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Birds’ dawn chorus is a daily period of high song output, which mainly occurs during the breeding season. Monitoring such chorus may provide important information about birds’ ecology and the function of bird vocalizations at dawn. In this study, we have recorded dawn singing activity from April to June 2019 at seven different sites in Yaoluoping National Nature Reserve (YNNR) in the eastern China and examined the effects of extrinsic factors such as temperature and time of the season on the dawn singing behavior of four common birds Alstrom’s Warbler (Phylloscopus soror), Streak-breasted Scimitar Babbler (Pomatorhinus ruficolli), Brownish-flanked Bush Warbler (Cettia fortipes) and Chinese Hwamei (Garrulax canorus). In total, we analyzed 1511 days of recordings, 417 days for Alstrom’s Warbler, 343 days for Streak-breasted Scimitar Babbler, 391 days for Brownish-flanked Bush Warbler, and 360 days for Chinese Hwamei. Our results showed that the dawn singing start time of Alstrom’s Warbler, Streak-breasted Scimitar Babbler and Brownish-flanked Bush Warbler were negatively affected by temperature in such a way that birds started singing later at the higher temperature; however, dawn singing start time of Chinese Hwamei was not affected by temperature change. As for Alstrom’s Warbler and Brownish-flanked Bush Warbler, their singing rate decreased significantly with high temperatures, whereas the singing rates of the other two species were not significantly related to the temperature. The Julian date did not affect the dawn singing start time of any species. The Julian date influenced the singing rate of Alstrom’s Warbler, Brownish-flanked Bush Warbler, and Chinese Hwamei. In contrast, the singing rate of Streak-breasted Scimitar Babbler remained constant with the seasonal progression. Our results indicated that bird’s dawn singing activity is species-specific and is sensitive to environmental factors such as temperature and time of the season.

We documented an adult Lesser Cuckoo Cuculus poliocephalus killing nine-day-old Japanese Bush Warbler Cettia diphone nestlings by ejecting them from their nest. Among the available hypotheses concerning brood-parasitic birds destroying host nest contents, only the ‘farming hypothesis’ helps to explain this case, although the attack did not force the warbler to immediately re-nesting because one nestling survived. Considering the long breeding season and frequent re-nesting habit of the Japanese Bush Warbler, as well as the delayed arrival of the Lesser Cuckoo into the breeding area, such predatory behavior seems to be effective in creating replacement clutches for future parasitism.

As species serve as basic units of study in many fields of biology, assessments of species limits are fundamental for such studies. Here, we used a multilocus dataset and different coalescent-based methods to analyze species delimitation and phylogenetic relationships in the Brownish-flanked Bush Warbler Horornis fortipes complex, which is widespread in the Sino-Himalayan region. We also examined the vocal and morphometric divergence within this complex. Our genetic results suggested that Horornis fortipes is composed of at least three independently evolving lineages, which diverged 1.1–1.8 million years ago. However, these lineages have hardly diverged in song or morphometrics and only very slightly in plumage. Our result indicate that there are three incipient species in Horonis fortipes complex diverged in central Himalayas and Hengduan Mountains, but not between the continent and Taiwan island.

The breeding and wintering bird fauna at Ooyamazawa were monitored by point counting every year from 2010 to 2017. The abundance of bird species that feed in bushes, including the Japanese Bush Warbler (Cettia diphone) and Siberian Blue Robin (Luscinia cyane), decreased. On the contrary, the other bird species that feed in habitats other than bushy understory did not decrease significantly. In Ooyamazawa, deers have serious impact on the understory vegetation. Thus, deer browsing likely affected the number of birds using the understory vegetation.

A nest of the Chinese bush warbler (Tribura tacsanowskia) has been found and monitored in the Amur region for the first time. This is a poorly studied species distributed in southeastern Siberia, the Russian Far East, and the adjoining areas of Mongolia and China. Only seven nests of this species were found earlier, all of them in the Trans-Baikal Territory. Descriptions of those findings are given, including the habitat, location and structure of nests, egg clutch and downy chick, and behavior of adult birds at their nest. The time contributions of the male and female spent in percent in the nest, as well as to chick feeding and the ejection of chicks’ litter pellets have been calculated for the first time. The main parameters of nesting life have been revealed: daytime and nocturnal activity cycles of adult birds in the nest and daily graphs of nestling feeding hours. Observations of adult activity at the nesting site in the period of feeding the chicks in the nest and after their release from the nest are presented. Some other details of Chinese bush warbler behavior and nesting are presented.

Bird vocalizations are one of the important subjects in ecoacoustics because birds communicate diversely using various vocalizations such as songs and calls. We have developed a portable system, HARKBird to provide a basic function, i.e., birdsong localization, which automatically extracts sound sources and their direction of arrivals (DOA) using robot audition techniques based on HARK. In this paper, we introduce HARKBird 2.0 which is empowered for higher understanding of birdsongs. A new soundscape annotation tool for localization results is enhanced by an interactive interface for song classification based on an unsupervised feature mapping t-SNE. We show that HARKBird 2.0 provides bird researchers with an integrated framework to analyze spatio-spectro-temporal dynamics of birdsongs using the song analysis of Japanese bush warbler (Horornis diphone).

Despite numerous studies on the function of the avian dawn chorus, few studies have examined whether dawn singing may influence the singing of other species. Here, we built on our previous study which found male Brownish- flanked Bush Warblers (Horornis fortipes) increase their dawn singing intensity after conspecific playback on the previous day. We reanalyzed those recordings to quantify the start of dawn singing in other nine sympatric songbird species. Ranking- scaling analyses identified a distinctive sequential pattern of dawn singing among these bird species between the first and the second dawn chorus, and meta- analysis showed a signifi-cant trend to singing earlier in the bird community accompanied by the increase in dawn singing intensity in Brownish- flanked Bush Warbler. Species with songs most similar to that of the Brownish- flanked Bush Warbler and species that were phyloge-netically distantly related to the Brownish- flanked Bush Warbler showed a greater shift in the onset of dawn singing. Our study is one of the few studies showing how bird song influences heterospecific singing, and this may influence the temporal or-ganization of song activity in the community, and result in synchronization in singing activities among different species, such as singing in dawn and dusk chorus.

The Fukushima-Daiichi Nuclear Power Plant (F1NPP) accident is an IAEA level 7 event, the same as that of Chernobyl, while the amount of radionuclides released is not comparable. Radioactivity attributed to the F1NPP accident was detected 250 km away from the F1NPP. Although we have not yet systematically studied the effect of radionuclides on the environment and wildlife, one of three Japanese Bush Warblers (Cettia diphone), captured in Akaugi district in August 2011, was observed to have a conspicuous lesion near the cloaca, which is rare in Japan. All of the birds' feathers were strongly contaminated. Further study is needed to determine the significance of this result. We emphasize the importance of continuing assessment of the effects of the F1NPP accident on wildlife.

Island and mainland populations of birds often differ in their breeding biology because of differences in ecological conditions. We studied the breeding biology of Japanese Bush Warblers Cettia diphone on Hahajima in the Ogasawara (Bonin) Islands group. Based on observations of four nesting attempts, clutches consisted of three or four eggs, which is smaller than on the mainland. Males fed the chicks, although the frequency was fairly low. Brood sizes declined during the nestling period due to starvation. Neither such male behavior nor starvation, have been reported on the main islands of Japan or on their small peripheral islands. These features of their breeding biology may have resulted from food scarcity and strong intraspecific competition on the island.

The dawn chorus is a period of peak singing activity of many songbirds. Numerous studies have sought to understand this widespread phenomenon, and many hypotheses have been proposed to explain the dawn chorus. The social dynamics hypothesis proposes that dawn singing plays an important role in the announcement of territorial occupancy and the regulation of social relationships between males; it predicts that the dawn chorus vocal behavior varies with changes in social relationships. In this study, we tested the influence of territorial insertions and the number of neighbors, on the intensity of the brownish-flanked bush warbler (Cettia fortipes)’s dawn singing. We found that simulated territorial insertions (playback) caused the males to increase their dawn singing significantly the next day, and males that had many neighbors exhibited more intense dawn singing than did males with few neighbors. Our study provides evidence that dawn singing plays an important role in the announcement of territorial occupancy and the regulation of the social relationships between the males.

Soft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish-flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species.

Cettia diphone diphone is a subspecies of the Japanese Bush-warbler that is endemic to the Bonin and Volcano Islands of the Ogasawara Islands. Although the two island groups are physically distant and have different geological histories, genetic and morphological relationships between the two populations are unknown. A few individuals of an unidentified subspecies have been observed since 2007 on Mukojima of the Bonin Islands. They were possibly wintering birds of another subspecies in light of their song pattern and appearance. We examined the genetic and morphological differences among the Bonin and Volcano populations of C. d. diphone, C. d. cantans, and C. d. sakhalinensis populations and determined the identity of the unidentified subspecies on Mukojima by comparing sequences of the CO1 region of the mitochondrial DNA (mtDNA) and conducting a canonical discriminant analysis (CDA) using five measurements per bird. Our results indicate that these populations (except C. d. sakhalinensis) are genetically and morphologically different. They did not share any haplotypes of mtDNA and indicated high discrimination rates (over 75%) based on CDA. Because the Volcano population inhabits only one island, it is a priority for conservation. The unidentified individuals on Mukojima Island are not the native subspecies. Migratory individuals might colonize Mukojima due to improved habitat conditions and an available niche. Continuous monitoring of the Mukojima population and its impact on native C. d. diphone is required.

Wildlife, mainly 69 bird (Aves) species, has been observed in Abukuma Mountains, northeastern Fukushima Prefecture, which is the most radioactively contaminated area, over the seasons since July 2011. However, it is still unclear whether the changes in the bird community have been caused by the radioactive contamination and/or by changes in human activity, adding to the natural dynamics. The aerial dose rate at the survey area was initially estimated to be more than 100 μSv/h (mainly 137Cs, 134Cs, and 131I), which decreased in the summer of 2014 to 0.1–20 μSv/h (mainly 137Cs and 134Cs). Radioactivity in wild habitats is heterogeneous among the microhabitats and is dynamic through time and seasonal conditions. Microhabitat radio-heterogeneity was clearly indicated by the 2-month-long measurement with 200 dosimeter badges in this study. The ecological factors related to free living (in-situ) wildlife in the highly contaminated area of Fukushima are discussed.

The distributions of the Little Cuculus poliocephalus and Oriental C. saturatus cuckoos differ throughout Japan. In Honshu, the Little Cuckoo parasitizes mainly the Japanese Bush Warbler Cettia diphone and lays reddish mimetic eggs. The Oriental Cuckoo mainly parasitizes the Eastern Crowned Leaf Warbler Phylloscopus coronatus and lays whitish eggs. However, in central Hokkaido, where no Little Cuckoos breed, Oriental Cuckoos parasitize Japanese Bush Warblers as their main hosts, in whose nests they lay reddish eggs. Anecdotal evidence suggests that they also parasitize Eastern Crowned Leaf Warblers, laying reddish eggs, but this has not been confirmed. Here, we report the first complete evidence in which an Oriental Cuckoo chick, which hatched from a non-mimetic reddish egg, was raised by Eastern Crowned Leaf Warbler hosts in Hokkaido.

The role of the Orii's flying-fox, Pteropus dasymallus inopinatus, in the reproduction of Mucuna macrocarpa was investigated through captive and wild observations on Okinawajima Island in the Ryukyu Archipelago, Japan. When Orii's flying-fox fed on flowers of M. macrocarpa, it pushed its nose to the basal portion of the flowers to feed on nectar. This caused the hard petals of flowers to explode and consequently opened the carina. When a flying-fox's face pointed in the same direction as a flower, there was a significantly higher explosive opening rate compared with approaches from the side or the opposite direction (χ2 test; P < 0.001). In total, in the captive setting, 32.2% of the flowers exhibited explosive opening. During such events, stamens with pollen and pistils emerged and attached to the throat and forehead of the flying-fox. Other main flower visitors were the brown-eared bulbul, the Japanese white-eye, the Japanese bush warbler, and the honeybee, but they did not stimulate explosive...

Bird songs in island populations have often been reported to be simplified, in that island birds have a smaller number of song types and song-element types compared to mainland birds. However, there is less information on the characteristics of acoustic structure in island songs. I investigated song structure of one mainland and three island populations of Japanese bush warblers, Cettia diphone, and found that island songs had an acoustically simple structure. The frequency-modulated (FM) portions of the songs were shorter and had fewer frequency inflections in the insular populations than in the mainland population, while the number of FM notes, the frequency range of these notes, and the song repertoire sizes of males did not differ between the islands and the mainland. I also investigated whether the song complexity is related to sexual selection pressure using the degree of sexual size dimorphism as a proxy for the latter. The degree of dimorphism in body mass was larger on the mainland. Thus, weakened sexual selection on islands is a possible factor in the formation of simple songs. Further studies related to male–male competition and female choice on islands are required.

SummaryThe Timor Bush Warbler Locustella timorensis was first collected by Georg Stein on Mount Mutis, West Timor in 1932, but there have been no confirmed field observations since. Here we report on the discovery of a new population of bush warbler on Alor (9 September 2009), which prompted a search for, and subsequent rediscovery, of the nominate Timor Bush Warbler (20 December 2009) in Timor-Leste. We also undertook the first bush warbler searches in the mountains on Atauro Island, and the first ornithological exploration of the mountains of Pantar and Wetar islands. On Alor, at least 13 male bush warblers were heard singing from shrub and grass beneath woodland and forest edge at 859–1,250 m. On Timor, at least 40 males were heard during December, April and July from tall grassland below Mount Ramelau (1,720–2,100 m), Timor-Leste. The song structure of the Alor and Timor birds is similar, and close to Javan Bush Warbler L. montis of Java and Bali, as well as to recordings of Russet Bush Warbler L. mandelli of mainland Asia and Benguet Bush Warbler L. seebohmi from the Philippines. The song of the Alor bird is substantially higher pitched (mean min/max 3,233–4,980 kHz) than the Timor bird (2,928–4,761 kHz) and both are substantially higher pitched than Javan birds. Recordings of Russet Bush Warbler from mainland Asia are higher pitched than songs of all insular taxa, and the song of Benguet Bush Warbler is of a similar pitch to the Timor bird. Recent molecular studies have found that divergences between Javan Bush Warbler and the Russet Bush Warbler are slight, and the high degree of song similarity of the Alor and Timor populations to Javan Bush Warbler places them close to the Benguet Bush Warbler complex. The Timor Bush Warbler is recognised as ‘Near Threatened’ by IUCN, but this will require re-evaluation. On Alor, suitable habitat is extensive and under little threat, but grassland in the uplands of West and East Timor is intensively grazed and regularly burnt. Further field surveys are needed on both Timor and Alor to capture birds, clarify taxonomic relationships using molecular approaches, and further define habitat use and conservation status. Bush warblers were not recorded from Pantar, Atauro and Wetar islands.

We analyzed the structure and variation of the songs of the Brownish-flanked Bush Warbler (Cettia fortipes), a species common in southeastern Asia, including southwestern China, site of our study. During the breeding season of 2009, we investigated the possibility of distinguishing individuals by song. Most Brownish-flanked Bush Warblers we studied had a unique song repertoire composed predominantly of two song types. Whether singing spontaneously or in response to playback, the birds deliver the two types alternately. We defined type alpha as a song consisting of two notes, type beta as a song consisting of three notes. Both song types varied from individual to individual. Discriminant analysis revealed that the songs of individual Brownish-flanked Bush Warbler songs were distinct; rates of correct classification were 98% for the alpha song and 99% for the beta song.

We investigated bird nest predation on Miyake Island where the Japanese Weasel Mustela itatsi has been introduced. From observations of Japanese Bush Warbler nests, we estimated survival rates of 0.498 and 0.848 in incubation and nestling stages, respectively. Artificial nests coupled to an automatic image recording system showed that weasels were bird nest predators on three occasions. No other potential predators visited the nests; before the weasel introduction, nest predation was rarely reported on the island. The incidence of predation on artificial nests increased as a function of the density of predated artificial nests in the neighborhood. Other nest-site characteristics were not related to nest predation, except for height above the ground. Lower nests had slightly higher risks of predation. Hence, the fate of a nest appears to depend on whether it is located within home ranges of the Japanese Weasel. Weasels may easily find nests located within their activity ranges irrespective of thei...

In 2005, we surveyed the birds inhabiting the Tokyo University Forest in Chichibu, in western Saitama Prefecture, Japan. Special attention was given to the Bush Warbler Cettia diphone, which appeared at the study site after 22nd March. We captured seven male Bush Warblers and banded them with individually unique combinations of color rings. Six males of them maintained the same home ranges (territory) throughout the study period, and no other males were observed. The population density of the males was 19.2 individuals per km2. Although we were unable to locate an active nest to study the breeding and rearing process, juveniles were captured in August. The tarsus length of juveniles reached the size of adults earlier than the natural wing length. Thus, in the juveniles, sexual size dimorphism was evident in the tarsus length to the same extent as seen in adults. We found nests of the Japanese White-eye Zosterops japonicus, Long-tailed Tit Aegithalos caudatus, Short-tailed Bush Warbler Urosphena squameiceps, Blue-and-white Flycatcher Cyanoptila cyanomelana and Red-billed Leiothrix Leiothrix lutea. The clutch of the Short-tailed Bush Warbler was believed to have been parasitized by the Oriental Cuckoo Cuculus saturatus. We confirmed that 40 species of birds occurred in the study area during the study period.

We demonstrate the importance of using multiple criteria in species delimitations, whatever the conceptual base for species delimitation. We do this by studying plumage, biometrics, egg coloration, song, mitochondrial DNA and habitat/altitudinal distribution in the Spotted Bush Warbler Bradypterus thoracicus (Blyth) complex, and by conducting playback experiments. Taxa that we suggest are best treated as separate species [B. thoracicus (Blyth), B. davidi (La Touche) and B. kashmirensis (Sushkin)] differ in most or all of these aspects, particularly in song and mitochondrial DNA, while those that we treat as subspecies (suschkini) or synonyms (przevalskii) differ slightly and only in morphology.

We investigated the phylogenetic relationship and differences in the song structure between the Philippine Bush Warbler (Cettia seebohmi) and the Japanese Bush Warbler (C. diphone). We compared complete sequences of the mitochondrial cyt-b gene of C. seebohmi to those of other Cettia taxa from GenBank and found C. seebohmi formed a monophyletic group with C. haddeni and C. diphone. The phylogenetic tree also suggests that C. seebohmi is more closely related to C. haddeni than to C. diphone although this was not strongly supported due to the low bootstrap values. The estimated nucleotide differences between C. seebohmi and C. haddeni (4.37%), and between C. seebohmi and C. diphone (3.87–4.37%) were larger than the inter-subspecific difference between C. diphone borealis and C. d. cantans (2.44%). Cettia seebohmi, C. haddeni, and C. diphone diverged prior to the subspecies divergences of C. diphone. The basic structure of songs was similar in C. seebohmi and C. diphone; all songs consisted of pure ...

Artificial eggs of six different colours and control eggs of Bush Warblers Cettia diphone were introduced into nests of Bush Warblers, a host of both Little and Himalayan Cuckoos Cuculus poliocephalus and C. saturatw in Japan. All control (chocolate-brown) and artificial red eggs were accepted; all grey and all white eggs were rejected. The rejection rates of orange, pink and orange spots on grey eggs were 8%, 369; and 55%, respectively. Bush arblers are more likely to reject eggs the more dissimilar they are from their own. The results strengthen the possibility that the chocolate-brown eggs of Little and Himalayan Cuckoos may have evolved through the discriminative ability of Bush Warblers and their intolerance towards dissimilar eggs.

We have studied in northern Japan the hitherto unidentified eggs of a species of cuckoo in the nests of the Bush Warbler Cettia diphone. The cuckoo in question appeared to be the Himalayan Cuckoo Cuculus saturatus which parasitizes mainly the Willow Warbler Phylloscopus occipitalis in southern Japan. The egg colour in this northern Cuckoo was chocolate-brown or orange-brown, similar to that of the Bush Warbler but unlike that of the southern Himalayan Cuckoo. Egg size was significantly larger than that of the southern Himalayan Cuckoo and instead similar to that of the Little Cuckoo C. poliocephalus which uses the same host species in southern Japan, to which the Little Cuckoo is confined. The shift in host species and egg colour in the northern Himalayan Cuckoo seems to be a case of character release in the absence of the Little Cuckoo.

高密度のソウシチョウの巣の存在にともなうウグイスの巣への捕食の増大という間接効果を検証するために，えびの高原（鹿児島県，宮崎県）において，ソウシチョウの巣の除去実験を行った．調査は2002年と2003年の繁殖期に，ソウシチョウの巣を繰り返し除去し，除去を行わない対照区との間で，ウグイスの巣に依存する期間の生存確率を比較した．除去の結果，2002年は巣密度の低くなった除去区では対照区より全期間生存確率は有意に高かった．2003年はウグイスの営巣数が大きく減少したため，ソウシチョウの巣を除去したにもかかわらず両地区の巣密度差が小さく，生存確率に有意差が生じなかった．本研究の結果はソウシチョウの高密度な巣の存在がウグイスの偶発的な捕食の増加を引き起こし，ウグイスの低い繁殖成功をもたらしたことを示唆している．

Background The Russet Bush Warbler Locustella (previously Bradypterus) mandelli complex occurs in mountains in the eastern Himalayas, southern China, Vietnam, the Philippines, and Indonesia. The taxonomy has been debated, with one (L. seebohmi) to four (L. seebohmi, L. mandelli, L. montis and L. timorensis) species having been recognised. Methods We used an integrative approach, incorporating analyses of morphology, vocalizations and a molecular marker, to re-evaluate species limits in the L. mandelli complex. Results We found that central Chinese L. mandelli differed from those from India through northern Southeast Asia to southeast China in plumage, morphometrics and song. All were easily classified by song, and (wing + culmen)/tail ratio overlapped only marginally. Both groups were reciprocally monophyletic in a mitochondrial cytochrome b (cytb) gene tree, with a mean divergence of 1.0 ± 0.2%. They were sympatric and mostly altitudinally segregated in the breeding season in southern Sichuan province. We found that the Mt Victoria (western Myanmar) population differed vocally from other L. mandelli, but no specimens are available. Taiwan Bush Warbler L. alishanensis was sister to the L. mandelli complex, with the most divergent song. Plumage, vocal and cytb evidence supported the distinctness of the south Vietnamese L. mandelli idonea. The Timor Bush Warbler L. timorensis, Javan Bush Warbler L. montis and Benguet Bush Warbler L. seebohmi differed distinctly in plumage, but among-population song variation in L. montis exceeded the differences between some populations of these taxa, and mean pairwise cytb divergences were only 0.5-0.9%. We also found that some L. montis populations differed morphologically. Conclusions We conclude that the central Chinese population of Russet Bush Warbler represents a new species, which we describe herein, breeding at mid elevations in Sichuan, Shaanxi, Hubei, Hunan and Guizhou provinces. The taxonomic status of the other allopatric populations is less clear. However, as they differ to a degree comparable with that of the sympatric L. mandelli and the new species, we elevate L. idonea to species status, and retain L. seebohmi and L. montis as separate species, the latter with timorensis as a subspecies. Further research should focus on different populations of L. montis and the Mt Victoria population of L. mandelli.

Song repertoire size is often cited as a classic example of a secondary sexual trait in birds. Models of sexual selection and empirical tests of their predictions have often related secondary sexual traits to longevity. However, the relationship between repertoire size and longevity is unclear. Using capture-mark-recapture studies in two populations of the brownish-flanked bush warbler Cettia fortipes, we found that males with a repertoire size of three maintained territory tenure for a longer duration than did males with a repertoire size of two. These results provide evidence that even a minimal difference in repertoire size can serve as a potential signal of territory tenure capability.

The bush warblers (Cettia diphone) have been recognized to possess two types of songs: a normal song that plays roles in attracting mate and territorial defense, and an anomalous song. The present study suggests that the anomalous song functions as an alarm signal as well as other unknown signals. Field observations and playback experiments on the anomalous song of bush warbler were conducted in order to investigate the contextual information that occurred between sender and receiver. In the field observation, the males frequently emitted anomalous songs to potential predators. The males responded with an anomalous song to stuffed potential predators. The distance from where the anomalous song occurs to the stimulating source varied depending upon the kinds of stimulus. The males of bush warbler possibly show different responses to the anomalous song depending on the level of danger. When the anomalous song was played back to terrestrial males and females, no distinctive behavior was observed. The anomalo...

This paper describes the seasonal migration of the Bush Warbler Cettia diphone, at a coastal forest in Niigata City, Central Japan, based on the results of long-term banding. Over a 14-year period, 1988-2001, a total of 1, 959 birds (810 males and 1, 149 females) were banded in the spring (early April to middle May). Spring migrants showed a tendency towards a female-biased sex ratio (58.6±6.1%) and a sex-biased time lag; i. e., the males tended to migrate earlier than the females. In the autumns of the same 14-year period, a total of 7, 860 birds (4, 201 males and 3, 659 females), about four times more birds than were captured in the spring, were banded; and the major peaks of migration were seen in late October and early November. The number of males and females changed similarly, and no sex-biased time lag was recognized in the autumn migration. The recovery data suggest that the study area constitutes a pivotal location for migrating flyways of the Bush Warbler in Japan.

The Japanese bush warbler has a very distinctive song, shows marked sexual size dimorphism, and has a polygynous mating system. However, the physical traits of males and seasonal variation in such traits have remained unknown. Twenty-five anatomical measurements representing physical traits of males in the breeding (summer, n = 5) and non-breeding (winter, n = 5) seasons were examined morphologically and compared statistically. Differences were evident between summer and winter (P < 0.05, t test) in the following seven items: body mass (19.8 ± 0.7 g vs. 15.6 ± 1.2 g [mean ± SD]), mass of male reproductive organs (184.0 ± 25.7 mg vs. 6.0 ± 1.4 mg), hind limb (3789.2 ± 346.2 mg vs. 3003.4 ± 226.8 mg), leg muscles (883.0 ± 63.5 mg vs. 581.4 ± 33.2 mg in either side), skin around the neck/throat (1280 ± 34.9 mg vs. 287.2 ± 84.7 mg), and syrinx (35.8 ± 2.39 mg vs. 25.0 ± 3.24 mg), and circumference of the neck/throat (52.1 ± 2.3 mm vs. 38.3 ± 2.6 mm). In contrast to winter males, summer males had thickened flabby skin prominently in the neck/throat area and an inflatable esophagus, perhaps a morphological basis for the throat sac as a vocal resonator. Also, the remarkable development of the flexor muscles of the legs of summer males suggests that perching and movement using the legs increases during the breeding season. These distinct characteristics of summer males may be related to the polygynous mating system of this species.

Song complexity and the repertoire of the bush warbler Cettia diphone were studied in an island and a mainland population in Japan. The song complexity (number of modulations in a song) was lower in the island population than in the mainland one. On the other hand, the repertoire size (number of song types per male) was larger on the island. Founder effect probably does not influence the island song because colonization occurred a very long time ago. Sound transmission properties of the habitat and weak selection pressure for interspecific identification might have influenced the island song, but these cannot elucidate the simpler song on the island. There is a possibility that social conditions affect song complexity in the populations; the highly polygynous mating system of the mainland population yields strong selection pressure toward complex song through acquisition of mates and/or establishment of quality territories. On the other hand, variable songs on the island seem to be affected by cultural mutation.

Breeding ecology of the Short-tailed Bush Warbler Cettia squarneiceps was investigated in western Hokkaido during five seasons (1990-1994). The first arrival and first egg-laying dates were similar among years. Clutch sizes varied between 4-6 eggs, but they decreased as the breeding season progressed. The mean incubation and nestling period was 12.9±0.5 days (SD, n=18) and 10.0±0.4 days (SD, n=17), respectively. Only females incubated eggs and brooded nestlings for a long period of time. Most of the feeding of the young was conducted by males. Different (beta or gamma) males from the resident (alpha) male appeared and sometimes fed the young in 48.1% of twenty five nests observed. Some males were captured at locations far from their own nests, while there were only few cases in which a female was captured at a place distant from her mate's song area. As it was often observed that a beta male was the neighboring territory holder and his own nest was in the incubation period, it is hypothesized that some males who are emancipated from the incubation, might visit other territories to seek extra-pair copulations (EPC). We have, however, not observed mating between a female and a beta male except in the case of a widow. Within the breeding season, the females usually selected the same partner for the second brood. Main reason why the divorce rate within the season is low for the warbler in our study area is probably the high success rate for the first brood.

We compared the adrenocortical responses to acute stress in two free-living populations of bush warblers, Cettia diphone by measuring the increase in circulating levels of corticosterone in response to capture, handling and restraint over one hour. We wished to test the hypothesis that populations living in more severe habitats with shorter breeding seasons are likely to suppress the adrenocortical response to acute stresses during the nesting phase. We chose the bush warbler because males show no parental care which also has been shown to be an ecological correlate of stress modulation. Male bush warblers responded to playback of songs and long calls with aggressive behavior that was identical at the two sites (Furano, Hokkaido and Chichibu, Honshu). Plasma levels of testosterone were also similar in the two populations suggesting that they were in the same reproductive state when tested. Males of both populations showed marked increases in circulating corticosterone levels during the capture st...

Acoustic identification is increasingly being used as a non-invasive method for identifying individuals within avian populations. However, most previous studies have utilized small samples of individuals (

Japanese bush warblers, Cettia diphone , are a common species in Japan and have a poly-gynous breeding system. In the breeding ground some males have their own territories withmore than one female. Male floaters are also not uncommon in the breeding ground. Tounderstand breeding strategy in this species, exact parentage should be elucidated. In orderto obtain a tool for this purpose, we isolated 34 microsatellite loci from a genomic libraryin this species and developed primers for 12 loci. These primers were tested in the Japanesebush warbler and successfully amplified. In analyses of 49 unrelated individuals, allelicnumbers ranged from two to 22, and observed heterozygosity ( H O ) ranged from 0.27 to 0.854except for two loci (Cdi29 and Cdi35a) with H O < 0.1. Keywords : Cettia diphone , Japanese bush warblers, microsatellite, primer Received 8 August 2002; revision received 28 September 2002; accepted 28 September 2002 Japanese bush warblers ( Cettia diphone ) are distributedalong the eastern rim of the Eurasian continent and theJapanese islands and are one of the best known species inJapan because of their unmistakable songs (Hamao 1997).They are residents or short-distant migrants on Honshu(main) island in Japan. In early spring, males begin to singin wintering sites, such as bushes, parks, and backyardsof lowland areas and most of them migrate to highermountainsides and breed in bamboo bushes or grassmeadows. At the field site in Chichibu, Honshu island, weobserved their behaviour and collected blood samples forhormone measurement after capture with mist nets. Wefound that males sing from late March through August inthe breeding area and circulating testosterone is foundhigh during this period (Wada

1) Mating system of individually marked Japanese Bush Warblers Cettia diphone was studied at Myokokogen (36°52′N, 138°11′E, alt. 700m), central Japan, during the 1990-91 breeding seasons. 2) Territories were maintained for short periods. Although 35 territorial males were confirmed within a census area in a breeding season, only 10-14 (x=11.7, n=9) of them were observed on each survey. 3) Intrusions into territories by non-residential males were observed frequently. These intruders never sang there. In M98's territory, 15 intrusions by floating males and five intrusions by territorial males were observed.4) In three territories, multiple females were observed breeding. In M98's territory, seven breeding attempts were made by 6 or 7 females within a season. 5) Females built nests and took the full share of parental care, including incubation, feeding nestlings, rearing fledglings, and mobbing predators. 6) Breeding failures, which might have been caused by predation, were observed frequently. There was a trend for females to leave a territory after one breeding attempt. 7) At least 21 females appeared in M98's territory, which suggests the presence of many potential mates for the male.8) Home ranges of breeding females were much smaller than male territories. Female ranges seemed to be restricted to within male territories. The ranges of females nesting in the same territories overlapped. Agonistic behavior between them was not observed. 9) Singing activity of males was vigorous throughout the breeding season irrespective of the nesting stages of breeding females. No contacts between males and nesting females, including escorting behavior of females by males, were observed.10) These results strongly suggested that the mating system of the Japanese Bush Warbler was advanced polygyny characterized by lack of pair-bonds.