| 1. |
- Andueza, Miren, et al.
(författare)
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Connectivity in Reed Warblers Acrocephalus scirpaceus between breeding grounds in Europe and autumn stopover sites in Iberia
- 2013
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Ingår i: Ardea. - : Netherlands Ornithologists' Union. - 0373-2266. ; 101:2, s. 133-140
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Tidskriftsartikel (refereegranskat)abstract
- We determined the degree of connectivity in the Eurasian Reed Warbler Acrocephalus scirpaceus between breeding regions in central and northern Europe and stopover sites in Iberia, during the autumn migration. We used both recovery data and wing length analyses to achieve this. Biometric data were obtained during 2009 at 11 sampling localities in Iberia, which we amalgamated into four major migratory areas within the region (Central, Western, Eastern and Southwestern Iberia, hereafter CI, WI, EI, SW). From the EURING database, we selected birds captured at their breeding sites in Europe and recaptured in Iberia during the autumn migration. Reed Warblers passing through WI had shorter wings than those in CI, EI and SW, suggesting that birds in WI migrated shorter distances, a fact also supported by recovery data. Although Reed Warblers showed some population overlap when passing through Iberia, we found that birds passing through EI and CI came from areas further to the east (continental Europe) than those passing through WI (mainly British Isles), thus supporting parallel migration. Reed Warblers tended to converge in southwestern Iberia, suggesting an effect of nearby geographical barriers.
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| 2. |
- Andueza, Miren, et al.
(författare)
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Geographic variation in body mass of first-year Reed Warblers Acrocephalus scirpaceus in Iberia
- 2014
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Ingår i: Ornis Fennica. - 0030-5685. ; 91:2, s. 88-99
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Tidskriftsartikel (refereegranskat)abstract
- On their route to tropical Africa, European trans-Saharan migrants must cross two major geographical barriers, the Mediterranean Sea and the Sahara Desert, which necessitates the accumulation of large fuel loads. While northern Africa is the chief region where most migrants gain fuel for the Sahara crossing, Iberia is a target area to gain fuel before the sea crossing existing between Europe and Africa. Despite the large body of studies approach- ing the question of fuel accumulation before geographic barriers, it is still poorly known which factors apart from distance to a certain barrier shape the geographical pattern of fuel reserves. To investigate this question in detail we used data of first-year Reed Warblers from 12 localities within Iberia during the autumn migration period of 2009. We run linear models to analyze the effects of location in Iberia, date, and body size on body mass variation at each migratory flyway (eastern, central and western Iberia). Flight ranges from each site were also calculated. Our results showed that Reed Warblers in Iberia had the necessary fuel needed to arrive in northern Africa but not to tropical Africa. However, body mass patterns varied depending on the geographical region (eastern, central or west- ern Iberia). Date did not affect body mass in central and western Iberia, but in eastern Ibe- ria heavier birds tended to pass later. Thus, the factors shaping body mass of Reed War- blers in Iberia before the sea crossing to Africa seemed to be more complex than just the distance to this geographical barrier, with underlying stopover quality-associated factors possibly playing a relevant role.
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| 3. |
- Campos, Ana R., et al.
(författare)
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How do Robins Erithacus rubecula resident in Iberia respond to seasonal flooding by conspecific migrants?
- 2011
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Ingår i: Bird Study. - : Informa UK Limited. - 0006-3657 .- 1944-6705. ; 58:4, s. 435-442
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Tidskriftsartikel (refereegranskat)abstract
- Capsule The majority of Robins in Iberia are sedentary and stay in their nesting areas despite the pre- sumed increased competition that results from the seasonal flooding of the area by conspecific migrants. Aims To evaluate if Robins in Iberia are displaced from their nesting areas by the presence of large num- bers of competitors originating from higher latitudes. Methods Data from constant effort ringing sites were used to estimate the proportion of Robins that are strictly sedentary and the seasonal variation in Robin numbers. Hydrogen stable isotope ratios (d2H) in feathers, and sex ratios determined through molecular techniques, allowed an insight into the numerical importance of invading Robins from higher latitudes. Results Robins were more numerous outside the breeding season, with clear influxes in autumn. Around half of the locally nesting Robins were captured during winter, indicating they are truly sedentary. d2H in feathers suggests that a wide mixture of Robins from all European latitudes were present in winter, and these data, together with sex ratios, suggest that there may be similar numbers of local and foreign individ- uals in winter at the main study site. Conclusion Despite the occupation of their range by migrants, local birds are largely sedentary.
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| 4. |
- Catry, Paulo, et al.
(författare)
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Provenance does matter : links between winter trophic segregation and the migratory origins of European robins
- 2016
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 182:4, s. 985-994
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Tidskriftsartikel (refereegranskat)abstract
- Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ2H) in robin Erithacus rubecula feathers across Europe. We then use δ2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.
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| 5. |
- Correia, Edna, et al.
(författare)
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Migration strategy of white-spotted bluethroats (Luscinia svecica cyanecula and L. s. namnetum) along the eastern Atlantic route
- 2013
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Ingår i: Ardeola. - : Ardeola. - 0570-7358. ; 60:2, s. 245-259
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Tidskriftsartikel (refereegranskat)abstract
- The bluethroat Luscinia svecica is a particularly interesting species for the study of the mechanisms that control migration because it comprises several recently diverged subspecies that differ in migratory distance and direction. Here we use ringing data to describe the migration strategy and winter distribution of L. s. cyanecula and L. s. namnetum along the eastern Atlantic coast of Iberia and West Africa. No differences were found in autumn migration phenology between subspecies, ages and sexes. However, in contrast to L. s. namnetum, the mean wing length of L. s. cyanecula decreased and its body mass increased during this migratory period. The subspecies also differed in migration speed and stopover behaviour, with L. s. cyanecula travelling faster and refuelling during stopovers. The potential non-stop flight range was greater in L. s. cyanecula and increased with decreasing latitude, which is probably related to the need to overcome geographical barriers to reach the wintering grounds. During winter, the birds captured in sub-Saharan Africa were almost exclusively L. s. cyanecula, whereas L. s. namnetum wintered mainly in Iberia, and the probability of capturing adults increased with decreasing latitude. L. s. cyanecula captured in Africa had longer wings than those migrating through and wintering in Iberia, indicating a leapfrog migration pattern also within L. s. cyanecula populations.
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| 6. |
- Ellis, Vincenzo A., et al.
(författare)
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Explaining prevalence, diversity and host specificity in a community of avian haemosporidian parasites
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:9, s. 1314-1329
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Tidskriftsartikel (refereegranskat)abstract
- Many hypotheses attempt to explain parasite–host associations, but rarely are they examined together in a single community. For hosts, key traits are the proportion of infected individuals (prevalence) and the diversity of parasites infecting them. A key parasite trait is host specificity, ranging from specialists infecting one or a few closely related species to generalists infecting many species. We tested 10 hypotheses to explain host-parasite associations; five ‘host-centric’ (e.g. prevalence is related to host abundance) and five ‘parasite-centric’ (e.g. parasite abundance is related to host specificity). We analyzed a community of 67 locally transmitted avian haemosporidian parasite lineages (genera Plasmodium, Haemoproteus or Leucocytozoon), sampled from 2726 birds (64 species) in southern Sweden. Among host-centric hypotheses, Haemoproteus and Leucocytozoon prevalence and Haemoproteus diversity were related to host habitat preferences, whereas there were no relationships with host abundance or body mass. Haemoproteus and Leucocytozoon prevalences were more similar among closely related than among distantly related host species. Haemoproteus prevalence and diversity were lower in host species with few close relatives (‘evolutionarily distinct’ hosts). Among parasite-centric hypotheses, most lineages, even relative generalists, infected closely related host species more often than expected by chance. However, the host species of Haemoproteus and Leucocytozoon lineages overlapped less among lineages than expected by chance. Specialists did not reach higher prevalences than generalists on single host species. However, the abundance of Haemoproteus lineages was related to host specificity with generalists more common than specialists; this was driven by three closely related generalists. Host specificity of parasites was unrelated to the abundance or evolutionarily distinctiveness of their hosts. Parasite communities are likely structured by many factors and cannot be explained by hypotheses focusing solely on hosts or parasites. However, we found consistent effects of host phylogenetic relationships, plausibly a result of evolutionarily conserved host immune systems limiting parasite distributions.
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| 7. |
- Gordinho, Luís, et al.
(författare)
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Asymmetric song recognition between recently diverged subspecies of reed bunting
- 2016
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 27:5, s. 1413-1423
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic divergence among populations may result in assortative mating, behavioral isolation, and speciation. In birds, the recogni- tion of suitable mates depends to a large extent on learning, generally resulting in a tendency to discriminate against nonlocal stimuli. However, there may be geographical variation in the discrimination against nonlocal stimuli, and this may allow inferring the mechanisms behind the evolution of vocal recognition. We tested territorial males of 3 west European subspecies of reed bunting (Emberiza schoeniclus schoeniclus, Emberiza schoeniclus lusitanica, and Emberiza schoeniclus witherbyi) using song playback to determine the level of song discrimination. We found that witherbyi and, to some extent lusitanica, males largely ignored schoeniclus songs. However, witherbyi reacted less strongly to the songs of lusitanica than lusitanica did to songs of witherbyi. In contrast, schoenic- lus males did not discriminate the songs of the different subspecies, reacting strongly to all. Differential territorial defense behavior suggest that intruding males with different songs do not represent the same competitive threat, and provide evidence of premating reproductive isolation among these recently evolved subspecies. The high discrimination exhibited by witherbyi and lusitanica seems associated with the high level of local adaptation. Overall, the pattern of premating reproductive isolation appears to agree more with the ecological than with the neutral genetic divergences between subspecies, suggesting that there is an ongoing process of ecological speciation in this study system.
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| 8. |
- Gordinho, Luís de Oliveira, et al.
(författare)
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Song divergence between subspecies of reed bunting is more pronounced in singing styles under sexual selection
- 2015
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 107, s. 221-231
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Tidskriftsartikel (refereegranskat)abstract
- Song divergence between populations of a species can lead to reproductive isolation and speciation. However, birds may have different singing styles used in distinct social contexts, and songs of each style may change at different rates over time and space. Here, we tested whether song divergence between subspecies of reed bunting, Emberiza schoeniclus, differs with singing style, by comparing song traits of its three singing styles among three subspecies breeding in northern and western Europe. We show that the two singing styles under sexual selection (dawn and fast songs, related to obtaining extrapair and social mates, respectively) diverged significantly more than the slow songs (used as an all-clear signal to nest- attending social females). Multiple song traits differed significantly between the subspecies in all singing styles, with E. s. lusitanica generally being intermediate between E. s. schoeniclus and E. s. witherbyi, and the pattern of song complexity opposing the expected latitudinal gradient (of increasing complexity with increasing latitude). Cluster analyses of populations indicate that sexually selected singing styles are better for discriminating subspecies, describing a scenario of a major split in song features between the migratory, northern E. s. schoeniclus and the two resident, southern subspecies, rather than a clinal variation. The greater song divergence in fast and dawn singing styles suggests that sexual selection may be playing an important role in the incipient speciation of reed buntings.
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| 9. |
- Hamed, Tareq Abu, et al.
(författare)
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Multiscale in modelling and validation for solar photovoltaics
- 2018
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Ingår i: EPJ Photovoltaics. - : EDP Sciences. - 2105-0716. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Photovoltaics is amongst the most important technologies for renewable energy sources, and plays a key role in the development of a society with a smaller environmental footprint. Key parameters for solar cells are their energy conversion efficiency, their operating lifetime, and the cost of the energy obtained from a photovoltaic system compared to other sources. The optimization of these aspects involves the exploitation of new materials and development of novel solar cell concepts and designs. Both theoretical modeling and characterization of such devices require a comprehensive view including all scales from the atomic to the macroscopic and industrial scale. The different length scales of the electronic and optical degrees of freedoms specifically lead to an intrinsic need for multiscale simulation, which is accentuated in many advanced photovoltaics concepts including nanostructured regions. Therefore, multiscale modeling has found particular interest in the photovoltaics community, as a tool to advance the field beyond its current limits. In this article, we review the field of multiscale techniques applied to photovoltaics, and we discuss opportunities and remaining challenges.
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| 10. |
- Kvist, Laura, et al.
(författare)
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Endangered subspecies of the Reed Bunting (Emberiza schoeniclus witherbyi and E. s. lusitanica) in Iberian Peninsula have different genetic structures.
- 2011
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 152:3, s. 681-693
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Tidskriftsartikel (refereegranskat)abstract
- In the Iberian Peninsula, populations of two subspecies of the Reed Bunting Emberiza schoeniclus have become increasingly fragmented during the last decades when suitable habitats have been lost and/or the popula- tions have gone extinct. Presently, both subspecies are endangered. We estimated the amount of genetic variation and population structure in order to define conservation units and management practices for these populations. We found that the subspecies lusitanica has clearly reduced genetic variation in nuclear and mitochondrial markers, has a drastically small effective population size and no genetic differentiation between populations. In contrast, the sub- species witherbyi is significantly structured, but the popu- lations still hold large amounts of variation even though the effective population sizes are smaller than in the non- endangered subspecies schoeniclus. We suggest several management units for the Iberian populations. One unit includes subspecies lusitanica as a whole; the other three units are based on genetically differentiated populations of witherbyi. The most important genetic conservation mea- sure in the case of lusitanica is to preserve the remaining habitats in order to at least maintain the present levels of gene flow. In the case of the three management units within witherbyi, the most urgent conservation measure is to improve the habitat quality to increase the population sizes.
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| 11. |
- Mátrai, Norbert, et al.
(författare)
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Do the European Great Reed Warblers (Acrocephalus arundinaceus) reach South Africa during wintering?
- 2012
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 153:2, s. 579-583
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Former studies have shown that the Great Reed Warbler (Acrocephalus arundinaceus) has two genetically distinguishable haplogroups (a ‘‘western’’ and an ‘‘eastern’’ clade). The species occurs in South Africa from January to late March, yet, in the whole database of EURING, there are no recoveries to the south of the Congo. There are at least three hypotheses concerning which birds are seen wintering in South Africa: (1) the European breeders reach South Africa, but there are no ringing recoveries; (2) a mixed population of birds originating from Turkey, Iran and Kazakhstan (Near and Middle East) winters in South Africa; and (3) birds from Europe and the Near and Middle Eastern populations both reach South Africa. We have sequenced a 492-bp part of the mtDNA control region II in 146 samples from five European breeding and one South African wintering population of Great Reed Warblers. The results show that over 60% of the wintering birds in South Africa carry European haplotypes, belonging to both ‘‘eastern’’ and ‘‘western’’ clades. Since the exact haplotypic constitution of the Near and Middle Eastern populations are not known to us, we cannot exclude that a mixed wintering population is formed from birds originating from these regions, but it seems more likely that the European breeders reach South Africa.
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| 12. |
- Neto, Julio, et al.
(författare)
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Autumn migration of Savi's Warblers Locustella luscinioides in Portugal: differences in timing, fuel deposition rate and non-stop flight range between the age classes
- 2008
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Ingår i: Bird Study. - 0006-3657. ; 55:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- Capsule The autumn migration strategy of Portuguese Savi's Warblers differs between age classes in timing, fuel deposition rate and flight range. Aims To describe the autumn migration strategy of Savi's Warblers, and compare the age classes. Methods Data from 533 first captures and 149 retraps, held by the Portuguese Ringing Centre, were analysed, and potential non-stop flight ranges were estimated. Results Juveniles started migrating in early August whereas adults departed at the end of August and both vacated the breeding quarters in early October. In contrast to juveniles, adults showed a marked increase in mass and fat from the end of August and had a significantly greater fuel deposition rate. Accordingly, in adults, the average potential still-air flight range increased dramatically from 600 km in August to 1500 km in September, whereas in juveniles it remained approximately the same (about 150 km). The fattest adults had an average flight range of 2750 km, and so were able, theoretically, to reach the winter quarters without refuelling. Conclusions The autumn migration strategy of Portuguese Savi's Warblers differs between age-classes in timing, fuel deposition rate and flight range. Adult Savi's Warblers are time-selected migrants in autumn. The early departure of juveniles with smaller fuel stores is consistent with their lower fuel deposition rates, as expected under time-minimizing migration models, as is the fuel-overloading and bypassing of potential staging sites seen in adults. However, energy-selected migration cannot be excluded as a possible explanation for the juvenile migration pattern, as these birds left the breeding quarters with only enough fuel to reach the next staging site.
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| 13. |
- Neto, Julio, et al.
(författare)
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Biometrics and sub-specific identification of white-spotted Bluethroats (Luscinia svecica cyanecula and L. s. namnetum) during autumn and winter.
- 2012
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Ingår i: Ardeola. - 0570-7358. ; 59:2, s. 309-315
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Detailed analyses of the biometrics of white-spotted bluethroats captured in the Iberian Peninsula and sub-Saharan Africa show that previous criteria for diagnosing subspecies are inadequate. This deficiency seems to result from feather wear during the breeding period and so new criteria are proposed for the migratory and wintering periods. Foreign recoveries in Portugal indicate that the new criteria work better during these periods but, a small proportion of misidentifications are still likely to occur. As bimodality is shown by biometric traits other than wing length, further refinements should consider the use of multiple traits as well as genetic markers.
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| 14. |
- Neto, Julio, et al.
(författare)
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Distribution, phenology and condition of Aquatic Warblers Acrocephalus paludicola migrating through Portugal.
- 2010
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Ingår i: Ardeola. - 0570-7358. ; 57:1, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- We show that the low number of aquatic warblers Acrocephalus paludicola ringed in Portugal is explained by the low ringing effort, and that Portugal is an important country for its migration. Most of the seven sites where the species was detected are recognized for their biological importance and protected. There seemed to be a decline in the number of birds caught, particularly of juveniles, which might be associated with a decline in breeding success. All aquatic warblers were captured in August and September, showing a peak at the end of August, and adults migrated significantly earlier than juveniles. Both age classes significantly increased in body condition during the season. The potential non-stop flight range varied substantially between individuals: some birds would be able to migrate to the wintering quarters without refueling, but the low flight range of many individuals suggests that some fueling takes place in Portugal.
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| 15. |
- Neto, Julio, et al.
(författare)
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Low frequency of extra-pair paternity in Savi's Warblers (Locustella luscinioides)
- 2010
-
Ingår i: Behaviour. - 1568-539X. ; 147:11, s. 1413-1429
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Tidskriftsartikel (refereegranskat)abstract
- Although the frequency of extra-pair paternity (EPP) has been described for many species, the relative importance of the various contemporary and historical factors explaining EPP variation is still the subject of debate. In this study, we found 11 polymorphic microsatellite loci in the Savi's Warbler (Locustella luscinioides), and used eight loci to analyze the paternity of 392 nestlings belonging to 102 broods of this little-known species. The frequency of EPP was 4.1% of nestlings and 5.9% of broods, which is surprisingly low given what is known about Savi's Warbler's life history and ecology, and among the lowest found of any socially-monogamous passerine bird. Comparisons with similar species indicate that this low frequency is unlikely to have been determined by the ancient evolution of life history strategies. Our observations suggest that the costs of engaging in extra-pair copulations might be high for the females. Larger males, particularly those with longer bill and tarsus, are more likely to be cuckolded; and the few possible comparisons between cuckolded males and extra-pair sires reveal a similar pattern. We further show that bill and tarsus lengths correlate with arrival date, which is associated with individual quality in many migratory bird species.
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| 16. |
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| 17. |
- Neto, Júlio Manuel, et al.
(författare)
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Seasonal dynamics of haemosporidian (Apicomplexa, Haemosporida) parasites in house sparrows Passer domesticus at four European sites : comparison between lineages and the importance of screening methods
- 2020
-
Ingår i: International Journal for Parasitology. - : Elsevier BV. - 0020-7519. ; 50:6-7, s. 523-532
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Tidskriftsartikel (refereegranskat)abstract
- Infectious diseases often vary seasonally in a predictable manner, and seasonality may be responsible for geographical differences in prevalence. In temperate regions, vector-borne parasites such as malaria are expected to evolve lower virulence and a time-varying strategy to invest more in transmission when vectors are available. A previous model of seasonal variation of avian malaria described a double peak in prevalence of Plasmodium parasites in multiple hosts resulting from spring relapses and transmission to susceptible individuals in summer. However, this model was rejected by a study describing different patterns of seasonal variation of two Plasmodium spp. at the same site, with the double peak only apparent when these species were combined. Here, we assessed the seasonal variation in prevalence of haemosporidian parasites (Plasmodium, Haemoproteus and Leucocytozoon) in house sparrows (Passer domesticus) sampled across 1 year at four temperate European sites spanning a latitudinal range of 17°. We showed that parasite prevalence and diversity decreased with increasing latitude, but the parasite communities differed between sites, with only one Plasmodium lineage (P_SGS1) occurring at all sites. Moreover, the nested PCR method commonly used to detect and identify haemosporidian parasites strongly underestimated co-infections of Haemoproteus and Plasmodium, significantly biasing the pattern of seasonal variation, so additional molecular methods were used. Finally, we showed that: (i) seasonal variation in prevalence of haemosporidian parasites varied between study sites and parasite lineages/species/genera, describing further cases where the double peak model is not met; (ii) the seasonal dynamics of single lineages (P_SGS1) varied between sites; and (iii) unexpectedly, seasonality was greatest at the southernmost site, a pattern that was mostly driven by lineage H_PADOM05. Limitations of the genotyping methods and consequences of pooling (parasite lineages, sites and years) in studies of haemosporidian parasites are discussed and recommendations proposed, since these actions may obscure the patterns of prevalence and limit ecological inferences.
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| 18. |
- Neto, Júlio Manuel, et al.
(författare)
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Stable isotopes reveal differences in diet among reed bunting subspecies that vary in bill size
- 2017
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 48:2, s. 284-294
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Tidskriftsartikel (refereegranskat)abstract
- Reed bunting Emberiza schoeniclus subspecies vary considerably in bill size and shape and seem to be at an early stage of speciation, in which bill might be indirectly causing reproductive isolation. Hence, we evaluated whether bill size, as well as age and sex, are associated with foraging niche in three west European subspecies of reed bunting: the thin-billed schoeniclus, the intermediate-billed lusitanica and the thick-billed witherbyi. Blood sampling was undertaken at three sites in southwest Europe during the winter (when these subspecies co-occur), and stable isotope analyses (carbon and nitrogen) were performed to assess their foraging niches. Stable isotope analyses of potential food items confirmed uniform baseline isotopic composition among sites. schoeniclus showed a significantly broader isotopic niche than lusitanica and witherbyi, which seemed otherwise similar despite the fact that witherbyi is more divergent in bill traits. Stable isotope ratios were consistent with the latter two subspecies feeding on C3-plant-feeding insects, whereas schoeniclus diet also included C4 plant material. Despite its lower sexual dimorphism, sex and age differences were found only in schoeniclus, but these differences vary between locations in a complex manner. Our results suggest that bill size and shape differentiated between northern, migratory and southern, resident subspecies as a consequence of natural selection through competition during the winter, which is now reflected in isotopic niche divergence between subspecies. The potential roles of sexual selection, reed thickness and summer temperature on the difference in bill size (and greater sexual dimorphism) between lusitanica and witherbyi are discussed.
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| 19. |
- Neto, Julio
(författare)
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Nest-site selection and predation in Savi’s Warblers, Locustella luscinioides.
- 2008
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Ingår i: Bird Study. - : Informa UK Limited. - 0006-3657 .- 1944-6705. ; 53:2, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- Capsule: Savi’s Warblers preferred sites dominated by high and dense Juncus and Rubus with thick litter, and avoided pure reeds; predation was higher in sites with less litter. Aim: To describe nest-site selection and identify which habitat and nest features influence predation risk. Methods: Comparisons were made between habitat characteristics measured at nest-sites and random points, and between predated and successful nests. Results: Total vegetation cover, litter thickness, habitat type, undergrowth height and undergrowth cover, which were higher or denser at nest-sites, were the most important variables influencing the distribution of Savi’s Warbler nests. Nests were most often predated in sites with low litter thickness. Conclusion: Savi’s Warblers are dependent on the presence of dense low vegetation and litter for nesting, which should be maintained close to or within reed-beds for their benefit.
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| 20. |
- Neto, Julio, et al.
(författare)
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Phenotypic Divergence among West European Populations of Reed Bunting Emberiza schoeniclus: The Effects of Migratory and Foraging Behaviours
- 2013
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Divergent selection and local adaptation are responsible for many phenotypic differences between populations, potentially leading to speciation through the evolution of reproductive barriers. Here we evaluated the morphometric divergence among west European populations of Reed Bunting in order to determine the extent of local adaptation relative to two important selection pressures often associated with speciation in birds: migration and diet. We show that, as expected by theory, migratory E. s. schoeniclus had longer and more pointed wings and a slightly smaller body mass than the resident subspecies, with the exception of E. s. lusitanica, which despite having rounder wings was the smallest of all subspecies. Tail length, however, did not vary according to the expectation (shorter tails in migrants) probably because it is strongly correlated with wing length and might take longer to evolve. E. s. witherbyi, which feed on insects hiding inside reed stems during the winter, had a very thick, stubby bill. In contrast, northern populations, which feed on seeds, had thinner bills. Despite being much smaller, the southern E. s. lusitanica had a significantly thicker, longer bill than migratory E. s. schoeniclus, whereas birds from the UK population had significantly shorter, thinner bills. Geometric morphometric analyses revealed that the southern subspecies have a more convex culmen than E. s. schoeniclus, and E. s. lusitanica differs from the nominate subspecies in bill shape to a greater extent than in linear bill measurements, especially in males. Birds with a more convex culmen are thought to exert a greater strength at the bill tip, which is in agreement with their feeding technique. Overall, the three subspecies occurring in Western Europe differ in a variety of traits following the patterns predicted from their migratory and foraging behaviours, strongly suggesting that these birds have became locally adapted through natural selection.
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| 21. |
- Neto, Julio, et al.
(författare)
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Phylogeography of a Habitat Specialist with High Dispersal Capability: The Savi’s Warbler Locustella luscinioides
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- In order to describe the influence of Pleistocene glaciations on the genetic structure and demography of a highly mobile, but specialized, passerine, the Savi’s Warbler (Locustella luscinioides), mitochondrial DNA sequences (ND2) and microsatellites were analysed in c.330 individuals of 17 breeding and two wintering populations. Phylogenetic, population genetics and coalescent methods were used to describe the genetic structure, determine the timing of the major splits and model the demography of populations. Savi’s Warblers split from its sister species c.8 million years ago and have two major haplotype groups that diverged in the early/middle Pleistocene. One of these clades originated in the Balkans and is currently widespread, showing strong evidence for population expansion; whereas the other is restricted to Iberia and remained stable. Microsatellites agreed with a genetic break around the Pyrenees, but showed considerable introgression and a weaker genetic structure. Both genetic markers showed an isolation-by-distance pattern associated with the population expansion of the eastern clade. Breeding populations seem to be segregated at the wintering sites, but results on migratory connectivity are preliminary. Savi’s Warbler is the only known migratory bird species in which Iberian birds did not expand beyond the Pyrenees after the last glaciation. Despite the long period of independent evolution of western and eastern populations, complete introgression occurred when these groups met in Iberia. Mitochondrial sequences indicated the existence of refugia-within-refugia in the Iberian Peninsula during the last glacial period, which is surprising given the high dispersal capacity of this species. Plumage differences of eastern subspecies seemed to have evolved recently through natural selection, in agreement with the glacial expansion hypothesis. This study supports the great importance of the Iberian Peninsula and its role for the conservation of genetic variation.
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| 22. |
- Neto, Julio, et al.
(författare)
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Post-juvenile and post-breeding moult of Savi’s Warblers Locustella luscinioides in Portugal.
- 2006
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Ingår i: Ibis. - 0019-1019. ; 148:1, s. 39-49
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Tidskriftsartikel (refereegranskat)abstract
- We describe the sequence and extent of the complex and little understood post-juvenile and post-breeding moults of Savi’s Warblers Locustella luscinioides. In contrast to previous studies, the post-juvenile moult occurred in at least 44% of the birds, 5% of which moulted some or all tertials and greater coverts. The timing of overlap between the filling and the post-juvenile moults, and the fact that later-moulting birds had no post-juvenile moult, strongly suggests that the moult extent is dependent on fledging date. From July onwards, all adult males overlapped breeding and moult, whereas only 11% of the females did so. The start of moult varied from 6 June to 25 August, and was significantly earlier in males. Only 18% of the birds completed the moult, whereas the remaining individuals retained a variable number of inner primaries and/or secondaries. Interestingly, not only was the number of retained primaries positively associated with the date of moult, but so too was the primary number of birds in which the moult started. We view this as an adaptation allowing the replacement of the most important feathers for flight when the time available for moult is short. Body condition did not vary with the progress of moult when date was taken into account, but fat reserves still tended to decrease and then increase. The body condition was correlated positively with the wing raggedness, so Savi’s Warblers do not compensate for an increasing wing load during moult.
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| 23. |
- Neto, Julio, et al.
(författare)
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Prevalence and diversity of Plasmodium and Haemoproteus parasites in the globally-threatened Aquatic Warbler Acrocephalus paludicola.
- 2015
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Ingår i: Parasitology. - 1469-8161. ; 142:9, s. 1183-1189
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Tidskriftsartikel (refereegranskat)abstract
- The diversity and prevalence of malaria parasites of the genera Plasmodium and Haemoproteus were determined in the globally-threatened Aquatic Warbler Acrocephalus paludicola. Birds were sampled during migration in Portugal and at the wintering quarters in Senegal and parasites were detected using molecular methods. Only three generalist parasite lineages (Plasmodium) were found. There were no significant differences in the prevalence of parasites between sexes in Europe, but adults had higher prevalence than first-year birds, and birds in Europe had higher prevalence than those captured in Africa. When comparing with other Acrocephalus species and taking sample size into account, Aquatic Warblers had the lowest prevalence and, together with another threatened species, the Seychelles Warbler Acrocephalus sechellensis, the lowest diversity of malaria parasites. We hypothesize that the low diversity of parasites and absence of specialist lineages of Aquatic Warblers are caused by its small population size and fragmented distribution. Furthermore, Aquatic Warblers' extreme habitat specialization may decrease their exposure to malaria parasites, but other explanations such as high mortality (which would constraint the sampling of infected birds) or, in contrast, very efficient immunological system in clearing the infections cannot be ruled out. This study contributes to explain variation in prevalence and diversity of malaria parasites among hosts.
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| 24. |
- Neto, Julio, et al.
(författare)
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Sex allocation in Savi’s Warblers Locustella luscinioides: multiple factors affect seasonal trends in brood sex ratios.
- 2011
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 1432-0762 .- 0340-5443. ; 65:2, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- Sex allocation theory predicts that whenever the relative fitness of sons and daughters differ, females should invest more in the sex with the greatest fitness return. In this study, we evaluated the influence of various ecological factors on the brood sex ratio (BSR) of Savi’s warblers (Locustella luscinioides) across several breeding seasons. There was a slight but significant female production bias at the population level, which is consistent with the ‘local resource competition’ hypothesis, as the breeding density is very high and females are more prone to disperse. We found that there was a significant decline in BSR during the breeding season, but no influence of male size, female size, social status nor extra-pair paternity were detected. The seasonal decline in BSR was further evaluated by assessing the within- and between-female effects, which indicated that multiple factors were operating simultaneously in our study population. First, there was a significant within- female decline in BSR, which was consistent with the decline in female condition due to the reproductive effort associated with multiple brooding (supporting the Trivers and Willard hypothesis). Second, a significant decline in BSR with the laying date of first clutches of different pairs indicated that male and/or female qualities are also associated with the seasonal variation in BSR. Finally, a comparison between the sex of the youngest nestling with the remaining ones did not suggest any bias, indicating that females do not compensate for the increased mortality of the last nestling (caused by asynchronous hatching) by producing a male from the last laid egg.
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| 25. |
- Neto, Julio, et al.
(författare)
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Using stable isotope analysis to determine the winter moult extent in migratory birds: the complex moult of Savi’s Warblers Locustella luscinioides.
- 2006
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 37:1, s. 117-124
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Tidskriftsartikel (refereegranskat)abstract
- Patterns of feather wear in birds captured in spring have traditionally been analysed to describe the extent of winter moult in long-distance migrants. However, the interpretation of feather wear may be rendered extremely difficult due to long moult periods, by the progress of the season, and by the existence of complex moult patterns. Here, stable isotope analysis is used to determine the origin of the wing feather generations present in Savi’s warblers Locustella luscinioides captured in Portugal. Carbon, nitrogen and hydrogen isotope ratios of feathers of known European origin differed significantly from those known to have grown in Africa. A discriminant analysis, in which 91.1% of the cross validated samples were correctly classified, was used to determine the origin of tail and wing feathers collected from birds caught when they returned to the breeding quarters. The interpretation of feather-wear generally agreed with the stable isotope analysis, but some inconsistencies were identified. The extent of winter moult in Savi’s warblers is described and its moult strategy discussed.
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| 26. |
- Neto, Julio, et al.
(författare)
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Variation in body condition of breeding Savi's Warblers Locustella luscinioides: the reproductive stress and flight adaptation hypothesis revisited
- 2010
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7206 .- 2193-7192. ; 151:1, s. 201-210
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Tidskriftsartikel (refereegranskat)abstract
- Current theory suggests that mass change in adult birds while breeding may be adaptive (to reduce wing-loading during nestling feeding) or result from physiological stress. To test which might be more important in determining mass loss in breeding Savi's Warblers (Locustella luscinioides), we used a new approach in which the variation in four indices of body condition was described: weight, fat score, muscle score and lean weight (i.e. excluding fat and muscle). We expected weight variations to be adaptive if they involved changes in fat and lean weight, whereas physiological stress should influence the muscle score to a greater extent. As in other species, females showed a greater variation in weight, and carried more fat, than males during the breeding cycle. During incubation, females had greater weight and fat score than males. The weight remained constant and lean weight declined in both sexes, whereas females increased in muscle, which probably reflects the regression of the reproductive organs. During the nestling stage, both sexes declined significantly in all four indices of condition, showing evidence of physiological stress. However, the greater decline in weight in females than in males is consistent with the flight-adaptation hypothesis, as are the cyclic changes in lean weight associated with the various nesting attempts. The fact that both sexes declined significantly in weight, muscle and lean weight with an increasing number of nesting attempts, but not in fat, which was recovered after each nestling period, also indicates that both reproductive stress and adaptive changes occur during breeding. When the whole breeding season was considered, females showed a greater decline in muscle than males, which we interpret to be evidence for a greater reproductive stress in females. We suggest that the small breast muscle size and depleted protein reserves at the end of the breeding period might influence future survival through impaired flight ability and a compromised post-breeding moult.
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| 27. |
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| 28. |
- Norte, Ana Cláudia, et al.
(författare)
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Host dispersal shapes the population structure of a tick-borne bacterial pathogen
- 2020
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 29:3, s. 485-501
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Tidskriftsartikel (refereegranskat)abstract
- Birds are hosts for several zoonotic pathogens. Because of their high mobility, especially of longdistance migrants, birds can disperse these pathogens, affecting their distribution and phylogeography. We focused on Borrelia burgdorferi sensu lato, which includes the causative agents of Lyme borreliosis, as an example for tick-borne pathogens, to address the role of birds as propagation hosts of zoonotic agents at a large geographical scale. We collected ticks from passerine birds in 11 European countries. B. burgdorferi s.l. prevalence in Ixodes spp. was 37% and increased with latitude. The fieldfare Turdus pilaris and the blackbird T. merula carried ticks with the highest Borrelia prevalence (92 and 58%, respectively), whereas robin Erithacus rubecula ticks were the least infected (3.8%). Borrelia garinii was the most prevalent genospecies (61%), followed by B. valaisiana (24%), B. afzelii (9%), B. turdi (5%) and B. lusitaniae (0.5%). A novel Borrelia genospecies “Candidatus Borrelia aligera” was also detected. Multilocus sequence typing (MLST) analysis of B. garinii isolates together with the global collection of B. garinii genotypes obtained from the Borrelia MLST public database revealed that: (a) there was little overlap among genotypes from different continents, (b) there was no geographical structuring within Europe, and (c) there was no evident association pattern detectable among B. garinii genotypes from ticks feeding on birds, questing ticks or human isolates. These findings strengthen the hypothesis that the population structure and evolutionary biology of tick-borne pathogens are shaped by their host associations and the movement patterns of these hosts.
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| 29. |
- Nus, Tim Van, et al.
(författare)
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Urban Roost of Wintering Barn Swallows Hirundo rustica in Aveiro, Portugal
- 2017
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Ingår i: Ardea. - : Netherlands Ornithologists' Union. - 0373-2266. ; 105:1, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- We describe the finding of an urban roost of wintering Barn Swallows Hirundo rustica in Aveiro, Portugal, which remained stable with c.150 individuals from at least early December to mid-January 2015/16. The stability in numbers and the occurrence of freshly-shed primary feathers below the roost strongly indicate that these were indeed wintering birds that completed their annual moult and suffered a relatively low mortality during this period. The number of roosting Barn Swallows steeply declined in late January, coinciding with the appearance of singing males in the area and the arrival of numerous migrants from Africa to Portugal. The site characteristics and roosting behaviour are described, and the potential advantages of urban roosting discussed. Although this particular winter was unusually mild, observations indicate that this roost may have been present in previous years, and others may occur elsewhere in the Iberian Peninsula.
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| 30. |
- Prochazka, Petr, et al.
(författare)
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Using stable hydrogen isotopes (delta H-2) and ring recoveries to trace natal origins in a Eurasian passerine with a migratory divide
- 2013
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Ingår i: Journal of Avian Biology. - 0908-8857. ; 44:6, s. 541-550
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Tidskriftsartikel (refereegranskat)abstract
- Despite recent advances in technology, it remains difficult to connect breeding and non-breeding areas of populations of migratory organisms due to the challenges of year-round tracking. Here, we used the Eurasian reed warbler Acrocephalus scirpaceus, a passerine with a pronounced migratory divide to demonstrate the promise of integrating several sources of information within the Bayesian modelling framework for the study of migratory connectivity. To this end, we combined data from stable hydrogen isotope ratios (H-2) of feathers, ring recoveries, and the geographic delineation of sub-populations on either side of the migratory divide. Feather H-2 measurements from local juvenile birds sampled across the breeding range tightly correlated with amount-weighted mean annual precipitation H-2 values predicted for the natal sites. Predicted natal origins of birds intercepted en route in the Mediterranean region largely differed among the five stopover sites. Thanks to the different migratory pathways used by different breeding populations and the existence of a migratory divide, we were able to effectively narrow the assigned regions of origin. Our results show that spatial resolution of likelihood-based assignments of geographic origins based on H-2 measurements may improve significantly when prior probabilities derived from population-specific migratory directions are included. Integrating information from stable isotopes, ring recoveries, geolocators and other sources within the Bayesian modelling framework will provide an extremely useful toolbox for the study of animal movements in the future.
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| 31. |
- Raković, Marko, et al.
(författare)
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Geographic patterns of mtDNA and Z-linked sequence variation in the Common Chiffchaff and the ‘chiffchaff complex’
- 2019
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The Common Chiffchaff Phylloscopus collybita is an abundant, polytypic Palearctic bird. Validity of some of its subspecies is controversial and birds from some parts of the species range remain unclassified taxonomically. The relationships among populations from different geographic areas have not been sufficiently explored with molecular data. In this study we analyzed the relationships among the four species in the ‘chiffchaff complex’ (Common Chiffchaff, Iberian Chiffchaff P. ibericus, Canary Islands Chiffchaff P. canariensis and Mountain Chiffchaff P. sindianus), and the patterns of intraspecific geographic variation in the mtDNA ND2 gene and intron 9 of the Z-linked aconitase gene (ACO1I9) across the Common Chiffchaff range, including a recently discovered population breeding on Mt. Hermon (Anti-Lebanon mountains). Our data supported the monophyly of the chiffchaff complex and its current systematics at the species level. Within the Common Chiffchaff, the Siberian race P. c. tristis was the most differentiated subspecies and may represent a separate or incipient species. Other Common Chiffchaff subspecies also were differentiated in their mtDNA, however, lineages of neighboring subspecies formed wide zones of introgression. The Mt. Hermon population was of mixed genetic origin but contained some birds with novel unique lineage that could not be assigned to known subspecies. All Common Chiffchaff lineages diverged at the end of the Ionian stage of Pleistocene. Lineage sorting of ACO1I9 alleles was not as complete as that of mtDNA. Chiffchaff species were mostly distinct at ACO1I9, except the Common and Canary Islands Chiffchaffs that shared multiple alleles. An AMOVA identified geographic structure in Common Chiffchaff ACO1I9 variation that was broadly consistent with that of mtDNA ND2 gene. The genetic and other data suggest the chiffchaff complex to be a group of evolutionarily young taxa that represent a paradigm of ‘species evolution in action’ from intergrading subspecies through to apparently complete biological speciation.
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| 32. |
- Tobler, Michael, et al.
(författare)
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Telomeres in ecology and evolution : A review and classification of hypotheses
- 2022
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 31:23, s. 5946-5965
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Forskningsöversikt (refereegranskat)abstract
- Research on telomeres in the fields of ecology and evolution has been rapidly expanding over the last two decades. This has resulted in the formulation of a multitude of, often name-given, hypotheses related to the associations between telomeres and life-history traits or fitness-facilitating processes (and the mechanisms underlying them). However, the differences (or similarities) between the various hypotheses, which can originate from different research fields, are often not obvious. Our aim here is therefore to give an overview of the hypotheses that are of interest in ecology and evolution and to provide two frameworks that help discriminate among them. We group the hypotheses (i) based on their association with different research questions, and (ii) using a hierarchical approach that builds on the assumptions they make, such as about causality of telomere length/shortening and/or the proposed functional consequences of telomere shortening on organism performance. Both our frameworks show that there exist parallel lines of thoughts in different research fields. Moreover, they also clearly illustrate that there are in many cases competing hypotheses within clusters, and that some of these even have contradictory assumptions and/or predictions. We also touch upon two topics in telomere research that would benefit from further conceptualization. This review should help researchers, both those familiar with and those new to the subject, to identify future avenues of research.
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| 33. |
- Watson, Hannah, et al.
(författare)
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Only rare classical MHC-I alleles are highly expressed in the European house sparrow
- 2024
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - 0962-8452. ; 291:2017
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Tidskriftsartikel (refereegranskat)abstract
- The exceptional polymorphism observed within genes of the major histocompatibility complex (MHC), a core component of the vertebrate immune system, has long fascinated biologists. The highly polymorphic classical MHC class-I (MHC-I) genes are maintained by pathogen-mediated balancing selection (PMBS), as shown by many sites subject to positive selection, while the more monomorphic non-classical MHC-I genes show signatures of purifying selection. In line with PMBS, at any point in time, rare classical MHC alleles are more likely than common classical MHC alleles to confer a selective advantage in host–pathogen interactions. Combining genomic and expression data from the blood of wild house sparrows Passer domesticus, we found that only rare classical MHC-I alleles were highly expressed, while common classical MHC-I alleles were lowly expressed or not expressed. Moreover, highly expressed rare classical MHC-I alleles had more positively selected sites, indicating exposure to stronger PMBS, compared with lowly expressed classical alleles. As predicted, the level of expression was unrelated to allele frequency in the monomorphic non-classical MHC-I alleles. Going beyond previous studies, we offer a fine-scale view of selection on classical MHC-I genes in a wild population by revealing differences in the strength of PMBS according to allele frequency and expression level.
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| 34. |
- Wojczulanis-Jakubas, Katarzyna, et al.
(författare)
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Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration
- 2017
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Ingår i: Die Naturwissenschaften. - : Springer Science and Business Media LLC. - 1432-1904. ; 104:11-12, s. 101-101
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Tidskriftsartikel (refereegranskat)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.
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| 35. |
- Zhao, Tianhao, et al.
(författare)
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Autumn migration direction of juvenile willow warblers (Phylloscopus t. trochilus and P. t. acredula) and their hybrids assessed by qPCR SNP genotyping
- 2020
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Ingår i: Movement Ecology. - : BMC. - 2051-3933. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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