in parental care and offspring habitat by stage of offspring development, this study demonstrates that more favorable conditions for offspring development promote the evolution of larger offspring in smaller broods and reveals that the diversity of parental care forms influences the trade-off in more nuanced ways than previously appreciated.

Different environment, different reproductive strategies? Unexpected field observations in the harvestmen Discocyrtus prospicuus (Laniatores: Gonyleptidae).

The evolution of reproductive strategies depends on the relative balance between current benefits and future costs. Geographic variation in demographic and ecological factors has the potential to affect reproductive strategies by altering this optimal cost-benefit balance. Here, we studied a population of the harvestmen Discocyrtus prospicuus inhabiting an environment never studied before in this context: a tidal freshwater wetland. We made monthly observations of male-female interactions and their association with egg clutches during a two-year field survey. Our results do not match the expected pattern for this species, consisting of males deserting females immediately after copulation, and females laying isolated eggs and abandoning them after oviposition. Conversely, we show for the first-time pairs D. prospicuus, formed by a female and a male, resting together before and after oviposition. Females of this wetland population lay the eggs in small clutches and some of the clutches had eggs in more than one stage of development. Also, we found many females alone over or near the egg clutch in the typical resting position. These findings markedly widen the behavioral specter previously reported for this species and set the stage for future research to determine the causes of these variations.

Don't put all your eggs in small baskets: Ineffective guardians, incidence of parasitoids and clutch size of Latrodectus geometricus (Araneae, Theridiidae) along an urban gradient

Maternal care is common in spiders, but the effects of egg protection by mothers on offspring survival remains understudied for most species, especially against parasitoids. Parasitoid incidence can also be modulated by host clutch size (since larger egg masses provide the opportunity of producing larger clutches for the parasitoids) and urbanization (by creating conditions that may restrict the occurrence of less tolerant species). In this study, we conducted field experiments with the brown widow spider Latrodectus geometricus to investigate the following hypothesis: (1) females are effective in the defense of eggs against parasitoids; (2) large clutch sizes are attacked more often by parasitoids than the smaller ones; and (3) the incidence of parasitoids in egg sacs decreases in a gradient from a preserved area to an urbanized one. The presence of caring females reduced by three times the incidence of two parasitoids, Baeus latrodecti (Hymenoptera, Scelionidae) and an unidentified Eulophidae wasp, compared to unattended egg sacs, but this distinction did not differ from a random distribution. Parasitoids were most often found in egg sacs containing few eggs. The incidence of B. latrodecti in egg sacs was highest in the area with an intermediate degree of urbanization, but Eulophidae wasps were unaffected by the urbanization gradient. We concluded that (1) females are generally ineffective at protecting their egg sacs against parasitoids, that (2) egg sacs containing small clutch sizes are usually more vunerable to parasitoid attacks, and that (3) urbanization does not reduce the incidence of the egg parasitoids identified here. Our study provides an important step towards our understanding of the interactions between spiders with parental care and egg parasitoids, suggesting new aspects to be investigated in future studies.

Composition of ‘fast–slow’ traits drives avian community stability over North America

AbstractRapid biodiversity loss has triggered decades of research on the relationships between biodiversity and community stability. Recent studies highlighted the importance of species traits for understanding biodiversity–stability relationships. The species with high growth rates (‘fast’ species) are expected to be less resistant to environmental stress but recover faster if disturbed; in contrast, the species with slow growth rates (‘slow’ species) can be more resistant but recover more slowly if disturbed. Such a ‘fast–slow’ trait continuum provides a new perspective for understanding community stability, but its validity has mainly been examined in plant communities. Here, we investigate how ‘fast–slow’ trait composition, together with species richness and environmental factors, regulate avian community stability at a continental scale.We used bird population records from the North American Breeding Bird Survey during 1988–2017 and defined avian community stability as the temporal invariability of total community biomass. We calculated species richness and the community–weighted mean (CWM) and functional diversity (FD) of four key life‐history traits, including body size, nestling period (i.e. period of egg incubation and young bird fledging), life span and clutch size (i.e. annual total number of eggs). Environmental factors included temperature, precipitation and leaf area index (LAI).Our analyses showed that avian community stability was mainly driven by the CWM of the ‘fast–slow’ trait. Communities dominated by ‘fast’ species (i.e. species with small body size, short nestling period and life span and large clutch size) were more stable than those dominated by ‘slow’ species (i.e. species with large body size, long nestling period and life span and small clutch size). Species richness and the FD of the ‘fast–slow’ trait explained much smaller proportions of variation in avian community stability. Temperature had direct positive effects on avian community stability, while precipitation and leaf area index affected community stability indirectly by influencing species richness and trait composition.Our study demonstrates that composition of ‘fast–slow’ traits is the major biotic driver of avian community stability over North America. Temperature is the most important abiotic factor, but its effect is weaker than that of the ‘fast–slow’ trait. An integrated framework combining ‘fast–slow’ trait composition and temperature is needed to understand the response of avian communities in a changing environment.A freePlain Language Summarycan be found within the Supporting Information of this article.

Neither sex appears to benefit from divorce within migratory Northern Flickers consistent with accidental loss and bet-hedging

AbstractDivorce is widespread among species of birds and may either be an adaptive strategy to secure a better mate or territory or be a nonadaptive result of a failure to maintain the pairbond. I examined the causes and consequences for divorce in the Northern Flicker (Colaptes auratus), a migratory woodpecker with a high annual mortality rate. In a long-term population study of 1,793 breeding pairs over 17 years, the within-season divorce rate was 4.6% and the between-season divorce rate was 15.5%. Retained pairs within a season initiated their renest 5 days faster than divorced birds that had no greater fledgling production, suggesting that within-season divorce was making the best of a bad job with severe time constraints. Poor performance in the year prior to divorce was not strongly associated with divorce, and analysis of multiple breeding stages revealed that divorcing individuals in the subsequent year had later laying dates, smaller clutches, and fewer fledglings than retained pairs but no better performance than widowed individuals. Analyzing the data separately by sex showed that neither males nor females benefitted from divorce. Thus, there is a reproductive cost linked to finding a new partner per se, but no reproductive advantage associated with divorce. New mates after divorce were usually not older (not higher quality) than previous mates, so intrasexual competition was probably not driving partnership splits. The most plausible explanation seems to be a “bet-hedging” hypothesis in which birds re-pair rapidly in spring if their previous mate does not quickly arrive during spring migration. Divorce in Northern Flickers does not appear to be adaptive and future studies on arrival and interactions of individuals in spring will elucidate proximate constraints on relocating the previous partner.

Double brooding of Tree Swallows (Tachycineta bicolor) in southeast Tennessee

Double brooding, a second breeding attempt following the successful fledging of a previous brood, has the potential to substantially increase annual reproductive success of a given bird species. Tree Swallows (Tachycineta bicolor) have a wide breeding distribution, which makes them suitable subjects for looking at effects of environmental variation on their breeding biology. One aspect of Tree Swallow breeding that is not well studied is double brooding. During this study, double brooding was frequent, ranging from 37% to 57% each year. Single broods and first broods did not differ from each other, however second broods had smaller clutches, fewer fledglings, and reduced hatching success. Double brooded females had a median date of first egg laying that was 5 d earlier than single brooded females. Based on other studies of double brooding in Tree Swallows, the observed differences may be attributable to factors such as reduced food supplies later in the season, female age, breeding experience, and/or nesting date. The results demonstrate the necessity for studying this species over a broader portion of its range to better understand its population dynamics and reproductive potential.

The influence of phylogeny and life history on telomere lengths and telomere rate of change among bird species: A meta-analysis.

Longevity is highly variable among animal species and has coevolved with other life‐history traits, such as body size and rates of reproduction. Telomeres, through their erosion over time, are one of the cell mechanisms that produce senescence at the cell level and might even have an influence on the rate of aging in whole organisms. However, uneroded telomeres are also risk factors of cell immortalization. The associations of telomere lengths, their rate of change, and life‐history traits independent of body size are largely underexplored for birds. To test associations of life‐history traits and telomere dynamics, we conducted a phylogenetic meta‐analysis using studies of 53 species of birds. We restricted analyses to studies that applied the telomere restriction fragment length (TRF) method, and examined relationships between mean telomere length at the chick (Chick TL) and adult (Adult TL) stages, the mean rate of change in telomere length during life (TROC), and life‐history traits. We examined 3 principal components of 12 life‐history variables that represented: body size (PC1), the slow–fast continuum of pace of life (PC2), and postfledging parental care (PC3). Phylogeny had at best a small‐to‐medium influence on Adult and Chick TL (r 2 = .190 and .138, respectively), but a substantial influence on TROC (r 2 = .688). Phylogeny strongly influenced life histories: PC1 (r 2 = .828), PC2 (.838), and PC3 (.613). Adult TL and Chick TL were poorly associated with the life‐history variables. TROC, however, was negatively and moderate‐to‐strongly associated with PC2 (unadjusted r = −.340; with phylogenetic correction, r = −.490). Independent of body size, long‐lived species with smaller clutches, and slower embryonic rate of growth may exhibit less change in telomere length over their lifetimes. We suggest that telomere lengths may have diverged, even among closely avian‐related species, yet telomere dynamics are strongly linked to the pace of life.

How much calcium to shell out? Eggshell calcium carbonate content is greater in birds with thinner shells, larger clutches and longer lifespans.

The avian eggshell is a bio-ceramic structure that protects the embryo. It is composed almost entirely of calcium carbonate and a small amount of organic material. An optimal amount of calcium carbonate in the eggshell is essential for the embryo's development, yet how the ratio of calcium carbonate to organic matter varies between species has not been investigated. Calcium is a limiting resource for most birds, so its investment in their eggs should be optimized for a bird's life history. We measured the relative calcium carbonate content of eggshells in 222 bird species and tested hypotheses for how this trait has evolved with the life-history strategies of these species and other traits of their respective egg physiologies. We found that (i) eggshell calcium carbonate content was positively correlated with species having thinner eggshells and smaller than expected eggs relative to incubating parental mass, (ii) species with small mean clutch sizes had lower calcium carbonate content in their eggshells, and (iii) for species with larger clutch sizes, eggshell calcium carbonate content was negatively correlated with their mean lifespan. The pattern of lower eggshell calcium carbonate in longer lived, larger clutched birds suggests that calcium provision to the eggshell has long-term costs for the individual.

Basal metabolic rate in free-ranging tropical birds lacks long-term repeatability and is influenced by ambient temperature.

Tropical birds live longer, have smaller clutches and invest more resources into self-maintenance than temperate species. These "slow" life-histories in tropical birds are accompanied by low basal metabolic rate (BMR). It has recently been suggested that the low BMR of tropical species may be related not to their slow "pace of life" or high ambient temperatures (Ta ) in tropical latitudes, but to the stability of environmental conditions in tropics. Since the repeatability of metabolic traits is higher in stable environments, such as laboratory conditions, we predicted that long-term repeatability of BMR in a tropical climate should be higher than in a temperate one. Contrary to our predictions, the repeatability of mass-independent BMR in 64 individuals of free-living tropical birds from Vietnam was low and insignificant after the species affiliation was taken into account. It indicates that BMR cannot be used as an individual long-term characteristic of tropical birds. On the other hand, tropical birds showed consistent differences in their mass-independent BMR at the interspecific level. Using BMR measurements from 1543 individuals of 134 species, we also found that different characteristics of Ta within the week preceding BMR measurements had a significant impact on the mass-independent BMR of tropical birds. The most significant effect was the difference between the absolute maximum and minimum Ta within a single week. Our results indicate that the physiology of tropical birds is more subject to changes than would be expected based on the notion of the stability of climatic conditions in the tropics.

Quantifying the relative importance of direct and indirect effects influencing bird nestling growth.

Nestling growth parameters are integral components of avian life-history strategies as they are crucial determinants of individual survival. Although many factors impact on nestling growth, the relative contribution of each one is still debated in the literature. Most studies rely on the assumption that each factor directly affects nestling growth, but indirect effects mediated by other factors are usually the rule in nature. In this study, we present a comprehensive view of both direct and indirect factors affecting nestling growth using the Red-crested Cardinal (Paroaria coronata) as model system. We evaluated the relative importance of different habitat (forest structure), biotic interactions (botfly larvae ectoparasitism, number of siblings, hatching order), and temporal factors (time of breeding) on nestling growth parameters in 278 nestlings of 128 nests by using piecewise structural equation models. We found that botfly ectoparasitism had the strongest direct effect on nestling growth and, in turn, forest structure increased the probability of botfly occurrence. Besides, the interaction between the number of siblings and hatching order influenced nestling growth, indicating that the first and second nestlings had disproportionately higher growth rates in large than in small clutches. Time of breeding also showed a strong positive indirect effect on botfly occurrence, as well as a weak direct positive effect on nestling growth. Our results demonstrate that, under natural conditions, nestling growth is driven by different factors acting not only directly, but also indirectly on this essential life history trait, and that these factors weave a complex web of interrelated variables.

No evidence that nest site choice in Pied Flycatchers is mediated by assessing the clutch size of a heterospecific, the Great Tit

Among species that use similar resources, an individual may benefit by observing and copying the behavioural decision of a heterospecific. We tested the hypothesis of heterospecific social learning in passerine birds, namely that a migrant species, the Pied Flycatcher Ficedula hypoleuca, uses external markings on the nest cavities of a resident species, the Great Tit Parus major, as cues when choosing a nest site. Others have suggested that prospecting flycatchers assess the clutch size of tit “demonstrators” by entering their nest boxes and, assuming that a large clutch indicates a high-quality individual, will copy the nest appearance of tits with large, but not small clutches. During a 4-year period in Norway, we designed a similar study but did not find that flycatchers based their nest choice on the clutch size of tits. Neither were there any relationships between clutch size of the tit and its laying date, incubation behaviour, or the number of eggs visible through nest material during egg-laying so Pied Flycatchers did not use these indirect cues to assess quality of the tutor. Filming of tit nests showed that prospecting flycatchers did not enter tit nest boxes to assess the content. Indeed, incubating female tits only left their nest boxes for short bouts of unpredictable duration so there was little opportunity for flycatchers to inspect the nest contents unnoticed. Our study calls into question the mechanism of using the content of tit nests as public information for choosing traits of nest sites based on external characteristics. We suggest that similar studies of nest site choice in relation to possible social information transfer be replicated more widely.

Variation in incubation length and hatching asynchrony in Eastern Kingbirds: Weather eclipses female effects

Abstract Incubation length and hatching asynchrony are integral elements of the evolved reproductive strategies of birds. We examined intra- and interpopulation variation in both traits for Eastern Kingbird (Tyrannus tyrannus) populations from New York (NY), Kansas (KS), and Oregon (OR) and found that both incubation length and hatching asynchrony were not repeatable among females, after controlling for a repeatable trait, clutch size. Instead, incubation length and clutch size were influenced by ambient temperature and precipitation. Incubation length exhibited the same median (15 days) and range (13–17 days) at all sites. Model selection results indicated that incubation periods for the smallest and largest clutches were longer in NY than KS when rain was frequent throughout incubation, in replacement nests, and likely when ambient temperatures were low during egg-laying. Full hatching usually required 2 days (but up to 3), with synchronous hatching associated with small clutch sizes, short incubation periods, frequent rain during the egg-laying period, and low ambient temperatures during the first half of incubation. Nestling starvation was uncommon (5–9% of nestlings monitored) and not associated with greater hatching asynchrony. These results indicate that while clutch size, a repeatable female trait, contributed to variation in incubation length and hatching asynchrony in Eastern Kingbirds, weather was a greater source of variation, especially for incubation length.

Risk assessment of genetically modified zoysiagrasses (Zoysia japonica) in a zebrafish model

Genetically modified (GM) plants have been mainly advanced for the mass production of agricultural plants. However, there are concerns about GM crops which cause side effects on ecosystems and human beings. Zebrafish is a better in vivo model and possess the advantages; small size, large clutches, transparency, low cost, and physiological similarity to mammals. The objective of this study was to assess the safety of non-GM and GM grasses (Zoysia japonica) including JG21, JG21-MS1, JG21-MS2 in zebrafish embryos by examining the survival rates, heart-beating rate, yolk sac edema size, cell death, and morphology. The survival rates, heart-beating rates, and yolk sac edema sizes in non-GM and GM grass-treated zebrafish were similar change with the control group. And, all the groups did not show a significant difference within less than 1.0-fold in cell death by fluorescence levels. These results indicate that the zebrafish model is a useful and simple tool and can be used for risk assessment of GM plants.

Sex ratio of Western Bluebirds Sialia mexicana is mediated by phenology and clutch size.

Mothers may produce more of one sex to maximize their fitness if there are differences in the cost of producing each sex or there are differences in their relative reproductive value. Breeding date and clutch size are known to influence offspring sex ratios in birds through sex differences in dispersal, social behaviours, differential mortality, and available food resources. We tested if breeding date, clutch size and drought conditions influenced offspring sex ratios in a sexually size-monomorphic species, the Western Bluebird, by interrogating a 21-year dataset. After controlling for differential mortality, we found that hatch dates late in the breeding season were associated with the production of more females, suggesting that the value of producing males declines as the breeding season progresses. When clutch size was taken into account, small clutches yielded significantly more females late in the breeding season compared to the early and middle parts of the breeding season that produced significantly more males. Large clutches early in the season tended to produce more females, although this was not significant. Drought severity was not correlated with sex ratio adjustment. We propose and discuss several explanations for these patterns, including male offspring, but not female offspring, acting as helpers, increased female nestling provisioning late in the breeding season, differences in food abundance, and egg-laying order. Future work will help to uncover the mechanisms leading to these patterns. Identifying patterns and mechanisms of sex ratio skew from long-term datasets is important for informing predictions regarding life-history trade-offs in wildlife populations.

Redescription of Omophoita octoguttata (Coleoptera: Chrysomelidae) and its immature stages, with notes on life history

ABSTRACT Given that many descriptions of Coleoptera were made with only external and superficial characters, an update to the original characterization of species is deemed necessary. This study focuses on updating the know morphological data for the adults of Omophoita octoguttata (Fabricius,1775) (Galerucinae, Alticini), a flea beetle native of southern Brazil. We also give insights on the morphology of its immature stages. The adult can be easily recognized by the pale macula at vertex, six large pale maculae, and two smaller in the humeral region at the elytra. The immatures are similar to other know Oedionychina. Eggs oval and orange. Mature larvae present setae bearing scoli, a reddened body, pygopod present, and lacking stemmata, but with curved hook-like tarsal claws. The pupae present slender black setae through its yellowed body, with the elytral and hind wing thecae curved around the body. The eggs are laid in small clutches in the soil and when the larvae eclode they stay in the aerial parts of plants. The mature larvae form a cocoon of soil matter around themselves for their pupal phase. Morphological remarks for larva and pupa of this species when compared to other members of the genus remain limited, demanding further studies with other species.