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Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity in jawed vertebrates, and theory predicts that there should be mate choice for optimizing MHC constitution in the offspring. In a previous study, we demonstrated a non-random female choice of extra-pair males in the bluethroat (Luscinia svecica), yielding offspring that was closer to an intermediate MHC class II (MHCII) allele count than their within-pair halfsiblings. The present study tests whether social pairs with only within-pair young (WPY) in their brood, in the same study population, had a combined MHC-constitution closer to a presumed intermediate optimum, than social pairs with extra-pair young (EPY), with a corresponding pattern in their offspring. As expected, we found that WPY from pure WPY-broods were more MHC-optimal than WPY from mixed broods, but only in broods of young (second year) males. Correspondingly, there was a tendency for social pairs with only WPY in their brood to be more MHC-compatible than social pairs with EPY in their brood, when the male was young. Older bluethroat males have considerably larger testes than young males, and their higher sperm competitiveness could help them secure paternity in their own brood, also when they are not MHC-compatible. In other words, in the sexual conflict over paternity, females may be more likely to realise their preference for a MHC-compatible mate when paired to a young male. As a possible fitness indicator, immune responsiveness to an injected antigen (PHA) was elevated for offspring closer to "the golden mean" in MHCII allele count. Significance statement: This study contributes to our understanding of MHC-based mate choice in extra-pair mating systems, by showing that female bluethroats (Luscinia svecica) with an MHCII-compatible social mate tend to have no extra-pair young in their brood, but only when the social male is young. This elucidates a possible sexual conflict, in which older social males are able to override female preferences and prevent other males from gaining paternity in their brood through higher sperm production. Studying systems in which extra-pair paternity occurs offers an insight into the genetic benefits of mate choice, as extra-pair males, in contrast to social males, generally contribute only sperm. Further, the strict and thorough genotyping scheme applied in this study enabled us to demonstrate a preference for "the golden mean" in MHC-diversity in a species with one of the highest MHC class II-diversity known to date. [ABSTRACT FROM AUTHOR]

The Bluethroat subspecies Cyanecula svecica svecia occurs throughout the northern Palearctic. European C. s. svecia has been shown to follow a route west of the Himalaya to winter quarters in southern Asia. Out of 30 Bluethroats tagged with geolocators in eastern Siberia, we obtained one track suggesting that it migrated east of the Himalaya to a wintering area located in Myanmar. The different routes of western and eastern C. s. svecia implicate the presence of a migratory divide in Siberia, either formed in situ during the post-glacial colonization process or resulting from a secondary contact between different refuge populations. [ABSTRACT FROM AUTHOR]

The relatively untouched character of the floodplain of the Morava River is related to the long-forbidden entry into the Slovak-Austrian border zone designated by this river. Since 1990 the area is reserved for nature protection. A lack of knowledge about breeding bird assemblages from this valuable area is a consequence. Nest monitoring of reed passerines, focusing on the occurrence of the bluethroat (Luscinia svecica cyanecula) was performed in April–July 2018 and 2020 in the riparian vegetation of a selected section of the Šrek oxbow. Relation of habitat and weather factors were studied in six recorded reed passerine species - Acrocephalus schoenobaenus, A. arundinaceus, A. scirpaceus, Emberiza schoeniclus, Locustella luscinioides and Luscinia svecica cyanecula. For the target criteria species the bluethroat, nesting was also proven in 2020, with estimated density of 4. 7 breeding pairs /10 ha. Significant affinity for the open water was documented in A. arundinaceus, when the bluethroat preferred the points with broadleaved riparian banks.

WHITE-SPOTTED BLUETHROAT Luscinia svecica cyanecula is the latest addition to the Swedish bird fauna, with the first breeding in Scania in 2015. There were only three records on the Swedish West Coast north of Scania through 2016 and the first breeding was reported in 2018. Censuses performed in 2020 and 2021 revealed 12 and 17 singing males, respectively. Out of 39 singing males 2017-2021, 36 were found in Halland. Most birds were found in coastal wetlands with reedbeds, to which they arrived mainly in April. Nine males represented breeding pairs and second clutches were later observed for four breeding pairs. The Swedish expansion should be seen in the context of Danish immigration in combination with a large-scale advance via the Netherlands and Germany. The White-spotted Bluethroat belongs to those range-expanding taxa that are expected to increase due to warmer climate. As there is plenty of appropriate habitats, not least rapeseed fields, the conditions favour a continued range expansion in southern Sweden. [ABSTRACT FROM AUTHOR]

Aim: In temperate mountain ranges, sharp spatial variations in habitat heterogeneity and climate provide a perfect study setup to assess genetic and phenotypic differentiation in bird populations. In this paper, we analysed morphological divergence patterns across geographical and environmental gradients, in correlation with genetic differentiation and geographical isolation, in the breeding grounds of a long‐distance migratory passerine. Location: Northwestern Iberian mountains. Taxon: The Iberian bluethroat, Luscina svecica azuricollis. Methods: We collected a sample of 625 Iberian bluethroats across their whole breeding range to measure body weight and tarsus length, as well as wing length and pointedness. Morphological differentiation across geographical (latitude and elevation) and environmental (climate and vegetation) gradients was assessed using generalized linear mixed models. Additionally, the role of genetic distance and geographical isolation as drivers of morphological differentiation was evaluated with Mantel tests. Results: Bird morphology varied significantly with latitude and elevation, but not with climate or vegetation. In the case of latitude, morphological differences in body size were contrary to Bergmann's rule statements. All biometric and morphometric variables diverged among localities. A similar trend was found for genetic clusters, except for wing shape. Body weight and wing length were both correlated with geographic distance, while only the former varied with genetic differentiation. The greatest genetic and phenotypic differentiation was detected in the southernmost mountain range, that holds the most geographically isolated genetic group. Main conclusion: Evidence suggests that the strong morphological differentiation observed in the Iberian breeding bluethroat across geographical gradients results from the combination of unambiguous deterministic forces, such as ecological selection mechanisms, and other factors, such as geographical isolation, that can be either deterministic, stochastic or both, all acting at different scales. [ABSTRACT FROM AUTHOR]

Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity, and theory predicts that the optimal number of alleles is intermediate rather than maximal. Support for such an intermediate optimum in MHC allele count has mainly been demonstrated in studies on parasite load and reproductive traits. In this study we tested if an intermediate number of MHC class II (MHCII) alleles based on positively selected sites was correlated with an increased skin‐swelling response to two consecutive injections of phytohaemagglutinin (PHA) in bluethroat Luscinia svecica nestlings. We found that nestlings that were closer to the population mean in their number of alleles had a higher response to the first injection, supporting an intermediate, optimal number of alleles. After the second PHA injection, we found that the skin swelling was associated with MHCII allele count only at the among‐brood level, and with paternity (extra‐pair offspring had a larger swelling than within‐pair offspring). We therefore conclude that the PHA response is partly correlated with MHCII allele count, but that additional factors must be involved in both the PHA response and in female extra‐pair mate choice in this species. [ABSTRACT FROM AUTHOR]

Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen‐mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra‐pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra‐pair males in a nonrandom, self‐matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra‐pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade‐off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra‐pair mating is adaptive through altered genetic constitution in offspring. [ABSTRACT FROM AUTHOR]

Copyright of Acta Ornithologica is the property of Polska Akademia Nauk, Muzeum i Instytut Zoologii and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Age-related variation in breeding performance is well-known in birds. Similarly, plumage ornamentation as a signal of male quality may affect breeding performance. However, because of inter-correlation between age and plumage ornamentation, it is difficult to estimate the relative contribution of these factors on breeding performance in natural variation. In the current study, we examined the relationship between breeding characteristics, age and throat ornament size of bluethroat males (Luscinia s. svecica). The study was conducted on 96 males in the Krkonoše Mountains, Czech Republic, in 2003-2011. The results show that older males had higher reproductive performance: they arrived earlier, were more likely to be territorial, had larger clutches and thus had more hatchlings. On the other hand, ornamentation had a few, inconsistent correlations with breeding performances: well-ornamented males had fewer mates but had more fledglings. Our results suggest that age rather than ornamentation size is the main correlate of variation in breeding performance. [ABSTRACT FROM AUTHOR]

Postcopulatory sexual selection may select for male primary sexual characteristics like sperm morphology and sperm motility, through sperm competition or cryptic female choice. However, how such characteristics influence male fertilization success remains poorly understood. In this study, we investigate possible correlations between sperm characteristics and paternity success in the socially monogamous bluethroat (Luscinia svecica svecica), predicting that sperm length and sperm swimming speed is positively correlated with paternity success. In total, 25% (15/61) of broods contained extra-pair offspring and 10% (33/315) of the offspring were sired by extra-pair males. Paternity success did not correlate significantly with sperm morphology or any aspects of sperm motility. Furthermore, sperm morphology and sperm motility did not correlate significantly with male morphological characters that previously have been shown to be associated with paternity success. Thus, the sperm characteristics investigated here do not appear to be strong predictors of paternity success in bluethroats. [ABSTRACT FROM AUTHOR]

Abstract: Genotyping of classical major histocompatibility complex (MHC) genes is challenging when they are hypervariable and occur in multiple copies. In this study, we used several different approaches to genotype the moderately variable MHC class I exon 3 (MHCIe3) and the highly polymorphic MHC class II exon 2 (MHCIIβe2) in the bluethroat (Luscinia svecica). Two family groups (eight individuals) were sequenced in replicates at both markers using Ion Torrent technology with both a single‐ and a dual‐indexed primer structure. Additionally, MHCIIβe2 was sequenced on Illumina MiSeq. Allele calling was conducted by modifications of the pipeline developed by Sommer et al. (BMC Genomics, 14, 2013, 542) and the software AmpliSAS. While the different genotyping strategies gave largely consistent results for MHCIe3, with a maximum of eight alleles per individual, MHCIIβe2 was remarkably complex with a maximum of 56 MHCIIβe2 alleles called for one individual. Each genotyping strategy detected on average 50%–82% of all MHCIIβe2 alleles per individual, but dropouts were largely allele‐specific and consistent within families for each strategy. The discrepancies among approaches indicate PCR biases caused by the platform‐specific primer tails. Further, AmpliSAS called fewer alleles than the modified Sommer pipeline. Our results demonstrate that allelic dropout is a significant problem when genotyping the hypervariable MHCIIβe2. As these genotyping errors are largely nonrandom and method‐specific, we caution against comparing genotypes across different genotyping strategies. Nevertheless, we conclude that high‐throughput approaches provide a major advance in the challenging task of genotyping hypervariable MHC loci, even though they may not reveal the complete allelic repertoire. [ABSTRACT FROM AUTHOR]

Telomere length is related to aging in many eukaryotes and the rate of telomere attrition has been suggested to reflect individual genetic quality. Telomere length could thus have implications for mate choice. We investigated telomere length variation in bluethroat Luscinia svecica families with mixed paternity, including social parents, extra-pair fathers and nestlings, testing whether telomere length is associated with social and/or extra-pair mate choice through assortative mating or selection of mates with relatively long telomeres. In adults, relative telomere length (rTL) did not differ between the sexes, nor between two age categories. In chicks, however, rTL decreased with body mass at sampling (an index of nestling age). We found a positive correlation between the rTL of social mates, suggesting assortative mating with respect to telomere length or a correlative thereof. However, extra-pair males did not differ from social mates in rTL, and accordingly there was also no difference between within- and extra-pair young (i.e. half-siblings) when controlling for the effect of mass. We found no relationships between telomere length, age and fitness-related traits in adults, but an intriguing year-difference in telomere length in both sexes. In conclusion, we found no support for the idea that females choose extra-pair males based on their telomere length, but social mate choice seems to be influenced by rTL, possibly through its co-variation with aspects reflecting individual quality, like early arrival at the breeding grounds. [ABSTRACT FROM AUTHOR]

The assessment of evolutionary divergences within subspecies complexes provide an effective short-cut for estimating intraspecific genetic diversity, which is relevant for conservation actions. We explore new evidence supplementing the existing knowledge about the singularity of Iberian bluethroats within the Luscinia svecica subspecies mosaic. We compared biometric traits of Iberian males (L. s. azuricollis) to the closest subspecies (L. s. cyanecula, L. s. namnetum and L. s. magna) using general linear models and analysed the correlations between biometric and genetic differentiation (based on nuclear microsatellites) among the target subspecieswith aMantel test. Biometric differenceswere calculated using 63 museum skins and 63 live specimens. Genetic distances were estimated in a sample of 136 individuals. An additional characterisation of the plumage of Iberian males was shaped from 22 live specimens. We highlight the distinctiveness of Iberian birds within the subspecies mosaic since L. s. azuricollis had longer wings than L. s. cyanecula and L. s. namnetum, but shorterwings than L. s. magna. Indeed, L. s. azuricollis had longer tarsus and bill than L. s. namnetum, but shorter bill than L. s. magna. Biometric divergence was not significantly associated with genetic distance. Iberian males showed an all-blue plastron in 77% of specimens, a mostly non-marked black band and no white band, which distinguished them from males of L. s. cyanecula and L. s. namnetum. We conclude the importance of considering phenotypic and genotypic differences at subspecies level, which is essential for designing realistic conservation strategies addressed to preserve species genetic diversity patterns. [ABSTRACT FROM AUTHOR]

We explored whether habitat characteristics surrounding the song posts that male Bluethroats (Luscinia svecica) use to attract females and defend their territories might be associated with males' quality, in terms of body condition and age (used here as a proxy of their experience). Data were collected at Sierra de Béjar (province of Salamanca, central- western Spain).Overall,we characterized the habitat and captured 44male Bluethroats at their song posts in 2011 and 2012. The characteristics of male Bluethroats' song posts and their surrounding habitat were associated with both the birds' age and body condition. Second-year Bluethroats were observed to sing in places with higher abundance of spi- ders as compared to older birds. Moreover, Bluethroats surrounded by a higher proportion of grasslands and with more Opiliones/spiders were found to carry more fuel. [ABSTRACT FROM AUTHOR]

This report presents data on scarce passerine migrants recorded in Britain during 2014. It was a record year for three of the birds discussed here: Red-breasted Flycatcher Ficedula parva, Little Bunting Emberiza pusilla and 'Siberian Chiffchaff' Phylloscopus collybita tristis, although there are just seven years of data for the last taxon. It was the second-best year on record for Barred Warbler Sylvia nisoria and Olive-backed Pipit Anthus hodgsoni, and the third-best for Short-toed Lark Calandrella brachydactyla. At the opposite end of the spectrum, 2014 was notable as a poor year for four species: Melodious Warbler Hippolais polyglotta, Aquatic Warbler Acrocephalus paludicola, Bluethroat Luscinia svecica and Ortolan Bunting £. hortulana. Numbers of all four of these species appear to be in continuing decline, and much the same applies to Golden Oriole Oriolus oriolus and Tawny Pipit A. campestris. [ABSTRACT FROM AUTHOR]

The present study was performed in the dry steppe subzone of the Saratov Trans-Volga region during six breeding seasons (years 2010-2015). Habitat features that affected the structure of bluethroat ( Luscinia svecica) population were analyzed. The biotopes present in the area investigated differed greatly with regard to the dynamics of environmental conditions during the breeding season. Population density and spatial distribution of nesting territories in each habitat were used to characterize habitat selection, and the breeding productivity was used to assess the result of this selection. Bluethroat population density was always higher in uniformly suitable habitats that provided favorable conditions for nest building and feeding. Part of the population occupied habitats of a lower quality; however, these habitats might be used as 'reserve habitats' during breeding seasons characterized by extreme conditions of the environment. Moreover, the contribution of a number of reproductive parameters to the overall breeding productivity was assessed. The present study showed that the starting date and length of fertile period, as well as nest mortality, are the major parameters that determine the variation in breeding productivity between different habitats and seasons. The results are discussed in view of the contributions of population groups to reproduction. [ABSTRACT FROM AUTHOR]

Male colouration has a key role in signalling individual quality during the breeding season. Although winter plumage probably correlates with summer plumage, few studies have focused on the determinants of male colouration during the non-breeding period. If plumage colouration is related to an individual's age or is strongly correlated with body condition during the non-breeding period, this trait could be used by conspecifics to assess quality, origin or status of a given individual.Here,we analysed plumage colouration and body size of male Bluethroats (Luscinia svecica cyanecula) wintering in SE Iberia. We found that young individuals had narrower black bands and wider white bands than adult individuals in their throat patch.Also, thewidth of the chestnut band increased with later capture date. Finally, blue throat colouration was positively correlated with tail length and negatively correlatedwith tarsus length.We could not find any significant relationship between throat patch colouration and bodymass.We concluded that individual's age and capture date were significantly related to black and chestnut throat colouration, respectively. Therefore, these coloured bands could provide reliable cues on individual's age and their geographical origins. The variability of plumage colouration of wintering Bluethroats provides an excellent study system in which to test further hypotheses on the role of the throat patch colouration outside the breeding season. [ABSTRACT FROM AUTHOR]

The highly fragmented landscape structures of coastal salinas are known to result in decreased terrestrial bird abundance, species richness and diversity but to promote original assemblages dominated by specialist species, such as the Bluethroat Luscinia svecica namnetum. This species is mainly found at the core of these salinas, where the landscape characteristics are a priori the most hostile for terrestrial birds. The aim of this study was to test whether individuals of a specialized species like the Bluethroat may offset such landscape constraints by expanding their home ranges. We therefore radio-tracked 21 males in 2013 and 2014 in the salinas of the Marais du Mès (Parc Naturel Régional de Brière, Western France). The data of the 18 best-monitored males were used to carry out a hierarchical partitioning of variance to test the relative influence of landscape characteristics, individual characteristics and distance to other males on their home-range sizes. We found that landscape characteristics were the factors that best explained home range sizes. Home-range sizes were significantly smaller in diversified landscapes composed of tidal creeks and salt-marsh patches and tended to be larger in landscapes dominated by the aquatic matrix consisting of water ponds. The results of this study demonstrate that although a few bird species are able to select a priori hostile landscapes, they can offset such constraints by expanding their home-range size. [ABSTRACT FROM AUTHOR]

Long-distance migratory birds are potentially exposed to a range of blood sucking arthropods that transmit avian blood parasites. Because of differential vector exposure, the parasite fauna may vary in different habitat types, among populations, or even within populations where individuals travel to different areas during migration. We applied PCR-based molecular techniques to determine patterns of blood parasite occurrence in adults of seven geographically isolated Bluethroat populations, belonging to three distinct subspecies differing in habitat preferences and wintering areas ( Luscinia svecica svecica, L. s. cyanecula, L. s. namnetum). Moreover, to elucidate potential transmission of blood parasites on breeding sites, we tested adults of the relatively sedentary White-throated Dipper ( Cinclus cinclus) from a Norwegian population. Across populations, we detected infection of at least one blood parasite genus in 68.5 % (139/203) of adult Bluethroats. The most common parasite genus was Plasmodium (10 lineages, 33.5 % of surveyed individuals), present in all seven populations, followed by Leucocytozoon (four lineages, 31.5 %) and Haemoproteus (two lineages, 4.9 %). We recorded multiple infections in 26.1 % of individuals. Leucocytozoon was found only in svecica inhabiting mountainous/subalpine areas with high abundance of blackflies, the main vector for this parasite. In Plasmodium, two lineages (BT6 and GRW4) were confined to specimens from svecica populations. In contrast, Lineage SGS1 was dominated by southern birds of the subspecies cyanecula and namnetum. Our data suggest transmission of Leucocytozoon on the breeding grounds in Norway as the same lineages were found in relatively sedentary White-throated Dippers as in migratory Bluethroats. We discuss these results in light of the ecological differences between the host populations, affecting their exposure to potential blood parasite vectors. [ABSTRACT FROM AUTHOR]

The leg bones of a small passeriform bird are described from the early Oligocene (29 Mya) of Poland. The specimen is the earliest complete passerine leg with elements in articulation described so far, and increases the known diversity of the very scanty records of the oldest European passeriforms. In general proportions the leg bones resemble those of Luscinia svecica and other species that live in shrubs. Assignment to a family within the passerines is not possible because of the incompleteness of the fossil. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined the migration strategy and winter distribution of Luscinia (L.) svecica (s.) cyanecula and L.s. namnetum along the eastern Atlantic coast of Iberia and West Africa. Topics discussed include the increase in the body mass of cyanecula during the migratory period, the differences in the migration speed and stopover behaviour of the subspecies and the greater potential non-stop flight range in cyanecula.

Spermatozoa are among the most variable animal cell types, and much research is currently directed towards explaining inter- and intraspecific variation in sperm form and function. Recent comparative studies in passerine birds have found associations between the level of sperm competition and both sperm length and sperm velocity. In species with sperm competition, postcopulatory sexual selection may shape the morphology of sperm as adaptations to the female environment. The speed of evolutionary change in sperm morphology at the species level is largely unknown. In this study, we analysed variation in sperm morphology among morphologically distinct and geographically isolated bluethroat subspecies in Europe. Consistent with previous studies, our analyses of mtDNA and nuclear introns suggest recent divergence and lack of lineage sorting among the subspecies. We found significant divergence in total sperm length and in the length of some sperm components (i.e. head and midpiece). There was a significantly positive relationship between pairwise divergences in sperm morphology and mitochondrial DNA, suggesting a role for genetic drift in sperm divergence. The magnitude of sperm length divergence was considerably higher than that in other geographically structured passerines, and even higher than that observed between several pairs of sister species. We hypothesize that the rapid sperm evolution in bluethroats is driven by sperm competition, and that strong postcopulatory sexual selection on sperm traits can lead to rapid speciation through reproductive incompatibilities. [ABSTRACT FROM AUTHOR]

The article reports on the spatial behaviour and habitat use of first-year Bluethroats Luscinia svecica during migration. It examines the impact of tide on home range size of Bluethroats at coastal marshes by using data on radio-tagged birds in Northern Iberia. It discusses the role played by coastal marshes as stopover and fuelling sites for birds during migration period. It mentions the stopover behavior of land birds, which depend on these sites.

Breeding site fidelity can be determined by environmental features, which depending on their heterogeneous distribution may shape the genetic landscape of a population. We used 10 microsatellite loci to study the genetic variation of 83 bluethroats (Luscinia svecica azuricollis) across 14 localities within the Spanish breeding population and assess the relative influence of different habitat characteristics (physiography and vegetation) on genetic differentiation. Based on the genetic variation of this population, we identified 3 geographically consistent genetic clusters that on average showed a higher genetic differentiation than among other north European populations, even those belonging to different subspecies. The inferred genetic clusters occurred in geographic areas that significantly differed in elevation. The highest genetic differentiation was observed between sites at different mountain ranges, as well as between the highest altitude sites in the northeastern locale, whereas vegetation type did not explain a significant percentage of genetic variation. The lack of correlation between geographic and genetic distances suggests that this pattern of genetic structure cannot be explained as a consequence of isolation by distance. Finally, we discuss the importance of preserving areas encompassing high environmental and genetic variation as a means of preserving evolutionary processes and adaptive potential. [ABSTRACT FROM PUBLISHER]

The article presents a study on the relationship level of breeding and non-breeding areas of European white-throated bluethroats. It determines the principal migration areas, wintering locations, and migration patterns of this species using information obtained during migration periods in autumn, winter, and spring. It discovers that the bluethroats migrate in a loop-migration pattern within the Mediterranean region particularly in Iberia.

Copyright of Opera Corcontica is the property of Sprava Krkonosskeho Narodniho Parku and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In birds, the number of sperm trapped between the perivitelline membranes around the ovum is an estimate of sperm numbers present at the time and place of fertilisation in the female reproductive tract. Sperm numbers may vary among species and between eggs in a clutch and can provide information about sperm utilisation and mechanisms of sperm competition. Here, we describe patterns of variation in sperm numbers through the egg-laying sequence in three passerines in which extra-pair paternity is common, but copulation behaviour differs. Sperm numbers showed no systematic change across the laying sequence in blue tits ( Cyanistes caeruleus), but decreased significantly with laying order in bluethroat ( Luscinia svecica) and tree swallow ( Tachycineta bicolor) clutches. This is consistent with observations that blue tits regularly copulate throughout the laying sequence, while bluethroats stop mate guarding and tree swallows reduce their copulation frequency once the first egg is laid. Nevertheless, cases of a sudden increase in sperm numbers in clutches of bluethroats and tree swallows suggest that successful inseminations also occurred after laying started. In blue tits and bluethroats, sperm numbers were not higher on extra-pair sired eggs than on eggs sired by the social male, suggesting that extra-pair copulations are not timed to the period of peak fertility for each egg. More extra-pair offspring originated from eggs laid early in the sequence in blue tits, while there was no systematic bias in bluethroats. Our results suggest that copulations during the laying sequence are predominantly performed by within-pair males in our study species. [ABSTRACT FROM AUTHOR]

As part of the expanding cultivation of renewable primary products, oilseed rape has become a prominent part of the agricultural landscape of many European countries. However, the ecological impacts of increasing cultivation of oilseed rape have received little attention so far. In this study, we provide the first systematic investigation of the suitability of oilseed rape as a habitat for the Bluethroat ( Luscinia svecica cyanecula), an endangered and highly specialized bird species. We conducted territorial mapping and a habitat analysis, revealing the distinct habitat requirements of L. s. cyanecula in oilseed rape fields over three breeding seasons. The soil type was identified as the crucial factor for habitat occupancy. It acts as a surrogate for soil moisture and this in turn decisively influences food availability. Ditches can further improve habitat quality, whereas reed is not a necessary structure, although it is a regular feature in the primary habitat of the Bluethroat. Occupied oilseed rape stands were structurally different from the semi-natural reed habitat, but provided similar essential habitat requirements, such as shelter from predation and moist, bare soil. Our results clearly demonstrate the utilization of oilseed rape by a rare and threatened wetland bird species and suggest that this crop may act as a secondary habitat. [ABSTRACT FROM AUTHOR]

The article discusses research on plumage variability and biometric features of bluethroat Luscinia svecica in central Iberia. The bird is described as a polytypic and territorial passerine that displays sexual dimorphism through plumage coloration. It is noted that the intensity of the blue throat patch of the male bird depends on sexual selection and affects female mate choice. Details concerning site selection and bird subject collection are reported. Aside from the presence or absence of throat spot colour, the study also noted colour variation of lore feathers.

Differences in vocalization between subspecies of songbirds may influence intraspecific interactions including mate choice and territorial behavior, and contribute to their further divergence by strengthening pre-mating reproductive isolation. We have recently shown that songs of two Bluethroat subspecies, Luscinia svecica svecia and L. s. cyanecula, differ in spectral characteristics and structure. Here, in a first experimental test of whether these differences are biologically relevant, we compared responses of L. s. svecica males to both types of songs. Altogether 19 males from a subartic population in Abisko, Sweden, were exposed to playbacks of songs from the two subspecies, accompanied by display of a stuffed Bluethroat lacking subspecies-specific colour marks. These stimuli were presented in random order, separated by over 1 h. We evaluated two largely uncorrelated components of male responses: non-vocal territorial behavior, and singing activity. A significant difference in reaction to subspecies playbacks was observed in aggressive behavior: independently of the song order, males generally responded more strongly to playback of their own subspecies. In contrast, playback order rather than subspecies identity significantly influenced the singing activity, which usually increased in the second trial. A more detailed analysis nevertheless suggested that vocal responses of birds exposed first to playback of their own subspecies were stimulated in the subsequent trial but not vice versa. Our results show that Bluethroats clearly discriminate the two song types, indicating the potential for subspecies recognition. Further experimental work is needed to assess the general validity of these patterns. [ABSTRACT FROM AUTHOR]

The article presents information on a study which examined variation in characteristics of Bluethroat, Luscinia svecica, at subspecies and population levels. A review of the related literature is given. The subspecies considered for the study were the svecica and cyanecula. The field observations were conducted out during the breeding season of April to June, 2006-2009. A Marantz PMD 222 3-head monotape recorder, Sennheiser MKH 70 or MKH 50 directional microphones, and Sony UX-S 60 audio tapes were utilized to record songs made by males of both subspecies. Identified factors that influenced variation included body size and habitat selection.

We examined the influence of point-of-departure climatic variables in autumn, namely surface ambient temperature, the number of wet days and growing season length (GSL), and the influence of the point-of-departure surface ambient temperature in spring on the passage dates of 2 long-distance migrant passerine species, the lesser whitethroat Sylvia curruca and the bluethroat Luscinia svecica, at Eilat, Israel, from 1985 to 2004. Ambient temperature at the breeding grounds of the lesser whitethroat increased at a rate of 0.147°C yr-1. There was no significant change in the ambient temperature at the breeding grounds of bluethroat, nor was there a change in the number of wet days or GSL at the breeding grounds of either species. We found that the median autumn passage date of lesser whitethroat in Eilat was delayed by 21.5 d, or by 5.43 d for every 1°C increase in ambient temperature at their breeding grounds. We found no change in the median autumn passage date of bluethroat in Eilat. The median spring passage date and the ambient temperature at the wintering grounds of both species did not change significantly. We found no significant correlation between the median spring passage dates of birds of either species and the ambient temperature at their wintering grounds. We conclude that migration phenology of long-distance migrants can be strongly correlated with fluctuations in climatic variables, especially the ambient temperature at the breeding grounds of a species. [ABSTRACT FROM AUTHOR]

The genes of the major histocompatibility complex (MHC) are important model genes for understanding selective forces in evolution. Here, we document, using a cloning and sequencing approach, high polymorphism at the exon 2 of the MHC class II B (MHCIIB) genes in the bluethroat ( Luscinia svecica); a minimum of 61 unique alleles were detected in 20 individuals, and at least 11 functional loci. In addition, several pseudogenes were revealed. The specimens originated from three different bluethroat subspecies ( azuricollis, cyanecula and svecica), and we also analysed four specimens of the closely related thrush nightingale ( L.  luscinia) for comparison. Phylogenetic analyses of the functional alleles revealed 258 equally parsimonious trees with poor statistical support for the majority of nodes. The distribution of the sequences in the trees point to an ancestral origin of the polymorphism in MHC class II B genes, a portion of which predated the phylogenetic split between the bluethroat and the thrush nightingale. Strong signatures of balancing selection were uncovered for the codons coding for the peptide-binding residues of the functional MHCIIB exon 2 alleles. Our results highlight the importance of duplication and recombination events for shaping passerine MHC and give insights in the evolutionary dynamics of MHC variation among closely related taxa. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the migration strategy, specifically stopover duration and fuel load, of bluethroats Luscina svecica cyanecula in northern Iberia during the autumn migration period. Data were obtained in the reed bed Phragmites australis that surrounds the Badina de Escudera lagoon near Villafranca, Spain. Stopover duration was calculated by means of minimum stopover duration and Cormack-Jolly-Seber models. Findings reveal that the stopover duration was nearly 30 days and that adults were more fuel loaded than juveniles. The article notes that the results suggest that birds with long stopovers were not true fuelling migrants but wintering birds with balanced energy budgets.

Extra-pair paternity is common in birds and much research has focussed on the selective advantage of extra-pair matings for both sexes. In contrast, little attention has been given to the fact that in most species the majority of offspring are sired by the social male. We investigated whether extra-pair matings of female bluethroats ( Luscinia svecica) are constrained by the presence of the pair male, by detaining males in cages on their territories for one morning during the peak of female fertility. The proportion of offspring sired by extra-pair males was higher in broods where males had been detained (35%) than in control broods (16%), while the proportion of broods that had at least one extra-pair offspring did not differ significantly between experimental (65%) and control broods (44%). Within the experimental group, levels of extra-pair paternity were not related to the day of experiment in relation to start of egg laying, but males caught early in the morning lost more paternity than males caught later on. Our results show that pair males exert constraints on the frequency of extra-pair paternity by being present during the period of peak fertility, which could be a direct effect of their mate guarding effort and/or due to an advantage in sperm competition for pair males. [ABSTRACT FROM AUTHOR]

The optimal mating system is rarely the same for males and females—whereas males usually benefit from attracting additional females to the territory, this could incur costs for the resident female. Females should therefore prevent prospecting females from settling on the territory. We studied the male and female behavioral and hormonal responses to simulated female territorial intrusions in free-living bluethroats during the pre-laying period. In the study population, polygyny occurs with potential fitness costs for the resident female. We recorded different aspects of aggressive behavior before and after presentation of a live female decoy and playback of female song. These behaviors were compared with a set of intrusions using a male decoy. At the end of a trial, the birds were captured, and blood samples were analyzed for androstenedione, testosterone, estradiol and corticosterone. During the pre-intrusion period, none of the females were observed. Females generally responded strongly to the female decoy by increased flight rate, vocalizations, and by conspicuous perching. Nearly half of the males displayed to the female decoy but never while the resident female was present. We suggest that resident female aggression in bluethroats prevents courtship by her mate and signals her mating status to the female intruder. Female aggression could therefore prevent additional females to settle on the territory and shape the mating system. Females that responded with song had higher levels of estradiol. These findings suggest that estradiol may support aggression in breeding female birds. [ABSTRACT FROM AUTHOR]

The key patch approach assumes that metapopulations in fragmented landscapes are likely to be viable with at least one "key" sub-population that is sufficiently large to ensure re-colonization of surrounding minor habitat patches. It is based on a minimum viable number of breeding pairs and within-breeding season dispersal distance, linked to size of the animal and longevity. It was tested using census data of 15 wetland bird species (bearded tit, bluethroat, great reed warbler, sedge warbler, Savi's warbler, grasshopper warbler, spotted crake, water rail, common snipe, common teal, garganey, little bittern, night heron, great bittern and marsh harrier) in 14 wetland complexes of variable size (3-55 km2) spread across the Netherlands (distances ranging 4-156 km). First, for each species it was assessed whether a wetland harbored a key subpopulation, which was the case for the sedge warbler (7 key subpopulations), grass-hopper warbler (2), water rail (2), bearded tit, bluethroat, Savi's warbler, common teal, garganey, great bittern and marsh harrier (all one key subpopulation).Together with the adjacent sub-populations present within breeding season dispersal distance, 10 out of the 15 studied species formed viable meta-populations. This was compared with the trend in the census data of 13 species for 1990-2000 and was found to correspond significantly (likelihood ratio test, P = 0.003): species without a viable meta-population had declined (2 out of 4) or remained stable (2 out of 4), whereas viable meta-populations had increased (6 out of 9) or remained comparatively stable (2 out of 9). One wetland complex, the Oostvaardersplassen, stood out in that it haboured key sub-populations for 9 out of the 15 species studied. Variation in quantity of specific habitat (area or perimeter marshland, woodland or open water) in a wetland complex was of limited importance explaining abundance patterns, since all covaried strongly with total area among the wetland complexes, with the exception of water perimeter. Apparently, these wetlands on peat harbour largely similar landscapes. Indeed, population sizes of most birds covaried strongly and in a PCA two distinct clusters of species were identified that shared high numbers of breeding pairs in the same, larger, wetland complexes, the first (3 species) including the great reed warbler, and the second (9 species) the water rail. [ABSTRACT FROM AUTHOR]

In passerine species with frequent extrapair mating, young (second calendar year) males often have a lower fertilization success than older (after second calendar year) males. This pattern might be explained by male- or female-driven mechanisms, such as female preference for older males or higher competitive ability of older males. In this study we measured the size of the testes, the seminal glomera and the cloacal protuberance as well as the size and motility of the sperm, in individual bluethroats Luscinia svecica. In this species, nearly all extrapair fertilizations (EPFs) are obtained by older males. We found that the mass of the testes and the seminal glomera were highly positively correlated and that older males had significantly larger testes (38%), seminal glomera (15%) and cloacal protuberance (23%) than young males. In contrast, there was no difference between age groups in average sperm size or sperm motility. Our results are consistent with the idea that higher fertilization success by older males in this species is due to their higher rate of sperm production, allowing larger ejaculates and/or more frequent copulations. Unequal sperm production capacities by young and older males have important implications for the interpretation of paternity patterns in extrapair mating systems. [ABSTRACT FROM AUTHOR]

Many species of birds show evidence of secondary contact zones and subspeciation in their Scandinavian distribution range, presumably resulting from different post-glacial recolonization routes. We investigated whether this is the case also in the Scandinavian bluethroat Luscinia svecica, a species that has been suggested to consist of two separate populations: one SW-migrating and long-winged ( L. s. gaetkei) breeding in southern Norway, and one shorter-winged ESE-migrating ( L. s. svecica) in northern Scandinavia. We sampled males at eleven breeding sites from southern Norway to northernmost Sweden. There were no morphological differences or latitudinal trends within the sample, neither were there any genetic differences or latitudinal trends as measured by variation in AFLP and microsatellite markers. Stable isotope ratios of throat feathers moulted on the wintering grounds showed no, or possibly marginal differences between birds from southern Norway and northern Sweden. We also re-measured old museum skins that in previous studies were classified as L. s. gaetkei, and found marginally longer wings in birds from the southern part of the Scandinavian breeding range. The difference, however, was much smaller than proposed in earlier studies. We conclude that there is no evidence of a genetic population structure among Scandinavian bluethroats that would suggest the presence of a zone of secondary contact. Finally we discuss whether the presumed subspecies gaetkei ever existed. [ABSTRACT FROM AUTHOR]

The adaptive function of female extrapair mating in socially monogamous passerines is currently debated. In the bluethroat ( Luscinia s. svecica), a previous study showed that offspring sired by extrapair males had a higher cell-mediated immunity than their within-pair half siblings, suggesting an immunogenetic benefit of extrapair mating in this species. Here, we expanded that dataset with two more years and investigated the association between extrapair paternity and microsatellite multilocus heterozygosity, in addition to cell-mediated immunity. We found that extrapair offspring were more heterozygous than their within-pair half siblings, and corroborated the previous finding of enhanced cellular immunity in extrapair offspring in this four-year dataset. The increased heterozygosity among extrapair offspring appeared to be a result of extrapair mates being less genetically similar than pair mates, and also less genetically similar than expected by random choice. Together with previous findings in this species, showing that the majority of females participate in extrapair copulations, our results indicate a postcopulatory cryptic female choice of genetically dissimilar males. The enhanced cellular immunity and increased heterozygosity were not related to each other, and hence our results indicate two independent genetic benefits of extrapair mating in the bluethroat. [ABSTRACT FROM AUTHOR]

Information about male infertility in free-living birds is scarce, but anecdotal and circumstantial evidence suggests that it does occur regularly at a low frequency. In this paper we document three cases of azoospermia in two passerine species, the willow warbler Phylloscopus trochilus and the bluethroat Luscinia svecica at their breeding grounds in South Norway. In willow warblers, two males out of a sample of 50 territory holders had no sperm in their seminal glomera, the storage site of sperm ready for ejaculation. The two males also had very small testes. One out of 48 bluethroat males also had no sperm in the seminal glomera. This male had an extreme asymmetry of the testes, with the right testis being about twice as large as the left. He also failed to fertilize any eggs in his own nest, as well as in neighbouring nests, as revealed by microsatellite genotyping. Thus, the proportion of males without sperm seems to be at a magnitude of a few (2–4) percent in both species. These are among the first estimates of the frequency of azoospermia in wild birds. Our results indicate a significant risk for sexually monogamous females of laying unfertilized eggs, which could favour the evolution of extra-pair copulation as a fertility insurance strategy in females. [ABSTRACT FROM AUTHOR]

Subspecies complexes may provide valuable insights into the early stages of the speciation process. The bluethroat ( Luscinia svecica) consists of many morphologically distinct subspecies that differ most strikingly in the ornamental colour pattern of the male throat. We investigated the genetic and phenotypic differentiation in this subspecies complex, using (i) microsatellite genotyping (11 loci) of a sample of 364 individuals from bluethroat populations in Europe and Asia, and (ii) spectrometric and morphological measurements of a sample of 131 museum skin specimens. Population genetic analyses, based on microsatellite allele frequency variation, revealed a slight but significant overall population differentiation ( FST = 0.042). There was a well-differentiated southern group of subspecies with white or no throat spots and a less-differentiated northern group of chestnut-spotted populations. Phylogenetic analyses indicated that the southern all-blue and white-spotted forms are ancestral to the chestnut-spotted subspecies. In addition to the qualitative variation in throat plumage pattern already described in the literature, we found significant quantitative variation among subspecies in hue, chroma and brightness of the ultraviolet (UV)/blue throat coloration, and this variation seemed to be unrelated to the phylogenetic distance between subspecies. [ABSTRACT FROM AUTHOR]

Extrapair paternity in birds has been the focus of an increasing number of studies over the last decades. Nevertheless, there is little knowledge about extrapair copulation (EPC) behavior. In this study, we investigate whether female bluethroats ( Luscinia s. svecica) with no extrapair offspring (EPO) in their broods really have been sexually monogamous or if they have copulated with extrapair males. We used an experimental approach to prevent transfer of sperm from the social male during copulation by fitting a rubber tube around the cloaca of randomly chosen males. If the females mated to these males do not participate in EPCs, they will produce infertile eggs, whereas females that copulate with extrapair males will only produce EPO. We found that 87% ( n=15) of the experimental pairs compared to only 36% ( n=51) of unmanipulated pairs produced EPO. Our result therefore suggests that females having no EPO may still have copulated with extrapair males and that promiscuity may be an obligate sexual strategy among bluethroat females. [ABSTRACT FROM AUTHOR]

The brilliantly coloured throat patch in male bluethroats, Luscinia s. svecica, influences their social mating success and both within- and extra-pair paternity. Female bluethroats are highly variable in their extent of throat coloration, from entirely drab to almost male-like. The ornament in females could be due to a genetic correlation between the sexes. However, it has been shown that male bluethroats prefer brightly coloured females, suggesting that female ornamentation has evolved by direct sexual selection on females through male choice. Males may prefer extravagant traits in females if these reliably signal female quality, such as resistance to disease. We investigated whether variation in the extent of structural and melanin plumage ornamentation in female bluethroats reflects cell-mediated immune response. We caught the females at their nests and measured their immune response as a swelling following a challenge by phytohemagglutinin. An analysis of the data from two years of study revealed that the cell-mediated immune response was not related to female ornamentation. However, the immune response was strongly correlated with female body condition. Thus, our results do not support the hypothesis that female ornament expression signals quality in terms of cell-mediated immunity. [ABSTRACT FROM AUTHOR]

Abstract: Between 1984 and 2002, a total of 7643 Bluethroats were ringed and 1054 of these were re-captured at the International Birding and Research Center (IBRCE) in Eilat, Israel (29°33′N, 34°57′E). The autumn migration of Bluethroat begins in September and ends in early December (median 01-Nov). The spring migration starts in early March and continues till May (median 21-Mar). Wintering Bluethroats arrive during October and November and stay in Eilat until March and April. The Bluethroats remain at the winter quarters for up to 4 months, though some individuals could linger for as long as more than 5 months. The majority of the wintering population was males (65.3%) and adult birds (66.1%), the sex ratio during winter (65:35) did not differ significantly from the sex ratio during autumn migration (60:40). The ratio between young and adult birds at Eilat during winter (66:34) differed significantly from the autumn migration (75:25). Wintering site fidelity for six seasons (consecutive autumn through spring) from 1996 to 2001 was 1.8%. Wintering site fidelity of Bluethroats when compared between birds that winter for the second and third season shows a recovery rate of 37.1%. [Copyright &y& Elsevier]

The BluethroatLuscinia svecicais a migratory passerine that exhibits a socially monogamous pair bond and a high level of parental care. Males are territorial both when wintering and breeding whereas females are territorial only in winter. We investigated changes in body condition and testosterone levels during successive life-history stages and determined their relationships. Sex-specific patterns were observed in the variation in body condition and testosterone level. Male body condition varied mainly during the winter. It peaked at the onset of the prenuptial moult and then decreased, whereas it remained stable throughout breeding. In contrast, female body condition varied mainly during the breeding season. It increased during the prelaying stage and then abruptly decreased until fledgling provisioning. As in other monogamous and territorial passerines, testosterone levels in Bluethroat males were low during winter, increased in late winter, peaked during the prelaying stage and then decreased when provisioning young. In wintering females, territorial competition caused testosterone levels to rise. These females were able to produce territorial vocalizations and exhibit aggressive postures. Females showed higher mean testosterone levels than males when wintering whereas the opposite was observed when breeding. Our data from wintering female Bluethroats support the‘challenge hypothesis’ under which high testosterone levels are associated with periods of social instability, and testosterone can regulate female territorial behaviour during this period. [ABSTRACT FROM AUTHOR]