Reproductive Ecology Research Articles

Scent-mediated bee pollination and myrmecochory in an enigmatic geophyte with pyrogenic flowering and subterranean development of fleshy fruits.

Volatile emissions from flowers and fruits play a key role in signalling to animals responsible for pollination and seed dispersal. Here, we investigated the pollination biology and chemical ecology of reproduction in Apodolirion buchananii, an African amaryllid that flowers in a leafless state soon after grassland vegetation is burnt in the dry late-winter season. Pollinators were identified through field collection and pollen loads were quantified. Floral traits including spectral reflectance and scent chemistry were documented. Bioassays using cup traps were used to test the function of floral volatiles. Fruiting biology was investigated using controlled hand-pollination experiments and chemical analysis of fruit scent. Seed germination was scored in greenhouse trials. Seed dispersal was monitored using observations and camera trapping. The sweetly scented white flowers of A. buchananii are pollen-rewarding and pollinated mainly by a diverse assemblage of bees. Cup-trap experiments demonstrated that pollinators are attracted to phenylacetaldehyde, the dominant volatile in the floral scent. Plants are shown to be self-incompatible, and the fleshy fruits were found to emerge from the soil six months after pollination during the peak of the summer rains. Fruits emit a diverse blend of aliphatic and aromatic esters and contain large fleshy recalcitrant seeds which germinate within days of fruits splitting open. Seed dispersal by ants was recorded. This first account of the reproductive biology of a species in the genus Apodolirion highlights an outcrossing mating system involving bees attracted to color and scent as well as the unusual fruiting biology and ant-mediated system of seed dispersal.

Anthropogenic and climate change-driven coastline dynamics will erode future nesting habitats of the kentish plover on the central adriatic coast

Shorebirds play a crucial role in assessing the health of coastal ecosystems due to their life history, behaviour, migratory patterns, and feeding preferences. Many shorebird species are experiencing population declines worldwide, driven by habitat loss and climate change. Understanding these challenges requires extensive data on their distribution and breeding ecology. The Kentish Plover (Anarhynchus alexandrinus) is a small shorebird that constructs its nests on sandy beaches. However, there is a scarcity of data regarding the reproductive ecology of this species in many areas, including the Molise region of Southern Italy. This study aimed at assessing the potential role of environmental variables derived from remote sensing to model current and future Kentish Plover nesting habitat suitability accounting for future scenarios of coastal dynamics in 2040. Data on Kentish Plover nests were collected along the Molise coast over several years and used to calibrate ecological niche models (ENMs) relying on environmental variables derived from coastal images. Kentish Plover nesting habitat suitability was mostly affected by distance from open sand, artificial surfaces, shoreline, and herbaceous vegetation and forested areas. The study predicts an average decline of more than 22% in suitable nesting environments for the Kentish Plover within the next two decades. Results indicated that our modelling approach can offer valuable insights for the conservation strategy of Kentish Plover in the region. In conclusion, we assert that preserving the nesting habitat of the Kentish Plover will not only safeguard this species, but also other species that inhabit similar environments, along with providing protection for coastal landscapes and associated ecosystem services.

Physalia gonodendra are not yet sexually mature when released

The blue bottle genus Physalia is one of the well-known siphonophore belonging to the Cnidaria, Hydrozoa. Physalia is also known as a ferocious predator, occasionally stinging and fatally wounding humans, but key details of its life cycle and reproductive biology are unclear. Physalia have separate sexes, and sexual reproduction occurs through the release of complex structures called gonodendra that contain many gonophores that will release either eggs or sperm. It is not known how mature the gonophores are when the gonodendra are released. In this study, we aim to characterize germ cell maturation by conducting histological, cytological, and gene expression analyses of the gonodendron of Physalia utriculus from Japan. We found a layered structure of the gonophore, consistent with other studies; however, gametes were not found even in gonophores that were within the released gonodendra. Moreover, haploid cells were not detected by flow cytometry. Analysis of the expression of putative germ cell marker and meiosis related genes showed high expression in the gonophore. These results strongly suggest that germ cells do not mature until after gonodendra are released. These findings provide valuable insights into the reproductive ecology and life cycle of Physalia.

Reproductive ecology and egg parasitism of the Samoan swallowtail butterfly

AbstractWe investigated the reproductive ecology and effects of egg parasitism on the Samoan swallowtail butterfly (Papilio godeffroyi), which survives only on Tutuila Island, American Samoa, after having disappeared from the much larger islands of Upolu and Savai‘i in independent Samoa. During monthly surveys of its only known host plant, Micromelum minutum, across eight sites in 2013 and 2014, we collected eggs, eggshells, larvae, pupae, and pupal exuviae. Live specimens were reared under laboratory conditions to determine reproductive outcomes, developmental rates, and sex ratios, as well as parasitoid attack frequencies, brood sizes, and sex ratios. Sixty‐six of 448 (14.7%) eggs produced larvae, 47 of which became adults. The sex ratio was approximately even overall and within each developmental stage. Eggs were slightly larger on individual host trees and in host tree stands that yielded more eggs per unit of foliage, indicating that ovipositing females responded to some features of host trees and stands. Eggs hatching female or male larvae were similar in size, and the sexes developed at similar rates. A newly described species of parasitoid wasp, Ooencyrtus pitosina (Encyrtidae), emerged from 73.6% of 382 butterfly eggs that failed to hatch in the laboratory (62.7% of 448 eggs overall). Forty‐one other eggs contained dead parasitoid larvae. An additional, unidentified Ooencyrtus wasp species emerged from a single P. godeffroyi egg. No parasitoids were reared from P. godeffroyi larvae or pupae. Of 656 P. godeffroyi eggshells collected in the field and examined in the laboratory, 62.2% showed signs of having been parasitized by O. pitosina. There was no evidence that parasitism rates were density‐dependent. O. pitosina brood sizes ranged from 1 to 5, with the sex ratio skewed toward females (2.40 F:1.00 M). Larger parasitoid broods were associated with slightly larger host eggs, indicating that female wasps may adjust brood size according to host egg size or that fewer wasp larvae are able to complete development in smaller eggs. Techniques used to rear both P. godeffroyi and O. pitosina in the laboratory could be applied to a captive‐rear, wild‐release program, which may facilitate reestablishment of the species in Samoa.

Carcass size, not source or taxon, dictates breeding performance and carcass use in a burying beetle.

Small vertebrate carcasses represent critical resources for many terrestrial organisms, including burying beetles, which rely on carcasses for survival and breeding. Carcass attributes can influence the reproduction of burying beetles, yet most studies on their breeding ecology have used laboratory-reared carcasses of limited sizes. We conducted breeding and feeding experiments using a wide size range of lab (laboratory mice) and wild carcasses (wild mammals, birds and reptiles) to investigate how carcass size, source and taxon affect various breeding outcomes (e.g. clutch size, brood size and brood mass) of the burying beetle Nicrophorus nepalensis. Our results reveal a hump-shaped relationship between carcass size and breeding performance, with optimal breeding outcomes occurring on medium-sized carcasses. Furthermore, despite the variation in carcass tissue nutritional composition, breeding outcomes and larval growth did not differ between the two carcass sources or among the three wild carcass taxa. Finally, we found a larval quality-quantity trade-off across the range of carcasses examined, with carcass size shaping the larval life-history traits. Overall, these results elucidate how carcass resources may influence the breeding performance of burying beetles. Importantly, our study provides solid evidence validating decades of research using lab carcasses to study the reproductive ecology of burying beetles.

Elevational shifts in reproductive ecology indicate the climate response of a model chasmophyte, Rainer's bellflower (Campanula raineri).

Elevation gradients provide 'natural experiments' for investigating plant climate change responses, advantageous for the study of protected species and life forms for which transplantation experiments are illegal or unfeasible, such as chasmophytes with perennial rhizomes pervading rock fissures. Elevational climatic differences impact mountain plant reproductive traits (pollen and seed quality, sexual vs. vegetative investment) and pollinator community composition; we investigated the reproductive ecology of a model chasmophyte, Campanula raineri Perp. (Campanulaceae), throughout its current elevational/climatic range to understand where sub-optimal conditions jeopardise survival. We hypothesised that: 1) reproductive fitness measures are positively correlated with elevation, indicative of the relationship between fitness and climate; 2) C. raineri, like other campanulas, is pollinated mainly by Hymenoptera; 3) potential pollinators shift with elevation. We measured pollen and seed quality, seed production, the relative investment in sexual vs. vegetative structures and vegetative (Grime's CSR) strategies at different elevations. Potential pollinators were assessed by combining molecular and morphological identification. Whereas CSR strategies were not linked to elevation, pollen and seed quality were positively correlated, as was seed production per fruit (Hypothesis 1 is supported). The main pollinators of C. raineri were Apidae, Andrenidae, Halictidae (Hymenoptera) and Syrphidae (Diptera), probably complemented by a range of occasional pollinators and visitors (Hypothesis 2 partially supported). Potential pollinator communities showed a taxonomic shift towards Diptera with elevation (particularly Anthomyiidae and Muscidae) and away from Hymenoptera (Hypothesis 3 was supported). Pollinator availability is maintained at all elevations by taxon replacement. However, reduced pollen quality and seed production at lower elevations suggest an impact of climate change on reproduction (especially <1200 m a.s.l., where seed germination was limited). Aside from guiding targeted conservation actions for C. raineri, our results highlight problems that may be common to mountain chasmophytes worldwide.

Reproductive ecology of fire corals in the northern Red Sea

AbstractScleractinian corals, the principal architects of coral reefs, face substantial threats from ongoing and anticipated climate change and other anthropogenic disturbances. This underscores the significance of investigating alternative reef-building organisms and their contribution to reefs’ resilience. Among these alternatives, colonial hydrozoans of the genus Millepora, commonly called ‘fire corals’, play substantial roles in contributing to coral reef structure and functionality by depositing calcareous exoskeletons. Despite the ecological importance of fire corals, fundamental knowledge gaps remain regarding their biology and reproductive ecology. Here, we present a comprehensive study on the population dynamics, reproductive ecology, phenology, and sex ratio of the three Red Sea fire corals—Millepora dichotoma, M. exaesa, and M. platyphylla—in the Gulf of Aqaba and Eilat. The abundance of M. dichotoma and M. exaesa seems to have remained consistent over the last 50 years across two of the three depth zones surveyed, indicating their potential resistance or resilience. However, at the third depth surveyed, their abundance appears to have decreased. Our extensive in-situ monitoring of breeding events over six consecutive years has revealed a previously undetected relationship between Millepora species breeding events and the lunar cycle. Histological analyses indicated remarkably short reproductive cycles of only 2–3 weeks, recurring multiple times within a single season, in both M. dichotoma and M. exaesa, which is a unique reproductive aspect compared to other reef-building corals. These results highlight the high reproductive and resilience potential of Millepora species. Consequently, fire corals could assume a more substantial role as keystone species in changing environments and future reefs, emphasizing their importance in reef conservation and management.

Reproductive Ecology and Spawning Behavior of the Natural Monumental and Endangered Species, Cobitis choii (Pisces: Cobitidae) in Geumgang (River), Korea

Reproductive Ecology and Spawning Behavior of the Natural Monumental and Endangered Species, Cobitis choii (Pisces: Cobitidae) in Geumgang (River), Korea

Reproductive ecology of the sand crab (Ovalipes punctatus) population in the Yellow Sea of Korea

AbstractUnderstanding the reproductive ecology of crustaceans is important for developing appropriate resource management policies. Because the demand for sand crabs (Ovalipes punctatus) as a food resource has recently surged in Korea, their reproductive ecological characteristics should be comprehensively described. In this study, the reproductive ecological characteristics—sex ratio, female gonad maturity, abdominal width (AW), condition factor (K), and gonadosomatic index (GSI)—of individuals of O. punctatus collected from the Yellow Sea in Korea (35°15′00″N, 125°15′00″E) from January to December 2021 were examined. Based on the sex ratio (1:1.61, females:males), we determined that males were more abundant than females. The monthly K for both the males and females reached its maximum in April. The monthly GSI revealed that the males were most numerous in December, whereas the females were most abundant in May. The GSI graph indicates that the main spawning season of O. punctatus is from May to July. The AW and GSI of the females increased as their gonads matured; based on this correlation, the maturity of female individuals can be determined by examining the abdominal flap morphology. The results of histological analysis indicated that females of O. punctatus exhibit synchronous development, by which oocytes develop simultaneously. Furthermore, the size at maturity, at which more than half of the individuals participated in spawning, was 75.6 mm. The findings of this study contribute to the development of policies for the sustainable fisheries of O. punctatus.

The integration of diel vertical migration and hydrodynamic process influences the transport of swimming crab zoea (Portunus trituberculatus)

AbstractVertical migration and dispersal processes during the marine crab larval stage markedly affect transport, habitat selection, population connectivity, and resource replenishment success rates. However, not much is known of the reproductive ecology of swimming crabs in the nearshore waters of the northwest Pacific shelf. Here, we investigated the diel vertical migration (DVM) characteristics and transport patterns of the swimming crab zoea (Portunus trituberculatus) in this area. A Lagrangian particle‐tracking algorithm coupled with a hydrodynamic model, incorporating a DVM pattern of zoeae based on observations from a field survey of the diurnal distribution of swimming crab zoea, was used to simulate the transport of zoeae, and the impact of zoeal transport on population connectivity was explored. The results revealed that particles were predominantly transported in a nearshore direction from the particle release point, with short dispersal distances during the zoeal stages. In nearshore waters on the continental shelf, the swimming crab zoeae are exposed to shoreward‐moving currents with the aid of prolonged daytime locations in the lower water column, whereas larvae migrate upward to the middle and upper layers of the water column at night rather than the most superficial layer, potentially avoiding surface offshore‐moving currents that may be responsible for the retention and shoreward transport of larvae. Most zoeae are transported to shallow waters, and the contribution of transport to population connectivity during the zoeal stages is relatively limited. The findings here have considerable implications for understanding the mechanisms governing the early recruitment dynamics of this species, as well as for fisheries management and conservation of marine biodiversity.

Reproductive ecology of the critically endangered pancake tortoise (Malacochersus tornieri) in the wild

Reproduction of the pancake tortoise in the wild has remained poorly known over the decades. This study fills the knowledge gap by investigating the reproductive ecology of the species in its natural habitats in Kenya. Data were collected using the time‐constrained search‐and‐seize method, group‐level scan sampling, radio tracking, and camera‐trapping. Our observations revealed a total of 19 mating events that occurred between December and April, predominantly during the rainy seasons. Mating duration averaged 15.2 ± 2.4 min. Male–male aggression was observed during the mating season, with the dominant male keeping off all other males and mating with the resident females. Nest preparation events occurred between April and June. Nine nesting events were recorded, but in only five of them was an egg deposited. The nests were dug in loose soil, appeared almost circular, and measured 8.4 ± 0.9 cm wide and 7.0 ± 0.1 cm deep (n = 7). The average clutch size was one egg. The eggs were white, hard‐shelled, oval, and elongated measuring 4.4 ± 0.4 cm long, 2.7 ± 0.04 cm wide and weighed 17 ± 0.6 g (n = 3). Incubation period lasted 177 ± 5.7 days (n = 2), and hatching coincided with the onset of the short rainy season in November, aligned with the availability of abundant food for the tortoises. The hatchlings were minimally wider than long, having an average straight carapace length of 4.5 ± 0.6 cm, an average width of 4.5 ± 0.4 cm, and on average weighed 14.7 ± 3.7g, (n = 9). They remained near the nest site for 4–5 days before relocating to tiny rock crevices away from the adult tortoise crevices. Egg and hatchling predation was high, with four of the total of six eggs, observed after they were laid, being destroyed. Three juveniles, out of nine, were also eaten by predators. These findings contribute useful information for the formulation of effective conservation and management strategies for this critically endangered species.

Pollination by multiple species of nectar foraging Hymenoptera in Prasophyllum innubum, a critically endangered orchid of the Australian Alps

Context Australia has numerous threatened species of terrestrial orchid, with a particularly high incidence of rarity in the genus Prasophyllum R.Br. Although there has been research on mycorrhizal associations and propagation, little is known about the reproductive ecology of threatened Prasophyllum. Understanding which animals are responsible for pollination and the impact of herbivores on reproduction may inform conservation actions. Aims For the nationally Critically Endangered Prasophyllum innubum, we aimed to determine the pollinator species, test for self-pollination, quantify levels of reproductive success and herbivory, and identify herbivores. Methods Pollinator observations were undertaken at wild populations of P. innubum, whereas an experiment testing for self-pollination was undertaken in shadehouse conditions. We quantified reproductive success and herbivory at two populations and attempted to identify herbivores using game cameras. Key results Pollination occurred via three species of bee and a sphecid wasp, all of which attempted feeding on floral nectar. Fruit set averaged 72–84% at wild sites, whereas only 6% of flowers set fruit via self-pollination when insects were excluded. Just 4% of inflorescences were completely consumed by herbivores, and no herbivory was captured on camera. Conclusions P. innubum has a generalist rewarding pollination system that confers high levels of reproductive success, with herbivory having little impact on reproduction. Implications Pollinator availability is unlikely to restrict conservation translocation site selection of P. innubum because of a generalist pollination system. If herbivores are a threat for this species, it is likely to be through alteration of habitat rather than direct grazing.

Discovery of interspecific alloparental care of silver-eared mesia nestlings by a mountain bulbul.

Although brood parasitism has been well documented among bird species, interspecific alloparenting, which is parenting behavior of adult individuals of one species toward the progeny of another species, is increasingly being reported. However, compared with the many reports of interspecific alloparenting behavior in North America and Europe, this phenomenon is less well known in China, with only two prior cases of interspecific alloparenting behavior in birds having been recorded. On June 23, 2022, we observed an instance of interspecific alloparental care provided by a mountain bulbul (Ixos mcclellandii) towards silver-eared mesia (Leiothrix argentauris) nestlings in Caihu Village, Jingdong County, Yunnan Province, southwestern China. We recorded 19.5 h of footage during the period in which the mountain bulbul provided care for the nestlings with the aim of documenting detailed observations of interspecific alloparenting to contribute to our overall understanding of this behavior. The alloparenting behavior of the mountain bulbul lasted for at least 5 days. During this period, both silver-eared mesia parents fed their nestlings 157 times and removed their nestlings' fecal sacs 5 times, while the mountain bulbul fed the nestlings 30 times and removed the nestlings' fecal sacs 4 times. In addition, the male silver-eared mesia parent chased the mountain bulbul away during nestling feeding. As there was no life history information for the mountain bulbul at that time, we were unable to directly determine why it exhibited interspecific alloparental care. Regardless of the reason for the mountain bulbul's behavior, these findings provide valuable information for future studies on the reproductive ecology of these two bird species.

A fine-scale examination of parturition timing in temperate ungulates.

Parturition timing has long been a topic of interest in ungulate research. However, few studies have examined parturition timing at fine scale (e.g., <1 day). Predator activity and environmental conditions can vary considerably with diel timing, which may result in selective pressure for parturition to occur during diel times that maximize the likelihood of neonate survival. We monitored parturition events and early-life survival of elk (Cervus canadensis) and mule deer (Odocoileus hemionus) in Utah, USA to better understand diel timing of parturition in temperate ungulates. Diel timing of parturition was moderately synchronous among conspecifics and influenced by environmental variables on the date of parturition. For elk, parturition events were most common during the morning crepuscular period and generally occurred later (i.e., closer to 12:00) when a relatively large proportion of the moon was illuminated. For mule deer, parturition events were most common during the diurnal period and generally occurred later (i.e., closer to 15:00) on cold, wet dates. Diel timing of parturition did not influence neonate survival, but larger datasets may be required to verify the apparent lack of influence. Although additional work could evaluate alternative variables that might affect parturition timing, our data provide an improved and finer scale understanding of reproductive ecology and phenology in ungulates.

First record of a neonate bluntnose sixgill shark (Hexanchus griseus) from Baja California Sur, Mexico.

The bluntnose sixgill shark (Hexanchus griseus) is a wide-ranged deep-water shark species found off continental and insular shelves. Despite its global distribution, little is known about the reproductive ecology of the species, particularly with regard to the location and timing of important phenological events such as mating and pupping. In this study, we report the landing of a neonate H. griseus individual from an artisanal fishing camp in Baja California Sur, Mexico. This represents only the ninth confirmed record of the species from the Mexican Pacific and the first to report a neonate specimen in Mexican waters. We discuss this specimen in the context of the environmental conditions in which it was found, ultimately suggesting that these shallow coastal waters may be an important pupping ground for H. griseus in the region. Furthermore, the specimen was found during the winter months (whereas all previous reports have suggested H. griseus pups during the summer), implying regional variation in reproductive periodicity, or the presence of multiple reproductive events per year. This study provides novel insight into the reproductive biology of H. griseus and the ecological characteristics of the species in the Northern Mexican Pacific.

Reproductive ecology of treefrogs: egg size promotes reproductive effort differences between females

Reproductive ecology of treefrogs: egg size promotes reproductive effort differences between females

Low seed viability of a rare aster

The reproductive ecology of rare plants is often unknown, yet the persistence of most plant populations depends on successful interactions with pollinators and favourable environmental conditions. Sexual reproduction maintains genetic diversity within plant populations using pollinators to transport pollen grains among plants of the same species and producing seeds. We investigated the reproduction of Yermo xanthocephalus Dorn (Desert yellowhead), a perennial member of Asteraceae endemic to central Wyoming, USA, which grows in only two locations within 8 km of each other. Our objectives were to assess the pollination and seed-set of Y. xanthocephalus. We conducted seed-set experiments in both populations to measure self-pollination and estimate if pollinating insects limited seed production. We used vane traps and pan traps to capture pollinators, and we examined pollen carried on bees. Yermo xanthocephalus can self-pollinate, but seed-set was extremely low. The number of viable seeds produced in flowerheads pollinated by insects did not differ from those produced by capitula hand-pollinated with excess pollen, indicating that pollinators did not limit seed production that year. Pollen from Y. xanthocephalus was carried by nine bee genera, suggesting that no one specific insect pollinates this plant. Only 12% of ovules produced viable seeds in the main population and 0% were viable in the other population, suggesting that something beyond pollinators limited seed-set. We recommend continued research to address what is limiting seed production to advance the knowledge and management of this declining plant species.

Fertilisation increases plant biomass and seed production but does not influence seed heteromorphism in Aegilops

Aegilops species are important crop wild relatives (CWR) characterised by seed heteromorphism. Within each spikelet seeds differ in terms of size, colour, phenology, abiotic stress tolerance among others. although the seed heteromorphism in Aegilops has a genetic component, the level of plasticity of this character has been poorly investigated. To fill this gap, we measured the effect of fertilization on seed heteromorphism in nine Aegilops species, to understand if nutrient availability can affect the reproductive ecology in this important CWR genus. We measured the number of stems per plant, number spikelets per stem, total dry plant biomass, seed weight and germination percentage in fertilized and control (non-fertilized) plants. Fertilization did not affect heteromorphism but increased the biomass and the number of flowering stems (hence spikelets and seeds) in fertilized plants. However, seeds produced by fertilized plants showed significantly lower germination than control plants, in a sort of trade-off between seed quantity and seed quality.

Flower visitor networks: Reduced reproductive success driven by antagonists in a hummingbird‐pollinated species

AbstractFlower–animal interactions encompass a continuum of mutualistic to antagonistic behaviors. Although the importance of pollinators in interaction networks has been widely reported, the role of floral antagonists remains overlooked. In Collaea cipoensis, an endemic shrub from southeastern Brazil, we modeled an individual‐based network assessing the flower visitors' functional behavior and tested if plant centrality increases fitness. Centrality indicates how well‐connected a given plant is with the rest of the conspecifics through shared flower visitors. Specifically, we tested if flower visitor interactions are amplified by many‐flowered individuals, and whether the relationship between centrality and plant fitness encompasses the effects of mutualists or antagonists. Subsequently, we quantified each visiting species' effectiveness. Antagonistic interactions were the most frequent in the network (97% of visits), primarily conducted by the nectar‐robbing bee Trigona spinipes (66%), which was also the most central species and detrimental antagonist. The hummingbirds Colibri serrirostris and Eupatomena macroura were the most efficient pollinators, with a high contribution to the quantity—floral visitation—and the quality—viable seeds—components, respectively. Many‐flowered plants showed greater centrality, which boosted the plant's cohesion in the network and increased flower visitation. Accordingly, many‐flowered plants were better connected, mainly due to antagonistic visitors. Thus, centrality increases were not positively translated into more reproductive success. Our results reinforce the dynamic scenarios of flower–animal interactions, with consequences to plant reproductive ecology. We highlight the importance of incorporating distinct types of interactions to unveil the complexity of interacting systems, that when not explored, hide potential evolutionary consequences for plant reproductive success.Abstract in Portuguese is available with online material.

Leucocytozoon Infection Does Not Influence the Survival of Boreal Owl Aegolius funereus Nestlings.

Leucocytozoon infection has been observed to impact the reproductive ecology and physiology of avian hosts, but its influence on nestling survival remains unclear. We investigated the effect of Leucocytozoon infection intensity, determined through triplicate PCR sample analyses, on the survival of 256 boreal owl (Aegolius funereus) nestlings during an 8-yr study. Contrary to our expectations, the survival probability of boreal owl nestlings was not influenced by their Leucocytozoon infection intensity. Nestling age and Leucocytozoon infection intensity in male and female parents also did not impact nestling survival. Instead, food abundance and hatching order were the key factors influencing nestling survival. Additionally, we observed a significantly higher Leucocytozoon infection intensity in male parents compared to female parents and nestlings. We suggest a distinct division of parental roles may lead females and nestlings staying within the nest boxes (cavities) to experience lower exposure to potential vectors transmitting blood parasites than their male counterparts. Our study shows that Leucocytozoon disease may not be lethal for boreal owl chicks, exhibiting a below-average infection intensity compared to their male parents.