Clutch Size Research Articles

Spatial and ontogenetic variance in local densities modify selection on demographic traits

Abstract Local density can affect individual performance by altering the strength of species interactions. Within many populations, local densities vary spatially (individuals are patchily distributed) or change across life stages, which should influence the selection and eco‐evolutionary feedback because local density variance affects mean fitness and is affected by traits of individuals. However, most studies on the evolutionary consequences of density‐dependent interactions focus on populations where local densities are relatively constant through time and space. We investigated the influence of spatial and ontogenetic variance in local densities within an insect population by comparing a model integrating both types of local density variance with models including only spatial variance, only ontogenetic variance, or no variance. We parameterized the models with experimental data, then used elasticity and invasion analyses to characterize selection on traits that affect either the local density an individual experiences (mean clutch size) or individuals' sensitivity to density (effect of larval crowding on pupal mass). Spatial and ontogenetic variance reduced population elasticity to effects of local density by 76% and 34% on average, respectively. Spatial variance modified selection and adaptive dynamics by altering the tradeoff between density‐dependent and density‐independent vital rates. In models including spatial variance, strategies that maximized density‐dependent survival were favoured over fecundity‐maximizing strategies even at low population density, counter to predictions of density‐dependent selection theory. Furthermore, only models that included spatial variance, thus linking the scales of oviposition and density‐dependent larval survival, had an evolutionarily stable clutch size. Ontogenetic variance weakened selection on mean clutch size and sensitivity to larval crowding by disrupting the relationship between trait values and performance during critical life stages. We demonstrate that local density variance can strongly modify selection at empirically observed interaction strengths and identify mechanisms for the effects of spatial and ontogenetic variance. Our findings reveal the potential for local density variance to mediate eco‐evolutionary feedback by shaping selection on demographically important traits. Read the free Plain Language Summary for this article on the Journal blog.

Rediscovery and phylogenetic position of the glassfrog "Centrolene"acanthidiocephalum (Ruiz-Carranza and Lynch, 1989) (Anura: Centrolenidae)with the description of its advertisement call and comments on clutches and tadpoles.

The lack of basic natural history and distributional data represents a challenge for the conservation of rare and endemic amphibian species. This is the case of "Centrolene" acanthidiocephalum, a poorly known glassfrog endemic to the Cordillera Oriental of the Colombian Andes. This species was formally described in the late 1980s and no records have been reported over the last quarter century. Therefore, little is known about its distributional boundaries, morphological variation, natural history, and evolutionary relationships. Here we report the finding of a population of "Centrolene" acanthidiocephalum from a locality around its historical range and provide additional information on its geographic distribution, clutch size, and adult morphology. We also present for the first time data on tadpole morphology, as well as a description of its advertisement call and a phylogenetic tree based on mitochondrial genetic data corroborating its generic position within Centrolene.

Female-dependent factors affect sex allocation in Lesser Kestrels Falco naumanni

Abstract The sex ratio of nestlings is a crucial population determinant in rare and/or endangered species. We investigated the role of female body condition and female-related traits in Lesser Kestrel (Falco naumanni) nestling sex allocation at a nest-box colony in central Greece. We used the total clutch volume and size, female weight, hatching dates, body length, wing length, tail length, tarsometatarsus, and bill length as explanatory variables of the number of male nestlings (the response variable) using CART model analysis. This analysis showed that the reproduction output was biased towards male nestlings when female parents were shorter in body length and clutch size and volume were smaller. The skewed sex ratio favoring females, 1:2.35, suggests that when female parents are in good condition, they invest most in good-quality female nestlings, providing a reproductive advantage and increased long-term fitness.

Variation in mesopredator abundance and nest predation rate of the endangered Strange‐tailed Tyrant (Alectrurus risora)

Nest predation is the main cause of nest failure in passerine birds and thus is a key determinant of breeding traits. Accordingly, nest predator community composition and abundance modulate nest predation rates. When top predators are absent, mesopredator populations may become unchecked, which in turn increases the predation pressure on their prey species. We evaluated whether nest predator abundance and breeding traits of an endangered grassland bird, the Strange‐tailed Tyrant Alectrurus risora, differed between two protected areas: Iberá National Park (INP), where top predators have been extinct for 50 years, and Reserva El Bagual (REB), where Pumas Puma concolor still have a stable population. We measured abundances of potential nest predator species and during the 2015–2018 breeding seasons we monitored Strange‐tailed Tyrant nests and set camera traps to identify nest predators. Mesopredator abundance was higher in INP, and foxes were identified as the main nest predators. Nest predation rate was also higher in INP, where the daily nest predation rate and cumulative probability of nest predation were 0.05 ± 0.006 and 0.81, whereas in REB they were 0.04 ± 0.004 and 0.70, respectively. The 10‐fold higher frequency of fox records in INP could explain the higher nest predation rate observed, suggesting that the extinction of top predators may increase nest predation rates of endangered grassland birds in protected areas through release of native mesopredator species. The lower nest predation observed in REB was compensated for by a higher nest abandonment rate, which resulted in a similar fledgling production in the two study sites. Clutch size, hatching success and number of nestlings did not differ between study sites. The low breeding success recorded for this endangered species despite its populations being in protected areas of high conservation value is alarming given the global decline that grassland bird populations are facing.

Traits shaping urban tolerance in birds differ around the world

As human density increases, biodiversity must increasingly co-exist with urbanization or face local extinction. Tolerance of urban areas has been linked to numerous functional traits, yet few globally consistent patterns have emerged to explain variation in urban tolerance, which stymies attempts at a generalizable predictive framework. Here, we calculate an Urban Association Index (UAI) for 3,768 bird species in 137 cities across all permanently inhabited continents. We then assess how this UAI varies as a function of ten species-specific traits and further test whether the strength of trait relationships vary as a function of three city-specific variables. Of the ten species traits, nine were significantly associated with urban tolerance. Urban-associated species tend to be smaller, less territorial, have greater dispersal ability, broader dietary and habitat niches, larger clutch sizes, greater longevity, and lower elevational limits. Only bill shape showed no global association with urban tolerance. Additionally, the strength of several trait relationships varied across cities as a function of latitude and/or human population density. For example, the associations of body mass and diet breadth were more pronounced at higher latitudes, while the associations of territoriality and longevity were reduced in cities with higher population density. Thus, the importance of trait filters in birds varies predictably across cities, indicating biogeographic variation in selection for urban tolerance that could explain prior challenges in the search for global patterns. A globally informed framework that predicts urban tolerance will be integral to conservation as increasing proportions of the world's biodiversity are impacted by urbanization.

The Effect of Local Weather Conditions on American Kestrel (Falco sparverius) Reproduction

ABSTRACT American Kestrel (Falco sparverius) populations have been declining in North America during recent decades and potential causes, including climate change, currently are under investigation. Many studies of migratory birds have demonstrated the effects of climate change, including changes in local weather conditions and the increase in extreme weather, but the relationship between local weather and kestrel ecology in the northeastern United States has received little attention. We examined the relationship of local weather conditions and kestrel breeding performance in northwestern New Jersey between 1996 and 2016. We also obtained temperature, rainfall, and snowfall data from weather stations within or adjacent to our study area. We did not detect significant changes in climate over the study period, but we did find significant associations between local weather conditions and kestrel breeding performance. Warmer temperatures during the breeding season were significantly correlated with earlier nesting, and early nesting had significant positive correlations with clutch size, hatching rate, nestling survival, and nesting success (raising at least one young to fledging). We did not detect a significant relationship between rainfall and nesting variables, but snowfall during autumn was strongly related to kestrel breeding performance the following year. Compared to years when there was no snowfall in our study area the preceding autumn, kestrels breeding in years following autumn snow had significantly smaller clutches, lower hatching rates, lower nestling survival rate, and lower nesting success. Kestrels in our region are partial migrants; first-year birds generally migrate to southern wintering grounds while older birds may remain in the region, presumably in response to local conditions. We suggest that substantial snow during autumn may drive a larger percentage of adults to migrate south, as indicated by the greater number of kestrels counted at representative autumn hawk watch sites during years with substantial autumn snow. Our study concludes that variations in local weather conditions throughout the year can affect the breeding performance of American Kestrels, whether or not they are associated with climate change.

Reproductive biology of the Whitehead’s Broadbill (Calyptomena whiteheadi)

ABSTRACT Whitehead’s Broadbill, Calyptomena whiteheadi, an endemic species on the island of Borneo, has a declining population, raising the question of whether reproduction might be a factor limiting population growth. We studied breeding biology based on 52 nests in Kinabalu Park, Sabah, Malaysian Borneo in 2009–2020. Length of the egg-laying season was 99 days with a median of 22 March. Clutch size was typical of tropical songbirds at 2.0 ± 0.13 eggs (SE). Nest success was relatively high at 52%, and daily nest predation rate was relatively low at 0.013 ± 0.004 (SE). Concordantly, length of incubation and nestling periods were relatively long at 19.0 ± 0.26 d and 26.8 ± 0.3 d (SE), respectively. Similarly, the growth rate constants (K) for mass, wing length and tarsus length were slow at 0.252, 0.161 and 0.188, respectively. Slow growth might result in part from their frugivorous diet, as we show using seed traps, but they are reported to include insects in their diets and food provided to their young. Feeding effort, as reflected by the number of fruit seeds dropped below the nest, increased through the nestling period. Brooding effort of parents for nestlings was high on hatch day and decreased until Day 10–15 when it stopped. Food and parental care efforts do not seem to cause their slow growth. Ultimately, our study population has reproductive success that suggests it is not limiting population growth, but studies are needed in other locations to determine if it is a problem elsewhere.

Breeding biology of the Cyprus Coal Tit (Periparus ater cypriotes) in the coniferous Paphos Forest, Cyprus, over a 9-year period

We studied the breeding biology of the endemic Cyprus Coal Tit (Periparus ater cypriotes) using artificial nest boxes in a coniferous forest from March through May 2010 to 2018. In total, 202 breeding pairs utilized the nest boxes, with a mean number of 22.2 pairs per year. The highest number of nests was observed in 2017, with 38 occupied nest boxes, reflecting a significant fivefold increase compared to 8 occupied nest boxes in 2011. Breeding attempts were not affected by temperature or precipitation prior to and during the breeding period. Average clutch size was 6.2±1.2 eggs and average brood size 6.1±1.2 young. Additionally, 51 pairs of Great Tit (Parus major aphrodite) bred in the nest boxes with a mean number of 5.7±1.66 pairs per year. Nest composition of the two species was similar, although Cyprus Coal Tits built heavier nests, composed of double the percentage of wool and feathers (60%) compared to Great Tits (33%).

Molecular identification, life history description and biotic potential of Plodia interpunctella (Lepidoptera: Pyralidae) feeding on amaranth (Amaranthus sp.) products in the state of Morelos, Mexico

The flour moth Plodia interpunctella (Hübner) is considered one of the most significant pests of stored and processed products, its adaptability allowing it to settle on new food hosts. In 2020 in Mexico, the presence of larvae and adults of P. interpunctella in amaranth products stored and processed for export was reported for the first time, causing considerable damage. The objective of this study was molecular identification of the insects found in amaranth products and description of the biotic potential of these pests grown in different amaranth products under laboratory conditions. For this purpose, molecular identification of P. interpunctella was carried out using the mitochondrial gene cytochrome oxidase subunit one (COI). Three cohorts with 200 eggs each, fed with three types of amaranth products (amaranth with chocolate, amaranth with honey and natural amaranth) were implemented, with hatching rates of 75% for amaranth with chocolate, 66.5% for amaranth with honey and 71.5% for natural amaranth. The larval period consisted of five instars and one prepupa, with the shortest life expectancy in the first instar. The life cycle of the insect varied from 51 days in chocolate amaranth, 54 days in honey amaranth and 64 days in natural amaranth. This lepidopteran presented a high fecundity when fed with chocolate amaranth with a mean clutch size of 257.0435.98 eggs per female during her whole life (h/h/v), followed by honey amaranth with 177.3836.23 (h/h/v) and finally by natural amaranth with 157.643.33 (h/h/v), with a mean fertility of 71%. In the population parameters, a generation time (T) of 25.08, 26.69 and 31.41 days and a net reproduction rate (R0) of 405.10, 253.82 and 215.49 were obtained for amaranth with chocolate, with honey and natural respectively, ensuring a high replacement over a short period of time; these values make this species an important pest of stored amaranth products.

Partial refuges from biological control due to intraspecific variation in protective host traits.

Predicting how much of a host or prey population may be attacked by their natural enemies is fundamental to several subfields of applied ecology, particularly biological control of pest organisms. Hosts or prey can occupy refuges that prevent them from being killed by natural enemies, but habitat or ecological refuges are challenging or impossible to predict in a laboratory setting-which is often where efficacy and specificity testing of candidate biological control agents is done. Here we explore how intraspecific variation in continuous traits of individuals or groups that confer some protection from natural enemy attack-even after the natural enemy has encountered the prey-could provide partial refuges. The size of these trait-based refuges (i.e., the proportion of prey that survive natural enemy encounters due to protective traits) should depend on the relationship between trait values and host/prey susceptibility to natural enemy attack and on how common different trait values are within a host/prey population. These can be readily estimated in laboratory testing of natural enemy impact on target or nontarget prey or hosts as long as sufficient host material is available. We provide a general framework for how intraspecific variation in protective host traits could be integrated into biological control research, specifically with reference to nontarget testing as part of classical biological control programs. As a case study, we exposed different host clutch sizes of target (pest) and nontarget (native species) stink bug (Hemiptera: Pentatomidae) species to a well-studied exotic biocontrol agent, the egg parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae). We predicted that the smallest and largest clutches would occupy trait-based refuges from parasitism. Although we observed several behavioral and reproductive responses to variation in host egg mass size by T. japonicus, they did not translate to increases in host survival large enough to change the conclusions of nontarget testing. We encourage researchers to investigate intraspecific variation in a wider variety of protective host and prey traits and their consequences for refuge size.

Differential effects of continuous and intermittent daytime food deprivation periods on metabolism and reproductive performance in diurnal zebra finches

We investigated whether food availability effects on metabolism and reproduction are the result of the sum effect of daily feeding (food availability) and starvation (food deprivation) periods. Adult zebra finches were paired and subjected to a time-restricted feeding (TRF) regimen consisting of continuous and intermittent daytime food deprivation periods. Birds were given food during the 12-h day for a total of 4-h in the evening (1 *4-h, hour 8–12), or in 2 splits of 2 h each (2 * 2-h) or 4 splits 1 h each (4 * 1-h), with controls on food ad libitum, until they had the first egg clutch. TRF caused significant changes in hepatic expression of metabolism-associated sirt1, egr1, pparα and foxo1 genes despite no difference in the food intake, body mass and blood glucose levels. Importantly, TRF resulted in a significant reduction in plasma testosterone and estradiol levels, delayed nest-building and egg laying, and reduced clutch size. Concurrently, under TRF regimes, we found a significantly lower expression of th and mtr genes linked with motivation and affiliation (but not of dio2, dio3, gnrh1 and gnih genes linked with gonadal maturation) in the hypothalamus, and of star and hook 1 genes in the testes and star, cyp19 and erα genes in the ovary. These results demonstrate the importance of daily food deprivation times on the metabolism and reproduction, and suggest a possible provisioning of energy available from daily feeding for the maintenance of body condition at the expense of reproduction performance in diurnal animals.

Smaller size of harlequin toads from populations long exposed to the fungal disease chytridiomycosis

AbstractPathogens can exert great selective pressures on the life history traits of their hosts. Species experiencing high mortality throughout their adulthood can benefit from breeding earlier. Chytridiomycosis, a fungal disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has been a major driver of extinction for harlequin toads (Atelopus) and continues to be frequent cause of adult mortality for species persisting with endemic infections. We compared the body size of Atelopus cruciger between a remnant population long exposed to Bd (post‐epidemic) and populations sampled before the presumed Bd outbreak in the late 80s (pre‐epidemic). Reproductive female and male toads from pre‐epidemic populations were significantly bigger than those from post‐epidemic populations at similar altitudes, suggesting that toads from post‐epidemic populations are breeding earlier. A significant positive relationship between body size and the number of eggs in oviducts suggests a trade‐off between the benefit of breeding earlier and the cost of smaller clutch sizes. This cost–benefit relationship is likely to change along elevation gradients because the number of eggs relative to body size tends to be lower at higher elevations. By breeding earlier harlequin toad populations long exposed to Bd can increase their demographic competence, particularly in lowland habitats, where the cost–benefit relationship of breeding earlier tends to be more favorable.Abstract in Spanish is available with online material.

Breeding biology of the African Pygmy Falcon: long-term variation and seasonal decline in breeding performance of an arid zone raptor

Birds of prey are apex predators and understanding their life history can serve as a valuable baseline for investigating their ecological role. Pygmy Falcons (Polihieraxsemitorquatus), Africa’s smallest diurnal raptor, have evolved to be obligate associates of Sociable Weaver (Philetairussocius) colonies throughout their southern African range. As a predator, Pygmy Falcons likely impact prey communities in this system including their host and other colony associates. However, no study has explored their breeding biology in detail using long-term data. We provide results from 10 years of data collected between 2011 and 2020. We followed 66 unique Pygmy Falcon territories and 323 breeding attempts in the Kalahari, South Africa. We explored annual variation in the population density of Pygmy Falcons and investigated between- and within-season variation in reproductive investment and output. The highest average density was recorded in 2015 and the lowest in 2019 and 2020. Our results show that the breeding occurs between early austral spring (August) and late summer (February), with a peak from September to December. The maximum and most frequent clutch size was three eggs and falcons usually initiated only one breeding attempt (but up to three) in a season. The incubation and nestling periods lasted on average 33 (±SD 4) and 37 (± 5) days, respectively. A three-egg clutch size and number of fledglings produced varied between seasons, and breeding success showed a seasonal decline across the breeding season. Falcons were 7 times less likely to lay a 3-egg clutch in 2019 than in 2011 and 2012, and breeding attempts initiated in September were 3.4 times more likely to be successful than those initiated in November. Predation accounted for 49.5% of breeding failures. Our results show significant variation in the breeding parameters of these falcons, but further studies are needed to understand what drives these variations.

Behavior, stress and metabolism of a parthenogenic lizard in response to flyover noise

The Colorado checkered whiptail (Aspidoscelis neotesselatus) is a parthenogenetic lizard that is listed as a “species of special concern” in the state of Colorado. A. neotesselatus occupies a small range that includes the US Army Fort Carson Military Base in Colorado Springs, Colorado. The species is exposed to a variety of military disturbances, including aircraft flyover noise. We sampled 82 females during the 2021 reproductive season to assess whether scheduled flyovers would impact the behavior, stress, and metabolism of A. neotesselatus, while controlling for size and reproductive stage differences. We measured corticosterone (CORT) as a marker of anthropogenically induced stress during flyovers compared to a control. We further tested for the downstream effects of flyovers on plasma glucose (free energy available to tissues), elevated metabolism with oxidative stress (ROMs), and ketone bodies (alternative cerebral energy substrates to glucose). When disturbed by flyovers, these lizards spent less time moving but more time eating. Aircraft noise also increased CORT when controlling for clutch size, indicating a stress response driven by flyovers, as well as an independent effect of reproductive investment on CORT. CORT did not affect plasma glucose. Flyovers led to a marginally decrease in circulating ROMs, with gravid females experiencing lower plasma ROMs than non-gravid females, but that later effect was independent of flyovers. Flyovers significantly increased ketone bodies, with smaller animals experiencing higher ketone concentrations than larger individuals, yet the effect of size on ketone bodies was independent of the flyover treatment. Although A. neotesselatus seem to adjust their behavior and eat more to buffer the potentially negative effect of flyovers on energetic pathways, they still appear to suffer a metabolic cost driven by the stress response via ketone accumulation, as well as a reproductive cost driven by clutch size investment that is independent of flyover disturbance. We suggest that military aircraft operators attempt to avoid dense populations of A. neotesselatus during the reproductive season or fly at altitudes that lead to decibel reads that fall below 50 dB at ground level, as a cautious management step that ensures the resilience and local abundance of A. neotesselatus at Fort Carson.

Characterization of ovarian follicles, serum steroid hormone concentration, and steroidogenic gene expression profiles in the developing ovarian follicles in White King pigeons

Paired pigeons only lay 2 eggs in a laying period, which is closely related to ovarian follicle development, but this process is not well understood. In this study, 60 pairs of 12-mo-old White King pigeons were selected and serum and follicles were collected at 4 stages of laying interval (LI), including the first (LI1), the third (LI3), the fifth (LI5), and the seventh day (LI7). Morphological results showed that paired pigeons normally had 2 preovulatory follicles and the second-largest follicle (F2) developed from LI3 and had been selected in LI5. Prehierarchical follicles were coupled and hierarchical, which was in accordance with its clutch size. The P4 concentration increased gradually from LI1 to LI5, reaching a maximum of 30.67 ng/mL in LI5 and decreasing to 27.83 ng/mL in LI7 (P < 0.05). The levels of T in LI1 and LI5 were higher than LI3 and LI7 (P < 0.05), although there was no significant difference in E2 in LI (P > 0.05), but it stayed at high levels. In the TCs of the largest follicle (F1), HSD3B1 mRNA and HSD17B1 mRNA levels peaked in LI7. The expression pattern of CYP17A1 and CYP19A1 was similar, increasing from LI3 to LI5 and then decreasing. In the TCs of F2, the expressions of HSD3B1 and CYP17A1 had no significant difference between LI5 and LI7 (P > 0.05), while the expression pattern of HSD17B1 and CYP19A1 was the opposite. In TCs of SF1, HSD3B1 mRNA level peaked in LI3 while CYP19A1 mRNA levels peaked in LI7. The expression of CYP17A1 had a minor change (P > 0.05) and the expression pattern of HSD17B1 was similar to F1. It was concluded that the morphological characteristics of follicles during the LI for the first time, including the number and diameter of small follicles (SFs) and hierarchical follicles in pigeon and the concentrations of steroid hormones and expressions of steroidogenic genes in TCs of different follicles could explain the growth and selection of 2 preovulatory follicles. This study facilitates further research into the regulation of ovulation and egg production in pigeons.

Coloniality and development impact intraclutch consistency of avian eggs: a comparative analysis of theindividual repeatability of eggshell size and shape metrics.

In oviparous animals, egg morphology is considered an aspect of the extended phenotype of the laying mother and, thus, can be directly assessed for consistency both within and between individual females. Despite a recently renewed interest in the evolution and mechanics of avian eggshell morphology, we still lack a large-scale, comparative understanding of which egg traits are individually plastic and whether individual consistency is shaped by ecological and life history traits at the species level. Here, we aimed to understand whether intraclutch repeatability per se of different eggshell metrics is an evolving trait that responds to selection pressures from socio-ecological contexts across a diverse group of avian species for which clutch-level eggshell morphology data were available to us. Coloniality, ontogeny, and incubation period had significant impacts on the comparative patterns of relative individual repeatability among two egg metrics (i.e., size and shape), whereas other life history traits (including adult size, clutch size, nest type, migration, breeding latitude, host status of brood parasitism) did not have statistical impacts. Our results also demonstrate that individual consistency has a more widespread phylogenetic distribution than expected by evolutionary contingency across avian diversity. Future analyses should also incorporate the effects of intra- and interspecific covariation in other morphological and physiological traits on the evolution of individual consistency, especially those relevant to egg recognition, including eggshell color and maculation.

Lead exposure is correlated with reduced nesting success of an urban songbird

Lead exposure is a concern in urban ecosystems, with physiological and behavioral effects well documented in humans. Wildlife inhabiting urban ecosystems are also exposed to lead, yet little work has documented the sublethal effects of lead exposure in urban wildlife. We studied northern mockingbirds (Mimus polyglottos) in three neighborhoods of New Orleans, Louisiana, two with high soil lead and one with low soil lead, to better understand how lead exposure may influence mockingbirds' reproductive biology. We monitored nesting attempts, measured lead concentrations in blood and feathers of nestling mockingbirds, documented egg hatching and nesting success, and assessed rates of sexual promiscuity in relation to neighborhood soil lead levels. We found that nestling mockingbirds’ blood and feather lead levels reflected the soil lead levels of their neighborhoods and nestling blood lead levels were similar to those of adult mockingbirds in the same neighborhoods. Nest success, as evaluated by daily nest survival rates, was higher in the lower lead neighborhood. Clutch sizes varied substantially across neighborhoods, but rates of unhatched eggs did not covary with neighborhood lead levels, suggesting that other drivers are influencing variation in clutch sizes and hatching success in urban habitats. At least one-third of nestling mockingbirds were sired by an extra-pair male, and there was no relationship between extra-pair paternity rates and neighborhood lead levels. This study provides insight on how lead contamination may influence reproduction in urban-dwelling wildlife and suggests that nestling birds could serve as useful bioindicators of lead levels in urban neighborhoods.

Characterization and performance evaluation of indigenous geese of Assam

The present study aimed to phenotypically characterize the indigenous geese of Assam, in North East India. These geese were observed to have two types of plumage colour (white and cinnamon) and plumage pattern (solid and bordered); and three different bill colours (black, orange, yellow). The shank and feet colour was found to be mostly orange and sometimes yellow. The eye colour was found to be black, brown and sometimes grey and skin colour as white. The least squares means for body weight at hatching, 4, 6-8 and 12 months and above age were 0.087±0.001, 3.030±0.022, 3.480±0.055 and 3.970±0.025 kg, respectively. The average age at first egg, annual egg production, clutch size and clutch interval were 320.196±2.882 days, 19.886±0.306, 9.897±0.143 and 59.206±0.531 days. Average fertility and hatchability percentage under natural condition were found to be 87.11% and 80.53%, respectively. The study revealed that the indigenous geese of Assam are heavier birds with high potential for meat production with two colour variants, viz. White and Cinnamon in the study area covering four districts. The study generated baseline information on physical characteristics, productive and reproductive performances of indigenous geese of Assam under native field condition which would be of great help in documentation and development of breed descriptors for registration, improvement and conservation.

Delayed egg-laying in Red-backed Shrike Lanius collurio in relation to increased rainfall in east-central Poland

Climate change has affected the breeding parameters of many animal species. In birds, most studies have focused on the effects of temperature on clutch phenology and clutch size. The long-term influence of other weather factors, including rainfall, on breeding parameters have been analysed much less often. Based on a 23-year dataset and 308 broods, we documented shifts in the timing of breeding, clutch size and mean egg volume in a long-distance migrant, the Red-backed Shrike Lanius collurio, from a central European population. We found a 5-day shift towards delayed breeding, but no differences in brood size or egg volume during those 23 years. The GLM analysis showed that the mean May temperature had a positive influence on the clutch initiation date, whereas the number of days with rain delayed laying. During the period 1999–2021, there was no change in the mean May temperature, but total precipitation and the number of days with rain in May increased. Thus, delayed nesting in this population was probably due to the increase in rainfall during this period. Our results provide a rare example of delayed nesting in birds in recent years. Predicted changes in the climate make it difficult to assess the long-term impact of global warming on the viability of Red-backed Shrike populations in east-central Poland.

Plasma Vitellogenin and Testosterone in Diamond-backed Terrapins (Malaclemys terrapin) during the Nesting Season in Coastal New Jersey

Vitellogenesis is the process in which female oviparous vertebrates synthesize the protein vitellogenin to develop egg yolk. In some species, vitellogenin has been used to investigate reproductive status, as a biomarker of clutch size and nesting frequency, and as a biomarker of exposure to endocrine-disruptive chemicals. The Diamond-backed Terrapin (Malaclemys terrapin) is an obligate coastal species that in the northern extent of its range nests in the spring and summer months. Diamond-backed Terrapins serve as a key indicator species of coastal ecosystem health; thus, furthering our understanding of the endocrine control of reproduction may inform biologists of the health and status of coastal ecosystems. The objective of this study was to quantify baseline values of vitellogenin and testosterone in Diamond-backed Terrapins during the nesting season, in the northern part of their range. Blood samples were taken from adult female terrapins from two populations in coastal New Jersey from June–August. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify vitellogenin (VTG) and testosterone (T) across the nesting season. VTG concentrations showed peak values in the earliest part of the nesting season, significantly declining through the summer before reaching basal values in August, with T showing a similar trend. This suggests that terrapins in New Jersey follow a similar reproductive cycle to other turtle species from temperate latitudes. Additionally, we found that larger females exhibited higher concentration of T and VTG than smaller females. This suggests that VTG and T are useful biomarkers of reproductive output in these animals. Lastly, we also noted that larger females tended to nest earlier in the nesting season than smaller females. We hypothesize that larger females may compete for resources more effectively and efficiently than smaller females, which may confer larger individuals a fitness advantage.