Rates Of Extra-pair Paternity Research Articles

Ultimate drivers of forced extra-pair copulations in birds lacking a penis: jackdaws as a case-study.

Forced copulation is common, presumably because it can increase male reproductive success. Forced extra-pair copulation (FEPC) occurs in birds, even though most species lack a penis and are widely thought to require female cooperation for fertilization. How FEPC persists, despite a presumed lack of siring success and likely non-negligible costs to the male, is unknown. Using the jackdaw (Corvus monedula) as a case study, we use SNPs to quantify the extra-pair paternity rate through FEPC and evaluate explanations for the persistence of FEPC in species without a penis. We then collate evidence for FEPC across penis-lacking birds. Combining genetic and behavioural analyses, our study suggests that the most likely explanations for the maintenance of FEPC in jackdaws are that it provides a selective advantage to males or it is a relic. Our literature review shows that across birds lacking a penis, FEPC is taxonomically widespread, and yet, little is known about its evolution. A broader implementation of the approach used here, combining both genetic and behavioural data, may shed light on why this widespread sexual behaviour persists. Additional work is necessary to understand whether a penis is needed for paternity through forced copulation and to quantify the costs of FEPC.

Plural breeding among unrelated females and other insights on complex social structure in the cooperatively breeding Variegated Fairywren

ABSTRACT Cooperatively breeding species vary widely in degree of social complexity, and disentangling relationships among group members can reveal the costs and benefits of cooperation. Here, we describe the social system of the cooperatively breeding Variegated Fairywren (Malurus lamberti) and explore how social complexity and group dynamics may affect cooperation and conflict. We used a combination of field-based population monitoring and detailed social association observations to determine group membership annually across four breeding seasons (2014–2017) and used a ddRAD-seq genotyping method to determine genetic relationships within social groups. Social groups ranged in size from two to eight individuals and nearly half of all social groups had multiple adult individuals of both sexes. Approximately half of all groups exhibited plural breeding, in which multiple females within the same social group nested individually in the same territory. Genetic relationships were diverse among social groups due to high rates of extra-pair paternity and immigration, with most groups containing close relatives and non-relatives of each sex. Notably, although related females were often present within a social group, co-breeding females in the same social group were never closely related to each other. Given the extensive variation in relatedness among group members, cooperation in the Variegated Fairywren is likely maintained by a combination of direct and indirect fitness benefits.

The evolution of extra-pair paternity and paternal care in birds.

Extra-pair paternity (EPP) influences the relatedness between social parents and offspring. Therefore, one might expect the level of EPP to influence levels of paternal investment. Here, we investigated the effect of variation in EPP rates on male contributions to parental care within a phylogenetic framework of up to 271 primarily socially monogamous bird species representing 85 families. We used proportion of male provisioning and occurrence of male incubation and nestbuilding as measures of paternal care. We tested the relationship between EPP rates and different components of paternal care while controlling for various life-history traits, namely lifespan, clutch size, and body mass in a phylogenetic path analysis framework. EPP was significantly negatively associated with the occurrence (i.e., whether males participate or not) of male nestbuilding and incubation, but not with the relative amount (proportion) of nestbuilding or incubation performed by the male. Importantly, the proportion of provisioning and biomass delivery by males was clearly negatively associated with EPP. These analyses thus confirm that the effect of EPP on proportion of provisioning visits by males is similar to proportion of biomass delivery, an often assumed but rarely tested assumption. Analysing only Passerine species provided similar results, although only proportion of provisioning was significantly negatively associated with EPP. This study, therefore, provides the most comprehensive support to date of a negative relationship between EPP and paternal care across species. However, a causal relationship between EPP and paternal care cannot necessarily be concluded. We also identify key methodological improvements for future research within the topic.

Extra-pair paternity, breeding density, and synchrony in natural cavities versus nestboxes in two passerine birds.

Most of what is known about extra-pair paternity in hole-nesting birds derives from studies using artificial nesting sites, such as nestboxes. However, it has rarely been investigated whether inference drawn from breeding events taking place in nestboxes matches what would be observed under natural conditions, that is, in natural cavities. We here report on a variation in promiscuity in blue tits and great tits nesting in natural cavities and nestboxes in an urban forest in Warsaw, Poland. Specifically, we tested whether local breeding density, local breeding synchrony, and extra-pair paternity (inferred from SNP data generated with a high-throughput genotyping by sequencing method) differed between birds nesting in natural cavities and nestboxes. In both blue tits and great tits, the frequency of extra-pair paternity was similar between the two cavity types. In blue tits, we observed shorter nearest neighbor distance, higher neighbor density, and higher synchronous neighbor density (i.e., density of fertile females) in nestboxes relative to natural cavities. No such pattern was found in great tits. Moreover, we detected a positive relationship between the proportion of extra-pair offspring in the nest and neighbor density around the nest in blue tits. Our results revealed that the provisioning of nestboxes did not change rates of extra-pair paternity, suggesting that conclusions drawn from nestbox studies might adequately represent the natural variation in extra-pair matings in some species or sites. However, the observed differences in spatiotemporal components of breeding dynamics highlight the fact that these parameters should be carefully considered when comparing mating behavior across studies and/or sites.

Extra-pair paternity and sexual dimorphism in birds.

Differences in the strength of sexual selection between males and females can lead to sexual dimorphism. Extra-pair paternity (EPP) can increase the variance in male reproductive success and hence the opportunity for sexual selection. Previous research on birds suggests that EPP drives the evolution of dimorphism in plumage colour and in body size. Because EPP increases the intensity of sexual selection in males, it should lead to increased dimorphism in species with larger or more colourful males, but decreased dimorphism in species with larger or more colourful females. We explored the covariation between EPP and sexual dimorphism in wing length and plumage colouration in 401 bird species, while controlling for other, potentially confounding variables. Wing length dimorphism was associated positively with the frequency of EPP, but also with social polygamy, sex bias in parental behaviour and body size and negatively with migration distance. The frequency of EPP was the only predictor of plumage colour dimorphism. In support of our prediction, high EPP levels were associated with sexual dichromatism, positively in species in which males are more colourful and negatively in those in which females are more colourful. Contrary to our prediction, high EPP rates were associated with increased wing length dimorphism in species with both male- and female-biased dimorphism. The results support a role for EPP in the evolution of both size and plumage colour dimorphism. The two forms of dimorphism were weakly correlated and predicted by different reproductive, social and life-history traits, suggesting an independent evolution.

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.

Combined roles for breeding synchrony, habitat and scale as predictors of extrapair paternity

Despite extensive research on passerine reproduction, it remains difficult to predict which traits of individuals, nesting populations and landscapes drive extrapair paternity (EPP). Two broad categories of drivers, habitat structure and population level factors, have been considered separately or at a single spatial or temporal scale. We used a 6-year nesting data set of scissor-tailed flycatcher, Tyrannus forficatus , which have high rates of cuckoldry (73% of nests, 59% of nestlings), to explore how nest density, breeding synchrony, habitat structure and clutch initiation date affect EPP rates. We further considered synchrony at two temporal and habitat structure at two spatial scales. We predicted that visual occlusion from vertical habitat structuring on breeding territories would allow extrapair males to go unnoticed and provide cover for extrapair copulations. Predictions for effects of nest density and fertility synchrony were double-edged: EPP may either increase as extrapair mate availability and ease of comparison with social mates increases or decrease as social mates increase their efforts to assure paternity. Using Bayesian techniques, we found a combination of population level factors and habitat structure, including interactions among the latter, at different scales best accounted for variation in EPP. EPP declined with increasing population synchrony. Variation in EPP was also explained by fine-scale habitat measures, decreasing with increasing nest tree diameter at breast height and woody vegetation cover but increasing with tree density. Notably, EPP increased with a coarse-scale habitat measure, linear extent of fence or powerline, suggesting a role for human alteration of habitat. Fences are used as communal perches by neighbours and floater males, potentially increasing interactions between asynchronous individuals. Our study demonstrates that breeding synchrony influences the probability of EPP and that habitat structure on individual territories is a strong predictor of paternity that acts independently of breeding density or synchrony at our scale of measurement. • We explore factors influencing cuckoldry in scissor-tailed flycatchers across 6 years. • Cuckoldry increased with populationwide fertility synchrony. • Cuckoldry was not related to spatial distribution of nests. • Cuckoldry increased with tree number and powerline/fence length and low shrub cover. • These correlates may impact cuckoldry via their effects on male mate guarding.

Seasonal variation in cuckoldry rates in the socially monogamous cichlid fish Variabilichromis moorii

Mating patterns in animal populations can respond to environmental conditions and consequently vary across time. To examine this variation in nature, studies must include temporal replicates from the same population. Here, we report temporal variation in genetic parentage in the socially monogamous cichlid Variabilichromis moorii from Lake Tanganyika, using samples of broods and their brood-tending parents that were collected across five field trips from the same study population. The sampled broods were either spawned during the dry season (three field trips) or during the rainy season (two trips). In all seasons, we detected substantial rates of extra-pair paternity, which were ascribed to cuckoldry by bachelor males. Paternity shares of brood-tending males were consistently higher, and the numbers of sires per brood were consistently lower, in broods that were spawned in the dry seasons compared to broods from the rainy seasons. In contrast, the strength of size-assortative pairing in our V. moorii population did not vary temporally. Seasonal fluctuations in environmental conditions, such as water turbidity, are proposed as a mechanism behind variable cuckolder pressure. Our data demonstrate the utility of long-term monitoring to improve our understanding of animal mating patterns.

Extra‐pair paternity correlates with genetic diversity, but not breeding density, in a Neotropical passerine, the black catbird

The frequency of extra‐pair paternity (EPP) varies widely across socially monogamous birds, but the proximate mechanisms driving this variation remain unclear. In this study, we tested two major factors hypothesized to influence extra‐pair mating – breeding density and genetic diversity – by comparing genetic mating patterns in two populations of black catbirdsMelanoptila glabrirostris. This Neotropical songbird is endemic to the Yucatán Peninsula, including eastern Mexico, and its offshore islands. We sampled one mainland (Sian Ka'an Biosphere Reserve) and one island (Isla Cozumel) population and used single‐nucleotide polymorphisms (SNPs) to quantify heterozygosity and genetic parentage over two breeding seasons. Moderate levels of EPP occurred in both populations (9.5–35% of offspring and 17–45% of nests). Contrary to predictions, breeding density did not affect EPP: although breeding densities were much higher on the mainland than on the island, EPP rates did not differ between populations, and local breeding density was not correlated with EPP at individual nests. In contrast, partial support emerged for the hypothesis that genetic diversity influences EPP: extra‐pair offspring were more heterozygous than within‐pair offspring. However, the two populations did not differ in genetic diversity, and neither the heterozygosity of social fathers nor within‐pair relatedness predicted EPP. These results are consistent with recent comparative studies suggesting that breeding density is not a critical driver of EPP rates, and that not all tropical songbirds exhibit low rates of EPP.

Extra-pair paternity drives plumage colour elaboration in male passerines.

The elaborate ornamental plumage displayed by birds has largely been attributed to sexual selection, whereby the greater success of ornamented males in attaining mates drives a rapid elaboration of those ornaments. Indeed, plumage elaboration tends to be greatest in species with a high variance in reproductive success such as polygynous mating systems. Even among socially monogamous species, many males are extremely colourful. In their now-classic study, Møller and Birkhead (1994) suggested that increased variance in reproductive success afforded by extra-pair paternity should intensify sexual selection pressure and thus an elaboration of male plumage and sexual dichromatism, but the relatively few measures of extra-pair paternity at the time prevented a rigorous test of this hypothesis. In the nearly three decades since that paper's publication, hundreds of studies have been published on rates of extra-pair paternity and more objective measures of plumage colouration have been developed, allowing for a large-scale comparative test of Møller and Birkhead's (1994) hypothesis. Using an analysis of 186 socially monogamous passerine species with estimates of extra-pair paternity, our phylogenetically controlled analysis confirms Møller and Birkhead's (1994) early work, demonstrating that rates of extra-pair paternity are positively associated with male, but not female, colouration and with the extent of sexual dichromatism. Plumage evolution is complex and multifaceted, driven by phylogenetic, ecological, and social factors, but our analysis confirms a key role of extra-pair mate choice in driving the evolution of ornamental traits.

Understanding Extra-Pair Mating Behaviour: A Case Study of Socially Monogamous European Pied Flycatcher (Ficedula hypoleuca) in Western Siberia

Extra-pair copulation (EPC) occurred in most socially monogamous bird species. The mechanisms leading to the frequent occurrence of extra-pair offspring (EPO, EPY) in socially monogamous couples, as well as the ‘function’ of EPC, are the subjects of strong debates and raise many unanswered questions. We studied the relationship between extra-pair paternity (EPP) and the different characteristics of males and females in the European pied flycatcher in Western Siberia (Russia). The analysis was based on the genotyping of 232 males, 250 females, 1485 nestlings (250 nests). The European pied flycatchers were predominantly socially and genetically monogamous, but about 20% of birds could be involved in EPP. Loss of paternity tended to be more frequent in one-year-old males. EPCs could be multiple: one individual may have up to three extra-pair partners. The EPP rate was independent of the breeding time. The extra-pair mates of an individual were mainly its near neighbours. The EPC status of an individual was unrelated to most of its morpho-physiological traits. The occurrence of EPP was almost twice as high in females nesting in good quality territories. The fitness of within-pair offspring, EPO, paternal half-sibs of EPO and maternal half-sibs of EPO did not differ statistically significantly. Assuming very low heritability of extra-pair mating, we argued that EPCs could be incidental side effects (by-product) of selection. We believe that the evolution and maintenance of extra-pair mating are the episelective processes in the case of the European pied flycatcher.

Microsatellite markers yield new insight into extra-pair paternity in Bobolinks (Dolichonyx oryzivorus)

Since the mid-1980s, our understanding of avian reproductive strategies has shifted as new molecular technologies have revealed how common promiscuity is in many monogamous avian species. However, the prevalence and importance of extra-pair paternity in polygynous species is less well studied. We used microsatellite loci from related icterid species to identify the extra-pair paternity rate in a polygynous population of Bobolinks (Dolichonyx oryzivorus) that bred in the Champlain Valley of Vermont from 2002 to 2018. We assigned paternity for 120 nestlings and found that 42% of nestlings were sired by extra-pair males. These results highlight the importance of extra-pair paternity in the reproductive behavior of Bobolinks that breed in agricultural habitats.

Local male breeding density affects extra‐pair paternity in a south temperate population of grass wrensCistothorus platensis

Demographic factors can affect the frequency of extra‐pair paternity (EPP) in birds, as the distribution and availability of potential mates in both space and time influence the rate of encounters between females and males. Over three breeding seasons, we intensively studied the breeding system of a south temperate population of grass wrensCistothorus platensisby genotyping 73 broods (319 nestlings) and estimating EPP rates for those broods. Using five different radii (80, 160, 240, 320 and 400 m) around each nest with assigned paternity, we examined the effects of local breeding synchrony, male breeding density and adult sex ratio (ASR) on the EPP rate. The majority of extra‐pair offspring (~80%) were sired by neighboring males. Neither local breeding synchrony nor ASR consistently explained the EPP rate variation as their effects were only statistically significant within 320 and 400 m. However, the EPP rate increased as the local male breeding density increased within every radius category, strongly suggesting that neighboring male abundance might play an important role in the extra‐pair mating behavior in this species. Our study also highlights the relevance of using a local scale approach when studying mating behavior.

Extra-pair paternity in a species with frequent extra-pair courtship feedings, few extra-pair copulations, and male-biased parental care

Patterns of extra pair paternity (EPP) and intraspecific brood parasitism (IBP) were studied in a Whiskered Tern Chlidonias hybrida population characterized by female brood desertion, a high level of extra pair courtship feedings (10%) and a low level of extra pair copulation (EPC; 0.6%). In this study, we used a set of microsatellite loci to analyse parentage in 56 Whiskered Tern families from southern Poland. Depending on the method, we detected that 1.4%–3.6% of chicks were sired by an extra-pair male, and extra-pair chicks were present in 3.6%–8.9% of broods. IBP was observed in 8.9%–14.3% of broods, corresponding to 3.6%–6.4% of the chicks. The low rate of EPP is in agreement with the hypothesis that in species with high male parental investment, females should avoid EPC. The low level of IBP indicates that intraspecific egg dumping is not a common female strategy in Whiskered Tern, similar to many other colonial waterbird species.

High level of extra-pair paternity in the socially monogamous Marsh Tits (Poecile palustris)

BackgroundExtra-pair copulation behavior has been widely studied among socially monogamous birds. Many species revealed high rates of extra-pair paternity. But few of the studies have been carried out in the Asian population.MethodsFrom 2012 to 2019, we explored the extra-pair paternity of Marsh Tits (Poecile palustris) in Xianrendong National Nature Reserve, Liaoning Province, China. During the study, adult Marsh Tits were captured with mist nets and parental birds, with nest-box traps. Blood samples were taken from the brachial vein. Parentage analyses were carried out using nine highly variable microsatellite loci through Cervus 3.0 software and maximum likelihood approach.ResultsForty-nine offspring (15.08%) from 20 nests (45.45%) were the results of extra-pair fertilization out of a total of 325 offspring in 44 nests. The average extra-pair offspring ratio was 33.54%, with a set varying from 11.11 to 71.43%. Nine extra-pair fathers had been successfully identified, four of whom were the close neighbors of the focus nest while the nests of the remaining five were relatively far. No significant difference was found in the genetic similarity between the social and extra-pair mates of the female, nor in the heterozygosis among the maternal half-siblings.ConclusionsIn general, our study proved that the extra-pair paternity in Marsh Tits and its extra-pair mating is independent of the genetic compatibility hypothesis. This complements the understudied bird’s extra-pair paternity in Asian area and contributes to the comprehensive insight of birds’ extra-pair paternity behaviors.

Large brain size is associated with low extra-pair paternity across bird species.

BackgroundGaining extrapair copulations (EPCs) is a complicated behavior process. The interaction between males and females to procure EPCs may be involved in brain function evolution and lead to a larger brain. Thus, we hypothesized that extrapair paternity (EPP) rate can be predicted by relative brain size in birds. Past work has implied that the EPP rate is associated with brain size, but empirical evidence is rare.MethodsWe collated data from published references on EPP levels and brain size of 215 bird species to examine whether the evolution of EPP rate can be predicted by brain size using phylogenetically generalized least square (PGLS) models and phylogenetic path analyses.ResultsWe found that EPP rates (both the percentage EP offspring and percentage of broods with EP offspring) are negatively associated with relative brain size. We applied phylogenetic path analysis to test the causal relationship between relative brain size and EPP rate. Best‐supported models (ΔCICc < 2) suggested that large brain lead to reduced EPP rate, which failed to support the hypothesis that high rates of EPP cause the evolution of larger brains.ConclusionThis study indicates that pursuing EPCs may be a natural instinct in birds and the interaction between males and females for EPCs may lead to large brains, which in turn may restrict their EPC level for both sexes across bird species.

The macroecology of extra-pair paternity in birds.

Extra-pair paternity (EPP) is a key aspect of the mating behaviour of birds and its frequency varies widely among populations and species. Several hypotheses predict patterns of geographical variation in the occurrence and frequency of EPP, but a global-scale study on variation in this trait is still lacking. We collected data on EPP from 663 populations of 401 avian species and explored the geographical variation in the frequency of EPP among populations, species and species assemblages. We modelled the variation in the frequency of EPP within the species' breeding range accounting for the specific ecological context of each population, and used the model predictions to compute frequencies of EPP at the level of species assemblages. A global map of assemblage-level EPP rates shows clear differences between zoogeographical realms, with the highest EPP values in the Nearctic realm. Our results show that the frequency of EPP (1) decreases with latitude and increases with the distance from the breeding range boundary within the species' breeding range, (2) is negatively associated with generation length and pair-bond duration among species, and (3) decreases with latitude at assemblage level. The latitudinal decline of EPP is consistent across zoogeographical realms.

Complex effects of helper relatedness on female extrapair reproduction in a cooperative breeder

Abstract In cooperatively breeding species, the presence of male helpers in a group often reduces the breeding female’s fidelity to her social partner, possibly because there is more than one potential sire in the group. Using a long-term study of cooperatively breeding superb fairy-wrens (Malurus cyaneus) and records of paternity in 1936 broods, we show that the effect of helpers on rates of extrapair paternity varied according to the helpers’ relatedness to the breeding female. The presence of unrelated male helpers in a group increased average rates of extrapair paternity, from 57% for groups with no unrelated helpers, to 74% with one unrelated helper, to 86% with 2+ unrelated helpers. However, this increase was due in equal part to helpers within the group and males in other groups achieving increased paternity. In contrast, helpers who were sons of the breeding female did not gain paternity, nor did they affect the level of extra-group paternity (which occurred at rates of 60%, 58%, 61% in the presence of 0, 1, 2+ helper sons, respectively). There was no evidence of effects of helpers’ relatedness to the female on nest productivity or nestling performance. Because the presence of helpers per se did not elevate extrapair reproduction rates, our results undermine the “constrained female hypothesis” explanation for an increase in extrapair paternity with helper number in cooperative breeders. However, they indicate that dominant males are disadvantaged by breeding in “cooperative” groups. The reasons why the presence of unrelated helpers, but not of helper-sons, results in higher rates of extra-group reproduction are not clear.

Hiphop: Improved paternity assignment among close relatives using a simple exclusion method for biallelic markers.

Assignment of parentage with molecular markers is most difficult when the true parents have close relatives in the adult population. Here, we present an efficient solution to that problem by extending simple exclusion approaches to parentage analysis with single nucleotide polymorphic markers (SNPs). We augmented the previously published homozygote opposite test (hot), which counts mismatches due to the offspring and candidate parent having different homozygous genotypes, with an additional test. In this case, parents homozygous for the same SNP are incompatible with heterozygous offspring (i.e., "Homozygous Identical Parents, Heterozygous Offspring are Precluded": hiphop). We tested this approach in a cooperatively breeding bird, the superb fairy-wren, Malurus cyaneus, where rates of extra-pair paternity are exceptionally high, and where paternity assignment is challenging because breeding males typically have first-order adult relatives in their neighbourhood. Combining the tests and conditioning on the maternal genotype with a set of 1376 autosomal SNPs always allowed us to distinguish a single most likely sire from his relatives, and also to identify cases where the true sire must have been unsampled. In contrast, if just the hot test was used, we failed to identify a single most-likely sire in 2.5% of cases. Resampling enabled us to create guidelines for the number of SNPs required when first-order relatives coexist in the mating pool. Our method, implemented in the R package hiphop, therefore provides unambiguous parentage assignments even in systems with complex social organisation. We also identified a suite of Z- and W-linked SNPs that always identified sex correctly.

Determining the level of extra-pair paternity in yellow-bellied prinias, a socially monogamous passerine

Previous work based on molecular evidence has shown that most socially monogamous birds follow a genetic polyandrous mating system. However, our knowledge about avian mating systems is heavily biased toward the north temperate zone, with data on tropical birds remaining relatively scarce. This uneven distribution of both phylogenetic and spatial sampling has hampered our understanding and interpretation of results. In this study, we investigated the frequency of extra-pair paternity (EPP) in a tropical population of yellow-bellied prinias (Prinia flaviventris) in Guangxi, southern China. A total of 129 individuals belonging to 24 nests were sampled, among which 12 out of 83 chicks (14.46%) in seven nests were found to be EPP offspring. In nests in which all nestlings were sampled, only five out of 56 chicks were EPP offspring, accounting for an unbiased EPP rate of 8.93%. This rate is below the average rate of EPP in the family Sylviidae. The possible causes of EPP in prinias and the occurrence of EPP in birds with high resource investment and intensive parental care are discussed. This study highlights the value of genome-wide markers in determining relatedness in a wild bird species without a reference genome.