Breeding Ecology Research Articles

No cultural transmission of use of nest materials in titmice Paridae

Bird nests often consist of stronger materials to maintain nest structure and a softer layer of lining materials to reduce heat loss. We studied whether early learning affected the use of nest materials by cross-fostering between two tit species with similar breeding ecology, the blue tit, Cyanistes caeruleus, and the great tit, Parus major, in a woodland area provided with nestboxes in Norway. In both species, only the female builds the nest. From previous studies, we know that early social learning affects a number of traits in these birds, including song repertoire, mate choice, foraging behaviour and nest site choice. Nests of the two species are similar but blue tits use more feathers than great tits. This was confirmed in the present study; however, female blue tits raised by great tit foster parents also supplied their nest with feathers, and female great tits raised by blue tits used few feathers. The only treatment effect was that fewer feathers were found in nests of cross-fostered females in both species than in nests of controls. This may have been caused by time and energetic constraints during nest building because cross-fostered birds seemed to forage less efficiently than controls. The amount of hair was slightly greater in blue tits than in great tits, but it was not affected by the cross-fostering either. We conclude that no cultural transmission was found in the use of lining materials in the nest of the two species, perhaps because young birds hatch after their parents have stopped constructing the nest.

Knowledge and beliefs of the city dwellers regarding dengue transmission and their relationship with prevention practices in Dhaka city, Bangladesh

ObjectivesThe objectives of the study were to explore knowledge, attitudes, and practice (KAP) of dengue fever among Dhaka city dwellers and the potential associated factors. Study designA cross-sectional survey was conducted among the city dwellers in Dhaka north and south city corporations using a standardized questionnaire from November to December 2019. MethodsHouseholds were selected by purposive sampling and interviewed face to face by the trained interviewers. The association between education and occupation with the dengue practice was tested using the chi-square test statistic. ResultsAround 96% of respondents claimed that they heard about Dengue, and 80% of them correctly identified its causes. Nearly half of the people did not know the breeding season and ecology of dengue vector mosquitoes. Though the city dwellers were well-known about Dengue’s burden, they were reluctant to take preventive measures to get rid of this disease. More than 70% of people mentioned that every family member regularly sleeps under a bed net. Moreover, we found a significant relationship between the education level (p<0.05), as well as the occupation of the respondents (p<0.05) with the practice to prevent and control Dengue. We did not find any information, education, and communication (IEC) activities in the city during our survey. ConclusionMany people didn’t know the specific preventive measures to minimize potential exposure to Dengue. This lack of knowledge is likely due to inadequate coverage with IEC activities. So, IEC intervention programs may need to start soon in highly dengue-endemic cities to reduce the burden.

Breeding ecology of Eurasian bullfinches Pyrrhula pyrrhula in an Iberian hedgerow habitat

ABSTRACT The breeding ecology of the Iberian subspecies of the Eurasian bullfinch, Pyrrhula pyrrhula iberiae, is addressed for the first time. The studied population occupied a hedgerow habitat in northwestern Spain. Individuals directly watched in the study area and details of these sightings were recorded over a six-year period, and a total of 56 nests were monitored. The earliest date of nest building was within 11–30 April for all years. Fledglings were recorded leaving the nest during all the ten-day periods from the end of May to mid-August. Nest attendance, from the early building stage to when nestlings were ready to leave the nest, lasted approximately 36 days. The overall mean clutch size was 4.56 eggs. Clutch size decreased significantly at the end of the breeding season. For all egg traits, the minimum values for standard deviation were obtained in the intra-clutch analysis, and egg length was more variable than width. Nesting success increased progressively from April–May to June–July and August. The main proximate cause of nest failure was egg desertion/predation, followed by nest desertion during nest building and nestling desertion/predation. Mammals were the main agents in nests where the probable predator could be identified. Approximately half of the eggs became fledglings leaving the nest, no significant seasonal differences being observed for this parameter. In August, the ratio of juveniles to adults was 2.5–4.1, juveniles representing approximately 70–80% of the individuals seen and identified that month. The absence of significant interannual variation in important reproductive parameters could have been due to lack of interannual variation in the availability of food resources. Compared to other subspecies, mean clutch size of Iberian bullfinches is the smallest recorded in the western Palearctic, and they showed an earlier start to the breeding season and shorter mean egg length than North European and Russian populations.

The secret life of Fairy Terns: breeding chronology and life history observations of Sternula nereis nereis in south-western Australia

This research describes the breeding ecology, behaviour and substrate preferences of the Australian Fairy Tern, Sternula nereis nereis, in four colonies around Perth, Western Australia between 2018 and 2020. Extensive field observations, supported by a bird banding study and sunrise to sunset video recording were used at colony and roosting sites to determine the processes of mating, colony formation, egg-laying and incubation periods, post-hatching care and breeding success (fledglings per pair). At a colony in North Fremantle, the median nest spacing was 0.71m (mean± s.e.= 0.89±0.05m), which increased over time. Birds establishing nests within a week of the first eggs being laid selected sites with significantly higher percentage beach shell cover (73.5±4.5%) than those laying later in the season (58.2±7.9%) and on average, birds selected sites with higher shell cover (64.9±2.8%, n=114) than a random sample of sites within the colony (53.7±4.4%, n=44). Incubation periods ranged from 17 to 26 days (n=86, mean=21±0.17 days). Incubation shift duration was highly variable, with both sexes contributing, almost equally to the care of the brood (mean=1.27±6.11h). Chicks fledged 21–23 (mean=22±0.21, n=10) days following hatching, with all banded juveniles leaving the colony site within 8 days of fledgling. The information gained from this research helps inform conservation strategies for this vulnerable species, where management interventions are frequently necessary to prevent population decline.

Breeding biology of a high altitudinal Aethopyga sunbird in southwestern China

ABSTRACT The breeding ecology of high-altitude birds in the Himalaya and the Hengduan Mountains remains poorly known. The present study describes the breeding biology of the Fire-tailed Sunbird Aethopyga ignicauda in southwestern China. Fieldwork was conducted at a high-altitude mountain pass in the Gaoligong Mountains from March to July 2014. Based on 20 nests found from 3102–3288 m a.s.l., we collect detailed information on life-history traits and breeding ecology parameters of the Fire-tailed Sunbird. The clutch size was one (n = 1) or two (n = 10) eggs, with fresh eggs weighing 1.28 ± 0.02 g (n = 8), and the nestling period lasting 19.5 days (n = 2). Both males and females participated in feeding nestlings, but females had significantly higher feeding frequencies than males. Compared to its low-altitude congeners, the Fire-tailed Sunbird elevated parental investments to their offspring by producing fewer eggs and providing more parental care to nestlings. This suite of life-history and behavioural strategies enables fledgling Fire-tailed Sunbirds to cope with harsh environments in higher altitudinal mountains.

Breeding ecology and nestling growth of the Madagascar Pond Heron Ardeola idae in a monospecific colony at Sofia Lake, northern Madagascar

The breeding ecology of the endangered Madagascar Pond Heron Ardeola idae was studied at Sofia Lake, northern Madagascar, during two consecutive breeding seasons (October 2017–April 2018 and October 2018– April 2019). Altogether 158 nests were documented at a monospecific breeding colony for both seasons combined. The breeding season occurred between November and April. Nest construction started from the middle of November and it took 8.2 ± 2.5 d on average to complete a nest (n = 158 nests, range = 5–13 d). All the nests were build inside clusters of Papyrus Cyperus madagascariensis. The nest density was 0.31 nests m−2 and 0.20 nests m−2 for Season 1 and Season 2, respectively. Egg laying took place between November and January, but it continued throughout February for renesting attempts (second clutches laid). Mean clutch size was 2.9 ± 0.68 eggs (n = 158, range = 2–4). Incubation started with the laying of the first egg, producing an asynchronous hatching. The incubation period averaged 20.6 ± 0.9 d (n = 158, range = 20–22 d). Of the 461 eggs laid in 158 nests, 399 (86.6%) hatched, and 326 (70.7%) of those hatchlings fledged, a reproductive success of 2.06 fledglings per nesting attempt. Data obtained from 34 measured nestlings showed a rapid growth of all measured biometric parameters, except for tarsus length. The mean daily growth rate was 9.02 g for body mass, 9.64 mm for body size length, 10.66 mm for wing length and 2.35 mm for tarsus length. Significant differences were recorded in growth rates between nestlings in the same brood in relation to their hatching sequence. The last nestlings to hatch had lower growth rates for all measured parameters than their older siblings.

Eye size and investment in frogs and toads correlate with adult habitat, activity pattern and breeding ecology.

Frogs and toads (Amphibia: Anura) display diverse ecologies and behaviours, which are often correlated with visual capacity in other vertebrates. Additionally, anurans exhibit a broad range of relative eye sizes, which have not previously been linked to ecological factors in this group. We measured relative investment in eye size and corneal size for 220 species of anurans representing all 55 currently recognized families and tested whether they were correlated with six natural history traits hypothesized to be associated with the evolution of eye size. Anuran eye size was significantly correlated with habitat, with notable decreases in eye investment among fossorial, subfossorial and aquatic species. Relative eye size was also associated with mating habitat and activity pattern. Compared to other vertebrates, anurans have relatively large eyes for their body size, indicating that vision is probably of high importance. Our study reveals the role that ecology and behaviour may have played in the evolution of anuran visual systems and highlights the usefulness of museum specimens, and importance of broad taxonomic sampling, for interpreting macroecological patterns.

Assessment of Rusty Blackbird Habitat Occupancy in the Long Range Mountains of Newfoundland, Canada Using Forest Inventory Data

Rusty blackbirds (Euphagus carolinus), once common across their boreal breeding distribution, have undergone steep, range-wide population declines. Newfoundland is home to what has been described as one of just two known subspecies (E. c. nigrans) and hosts some of the highest known densities of the species across its extensive breeding range. To contribute to a growing body of literature examining rusty blackbird breeding ecology, we studied habitat occupancy in Western Newfoundland. We conducted 1960 point counts across a systematic survey grid during the 2016 and 2017 breeding seasons, and modeled blackbird occupancy using forest resource inventory data. We also assessed the relationship between the presence of introduced red squirrels (Tamiasciurus hudsonicus), an avian nest predator, and blackbird occupancy. We evaluated 31 a priori models of blackbird probability of occurrence. Consistent with existing literature, the best predictors of blackbird occupancy were lakes and ponds, streams, rivers, and bogs. Red squirrels did not appear to have a strong influence on blackbird habitat occupancy. We are among the first to model rusty blackbird habitat occupancy using remotely-sensed landcover data; given the widespread availability of forest resource inventory data, this approach may be useful in conservation efforts for this and other rare but widespread boreal species. Given that Newfoundland may be a geographic stronghold for rusty blackbirds, future research should focus on this distinct population.

Ecology and conservation of the critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii): past, present and future

The northern hairy-nosed wombat (Lasiorhinus krefftii) is an iconic marsupial endemic to Australia, recognised globally for its status as the largest, herbivorous burrowing mammal. Owing to historical challenges, including anthropogenic conflict and environmental threats, the species was pushed to near extinction and was officially classified as Critically Endangered in 1996. Establishing an effective conservation plan is complicated by ongoing and novel threats as well as by aspects of the species’ ecology that remain unstudied due to its neophobic and nocturnal behaviour. To identify areas where additional research is needed, we conducted a comprehensive search of the literature published on the northern hairy-nosed wombat from 1980 to 2019 to identify where knowledge gaps exist and to suggest where future efforts may be focussed. We found that the breeding ecology, in particular, of the northern hairy-nosed wombat is largely unstudied but could be vital in conservation efforts. Further, there is a need to establish additional populations, and several threats – including disease, invasive species, and climate change – may require ongoing management action to ensure the species’ longevity.

Autonomous underwater videography and tracking of basking sharks

BackgroundBiologging studies have revealed a wealth of information about the spatio-temporal movements of a wide range of vertebrates large enough to carry electronic tracking tags. Advances in autonomous underwater vehicles (AUVs or UAVs) and unmanned aerial vehicles (commonly known as drones), which can carry far larger payloads of sensor technologies, have revealed insights into the environment through which animals travel. Some AUVs have been used to film target animals, but are generally limited to periods as long as a drone operator can actively follow an animal. In the present study, we use an AUV, the REMUS-100 SharkCam, paired with a custom transponder tag attached to the shark, to autonomously follow three basking sharks for a cumulative total of 10.9 h to collect video and environmental data on their sub-surface behaviour. The basking shark is the second largest fish in the world and is endangered globally, but despite being subject to various biologging studies, little is known of this species breeding ecology and their mating grounds remain unknown.ResultsWe detail the first successful autonomous tracking of basking sharks, comprising three missions that filmed basking sharks in mid-water and close to benthic habitats. Sharks spent very little time feeding, and travelled relatively close to sandy, rocky and algae-covered benthos. One basking shark was observed defecating. Conspecifics were not observed in the three missions, nor were courtship or breeding behaviours. AUV offset distances for videography were determined iteratively through tracking. These offsets varied depending on the trade-off of between water clarity and proximity of the AUV for obtaining useful video data and directly influencing shark behaviour.ConclusionsThe present study is the first successful use of an AUV to gain insight into the sub-surface behaviour of basking sharks.

Diurnal adult resting sites and breeding habitats of phlebotomine sand flies in cutaneous leishmaniasis endemic areas of Kurunegala District, Sri Lanka

BackgroundSand flies are responsible for the transmission of several disease pathogens including Leishmania. Sand flies breed in habitats with high levels of humidity and organic matter. They are nocturnal in nature and peak activity ranges from dusk to dawn. The scientific evidence on breeding ecology and diurnal resting sites of sand fly fauna are important aspects of planning and implementing vector control activities. However, such fundamental information is grossly inadequate in Sri Lanka to support the control efforts in the country. Therefore, the present study addresses some of the important aspects of sand fly breeding ecology and diurnal resting sites.MethodsPotential resting sites were thoroughly observed, and sand flies were collected using a battery-operated aspirator and sticky papers when appropriate from three selected Medical Officer of Health (MOH) areas (Polpithigama, Maho and Galgamuwa) in Kurunegala district, Sri Lanka. Soil samples were collected from each potential breeding site. Half of each soil sample was incubated for 45 days. The other half was screened for immature stages. Adult sand flies collected from field and emerged adults at the insectary under confined incubation were identified using morphological characteristics.ResultsPepper bushes and termite mounds were the most notable resting sites while, betel bushes, cattle huts, piles of coconut shells, latrines, manna bushes and tree holes were also positive for sand fly adults. Only two species, Phlebotomus argentipes and Sergentomyia punjabensis, were reported. Soil samples were collected from a total of 432 sites and 7 of them were positive for immature stages. Predominant breeding habitats identified during the present study were mud flats and moist soils of rice paddies, the soil below decaying hay, drying irrigational tank bottom moist soil, and the floors of cattle huts.ConclusionThis study demonstrates that the potential adult resting sites and breeding habitats are abundant in the Polpithigama, Maho and Galgamuwa MOH areas. Therefore, vector control activities targeting both adult and immature stages of sand flies are recommended.

Factors influencing Cinnamon Teal nest attendance patterns

Patterns of nest attendance in birds result from complex behaviours and influence the success of reproductive events. Incubation behaviours vary based on individual body condition, energy requirements and environmental factors. We assessed nest attendance patterns in Cinnamon Teal Spatula cyanoptera breeding in the San Luis Valley of Colorado in 2016–2017 using trail and video cameras to observe behaviours throughout incubation. We evaluated the effect of temporal, life‐history and environmental covariates on the frequency and duration of incubation recesses as well as the incubation constancy. There was considerable model uncertainty among the models used to evaluate recess frequency. Recess duration varied according to the interaction between nest age and a quadratic effect of time of day, with hens on older nests taking longer recesses in the afternoon and hens on nests earlier in incubation taking longer recesses in the morning and evening. Incubation constancy decreased with higher ambient temperatures in the study area. This study provides evidence that Cinnamon Teal modify their behaviour during incubation according to the age of the nest and the time of day. These results improve our knowledge of Cinnamon Teal breeding ecology and shed light on the behaviours that fast‐lived species may use to cope with environmental factors during nesting.

Arrival timing and the influence of weather experienced during the nonbreeding and breeding periods on correlates of reproductive success in female field sparrows (Spizella pusilla) breeding in northeastern Pennsylvania, USA.

Increasing evidence suggests that the environment encountered by migrating landbirds during the nonbreeding season, including temperature and precipitation, may influence individuals and population processes in subsequent seasons. However, to date, most studies have focused on linkages between factors encountered during the wintering and breeding periods in long-distance, primarily insectivorous landbirds. Here, we take advantage of a long-term (23 breeding seasons) data set on the arrival and breeding ecology of female field sparrows (Spizella pusilla), a granivorous, short-distance species that winters in the southeastern USA, to look for time periods (windows) over the preceding winter and spring migratory periods when average daily precipitation or temperature may have influenced when a female arrived at breeding grounds in northeastern Pennsylvania and correlates of seasonal reproductive performance. We employed a sliding window analysis approach using weather data obtained from the south of our site (to evaluate effects of weather experienced during the nonbreeding period) and, separately, near our site (to evaluate effects of weather experienced during the breeding period), finding windows in which temperature and precipitation during the nonbreeding period were associated with arrival timing and clutch initiation day and a window in which temperature experienced during the breeding period was associated with clutch initiation day. We did not, however, find evidence that temperature or precipitation, either during the nonbreeding period or breeding period, was associated with clutch size nor total egg volume. Finally, early arriving females initiated clutches early, produced larger clutches, more nests, and more total eggs than later arriving females. Our findings contribute to the growing body of evidence that events experienced prior to the breeding season may influence individuals and population processes in subsequent seasons.

Vernal pool amphibian breeding ecology monitoring from 1931 to present: A harmonised historical and ongoing observational ecology dataset.

BackgroundFor 88 years (1931-present), the Mohonk Preserve's Daniel Smiley Research Center has been collecting data on occupancy and reproductive success of amphibian species, as well as associated water quality of 11 vernal pools each spring (February to May). Though sampling effort has varied over the dataset range, the size of the dataset is unprecedented within the field of amphibian ecology. With more than 2,480 individual species sampling dates and more than 151,701 recorded individual occurrences of the nine amphibian species, the described dataset represents the longest and largest time-series of herpetological sampling with paired water quality data.New informationWe describe the novel publication of a paired dataset of amphibian occurrence with environmental indicators spanning nearly 90 years of data collection. As of February 2020, the dataset includes 2,480 sampling dates across eleven vernal pools and 151,701 unique occurrences of egg masses or individuals recorded across nine species of amphibian. The dataset also includes environmental conditions associated with the species occurrences with complete coverage for air temperature and precipitation records and partial coverage for a variety of other weather and water quality measures. Data collection has included species, egg mass and tadpole counts; weather conditions including precipitation, sky and wind codes; water quality measurements including water temperature and pH; and vernal pool assessment including depth and surface vegetation coverage. Collection of data was sporadic from 1931–1991, but data have been collected consistently from 1991 to present. We also began monitoring dissolved oxygen, nitrate concentrations and conductivity of the vernal pools using a YSI Sonde Professional Plus Instrument and turbidity using a turbidity tube in February 2018. The dataset (and periodic updates), as well as metadata in the EML format, are available in the Environmental Data Initiative Repository under package edi.398.

Applying economic and ecological criteria to design cost-effective monitoring for elusive species

Monitoring programs of long-lived and elusive species often incur high costs in terms of field effort and economical budget, but both components are often considered separately. Also, there is scant information on the use of reliable detectability estimates under imperfect detection conditions based on environmental factors, which is key to accurately estimate financial costs and define optimum monitoring strategies. In this study, we use an intensive survey program (2017–2018) of the Egyptian vulture Neophron percnopterus population in Bizkaia (northern Spain) to model detectability at nests taking into account imperfect detection. Our main goal is to estimate both the number and timing of surveys, and the allocation of survey effort/costs, in order to design cost-effective monitoring programs. Firstly, throughout the breeding seasons, we used focal sampling methods on 19 nesting territories historically occupied by the study species. Then, we employed single-season occupancy models to assess detectability considering different levels of effort (from 1 to 5 h) at each nest, including both species breeding phenology and environmental covariates that could modify detection probabilities. Our results showed that the species was more likely to be detected in dry years and when the nest was visible during the nestling period, investing five hours of the survey. The optimal number of monitoring days required to account for 95% of false negatives for a single nest was eight days, investing one hour per breeding stage. The optimal monitoring cost was reached in dry years when the nest was visible, investing one hour per breeding stage (ca. 242 €/nest). The cost of monitoring was highest in rainy years when the nest was not visible (ca. 1954 €/nest). The cost of monitoring entire occupied nesting territories without accounting for covariates was of 23,294 € (n = 19). In order to offer reliable species assessments, design rigorous surveys and accurately estimate monitoring costs, studies should account for imperfect detection, particularly for long-lived vertebrates. Here, we show that monitoring programs ought to (a) consider the effort necessary to detect the species while accounting for species-specific breeding ecology and, (b) adjust field effort based on lower costs and environmental conditions. Our results provide simple and practical guidelines for the efficient allocation of human and economic resources, which could be of interest to those practitioners involved in the regular monitoring of elusive species.

Temporal Changes in Number of Breeding Individuals of the Amami Tip-Nosed Frog

Abstract: Amami tip-nosed frog (Odorrana amamiensis) is an endangered species endemic to Amami-Oshima Island and Tokunoshima Island, in Japan. This species is threatened by invasive species and habitat destruction. Although action is needed to protect them, the breeding ecology of O. amamiensis is poorly understood. A better understanding of its breeding ecology would contribute to conservation efforts. This study reports temporal changes in number of O. amamiensis breeding individuals in Kinsakubaru area, Amami-Oshima Island from the 28 Nov. 2015 to the 5 Dec. 2015. A 20 m transect line was set at a stream to count the number of O. amamiensis individuals at night and during daytime for eight days. Over 200 individuals were observed and many of them were breeding with lively mating calls around the small stream at night for three days. The high density of individuals decreased rapidly afterwards. This is the first report quantifying the temporal changes in number of breeding individuals of O. amamiensis. The species is usually nocturnal, but some individuals were observed at breeding sites during the daytime as well. Field research on O. amamiensis is usually conducted at night, but it can be risky because the nocturnal poisonous snake Habu (Protobothrops flavoviridis) also inhabits Amami-Oshima Island. The results suggested that field research during daytime was relatively safer and perhaps an easier approach to find breeding sites of O. amamiensis compared to searching at night.

Reproductive biology of the land crab Epigrapsus politus Heller, 1862 (Brachyura: Gecarcinidae) on Iriomote-jima, Japan

Abstract The breeding cycle of the land crab Epigrapsus politusHeller, 1862 (Gecarcinidae) was studied through a mark-recapture experiment on subtropical Iriomote-jima, Japan between September and November 2017. The abundance of E. politus at the cobble shore increased during the breeding season, and then decreased. Crab density was estimated to be 423.5 over 20 m2. The population showed a bimodal and a monomodal body-length frequency for males and females, respectively. Lifespan was estimated to be between one and two or three years. Ovigerous (egg bearing) females were detected from early September to late November, with the highest abundance occurring between late September and early November. The proportion of embryonic development (non-eyed and eyed eggs) of ovigerous females and the presence or absence of embryos and embryonic development of recaptured females showed that larvae were released on the days after the full moon. In comparison, egg extrusion occurred during the period of the previous full moon, i.e., eggs were incubated for four weeks. Females produced one brood within a single breeding season. The breeding ecology of E. politus was characterized as being short and occurring in a cooler season than that of other gecarcinids inhabiting the subtropical islands of the northwest Pacific.

Nest-site selection and breeding success of two neotropical austral migrant birds in a semiarid forest: A comparison of sites with and without livestock

Understanding the mechanisms underpinning nest-site selection offers novel insights about selective forces shaping the breeding ecology of birds, and provides vital information for conservation planning. We evaluated and compared nest-site selection and breeding success of Vermilion Flycatchers (VEFL) and Fork-tailed Flycatchers (FTFL) in areas with and without livestock in the Espinal biome of La Pampa Province, Argentina. VEFL selected nest sites with greater tree cover, whereas FTFL nested in taller trees with narrower trunks. We found a weak positive effect of nest height, diameter of nest-support branches and the absence of livestock on VEFL nest survival, and a weak positive effect of nest orientation on FTFL nest survival. However, although some habitat characteristics varied between the two areas, nest site characteristics of both species in areas with and without livestock did not differ significantly. The nest survival was 12.7% for VEFL and 28.7% for FTFL, and did not differ significantly between these two flycatchers. The breeding ecology of these birds has likely been molded by a broad suite of selective pressures, such as severe weather, brood parasites and predators that characterize habitats in central Argentina.

The Cooper's Hawk: Breeding Ecology and Natural History of a Winged Huntsman.

The Cooper's Hawk: Breeding Ecology and Natural History of a Winged Huntsman.

Seasonality Predicts Egg Size Better Than Nesting Habitat in a Precocial Shorebird

Egg size represents a fundamental predictor of chick mass and body condition. Chicks from bigger eggs have significantly increased survival, especially in precocial species, where chicks must forage for themselves and cope with environmental threats, such as bad weather or predators. Therefore, our understanding of the factors influencing egg size is crucial both from the perspective of their breeding ecology as well as of their conservation. However, studies simultaneously addressing multiple factors and quantifying their influence on egg size in large samples are rare. Here, we test the effect of seasonality, clutch size and nesting habitat on egg size, measured as volume, in a ground-nesting shorebird, the Northern Lapwing Vanellus vanellus, using a sample of 4384 eggs from 1125 clutches in South Bohemia, Czech Republic, during the period between 1988 and 2018. We report a significant decline in egg size over the breeding season, on average bigger eggs in larger clutches with a significant difference between 2-egg and 4-egg clutches, and no direct effect of nesting habitat. From our review of the same predictors across 15 Northern Lapwing populations throughout Europe it is apparent that replacement or late clutches have on average 3–7% smaller eggs than first or early clutches. Nesting habitat only rarely affects egg size and there are no significant differences in egg size between 3-egg and 4-egg clutches. Earlier studies showed that chicks hatching from bigger eggs early in the breeding season performed better, and that there was higher food abundance available for chicks at that time. This fact, together with the documented seasonal decline in egg size, sends an important message to conservationists and policymakers that early breeding attempts may play a pivotal role in safeguarding shorebird breeding productivity.