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Dispersal is a key process for the maintenance of intraspecific genetic diversity by ensuring gene flow within and between populations. Despite the ongoing expansion of large carnivores in Europe, lynx populations remain fragmented, isolated, and threatened by inbreeding and loss of genetic diversity. In the course of large carnivore monitoring in the Czech Republic, several biological samples of Eurasian lynx were collected outside the permanent occurrence of this species. Using microsatellite genotyping we identified these as four dispersing lynx males and applied multiple methods (Bayesian clustering in STRUCTURE, Principal Component Analysis (PCA), frequency-based method in GENECLASS2, and machine-learning framework in assignPOP) to assign them to possible source populations. For this we used genotypes from five European lynx populations: the Bohemian-Bavarian-Austrian (N = 36), Carpathian (N = 43), Scandinavian (N = 20), Baltic (N = 15), and Harz (N = 23) population. All four dispersers were successfully assigned to different source populations within Europe and each was recorded at a distance of more than 98 km from the edge of the distribution of the source population identified. Such movements are among the longest described for lynx in Central Europe to this point. The findings indicate the ability of lynx males to disperse in human-dominated landscape thus facilitation of these movements via creation and/or protection of potential migratory corridors together with protection of dispersing individuals should be of high importance in conservation of this iconic predator in Central Europe.

The factors underlying gene flow and genomic population structure in vagile seabirds are notoriously difficult to understand due to their complex ecology with diverse dispersal barriers and extensive periods at sea. Yet, such understanding is vital for conservation management of seabirds that are globally declining at alarming rates. Here, we elucidate the population structure of the Atlantic puffin (Fratercula arctica) by assembling its reference genome and analyzing genome-wide resequencing data of 72 individuals from 12 colonies. We identify four large, genetically distinct clusters, observe isolation-by-distance between colonies within these clusters, and obtain evidence for a secondary contact zone. These observations disagree with the current taxonomy, and show that a complex set of contemporary biotic factors impede gene flow over different spatial scales. Our results highlight the power of whole genome data to reveal unexpected population structure in vagile marine seabirds and its value for seabird taxonomy, evolution and conservation., Kersten et al. sequence a draft genome for the Atlantic puffin and report its population structure, genetic diversity and gene flow among four main clusters of populations across the northern Atlantic. These results identify a secondary contact zone between the puffins from the High Arctic and other colonies and proposes a new population structure from the currently recognized three subspecies.

The Changeable Hawk-Eagle Nisaetus cirrhatus complex is represented by two taxa in mainland India: N. c. cirrhatus in the northern plains and peninsula and N. c. limnaeetus in the Himalayan foothills. Traditionally these taxa have been regarded as subspecies of one species, but recently they have been proposed to be different species. Here, we use an integrative taxonomic approach based on considerations of plumage, biometrics, genetics and vocalizations. Several plumage characters are significantly different between the two taxa, but crest length was the only one of 56 characters that was diagnostically different, with no overlap. About 30% of the birds had intermediate crest lengths, suggesting that they are hybrids or backcrosses, as also supported by the microsatellite results. PCAs of adult plumage show many intermediate individuals, irrespective of whether these birds were collected near a putative contact zone. There is restricted gene flow between the two taxa, presumably as a result of their largely allopatric distributions. On current knowledge, reproductive isolation appears to be weak at best, and we therefore recommend continuing to regard limnaeetus morphology, genetics, vocalization, integrative taxonomy

During their flightless summer moult, Taiga Bean Geese Anser fabalis fabalis gather at communal moulting sites. Individuals from the Nord-Trøndelag breeding area in Norway have been observed to join with local individuals on moulting sites in Vilhelmina Municipality, Sweden. These two groups show distinct features in breeding habitat and migratory behaviour, but are they also genetically distinct? We used 12 microsatellite loci for genotyping 109 blood, feather and faecal samples from three sampling areas (Røyrvik in Norway and Stalon and Nästansjö in Sweden) to examine genetic diversity and structure. Clustering and Principal Coordinate analyses of all samples unveiled at least two distinct clusters, which were unevenly distributed over the sampling sites. Grouped by sampling sites, AMOVA and FST analyses showed that samples from the three sites differed genetically. These differences were larger between Røyrvik and Nästansjö than between Stalon and the other two. Relatedness was high among the Røyrvik samples. From our results we conclude that one of the clusters describes the Røyrvik breeding subpopulation, while the other(s) breed mainly in Sweden. Although these subpopulations simultaneously use the same moulting area in Vilhelmina, they appear to be ecologically, behaviourally and genetically distinct, in particular the Røyrvik sub-population. For goose conservation and management, we suggest that the Nord-Trøndelag (Røyrvik) subpopulation is considered a separate flyway management unit. Unravelling the Swedish sub-populations will need further study. For bird conservation is general, we suggest active genetic sampling for detailed population structure analyses and subsequent differentiated conservation and/or management schemes. Birds of different feather flock together - genetic structure of Taiga Bean Goose in Central Scandinavia

Capsule: A description of the methods used for monitoring the Golden Eagle Aquila chrysaetos in Norway Aims: To provide a comprehensive description of monitoring methods. Methods: The intensive monitoring of the Golden Eagle in Norway started in 1991 as part of a national monitoring programme initiated by the Directorate for Nature Management (now the Norwegian Environment Agency). It has since become part of the Norwegian Large Predator Programme, and Golden Eagles are currently being monitored in 12 separate areas. Here we provide a comprehensive description of the current methods used in the intensive monitoring, with definitions, fieldwork and evaluation criteria for the final breeding status. In addition, a description of estimation of annual adult survival by genetic analysis is given. We describe the current methodology used in the intensive part of the Golden Eagle monitoring in Norway. Results: We present some results derived from the Norwegian monitoring system and discuss the potential for further analyses. In addition, we highlight aspects in the monitoring of the Golden Eagles where our methods deviate slightly from those applied in other countries and the potential effects of these. Conclusions: Intensive long-term monitoring programmes, such as this, will become increasingly valuable for monitoring the impact of environmental change, both from natural phenomena and from anthropogenic activities. To facilitate comparisons among the Golden Eagle monitoring programmes, detailed knowledge about the various methods applied is important.

Postcopulatory sexual selection (PCSS) in internally fertilizing vertebrates is a topic of great interest, yet relatively little is known about the characteristics of sperm and ejaculates that confer an advantage in PCSS. In this study, we investigated several measures of sperm morphology that potentially contribute to fertilization success under PCSS. We tested whether sperm morphology related to success in PCSS (via extra-pair paternity) in house wrens (Troglodytes aedon). We found no evidence that sperm morphology differed between extra-pair sires and the within-pair males they cuckolded, nor that sperm morphology correlated with the proportion of within-pair offspring sired, the number of extra-pair offspring sired, or the total annual reproductive success. Male behavioral strategies may affect the probability that their sperm compete with other males’ sperm and that their sperm succeed under competition. Effects of these behavioral strategies, as well as differences between males in sperm number, could mask the effects of sperm morphology on the outcome of PCSS. Despite moderate levels of extra-pair paternity, selection on sperm may be relatively weak in house wrens. Further work is needed to understand general patterns in how sperm morphology relates to fertilization success within species.

Spermatozoa vary greatly in size and shape among species across the animal kingdom. Postcopulatory sexual selection is thought to be the major evolutionary force driving this diversity. In contrast, less is known about how sperm size varies among populations of the same species. Here, we investigate geographic variation in sperm size in barn swallows Hirundo rustica, a socially monogamous passerine with a wide Holarctic breeding distribution. We included samples from seven populations and three subspecies: five populations of ssp. rustica in Europe (Czech, Italy, Norway, Spain, and Ukraine), one population of ssp. transitiva in Israel, and one population of ssp. erythrogaster in Canada. All sperm traits (head length, midpiece length, tail length, and total length) varied significantly among populations. The variation among the European rustica populations was much lower than the differences among subspecies, indicating that sperm traits reflect phylogenetic distance. We also performed a test of the relationship between the coefficient of between-male variation in total sperm length and extrapair paternity levels across different populations within a species. Recent studies have found a strong negative relationship between sperm size variation and extrapair paternity among species. Here, we show a similar negative relationship among six barn swallow populations, which suggests that the variance in male sperm length in a population is shaped by the strength of stabilizing postcopulatory sexual selection.

The evolutionary forces that shape and maintain variation in sperm traits across species in birds have recently attracted increased attention. Much less is known about the patterns, the causes and the consequences of variation in sperm traits within and, in particular, between populations of the same species. We here analyse intraspecific variation in sperm dimensions within and between two populations of the Coal Tit Periparus ater, a socially monogamous passerine with a high frequency of extra-pair paternity. Spermatozoa from a Norwegian population had a greater mean total length compared to those from a German population, mainly as a result of longer sperm heads. Sperm head length in the Norwegian population also accounted for a larger percentage of sperm total length suggesting differences in sperm proportions between populations. Furthermore, spermatozoa from the Norwegian population showed lower mean within-male variation in sperm length and there was significant between-male variation in sperm total length within each of the two populations. We discuss these results in the light of recent comparative evidence suggesting relationships between sperm length, and variation in sperm length, and the frequency of extra-pair paternity across passerine birds.

Sperm swimming speed is an important determinant of male fertility and sperm competitiveness. Despite its fundamental biological importance, the underlying evolutionary processes affecting this male reproductive trait are poorly understood. Using a comparative approach in a phylogenetic framework, we tested the predictions that sperm swim faster with (1) increased risk of sperm competition, (2) shorter duration of female sperm storage, and (3) increased sperm length. We recorded sperm swimming speed in 42 North American and European free-living passerine bird species, representing 35 genera and 16 families. We found that sperm swimming speed was positively related to the frequency of extrapair paternity (a proxy for the risk of sperm competition) and negatively associated with clutch size (a proxy for the duration of female sperm storage). Sperm swimming speed was unrelated to sperm length, although sperm length also increased with the frequency of extrapair paternity. These results suggest that sperm swimming speed and sperm length are not closely associated traits and evolve independently in response to sperm competition in passerine birds. Our findings emphasize the significance of both sperm competition and female sperm storage duration as evolutionary forces driving sperm swimming speed.

Frequent copulation is assumed to be an important male reproductive strategy for paternity assurance in species with female sexual promiscuity. However, the empirical evidence supporting this hypothesis is limited. We examined copulation behaviour in relation to within-pair paternity in the socially monogamous tree swallow, Tachycineta bicolor, a passerine bird species with frequent copulation, a lack of mate guarding and high levels of extrapair paternity. We found that the frequency of within-pair copulation attempts increased and peaked just before the appearance of the first egg. A marked drop in the frequency of copulation attempts was observed once the first egg was laid. Furthermore, the frequency of successful within-pair copulations was highly repeatable for particular pairs within the 3 days prior to appearance of the first egg. Finally, males that obtained a higher number of successful within-pair copulations during this time also sired a larger proportion of the offspring in their own brood. Our findings suggest that frequent copulations just before the start of egg laying is an adaptation to decrease the risk of being cuckolded in the presence of sperm competition, and thus provide empirical support for the paternity assurance hypothesis. Crown Copyright 2008 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. All rights reserved. Paternity assurance is critical to male fitness, particularly in species in which females frequently participate in extrapair copulations (EPCs) and males provide costly parental care. In response to fitness loss due to cuckoldry, several types of paternity assurance behaviour have evolved across taxa. One strategy is constant mate guarding by following, as males can protect their paternity by ensuring that no other male has an opportunity to mate with their paired female (Moller & Birkhead 1991). However, for some species, constant mate guarding may be constrained by territory protection or other activities. The paternity assurance hypothesis (Moller 1987; Simmons 1990), also known as the paternity confidence hypothesis (Eens & Pinxten 1995) and the sperm competition hypothesis (Birkhead et al. 1987), suggests that for species in which EPCs are common, males copulate frequently with their pair females to avoid being cuckolded. Males may minimize cuckoldry through frequent copulation by devaluing EPCs that their mates

Extrapair paternity seems to be common in socially monogamous passerines, but the genetic mating system of most species is currently unknown. Here, we report the first study of paternity in the socially monogamous Common Crossbill (Loxia curvirostra). We found no evidence of extrapair paternity among 96 offspring in 34 examined broods. An upper 95% confidence limit of 3.1% suggests that extrapair fertilizations were truly infrequent in our study population. Common Crossbills thus seem to represent an exception to the rule of extrapair mating among socially monogamous passerine bird species. A potentially important selective pressure preventing promiscuity in Common Crossbills is the harsh environmental conditions experienced during breeding at wintertime, which may increase the importance of paternal care and limit the time available for seeking extrapair copulations.

Spermatozoa are among the most diversified cells in the animal kingdom, but the underlying evolutionary forces affecting intraspecific variation in sperm morphology are poorly understood. It has been hypothesized that sperm competition is a potent selection pressure on sperm variation within species. Here, we examine intraspecific variation in total sperm length of 22 wild passerine bird species (21 genera, 11 families) in relation to the risk of sperm competition, as expressed by the frequency of extrapair paternity and relative testis size. We demonstrate, by using phylogenetic comparative methods, that between-male variation in sperm length within species is closely and negatively linked to the risk of sperm competition. This relationship was even stronger when only considering species in which data on sperm length and extrapair paternity originated from the same populations. Intramale variation in sperm length within species was also negatively, although nonsignificantly, related to sperm competition risk. Our findings suggest that postcopulatory sexual selection is a powerful evolutionary force reducing the intraspecific phenotypic variation in sperm-size traits, potentially driving the diversification of sperm morphology across populations and species.

Information about male infertility in free-living bird populations and its underlying causes are poorly documented in the literature. Here, we assessed sperm quality and infertility among males in a wild population of Blue Tits Cyanistes caeruleus, a socially monogamous passerine with frequent extra-pair mating. One of 30 males (3.3%) studied across two breeding seasons had morphologically abnormal and nearly immotile spermatozoa in combination with zero annual fertilization success. Demonstration of male functional infertility suggests the possibility that socially monogamous females of the study population could obtain a direct fitness benefit by mating polyandrously to increase fertilization success, which could contribute to selection on extra-pair mating behaviour.

Morphometric analysis of avian spermatozoa from sperm samples preserved in formalin is a frequently adopted procedure in basic science (e.g. evolutionary ecology) and applied disciplines (e.g. animal breeding). Many research questions such as individual-based longitudinal studies of sperm traits require comparisons of formalin-stored sperm samples collected across multiple sampling events, which may be separated by years. Such analyses presuppose that prolonged storage in formalin does not affect sperm morphology, an assumption often implicitly made in the analysis of avian sperm morphology. This assumption, however, has never been tested, although for many study designs a potential effect of sperm storage duration may well confound the focal analysis. Based on pairwise comparisons of 22 experimental ejaculates from three passerine bird species, we found no evidence that differential storage duration of more than 1 year had affected the total length of spermatozoa stored in a 5 % formaldehyde solution. This suggests that formalin-stored sperm samples from long-term studies or museum collections can be merged in combined analyses without confounding differential storage duration with natural between-year variation in sperm dimensions or age effects in longitudinal studies. Based on pairwise comparisons of 29 split ejaculates, we also found no evidence that spermatozoa differed in length when solved initially in either phosphate buffered saline or Dulbecco’s Modified Eagle Medium, a standard medium for videotaping live sperm, prior to preservation and storage in formalin. Sperm samples treated differently in this respect may thus be merged into combined analyses, too.

Social monogamy is common among passerines whereas genetic monogamy is regarded as rare. Here we report the first study of paternity in the genus Phoenicurus (Aves, Muscicapidae). In the socially monogamous common redstart (Phoenicurus phoenicurus) 2.0% (5/253) of offspring in 10.5% (4/38) of the broods examined were sired by extrapair males. The observed pattern of extrapair paternity was consistent among two geographically separate nest-box populations sampled over two years. Our findings reveal low rates of extrapair paternity compared with other passerine birds, suggesting only a minor role of sperm competition in this sexually dichromatic species.

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.

Females involved in extrapair mating are generally thought to obtain indirect benefits through increased offspring quality. We investigated this in the barn swallow, Hirundo rustica , a socially monogamous passerine in which females seem to have a preference for elaborately ornamented, high-quality males, both as social and extrapair mating partners. In this species, a variety of parasites and pathogens can potentially infect individuals, both during the nestling stage and later in life. The ability to cope with infections and hence the quality of the immune system may therefore have immediate survival or future fitness consequences. To evaluate whether females engage in extrapair mating to increase offspring cell-mediated immunity, a pivotal component of the avian immune system, we experimentally challenged nestling immunity. Body condition, rearing environment and gender affected the ability of nestlings to mount an immune response. Contrary to a prediction derived from the ‘genetic quality’ hypothesis, our results revealed no enhanced cell-mediated immune responsiveness in extrapair young compared to their maternal half-siblings reared in the same brood. Female barn swallows therefore do not seem to mate with multiple males in order to increase nestling cell-mediated immunity. Although we cannot reject the possibility that extrapair mating is beneficial to female barn swallows, our results offer no support to the hypothesis that females obtain genetic benefits through extrapair fertilizations.

In socially monogamous species, extra-pair paternity has the potential to increase the variance in male reproductive success, thereby affecting the opportunity for sexual selection on male extravagant ornamentation. In the European barn swallow (Hirundo rustica rustica), the tail streamer length is a sexually selected male ornament and an honest indicator of viability. The North American barn swallow (Hirundo rustica erythrogaster) also shows sexual dimorphism in tail streamer length, but whether this trait holds the same signalling function in this subspecies is a controversial issue, and the available literature is presently scarce. Here, we present data on paternity in the North American barn swallow, including a complete sampling of extra-pair sires in four colonies. We analysed how extra-pair paternity affected the variance in male fertilization success and examined whether male tail streamer (i.e. the outermost tail feather) length correlated with fertilization success (n=86 males). Extra-pair paternity constituted 31% of all offspring and significantly increased the variance in male fertilization success. The number of offspring sired by extra-pair males accounted for almost half of the total variance in male fertilization success. Males with naturally long tail streamers had a higher fertilization success than males with shorter tail streamers, and this pattern was mainly caused by a higher extra-pair success for males with long tail streamers. Males with long tail streamers also paired with early breeding females in prime body condition. These results are consistent with the idea that there is directional sexual selection on male tail streamer length, possibly mediated through male extra-pair mating success or the timing of breeding onset.

It has been hypothesized that females mate multiply to increase the heterozygosity of their progeny because heterozygous individuals are assumed to have a fitness advantage. Females can maximize heterozygosity of their offspring by mating with genetically unrelated and/or heterozygous males. We tested these predictions in a socially monogamous passerine, the reed bunting (Emberiza schoeniclus), where extrapair paternity occurs frequently. The results based on genotypes at nine microsatellite loci revealed that females were no less genetically related to the extrapair male(s) (EPMs) than to their pair male (i.e., breeding partner) and that EPMs were no more heterozygous than the males they cuckolded. In addition, a direct comparison of maternal half-siblings naturally raised in the same brood showed that extrapair young were no more heterozygous than within-pair young. Thus, female reed buntings do not seem to mate with EPMs to increase offspring heterozygosity. It is not yet known whether extrapair mating involves any benefits at all to females in this species. Key words: Emberiza schoeniclus, extrapair paternity, genetic benefits, half-sibling comparisons, heterozygosity. [Behav Ecol]

Female promiscuity is widespread in birds, as well as in other taxa. It is often assumed that in bird species with a socially monogamous mating system, females engage in extrapair copulations to obtain indirect (genetic) benefits. ‘Good genes’ and ‘compatible genes’ models predict that extrapair young (EPY) should be of higher quality than within-pair young (WPY), but the empirical evidence for this effect is limited. A recent study, however, indicated an enhanced cellular immunity in EPY in a passerine bird, the bluethroat, Luscinia svecica. To assess the generality of that finding, we replicated the study using the reed bunting, a passerine with an extrapair mating system similar to that of the bluethroat. Using the same immune assay protocol, we found no indication of enhanced cellular immunity in EPY compared with WPY. Female reed buntings thus do not seem to engage in extrapair copulations to achieve the same type of genetic benefit as in bluethroats. Furthermore, EPY in mixed-paternity broods did not grow faster and were not in better body condition close to fledging than WPY. We conclude that our results do not support the hypotheses assuming indirect benefits to female extrapair copulations. It appears that the adaptive value for females of pursuing extrapair fertilizations varies, even between species with similar extrapair mating systems.

There is growing evidence that post-copulatory sexual selection, mediated by sperm competition, influences the evolution of sperm phenotypes. Evidence for pre-copulatory sexual selection effects on sperm traits, on the other hand, is rather scarce. A recent paper on the pied flycatcher, Ficedula hypoleuca, reported phenotypic associations between sperm length and two sexually selected male traits, i.e. plumage colour and arrival date, thus invoking pre-copulatory sexual selection for longer sperm. We were unable to replicate these associations with a larger data set from the same and two additional study populations; sperm length was not significantly related to either male plumage colour or arrival date. Furthermore, there was no significant difference in sperm length between populations despite marked differences in male plumage colour. We also found some evidence against the previously held assumption of longer sperm being qualitatively superior; longer sperm swam at the same speed as shorter sperm, but were less able to maintain speed over time. We argue that both empirical evidence and theoretical considerations suggest that the evolution of sperm morphology is not primarily associated with pre-copulatory sexual selection on male secondary sexual traits in this or other passerine bird species. The relatively large between-male variation in sperm length in this species is probably due to relaxed post-copulatory sexual selection.

Sperm competition represents an important component of post-copulatory sexual selection. It has been argued that the level of sperm competition declines in birds towards the equator. However, to date, sperm competition estimates have been available mainly for avian species inhabiting the northern temperate zone. Here we apply a novel approach, using the coefficient of between-male variation (CV bm ) in sperm size as an index for sperm competition risk, in a comparative analysis of 31 Afrotropical and 99 northern temperate zone passerine species. We found no difference in sperm competition risk between the two groups, nor any relationship with migration distance. However, a multivariate model indicated that sperm competition risk was highest in species with a combination of low body mass and few eggs per clutch. The effect of clutch size was most pronounced in tropical species, which indicates that sperm competition risk in tropical and temperate species is differently associated with particular life-history traits. Although tropical species had lower sperm competition risk than temperate zone species for overlapping clutch sizes, the idea of a generally reduced risk of sperm competition in tropical birds was not supported by our analysis.