Geographic variation and divergence of songs in the Olive Sparrow species complex

Phenotypic traits such as songs are important in species recognition. Variation in acoustic traits can form barriers to gene flow and promote speciation. Therefore, understanding song divergence is crucial in groups with controversial taxonomy such as Olive Sparrows (Arremonops rufivirgatus), a widespread Neotropical species of songbird with multiple allopatric populations. Taxonomic authorities disagree on the number of Olive Sparrow subspecies, placing them into either two or three main groups. These groups may represent separate species based on morphological traits, but trait divergence within the complex has not been examined. We studied geographic variation in the characteristics of the songs of Olive Sparrows at two geographical levels: among three proposed groups and among five allopatric populations. In a second analysis, we evaluated the strength of acoustic divergence within the complex by comparing acoustic distances among groups and allopatric populations of Olive Sparrows with the acoustic distance among three recognized species in the genus Arremonops. We analyzed 802 songs from 174 individuals across 81 locations and measured 12 variables to describe the fine structural characteristics of the songs of Olive Sparrows, Green-backed Sparrows (A. chloronotus), Black-striped Sparrows (A. conirostris), and Tocuyo Sparrows (A. tocuyensis). We found significant acoustic variation in the Olive Sparrow complex at both geographical levels. Our divergence analysis also revealed that vocal divergence within the complex is similar to or greater than that found between recognized species in the genus. Together, these results suggest that acoustic diversity within the Olive Sparrow complex probably originated by isolation in tandem with selective and/or non-selective factors.     

Hydrogenosome-Methanogen Assemblages in the Echinoid Endocommensal Plagiopylid Ciliates,Lechriopyla mystax Lynch, 1930 and Plagiopyla minuta Powers, 19331

ABSTRACT. Lechriopyla mystax Lynch, 1930 and Plagiopyla minula Powers, 1933 contain hydrogenosome-methanogen assemblages similar to those reported for other plagiopylid ciliates. These assemblages are stacks of elongate ovoid hydrogenosomes alternating with methanogens; these stacks are surrounded by cisternae of the rough endoplasmic reticulum that are often accompanied by Golgi complexes. The individual methanogens in the larger ciliate, L. mystax, are about four times the volume of those in the smaller ciliate, P. minuta, but both ciliates appear to contain Gram-negative methanococcoid bacteria, possibly Methanoplanus sp. The endoplasmic reticulum-Golgi complex probably plays a significant role in exploitation of the methanogens by the host ciliate.     

Song dialects on the Atlantic islands: goldcrests of the Azores ( Regulus regulus azoricus, R. r. sanctae-mariae, R. r. inermis)

Territorial songs in island populations of songbirds are often highly divergent from those of neighbouring continental relatives. This is shown for the three goldcrest subspecies (Regulus regulus azoricus, R. r. sanctae-mariae and R. r. inermis) endemic on six islands of the Azorean archipelago. All investigated populations display a high intra- and inter-individual acoustic variation. On each island, up to six different song types have been found; and a single male sings up to three types. In contrast, all northwestern European populations of R. r. regulus and R. r. anglorum share only a single song type. In playback experiments, none of 18 tested dialect songs of Azorean goldcrests evoked notable territorial reaction in German and Czech goldcrest males (ssp. regulus). Two differing dialect groups of the goldcrest can be distinguished on the Azores. Populations of the eastern islands, São Miguel and Santa Maria, share common song types which are not found on the islands of the central and western groups. Dialect repertoires on the westernmost islands, Flores, Faial and Pico, are dominated by a different song type. In the geologically younger western crater of São Miguel, both western and eastern song types coexist. Acoustic similarities to a population from neighbouring Terceira suggest the western part of São Miguel as the origin for the westward expansion of R. regulus on the Azores.     

Social Guidance of Vocal Learning by Female Cowbirds: Validating its Functional Significance

Juvenile male M. a. ater cowbirds, who have never heard other male cowbirds sing, develop distinctively different repertoires when housed with M. a. ater females from their own area versus M. a. obscurus females from a distant population. Because female cowbirds do not sing, the differences in the males' songs do not arise through vocal imitation. Here we provide data demonstrating that the songs of female-housed males are functionally, as well as acoustically, distinctive. The songs of 8 groups of males were tested where the groups differed by age of singer, acoustic experience, and identity of social companion. The playback results demonstrate that non-singing female cowbirds not only stimulate the male to modify song content, but song potency. As such, they demonstrate the critical role female cowbirds may assume in the proximate and ultimate regulation of vocal development.     

COMPARISONS OF THE VOCALIZATIONS AND SOCIAL BEHAVIOUR OF SOUTHERN AFRICAN PYCNONOTUS BULBULS

Lloyd, P., Hulley, P.E. & Craig, A.J.F.K. 1996. Comparisons of the vocalizations and social behaviour of southern African Pycnonotus bulbuls. Ostrich 67: 118–125.

Vocalizations and associated behaviour of three Pycnonotus species are described, based on field observations and tape recordings from which sonagrams were produced. These species, which are locally sym-patric and hybridize, have similar vocalizations and displays; differences are most apparent in their contact calls and songs. Quantitative analysis of the songs showed that P. barbatus and P. capensis are easily distinguished, whereas the song characteristics of P. nigricans overlap those of both the other species. Playback experiments with territorial male P. barbatus in an area of allopatry showed similar responses to songs of conspecifics and of P. nigricans, but almost no response to the song of P. capensis.     

Vibrational communication and mating behaviour of Dichelops melacanthus (Hemiptera: Pentatomidae) recorded from loudspeaker membranes and plants

Vibrational communication is important for successful mating in various stink bugs species. The vibrational signals from males and females of Dichelops melacanthus Dallas (Hemiptera: Pentatomidae) are recorded from a nonresonant substrate (i.e. a loudspeaker membrane) to characterize the temporal and spectral properties of these vibrational signals, as well as on a resonant substrate (i.e. bean plants) to obtain information about how these signals are altered when they are transmitted through the plants. On the loudspeaker membrane, D. melacanthus males and females emit only one male or one female song, respectively. However, when the insects are placed on bean leaves, a more complex repertoire is recorded, with three different songs for each sex. The first female and male songs appear to have calling functions and the third male and female songs are emitted during courtship. The second female and male songs are emitted after the first song, although their functions in mating behaviour are not clear. The identified repertoire is similar to those of other Neotropical stink bugs, starting with songs 1 and 2 and developing into song 3. Frequency modulation is observed in the female songs recorded from the loudspeaker membrane and the plants. The signals recorded from plants present higher harmonic peaks compared with the signals recorded from the loudspeaker membrane. The presence of species and sex‐specific songs during mating confirms the important role of vibrational communication in mate location and recognition. The temporal and spectral characteristic signals are influenced by the substrate used to record the songs emitted by D. melacanthus.     

A narrow hybrid zone between the grasshoppers Stenobothrus clavatus and Stenobothrus rubicundus: courtship song analysis

The closely related grasshopper species Stenobothrus rubicundus and Stenobothrus clavatus are known to hybridize in a very narrow contact zone on Mt. Tomaros in northern Greece. These species produce very different and complex courtship songs accompanied with visual display. We analyzed the courtship songs and underlying stridulatory movements of the hind legs in natural hybrids from Mount Tomaros. The two species were also hybridized in the laboratory and their songs were compared with the songs of the natural hybrids. Some hybrid songs were shown to have intermediate features between parental songs, whereas other hybrid songs comprised completely new elements. The clavatus‐like song elements were found to dominate in hybrid songs. These song features may influence the mating success of hybrid males in the contact zone. A comparison of hybrid songs with the song pattern of the north European S. rubicundus populations allowed us to suggest a scenario of S. rubicundus and S. clavatus origin. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Vergleich des Strophenaufbaus und der Strophenabfolge an Ges?ngen von Sprosser (Luscinia luscinia) und Blaukehlchen (Luscinia svecica)

Zusammenfassung Ziel der Studie war es, die Elementabfolge sowie die Strophenabfolge des Gesanges von Sprosser und Blaukehlchen vergleichend zu untersuchen. Zur sonagraphischen Analyse wurden die Gesänge im Freiland aufgezeichnet. Der Abfolge (Syntax) der Strophenelemente lag bei beiden Arten ein hierarchisch organisiertes Verzweigungsschema zu Grunde. Bei beiden Arten konnten die Strophen anhand definierter Strukturparameter klar in drei Abschnitte gegliedert werden. Die Gesänge der Sprosser wurden von Serien aus Strophen gebildet, die jeweils in ihren beiden Anfangselementtypen übereinstimmten (gleiche Strophenklasse). Die Abfolge von Strophen verschiedenen Typs war durch bevorzugte Übergänge und ein gruppiertes Auftreten bestimmter Strophentypen charakterisiert. Beim Blaukehlchen traten Strophen, die in allen Abschnitten strukturell gleich waren, seltener im Gesang wieder auf. Die Blaukehlchen wechselten häufiger die Strophenklasse, wodurch es nur seltener zu einer Serienbildung von gleichklassigen Strophen kam. Die auffälligen Gemeinsamkeiten in der Gesangsorganisation zwischen Sprosser und Nachtigall sowie Blaukehlchen und Gartenrotschwanz liefern Hinweise auf Zusammenhänge zwischen der syntaktischen Organisation von Strophen und der Organisation der Strophenabfolge.

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Comparison of the song structure and song succession in the Thrush Nightingale (Luscinia luscinia) and the Blue Throat (Luscinia svecica)

Summary Songs of three Thrush Nightingales and three Blue Throats were recorded in the field and analyzed by visual inspection of frequency spectrograms. An analysis of the succession of elements within a song as well as the succession of songs in a song bout revealed the following results in both species: a) the succession of elements within songs was organized as a hierarchical branching structure, b) three structurally different sections could be found in all songs, c) songs were initialized by specific element types. A termination of songs by specific element types was only found in the thrush nightingale.Songs ot the Thrush Nightingale were organized as series of songs which corresponded in their first two element types (same song class). These series consisted of different song types, which succeeded with a high constancy. Different song types were sung in close sequential association and recurred preferably after intervals of 8–10 songs.In song bouts of the Blue Throat however songs which corresponded in all sections were rarely found. Those songs corresponding in the first two element types were often repeated immediately, but in comparison to the Thrush Nightingale series of these songs were rare.Besides many similarities in the song organization in both species the song of the Thrush Nightingale was more similar to the closely related Nightingale (Luscinia megarhynchos) — with regard to the syntactical organization of song and the organization of consecutive songs. The song organization of the Blue Throat showed more similarities to the European Redstart (Phoenicurus phoenicurus).These results indicate a relation between the syntactical organization of song and the sequential organisation of consecutive songs.

     

IMPROVISATION OF NEW NOTES DURING SINGING BY MALE SARDINIAN WARBLERS SYLVIA MELANOCEPHALA

ABSTRACT

The songs of Sardinian warblers Sylvia melanocephala are extremely complex and variable, and even consecutive songs uttered by the same male usually differ. To provide a better understanding of the nature of the variation recorded, an attempt has been made to determine size and composition of the note repertoire of three selected individuals. The analysis was carried out on samples each consisting of several dozen songs, and the various notes were sorted on the basis of the visual similarity of their spectrographs patterns. Each male turned out to have a very large note repertoire which does not show any overlap with those of other males, with the only exception a particular note found in the songs of all the males. In two birds out of three, however, the graphs of the occurrence of new notes in consecutive songs show no tendency to become asymptotic. This suggests that the assessment of note repertoire size in these birds is not accurate, as they continue inserting new notes in their songs even after they ha ve uttered several dozen songs. A table recording the presence or absence of the various notes in consecutive songs revealed that at least two of the three birds used different sets of notes in different bouts of songs, switching from one to another after short pauses made between two consecutive bouts. All this makes the attempt to assess the actual size of the note repertoire in these birds very difficult, and makes it probable that Sardinian warblers do not possess a finite repertoire of notes. The pattern of note selection observed for the three males in this study is best explained by assuming that these birds improvise new notes as they sing.     

Spring migration timing of Sylvia warblers in Tatarstan (Russia) 1957–2008

The timing of when migrant birds return to breed is a key component of studies of the impact of climate change upon bird populations. However, such data are not distributed evenly across the World, and in the Northern Hemisphere are underrepresented in Asia and the east of Europe. Therefore, to help rectify this bias, we analysed first arrival dates (FAD) of four species of Sylvia warblers (Blackcap Sylvia atricapilla, Whitethroat S.communis, Lesser Whitethroat S.curruca and Garden Warbler S.borin) collected in the Tatarstan Republic of Russia between 1957 and 2008. Over the whole period the species returned to their breeding sites between three and six days earlier; these trends were significant except for Whitethroat. Advances in arrival were especially apparent in the two earlier species, Blackcap and Lesser Whitethroat, mainly because local temperatures for March had risen substantially. Except for Whitethroat, FADs were significantly related to temperatures in the African wintering ground and/or in Tatarstan. Whilst significant correlations occurred between FADs of some of the species, there was considerable variability in these relationships indicating a species-specific response to rising temperatures. Changes in FADs in this eastern extremity of Europe were smaller than in Central and Western Europe.