Molecular evidence for gender differences in the migratory behaviour of a small seabird

Molecular sexing revealed an unexpectedly strong female bias in the sex ratio of pre-breeding European Storm Petrels (Hydrobates pelagicus), attracted to playback of conspecific calls during their northwards migration past SW Europe. This bias was consistent across seven years, ranging from 80.8% to 89.7% female (mean annual sex ratio ± SD = 85.5% female ±4.1%). The sex ratio did not differ significantly from unity (i.e., 50% female) among (i) Storm Petrel chicks at a breeding colony in NW France, (ii) adults found dead on beaches in Southern Portugal, (iii) breeding birds attending nest burrows in the UK, captured by hand, and (iv) adults captured near a breeding colony in the UK using copies of the same sound recordings as used in Southern Europe, indicating that females are not inherently more strongly attracted to playback calls than males. A morphological discriminant function analysis failed to provide a good separation of the sexes, showing the importance of molecular sexing for this species. We found no sex difference in the seasonal or nocturnal timing of migration past Southern Europe, but there was a significant tendency for birds to be caught in sex-specific aggregations. The preponderance of females captured in Southern Europe suggests that the sexes may differ in migration route or in their colony-prospecting behaviour during migration, at sites far away from their natal colonies. Such differences in migration behaviour between males and females are poorly understood but have implications for the vulnerability of seabirds to pollution and environmental change at sea during the non-breeding season

Are blackcaps sylvia atricapilla differential distance migrants by sex?

Aims: To investigate if male and female blackcaps show differences in the amplitude of migratory movements. Methods: The extent of movements of male and female British blackcaps were analysed using ringing recovery records. Furthermore, through a literature review and the collection of original field data, the sex-ratios of blackcap samples taken at several latitudes in Europe and Africa were compared. Results: There were no differences between British male and female blackcaps in relation to wintering latitude or distance moved during migration. Sex-ratios of blackcap samples were quite even across a wide range of latitudes. However, there was a significantly larger proportion of females in samples of birds that wintered in Africa. Conclusions: Laboratory data and morphological studies have yielded inconclusive results in relation to the question of whether or not European blackcaps are differential distance migrants. The results from the present study suggest that British blackcaps are not differential distance migrants. Furthermore, there is, at best, only a weak latitudinal segregation of the sexes of blackcaps wintering in Europe and Africa. The slightly higher proportion of males in European samples, when compared to Africa, could result from a differential behaviour of males and females in some blackcap populations, or simply result from differences in the sex-ratios of blackcap populations breeding and wintering in different areas. An absence of a pronounced latitudinal segregation in the size-monomorphic blackcap is interesting, and contrasts with the pattern found in more sexually dimorphic species, such as the chiffchaff Phylloscopus collybita or the robin Erithacus rubecula

Differential migration of chiffchaffs Phylloscopus collybita and P. ibericus in Europe and Africa

Differential migration is a widespread, but poorly understood, phenomenon in birds. In this paper, we present the first detailed field study of differential migration in the Old World warbler (Sylviidae) family. We studied two chiffchaff Phylloscopus [collybita ] semispecies: the common chiffchaff P. [c. ] collybita and the Iberian chiffchaff P. [c. ] ibericus. Using data collected at several latitudes in Europe and Africa, we present convincing evidence for differential distance migration of sexes in chiffchaffs, with females moving further than males. Interestingly, while there was a pronounced gradient in the sex-ratios in Europe and North Africa (with an increasing proportion of females with declining latitude), no clear pattern was found south of the Sahara, where sex-ratios were more male-biased than predicted by a simple latitude model. This suggests that, amongst the chiffchaffs wintering in West Africa, a large proportion is composed by Iberian birds, and provides support to previous suggestions that Iberian chiffchaffs are long distance migrants. Results from detailed studies in Senegal also show that chiffchaffs display differential timing of spring migration, with males leaving the winter quarters considerably earlier than females. The results are discussed in the framework of the three main (non-mutually exclusive) hypotheses attempting to explain the latitudinal segregation of the sexes. Given the relative failure of standard comparative studies to discriminate between competing single-factor hypotheses to explain differential migration, it is argued that the chiffchaff species complex might be particularly suited to study this issue using a new approach suggested by Cristol et al. (1999): detailed (further) comparisons between closely related species (such as the common and the Iberian chiffchaffs) could help identifying the key factors to be incorporated into optimality models that can predict relative distance of migration of different sex or age classes

Increased Stopover Duration and Low Body Condition of the Pied Flycatcher (Ficedula hypoleuca) at an Autumn Stopover Site

Simple SummaryMany bird species that migrate long distances are in decline partly because of environmental changes, such as climate change or land-use changes. Although much is already known on the effects of environmental change on birds that are on their spring migration or on their breeding grounds, little is known with regard to possible negative effects on birds that are on their autumn migration and visiting so-called stopover sites on their way to their wintering grounds. These stopover sites are vital for birds to refuel, and a potential deteriorating quality of the stopover sites may lead to individuals dying during migration. We investigated the impacts of local environmental conditions on the migration strategy and body condition of the Pied Flycatcher at an autumn migration stopover site using long-term ringing data and local environmental conditions. We found that although birds arrived and departed the stopover site around the same time over the years, the body condition of the individuals caught decreased, and the length of their stay at the stopover site increased. This suggests that conditions at the stopover site during the autumn migration period have deteriorated over time which may lead to the death of more birds during autumn migration.Many long-distance migratory bird species are in decline, of which environmental changes, such as climate change and land-use changes, are thought to be important drivers. The effects of environmental change on the migration of these birds have often been studied during spring migration. Fewer studies have explored the impacts of environmental change on autumn migration, especially at stopover sites. However, stopover sites are important, as the quality of these sites is expected to change over time. We investigated impacts of local environmental conditions on the migration strategy and body condition of the Pied Flycatcher (Ficedula hypoleuca) at an autumn migration stopover site using long-term ringing data (1996-2018) and local environmental conditions. We found that although the arrival and departure dates of birds at the stopover site remained unchanged, the body condition (fat score) of the individuals caught decreased, and the stopover duration increased. This suggests that conditions at the stopover site during the autumn migration period have deteriorated over time. This study emphasizes the importance of suitable stopover sites for migratory birds and stresses that changes in environmental conditions during the autumn migration period may be contributing to the current decline in long-distance migratory passerines

Increased stopover duration and low body condition of the pied flycatcher (Ficedula hypoleuca) at an autumn stopover site

Many long-distance migratory bird species are in decline, of which environmental changes, such as climate change and land-use changes, are thought to be important drivers. The effects of environmental change on the migration of these birds have often been studied during spring migration. Fewer studies have explored the impacts of environmental change on autumn migration, especially at stopover sites. However, stopover sites are important, as the quality of these sites is expected to change over time. We investigated impacts of local environmental conditions on the migration strategy and body condition of the Pied Flycatcher (Ficedula hypoleuca) at an autumn migration stopover site using long-term ringing data (1996–2018) and local environmental conditions. We found that although the arrival and departure dates of birds at the stopover site remained unchanged, the body condition (fat score) of the individuals caught decreased, and the stopover duration increased. This suggests that conditions at the stopover site during the autumn migration period have deteriorated over time. This study emphasizes the importance of suitable stopover sites for migratory birds and stresses that changes in environmental conditions during the autumn migration period may be contributing to the current decline in long-distance migratory passerines

Reliability of morphological criteria for sexing of birds during ringing, assessed using molecular methods - a study of thirteen species of passerines and near-passerines

Understanding the ecology and conservation of bird species often requires accurate sex determination of individuals. Species with sexually dimorphic plumage can usually be sexed in the hand based on consistent and definitive differences in plumage between sexes, but there are often challenges related to (1) how sexual dimorphism develops with age, (2) individuals that show intermediate visible morphological traits, or (3) consistent but subtle trait differences that require considerable experience to use reliably. Species with sexually monomorphic plumage, which constitute over half of all avian species globally, pose a greater challenge and can often not be sexed in the hand. The aim of this study was to use molecular methods to identify definitively the sex of individuals of both monomorphic and dimorphic species caught at a ringing site in south-west Portugal, in order to evaluate the standard morphological sexing techniques for species showing sexual dimorphism in plumage, or in biometric measurements. Blood samples were collected from a range of species during ringing, and DNA was extracted. Molecular methods were successful in identifying the sex of 202 individuals across 13 species of birds (eight species with sexually dimorphic plumage, and five sexually monomorphic in plumage). Molecular methods were consistent with the morphological sexing in the field for six of the eight species with dimorphic plumage, but discrepancies between the two methods were identified for Pied Flycatcher Ficedula hypoleuca and Eurasian Hoopoe Upupa epops. Finally, biometric measurements taken in the field were used to assess whether species with monomorphic plumage could have been correctly sexed based on the biometric differences between males and females reported in literature

Sex ratio of <i>Hydrobates pelagicus</i> controlled in different countries or re-trapped in Portugal.

<p>Sex ratio of <i>Hydrobates pelagicus</i> controlled in different countries or re-trapped in Portugal.</p

Frequency distribution of the expected number of runs of consecutive same-sex captures.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046330#s3" target="_blank">Results</a> based on 10,000 random samples drawn from a population of 116 males and 755 females. The dotted vertical lines show the 95% CI limits of the number of runs expected from a random sequence of males and females (189–215 runs), while the solid vertical line shows the observed number of runs (181). The smaller number of same-sex runs observed than expected indicates a greater degree of aggregation than would be expected if males and females are caught in a random sequence.</p

Field sites location.

<p>European Storm Petrels were sampled on migration (Portugal), at the breeding colonies (adults - Sanda Island and chicks - Brittany) and near a breeding colony (Ailsa Craig).</p

Rewiring of experimentally disturbed seed dispersal networks might lead to unexpected network configurations

The consequences of species extinctions in ecological communities may be buffered through the rearrangement (rewiring) of the interactions between the remaining species. The structural and functional consequences of such extinctions can be explored by means of computer simulations that try to predict secondary extinctions and the degradation of ecosystem services. However, to improve the accuracy of these simulations, it is pivotal to evaluate their performance in predicting changes observed in natural communities. In this study, we first described the avian seed dispersal networks in 17 sites throughout Portugal, and found that blackberry (Rubus ulmifolius) was the most dispersed species in 13 out of the 17 sites. Second, we performed a manipulative experiment to evaluate the effect of removing the most dispersed plant species and compared the observed outcome in the structure of the network with computer simulations with and without rewiring. Observed changes were consistent with some rapid network rewiring, with dispersers shifting to alternative fruit species. Although the observed network topology after the experimental removal was not accurately predicted, the extinction simulation with rewiring performed considerably better than that without rewiring. Individual species roles were even harder to predict than emergent network properties on both types of models. We show that incorporating rewiring rules can considerably increase the accuracy of species extinction models, however, the functional consequences of losing important resources might not be easily anticipated, and rewiring might occur in unexpected directions.We thank to the Portuguese ringing authority (CEMPA/ICNF) for providing ringing permits and bird rings. We also thanks to all observers that contributed to the data collection during ringing activities and to Jane Memmott for providing the code for drawing the networks. We also thank Christopher Kaiser-Bunbury and two anonymous reviewers whose comments greatly improved the manuscript. J.M.C., L.P.S., P.M.A., E.C., R.J.L., and R.H. were supported by Fundação para Ciência e Tecnologia (FCT) , and POPH/QREN/FSE (Grants: SFRH/BD/96292/2013 , SFRH/BD/77746/2011 , SFRH/BD/69238/2010 , PD/BD/52594/2014 , SFRH/BPD/84141/2012 , and IF/00441/2013 , respectively). R.H. was also supported by the Marie Curie action ( FP7-PEOPLE-2012-CIG-321794 ) and A.C.N. by FCT ( SFRH/BPD/62898/2009 ) and MARE strategic program financed by FCT ( MARE – UID/MAR/04292/2013 ). Appendix Ainfo:eu-repo/semantics/publishedVersio