Der sibirische Zilpzalp (Phylloscopus collybita tristis): Gesang und Reaktion einer mitteleurop?ischen Population im Freilandversuch

Zusammenfassung Der Gesang des sibirischen ZilpzalpsPhylloscopus collybita tristis unterscheidet sich markant von jenem der beiden mittel- und ost-europäischen SubspeziesPh. c. collybita undPh. c. abietinus. Unterschiede betreffen Qualität und Quantität des Element-Repertoires, Syntax, Rhythmus innerhalb der Strophen und Frequenzumfang der Strophe.Tristis verfügt über den reicheren und vielfältigeren Gesang. Das wird als apomorphes Merkmal betrachtet. Eine mitteleuropäischecollybita-Population reagiert auftristis-Gesang im Feld-Experiment fast nicht. Nur solche Kunst-Strophen aus natürlichen Elementen vontristis werden vergleichsweise gut beantwortet, die Elementen entsprechen, über die auch mitteleuropäischecollybita verfügen. Die sibirische Gesangsform ist auf über 4000 km W-O-Erstreckung offensichtlich nahezu konstant. Der westliche Arealteil vonc. tristis, oft alsc. fulvescens bezeichnet (Ural bis Jenissei-Tal, 2000 km W-O) kann nicht als Hybrid-Population angesehen werden (abietinus xtristis), da sich in diesem Gebiet keine Merkmale desabietinus-Gesanges nachweisen lassen.

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Territorial song of the siberian chiffchaff (Phylloscopus collybita tristis) and playback experiments within a central european population (Ph. c. collybita)

Summary Territorial songs of Siberian ChiffchaffsPhylloscopus collybita tristis distinctly differ from songs of the Central and East European subspeziesPh. c. collybita andPh. c. abietinus (which do not differ from each other). Differences betweentristis andcollybita/abietinus concern quality and quantity of the notes within the song verses, syntax, rhythm within the song verses, and frequency range of the song verses.Tristis disposes of richer and more manifold song which is said to be an apomorphic character.Ph. c. collybita from Central Europe (Mainz area) using much more limited numbers of differing notes, displays nearly no territorial response totristis song in the field experiments. Only those artificial verses consisting of notes which are used also byc. collybita, were reacted on. The Siberian form of chiffchaff song is apparently more or less constant to about 4000 km in W-E extension. The Western part of thetristis range, often calledc. fulvescens (Ural to Yenisei river, 2000 km W-E), is not to be considered a hybrid population ofabietinus andtristis proper, for no characteristics ofabietinus song are taceable in thefulvescens area.

     

Male‐biased gene flow across an avian hybrid zone: evidence from mitochondrial and microsatellite DNA

Mating pattern and gene flow were studied in the contact zone between two morphologically very similar Chiffchaff taxa (Phylloscopus collybita, P. brehmii) in SW France and northern Spain. Mating was assortative in brehmii, but not in collybita. Mixed matings were strongly asymmetric (excess of collybita male × brehmii female pairs), but did produce viable offspring in some cases. Sequence divergence of the mitochondrial cytochrome b gene was 4.6%. Haplotypes segregated significantly with phenotype (only five ‘mismatches’ among 94 individuals), demonstrating that mitochondrial gene flow was very restricted. The estimated proportion of F₁ hybrids in the reproductive population was significantly lower than expected under a closed population model, indicating strong selection against hybrids. Genetic typing of 101 individuals at four microsatellite loci also showed significant population differentiation, but nuclear gene flow was estimated to be 75 times higher than mitochondrial gene flow. This strong discrepancy is probably due to unisexual hybrid sterility (Haldane’s rule). Thus, there is a strong, but incomplete, reproductive barrier between these taxa.     

Gesangsformen und Verwandtschaft der asiatischen ZilpzalpePhylloscopus collybita abietinus undPh. c. sindianus

Zusammenfassung Die Territorialgesänge zweier geographisch isolierter Zilpzalp-Populationen werden untersucht.Ph. c. abietinus aus dem Elbursgebirge (Iran) ist von skandinavischenc. abietinus und von mitteleuropäischenc. collybita fast nicht verschieden.Ph. c. sindianus aus dem NW-Himalaya verfügt über Elemente, deren Frequenz zu Beginn ansteigt; sie machen etwa ein Drittel des Element-Repertoires aus.Ph. c. collybita undc. abietinus fehlen solche Elemente, jedoch besitzt sie der sibirischec. tristis in ganz ähnlicher Form.Attrappen-Versuche bestätigen den Unterschied. Original-Strophen vonc. sindianus werden von deutschenc. collybita deutlich schlechter beantwortet als die der lokalen Form, Kunst-Strophen aus ansteigenden Elementen gar nicht.Die Befunde über reaktionsauslösende Parameter des mZ früherer Autoren werden weitgehend bestätigt. Es ergeben sich einige Ergänzungen.1) Elemente, deren 2. Schenkel annähernd oder vollständig bis zur Höhe des 1. Schenkels aufsteigt (P6, J11, J12; Abb. 10, 12), können starke oder schwache Reaktion auslösen (nicht nur schwache). Das ist abhängig von weiteren Merkmalen des Elements, vor allem des 2. El.-Teiles.2) Elemente mit sehr steilem Anstiegswinkel (= schneller Frequenzabfall im 1. El.-Teil; maximal 91,5° : P7, ferner P6, J12; Abb. 10, 12) lösten starke Reaktion aus. El. kanarischer Zilpzalpe(c. canariensis) mit ebenso steilem 1. El.-Teil haben abweichende 2. El.-Teile; offensichtlich diese wirken im Versuch hemmend auf den mZ.Nach akustischen und morphologischen Merkmalen gehörtPh. c. sindianus in die Verwandtschaft vonPh. c. tristis; er kann nicht als eigene Art gelten (vgl.Voous 1977).Ph. c. abietinus steht der mitteleuropäischen Nominatform sehr nahe.

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Territorial songs and relationships of the Asian chiffchaffsPhylloscopus collybita abietinus andPh. c. sindianus

Summary The territorial songs of two geographically isolated chiffchaff populations are analyzed. Songs ofPh. c. abietinus (Elburz Mts., Iran) are nearly identical with those of Scandinavianc. abietinus and Central Europeanc. collybita. One third of the notes ofPh. c. sindianus (NW Himalayas) ascend in frequency at the beginning. Such notes are lacking inPh. c. collybita andc. abietinus, but exist in the Siberianc. tristis.Playback experiments confirm the differences. Original songs ofc. sindianus elicit a distinctly weaker reaction by Germanc. collybita than local songs. Artificial songs (made from natural notes) of ascendingsindianus notes elicit ro reaction (J4, fig. 11).Earlier findings on parameters important for releasing territorial behaviour in the Central Europeanc. collybita are largely confirmed and new results suggest minor differences only.1) Notes in which the frequency of the second part is as high as the first part (P6, J11, J12; fig. 10, 12) may release strong or weak reactions. This depends on additional characteristics of the note, mainly of its 2. part.2) Notes with very steep ascending angle (max. 91,5° : P7, also P6, J12, fig. 10, 12) release a strong reaction.Ph. c. canariensis with notes as steep as inc. abietinus andc. sindianus differ in the second part of the note. It inhibits the reaction ofc. collybita of Central Europe.Regarding acoustical and morphological characteristics,Ph. c. sindianus is close toPh. c. tristis. It cannot be treated a separate species. The nearest relative ofc. abietinus is the Central Europeanc. collybita.

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Results of the Himalaya Expeditions ofJ. Martens, No. 82. — No. 81: Reichenbachia,19 (18), 1981. — J. M. sponsored by Deutscher Akademischer Austauschdienst and Deutsche Forschungsgemeinschaft.     

Patterns of genetic,phenotypic, and acoustic variation across a chiffchaff (Phylloscopus collybita abietinus/tristis) hybrid zone

Characterizing patterns of evolution of genetic and phenotypic divergence between incipient species is essential to understand how evolution of reproductive isolation proceeds. Hybrid zones are excellent for studying such processes, as they provide opportunities to assess trait variation in individuals with mixed genetic background and to quantify gene flow across different genomic regions. Here, we combine plumage, song, mtDNA and whole‐genome sequence data and analyze variation across a sympatric zone between the European and the Siberian chiffchaff (Phylloscopus collybita abietinus/tristis) to study how gene exchange between the lineages affects trait variation. Our results show that chiffchaff within the sympatric region show more extensive trait variation than allopatric birds, with a large proportion of individuals exhibiting intermediate phenotypic characters. The genomic differentiation between the subspecies is lower in sympatry than in allopatry and sympatric birds have a mix of genetic ancestry indicating extensive ongoing and past gene flow. Patterns of phenotypic and genetic variation also vary between regions within the hybrid zone, potentially reflecting differences in population densities, age of secondary contact, or differences in mate recognition or mate preference. The genomic data support the presence of two distinct genetic clades corresponding to allopatric abietinus and tristis and that genetic admixture is the force underlying trait variation in the sympatric region—the previously described subspecies (“fulvescens”) from the region is therefore not likely a distinct taxon. In addition, we conclude that subspecies identification based on appearance is uncertain as an individual with an apparently distinct phenotype can have a considerable proportion of the genome composed of mixed alleles, or even a major part of the genome introgressed from the other subspecies. Our results provide insights into the dynamics of admixture across subspecies boundaries and have implications for understanding speciation processes and for the identification of specific chiffchaff individuals based on phenotypic characters.     

Ornithophilie auf den Canarischen Inseln

(1) On the Canary Islands and Madeira typical bird-flowers occur in at least twelve species of six genera, although true flower-birds are absent. This inconsistency is in part elucidated by field observations on exotic and wild plants of Tenerife. —(2) In the Botanical Garden of Orotava it could be observed that various ornithophilous plants, which were introduced there, were visited by indigenous birds for nectar and in one case (Orthostemon) for food tissue. Of the three bird species involved, an endemic race of Chiffchaff (Phylloscopus collybita) and resident Blackcaps (Sylvia atricapilla) exploit, and pollinate, flowers legitimously, while the Wild Canary (Serinus canaria) is predominantly a destructive nectar robber. —(3) The insular Chiffchaff also proved to be a regular pollinator in the wild, at least ofCanarina canariensis andIsoplexis canariensis, two ornithophilous paleoendemics. Ornithophily, thus, is naturally practised on the island, though by birds basically insectivorous. —(4) A list of Macaronesian plants bearing the more or less complete ornithophilous syndrome is presented, including newly recognizedTeucrium heterophyllum andScrophularia calliantha. —(5) On biogeographical and faunistic grounds it is presumed that the modern visitors of Canarian bird flowers are secondary rather than the original partners of the continental tertiary flora in which these plants originated. Palearctic immigrants, when becoming resident on the islands during and since the Pleistocene, adopted facultative nectar feeding, entering an orphaned food niche. Casual flower visits in Europe suggest a certain predisposition of the Chiffchaff and the Blackcap for the exploitation of flowers. — (6) The ability of unspecialized birds to acquire nectardrinking spontaneously and to pass this habit on to their offspring, is demonstrated by a population of Tree Sparrows (Passer montanus) which have visited ornithophilousKniphofia (Liliaceae) in Berlin for several years.

     

Breeding ground temperature rises,more than habitat change,are associated with spatially variable population trends in two species of migratory bird

Habitat loss and climate change are key drivers of global biodiversity declines but their relative importance has rarely been examined. We attempted to attribute spatially divergent population trends of two Afro-Palaearctic migrant warbler species, Willow Warbler Phylloscopus trochilus and Common Chiffchaff Phylloscopus collybita, to changes in breeding grounds climate or habitat. We used bird counts from over 4000 sites across the UK between 1994 and 2017, monitored as part of the BTO/JNCC/RSPB Breeding Bird Survey. We modelled Willow Warbler and Common Chiffchaff population size and growth in relation to habitat, climate and weather. We then used the abundance model coefficients and observed environmental changes to determine the extent to which spatially varying population trends in England and Scotland were consistent with attribution to climate and habitat changes. Both species' population size and growth correlated with habitat, climate and weather on their breeding grounds. Changes in habitat, in particular woodland expansion, could be linked to small population increases for both species in England and Scotland. Both species' populations correlated more strongly with climate than weather, and both had an optimum breeding season temperature: 11°C for Willow Warbler and around 13.5°C for Common Chiffchaff (with marginally different predictions from population size and growth models). Breeding ground temperature increases, therefore, had the potential to have caused some of the observed Willow Warbler declines in England (where the mean breeding season temperature was 12.7°C) and increases in Scotland (mean breeding season temperature was 10.2°C), and some of the differential rates of increase for Common Chiffchaff. However, much of the variation in species' population abundance and trends were not well predicted by our models and could be due to other factors, such as species interactions, habitat and climate change in their wintering grounds and on migration. This study provides evidence that the effect of climate change on a species may vary spatially and may switch from being beneficial to being detrimental if a temperature threshold is exceeded.     

Range expansion and the possibility of an emerging contact zone between two subspecies of Chiffchaff Phylloscopus collybita ssp.

The Chiffchaff Phylloscopus collybita is represented in Sweden by two different subspecies; the northern well-established abietinus and the southern recently established collybita which has expanded its range northward during the past two decades. At present, an area approximately 500 km wide separates the two subspecies. In order to document differences between the northern and southern populations we compared morphology, vocalisation, habitat choice, and neutral genetic variation in mitochondrial (mt) DNA and at four microsatellite loci of 30 male Chiffchaffs from each subspecies. Our results show significant differences in several morphological traits and in song. Playback experiments revealed a significant difference in aggressive behaviour depending on which population-specific song that was played to the birds. Mitochondrial DNA was geographically structured with ∼90% of the birds carrying a mt haplotype matching their sample population. No allelic differences at the microsatellite loci were found between populations. Our data demonstrate a substantial differentiation between the northern and southern populations despite gene flow, clearly separating them into the subspecies abietinus and collybita .     

Neighbour recognition in two sister songbird species with a simple and complex repertoire – a playback study

The ability of individuals to recognize others based on vocalizations has been proven in many species of birds. However, we are still far from understanding important aspects of the discrimination process. For example, it is still not fully understood whether, and why, repertoire size hinders discrimination between individuals. Further, the strategies and vocal cues used for discrimination between individuals are largely unexplored. In this study, we tested the ability of chiffchaffs Phylloscopus collybita and willow warblers Phylloscopus trochilus, two closely related species with different repertoire sizes and song organization, to differentiate between their neighbours on the basis of a single song of a neighbouring male. We did playback experiments within the ‘dear enemy’ paradigm in which we tested resident males with a single song of a neighbour broadcast from the correct and opposite, incorrect territory border. Both species displayed a strong ability to discriminate between their neighbours representing further evidence that repertoire size per se has no negative impact on individual recognition in songbirds. Using a single song for playback allowed us to speculate about the nature of the possible cues used by males for recognition. Individual recognition in both species is most likely based on the modulation of syllables or on general voice characteristics. We suggest that specific changes in song organization, for example the tendency of individuals to insert a distinct phrase at the beginning of each song, may facilitate individual recognition and compensate for increased repertoire size in willow warblers.     

Is earlier spring migration of Tatarstan warblers expected under climate warming?

We analysed data on the arrival dates of four species of leaf warbler (genus Phylloscopus) collected in Tatarstan between 1957 and 2004. There was no evidence over the whole period that the warblers returned to their breeding sites significantly earlier, mainly because local temperatures for April and May, months when the majority of birds arrived from their wintering grounds, did not increase significantly. However, arrival dates of two species (Chiffchaff P. collybita and Willow warbler P.trochilus) were strongly related to local temperature in April, and that of Greenish warbler P. trochiloides to that in May. As expected, arrival dates for the three species wintering in Africa (Chiffchaff, Willow and Wood warblers P. sibilatrix) correlated positively with one another (P < 0.01 in all cases), but were not correlated with arrival dates of Greenish warbler (P > 0.5 in all cases), a species wintering in the Indian sub-continent.     

Woodland area,species turnover and the conservation of bird assemblages in lowland England

A study over 4 years into the number of breeding bird species and species turnover (extinctions and colonisations) in relation to area was conducted in 35 woodlands, set in an intensively farmed landscape, in north-east Essex, UK. A total of 46 species was recorded. The number of species breeding increased with woodland area; the slope of the species–area relationship did not differ between years. Habitat diversity was the only other measured variable to influence species richness. Absolute species turnover was independent of woodland area but relative turnover declined with increase in woodland area. The numbers of territories of nine species were determined. For four summer visitors the number of woods occupied increased as the overall populations increased but, for the other species, changes in overall population size led to changes in numbers in occupied woods. Chaffinch Fringilla coelebs and Song Thrush Turdus philomelos were more associated with woodland edges, Nightingale Luscinia megarhynchos, Garden Warbler Sylvia borin, Chiffchaff Phylloscopus collybita and Willow Warbler P. trochilus with interiors. Several species showed an inverse relationship between population density and woodland area. Collections of small woods hold similar species richness to single large woods. While the acquisition of large woods for conservation purposes should be a priority, the extension of smaller woods to a size of about 10 ha would be highly beneficial to both the species richness and population stability of regional woodland bird assemblages.     

Mate fidelity in ChiffchaffPhylloscopus collybita

Two cases of year-to-year mate fidelity in Chiffchaff occurred in the subpopulation of 6 males and their females in a region of South Bohemia. The first nesting of both females failed in the first season. One of them was secondary female in the first season. Both pairs renested in a new territory in the second season. The nesting of both of them was successful in this season. This is probably the first record of remating between seasons in this species.

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Zusammenfassung Zwei Fälle von Partnertreue im Folgejahr wurden bei farbmarkiertenPhylloscopus collybita in S-Böhmen nachgewiesen. In beiden Fällen hatten die Weibchen 1992 ihre Brut durch Nestraub verloren. Ein Weibchen war sogar nur Zweitweibchen seines Partners gewesen. Trotzdem waren beide 1993 mit denselben Partnern verpaart, allerdings in neuen Territorien. Beide zogen 1993 ihre Brut erfolgreich auf. Dies ist der erste Nachweis für Partnertreue im Folgejahr beim Zilpzalp.

     

Differential rates of phenotypic introgression are associated with male behavioral responses to multiple signals

Sexual selection on multiple signals may lead to differential rates of signal introgression across hybrid zones if some signals contribute to reproductive isolation but others facilitate gene flow. Competition among males is one powerful form of sexual selection, but male behavioral responses to multiple traits have not been considered in a system where traits have introgressed differentially. Using playbacks, mounts, and a reciprocal experimental design, we tested the hypothesis that male responses to song and plumage in two subspecies of red‐backed fairy‐wren (Malurus melanocephalus) explain patterns of differential signal introgression (song has not introgressed, whereas plumage color has introgressed asymmetrically). We found that males of both subspecies discriminated symmetrically between subspecies’ songs at a long range, but at a close range, we found that aggression was equal for both subspecies’ plumage and songs. Taken together, our results suggest that male behavioral responses hinder the introgression of song, but allow for the observed asymmetrical introgression of plumage. Our results highlight how behavioral responses are a key component of signal evolution when recently divergent taxa come together, and how differential responses to multiple signals may lead to differential signal introgression and novel trait combinations.     

Contrasting patterns of genetic differentiation in Macaronesian lineages of Ilex (Aquifoliaceae)

Islands offer an interesting framework in which to study the effect of geographical isolation on population genetic differentiation. For plant species with high dispersal abilities, however, oceanic barriers may not represent a factor promoting strong population structure. In this work, we analysed seven nuclear microsatellite loci in Ilex (Aquifoliaceae), a bird‐dispersed plant group, to infer patterns of genetic differentiation among Macaronesian taxa: I. canariensis, I. perado ssp. lopezlilloi, I. perado ssp. platyphylla (Canary Islands) and I. perado ssp. azorica (Azores). In agreement with current taxonomic classification, our results revealed a high genetic differentiation between Ilex lineages (I. canariensis and the I. perado complex), and also supported previous hypotheses that these are the result of independent dispersal events to the islands. In contrast, genetic differentiation between I. perado ssp. azorica and the two subspecies from the Canaries was high, suggesting that taxonomic revision may be necessary. Levels of genetic variation at microsatellite loci in ssp. azorica were, in addition, the lowest reported among Macaronesian bird‐dispersed taxa. Lastly, low genetic differentiation was observed between subspecies occurring on the same island (sspp. platyphylla and lopezlilloi). In summary, our results revealed contrasting patterns between Macaronesian Ilex lineages: I. canariensis displayed moderate population structure across islands, whereas the I. perado complex showed strong differentiation among populations sampled on different islands. Thus, the Macaronesian Ilex taxa show that long‐distance dispersal syndromes (ornithochory) do not always ensure genetic connectivity across large areas in island systems. Plant groups that successfully colonized the islands on multiple occasions may have found barriers to gene flow within certain lineages. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 258–268.     

Genetic divergence of Troglodytes troglodytes islandicus from other subspecies of Eurasian wren in northwestern Europe

The Icelandic subspecies of Eurasian wren Troglodytes troglodytes islandicus has been described as a large wren which is sedentary on the island. It is one member of a large passerine complex which is widely distributed over the Holarctic except the Arctic. The taxonomic affiliation of the subspecies is mainly based on variation in plumage and on the song complexity. This study investigated the genetic differentiation of T. t. islandicus among the Eurasian wren subspecies in northwestern Europe, and especially in relation to its geographically proximate populations in the Faroe Islands, Scotland, southern Norway, Sweden and Denmark. Troglodytes t. islandicus and the Faroese subspecies (T. t. borealis) were genetically differentiated from the other subspecies (T. t. indigenus and T. t. troglodytes) with an estimated time of divergence from this group during the last glacial maximum; 21 thousand years before present (KYBP) [44–8]. A clear but a more recent split was observed between T. t. islandicus and T. t. borealis 12 KYBP [28–4].     

On the taxonomic status and denomination of the Iberian Chiffchaffs

We carried out a Principal Component Analysis on 196 Iberian and Common Chiffchaffs of both sexes (live and collection specimens), characterized by seven variables derived from wing, tarsus and bill measures. This method, complemented by colour comparison of the taxa, led us to the following conclusions. (1) Phyllopneuste brehmii , Homeyer, 1871, is a junior synonym of Sylvia collybita , Vieillot, 1817. The correct name for the Iberian Chiffchaff is Phylloscopus ibericus (Ticehurst 1937). (2) P. ibericus is itself represented by two subspecies: the southern form P. i. ibericus (Ticehurst 1937), and the northern form, for which we propose the name P. i. biscayensis ssp. nov . (3) The Common and Iberian Chiffchaffs are very distinct in the contact zone. But an overall geographical variation following Bergmann's and Allen's rules within both taxa generates an ecomorphological convergence, i.e. P. i. ibericus and the populations of P. c. collybita from northern central Europe have similar sizes. This may explain why previous authors were unable to diagnose the two taxa on morphological criteria alone.     

Laying dates and clutch size of open-nesting passerines in the Czech Republic: a comparison of systematically and incidentally collected data

Data are presented on laying date and clutch size (n) of Blackcap Sylvia atricapilla (1434), Song Thrush Turdus philomelos (298), Garden Warbler S. borin (260), Yellowhammer Emberiza citrinella (254), Blackbird T. merula (231), Chaffinch Fringilla coelebs (206), Chiffchaff Phylloscopus collybita (202), Icterine Warbler Hippolais icterina (95) and Dunnock Prunella modularis (89), recorded during an intensive study (since 1993) in woodland habitats of Eastern Bohemia, Czech Republic (49 °54 ′N, 16 °02 ′E). Results are compared with two other data sets (a local study and national nest record scheme) collected by Czech volunteer ornithologists during 1945–85 and with other published data from central Europe. There is no evidence that the laying dates and clutch size of the nine species changed at the regional scale over the past decades, and mean values generally match their known geographical variability. Significant species differences were found among the three Czech data sets in both laying dates and clutch size. Most of the differences could be explained as an artefact of seasonally biased sampling of nests, which in turn influenced mean clutch size. Even a systematic study with a standard searching effort on fixed plots provided biased data for some species.     

Song structure variability in passerine birds: Random variation or direct informative changes

The variability of the fine song structure was studied in the wood warbler (Phylloscopus sibilatrix), willow warbler (Ph. trochilus), greenish warbler (Ph. throchiloides viridanus), chaffinch (Fringilla coelebs), and gray shrike thrush (Colluricincla harmonica). The increase in the number of similar elements per phrase is shown to be related to the conspecific and heterospecific male-male song interactions in these birds. The responses of wood warbler males to playback conspecific songs with standard and prolonged (in the number of similar elements) second phrases differ significantly. The initial phrases of willow warbler songs become significantly longer in the populations with a high density as compared to those in populations of low density. The increase in the variability of both phrase combinations and song duration is shown to be related also to the song interaction with conspecific males for the willow warbler, greenish warbler, chaffinch, and gray shrike thrush. The within-song type variations turned out to play an important role during male-male interactions of different species. The results obtained suggest that similar ways of song responses may be quite widespread among passerine birds and reflect the general principles of changes in the song structure during acoustic interactions.     

Radiation and species limits in the Asian Pallas’s warbler complex (Phylloscopus proregulus s.l.)*

Pallass Warbler (Phylloscopus proregulus) of the Eastern Palaearctic (Siberia, China, Himalayas) resolves into a complex of four closely related but distinct allospecies forming a superspecies, P. [proregulus]. Assignment of species rank is based on cytochrome-b gene sequences and on vocalisations (territorial song and calls). Morphological divergence is poor, as is typical in Phylloscopus. It applies to size (nominate Siberian proregulus as opposed to the Sino-Himalayan taxa), and slight coloration differences among the latter taxa do not correspond to the cyt-b topology and are considered to be adaptive. Vocal differences relate to syntax (verse song vs endless song), frequency (broad vs narrow bandwidth, allocation of elements within the frequency band), form of elements (ascending vs descending parts, combination of these), and repertoire size. Strong premating isolating mechanisms are assigned to vocalisations. Contrary to current taxonomy, we propose the following constituent taxa of the Phylloscopus [proregulus] complex: Phylloscopus proregulus s.str. (Siberia, disjunct from the following taxa), P. kansuensis (China: Gansu, Qinghai), P. forresti (W/SW China, part of E Himalayas?), P. chloronotus with two subspecies: P. c. simlaensis (W Himalayas), and P. c. chloronotus (C and E Himalayas). Contact zones and possible hybridisation between the Sino-Himalayan taxa remain undetermined. A closely related isospecies is Phylloscopus yunnanensis (syn. P. sichuanensis), which is locally sympatric with and extremely similar morphologically to P. forresti and P. kansuensis. Cyt-b distance values range from 3.1% to 4.6% within the P. proregulus complex and from 7.5% to 8.4% between the latter and P. yunnanensis. This corresponds to differentiation times of 4.1 to 5.5 Myears (P. proregulus complex vs P. yunnanensis) and 1.7 to 3.2 Myears (within the P. proregulus complex).Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by A. Helbig*Results of the Himalaya Expeditions of J. Martens, No. 247. – For No. 246 see: Ann Zool Warszawa, 2004.This revised version was published online in July 2004 with corrections to a heading and species names.