Dataset Information

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration.

ABSTRACT: Differential migration has been extensively reported in spring, but less so in autumn, particularly in relation to sex in monomorphic bird species. Here, we analysed the autumn passage of a monomorphic, globally threatened passerine, the Aquatic Warbler Acrocephalus paludicola throughout Western Europe, with regard to age and sex. We showed that, overall, adults migrated earlier than first-year birds, and males migrated earlier than females during the autumn migration. This may be caused by an overall social dominance of adults over immatures, and differentiated migration strategy of males and females. In addition, we found male-skewed sex proportions, with a tendency to an equalised ratio in more southern stopover sites. This may indicate a male bias in the global population or different migration strategies of the sexes. Differential migration may cause the age and sex classes to be exposed differently to various threats affecting demographic structure of the species.

SUBMITTER: Wojczulanis-Jakubas K

PROVIDER: S-EPMC5686252 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration.

Wojczulanis-Jakubas Katarzyna K Chrostek Małgorzata E ME Jiguet Frédéric F Martínez Carlos Zumalacárregui CZ Miguélez David D Neto Júlio M JM

Die Naturwissenschaften 20171114 11-12

Differential migration has been extensively reported in spring, but less so in autumn, particularly in relation to sex in monomorphic bird species. Here, we analysed the autumn passage of a monomorphic, globally threatened passerine, the Aquatic Warbler Acrocephalus paludicola throughout Western Europe, with regard to age and sex. We showed that, overall, adults migrated earlier than first-year birds, and males migrated earlier than females during the autumn migration. This may be caused by an o ...[more]

PMID: 29138941

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Project description:Backgrounds:Geographic regions, where two closely related taxa with different migration routes come into contact, are known as migratory divides. Hybrids originating from migratory divides are hypothesized to migrate intermediately relative to the parental populations. Few studies have tested this hypothesis in wild birds, and only in hybrids that have completed the migration back to the breeding grounds. Here, we make use of the well-established migration routes of willow warblers (Phylloscopus trochilus), for which the subspecies trochilus and acredula have migration-associated genetic markers on chromosomes 1 and 5. The genetic approach enabled us to analyze the geographic distribution of juveniles during their first autumn migration, predicting that hybrids should be more frequent in the central flyway over Italy than along the typical SW routes of trochilus and SE routes of acredula. Methods:Blood and feather samples were collected from wintering birds in Africa (n =?69), and from juveniles during autumn migration in Portugal (n =?33), Italy (n =?38) and Bulgaria (n =?32). Genotyping was carried out by qPCR SNP assays, on one SNP each on chromosome 1 (SNP 65) and chromosome 5 (SNP 285). Both these SNPs have alternative alleles that are highly fixed (>?97%) in each of the subspecies. Results:The observed combined genotypes of the two SNPs were associated with the known migration routes and wintering distributions of trochilus and acredula, respectively. We found hybrids (HH) among the juveniles in Italy (5/38) and in Portugal (2/33). The proportion of hybrids in Italy was significantly higher than expected from a background rate of hybrid genotypes (1.5%) in allopatric populations of the subspecies. Conclusions:Our genetic approach to assign individuals to subspecies and hybrids allowed us to investigate migration direction in juvenile birds on their first migration, which should better reflect the innate migratory direction than studies restricted to successful migrants. The excess of hybrids in Italy, suggests that they employ an intermediate route relative to the parental populations. Our qPCR SNP genotyping method is efficient for processing large sample sizes, and will therefore be useful in migration research of species with known population genetic structure.

Dataset Information

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration.

Publications

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration.

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