The global diversification of songbirds (Oscines) and the build-up of the Sino-Himalayan diversity hotspot

Over the last decade, molecular phylogenetic studies have provided the foundation for a comprehensive analysis of the global diversification of songbirds (Oscines), which comprise nearly half of all the birds of the world. By comparing the spatial distribution of species representing basal and terminal root-path groups, this paper provides graphical illustrations of the global pattern of diversification for the major songbird clades. The worldwide expansion of songbirds started as an island radiation in the area where New Guinea is now located, but the mountains of southern China represent a principal center for more recent diversification. The paper suggests priorities and perspectives for further research aiming to understand what determines the variation in biodiversity on different spatial scales.

Responses of early-successional songbirds to a two-stage shelterwood harvest for oak forest regeneration

Background: The early stage of forest succession following disturbance is characterized by a shift in songbird composition as well as increased avian richness due to increased herbaceous growth in the forest understory. However, regeneration of woody species eventually outcompetes the herbaceous understory, subsequently shifting vegetation communities and decreasing availability of vital foraging and nesting cover for disturbance-dependent birds, ultimately resulting in their displacement. These early stages following forest disturbance, which are declining throughout the eastern United States, are ephemeral in nature and birds depend on such disturbances for nesting and other purposes throughout their lives.Methods: We investigated the use of a two-stage shelterwood method to manage long-term persistence of seven early successional songbirds over a 13-year period in an upland hardwood forest within the southern end of the midCumberland Plateau in the eastern United States.Results: Canopy and midstory gaps created after initial harvest were quickly exploited by tree growth and canopy cover returned to these areas, accelerating the displacement of early-successional species. Woody stem densities increased substantially following stage two harvest as advanced tree regeneration combined with the re-opening of the overstory layer increased resource competition for early-successional plants in the understory. Carolina Wren(Thryothorus ludovicianus), Eastern Towhee(Pipilo erythrophthalmus), Indigo Bunting(Passerina cyanea), and Yellowbreasted Chat(Icteria virens) were characterized by immediate increases following initial harvest in 2001; while the American Goldfinch(Spinus tristis), Prairie Warbler(Setophaga discolor), and White-eyed Vireo(Vireo griseus) did not show an immediate response. Stage two harvest in 2011 rejuvenated vegetation which benefitted focal species, with six of seven species showing increases in densities between 2010 and 2012.Conclusion: The two-stage shelterwood method created conditions advantageous to early-successional birds by helping to re-establish understory vegetation through periodic disturbance to the canopy layer. This method provides evidence that early-successional species can be managed long-term(> 15 years) while using relatively small spatial disturbance through the two-stage shelterwood method.

Infection Prevalence of <i>Borrelia burgdorferi</i>in Ticks Collected from Songbirds in Far-Western Canada

Worldwide, wild birds play a vital role in the dispersal of ticks that harbour tick-borne pathogens, including Borrelia burgdorferi, the Lyme disease bacterium. Using PCR testing, we found 124 (31%) of 405 ticks (4 species), which were collected from 21 species of birds in far-western Canada, to be infected with B. burgdorferi. Transstadial transmission of B. burgdorferi occurred from larva to nymph, plus nymph to adult, in the avian coastal tick, Ixodes auritulus, collected from songbirds in British Columbia (B.C). Collectively, all 3 motile life stages (larva, nymph, adult) of this tick had an infection prevalence of 31% for B. burgdorferi, which suggests vector competency. A Pacific Wren was highly infested with I. auritulus immatures, and 20 (44%) of 45 ticks (2 nymphs, 43 larvae) were infected with B. burgdorferi. This heavy infestation shows the high potential to initiate a new population of ticks and to disseminate Lyme spirochetes. Epidemiologically, B. burgdorferi-infected I. auritulus larvae collected from the Spotted Towhee, Swainson’s Thrush, Pacific Wren, and Fox Sparrow suggest that these avian hosts act as reservoirs for B. burgdorferi. In this study, the western blacklegged tick, Ixodes pacificus, and Ixodes spinipalpis played a limited role in the enzootic transmission cycle of B. burgdorferi along coastal B.C. We document the first record of I. spinipalpis on a bird in Alberta. Because songbirds widely disperse Lyme disease vector ticks, primary health providers and the general public must be vigilant that outdoors people may be bitten by B. burgdorferi-infected ticks throughout far-western Canada.

Riparian and Riverine Wildlife Response to a Newly Created Bridge Crossing

Construction of man-made objects such as roads and bridges can influence wildlife presence and abundance. We investtigated waterbirds, songbirds, anurans, turtles, small mammals, and furbearers along the Ohio River, WV, at a new bridge crossing, a 45-year old bridge, and 1 or 2 islands with no bridge and at 3 distances from the bridge or center point at each site (0 m,100 m, and300 m). We sampled 19 waterbird, 60 songbird, 7 anuran, 5 turtle, 9 small mammal, and 4 furbearer species. Great blue heron (Ardea herodias) abundances were greater at the site with no bridge. Songbird composition differed among sites and between transects under and away from the bridge with higher abundances or association of rock pigeon (Columba livia) and cliff swallow (Petrochelidon pyrrhonota) under the bridges and lower abundances ofCarolinawren (Thryothorus ludovicianus) and common yellowthroat (Geothlypis trichas) under the bridges. Total small mammal abundance, diversity, and richness were lower under the new bridge compared to other sites and distances. We conclude that overall the new bridge is causing minimal relative abundance impacts to wildlife. However, great blue heron abundance may be altered due to noise and activity from the presence of the bridge and minor short-term impacts to some songbirds and small mammals directly under the bridge in the form of habitat conversion, fragmentation, and loss due to removal of vegetation is apparent.

A new bird record in China： Moustached Warbler (Acrocephalus melanopogon) and its song characteristics

Moustached Warbler （Acrocephalus melanopogon）, belonging to the genus of Acrocephalus and the family of Acrocephalidae, breeds widely but locally in the warm temperate regions from Northwest Africa and eastern Iberian Peninsula to eastern Kazakhstan. However, this species has never been scientifically recorded in China. On 22 April 2016, a Moustached Warbler was observed in Ulanbuy wetland （43°36′N, 87°43′E; 1114 m a.s.l.）, Urumqi, Xinjiang of China. This was the first photography-confirmed record of Moustached Warbler in China. As Moustached Warbler is a songbird, the songs were then recorded on 18 May 2016 using a Sony PCM D-100 recorder and the song characteristics were analyzed using Avisoft-SASLab software. The result showed that the mean maximum frequency of song strophes was 6.64 （±0.47） kHz and the mean minimum frequency of song strophes was 1.72 （±0.14） kHz. This study could considered as a supplement of the checklist of birds in China.

Quiet in the nest:The nest environment attenuates song in a grassland songbird

The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.

Detection of Borrelia americana in the Avian Coastal Tick, Ixodes auritulus (Acari: Ixodidae), Collected from a Bird Captured in Canada

We document the first record of Borrelia americana in Canada. This Borrelia was detected in an avian coast tick, Ixodes auritulus (Acari: Ixodidae), collected from a Varied Thrush, Ixoreus naevius, along coastal British Columbia. Using real-time PCR and DNA sequencing of the flagellin gene, we determined that the borrelial amplicon from the I. auritulus nymph was 99% homologous with B. americana type strain SCW-41. Because patients infected with B. americana can be seronegative for Lyme disease, medical professionals should be willing to pursue molecular analyses and consider treatment for patients with Lyme disease-like symptoms.

Novel insights into the historical biogeography of the streak-breasted scimitar babbler complex （Aves： Timaliidae： Pomatorhinus ruficollis complex）

The Streak-breasted Scimitar Babblers of the Pomatorhinus ruficollis species complex are found in most of the forested habitats across southern and eastern Asia. The diversification history of this group is obscured by high plumage variation across populations and conflicting genetic signal across loci. We combined genetic and geographic data from several recent studies to investigate how these species diversified across China using both phylogenetic and ecological niche modeling analyses. These two lines of evidence are consistent in showing that two well-sampled species, P. reconditus and P. nigrostellatus, in central and southern China respectively, likely experienced a history of isolation and expansion as suitable habitat contracted during the last interglacial and expanded in patchy extent during the glacial maximum. The genetic analysis showed that populations of P. nigrostellatus on Hainan Island are very similar to the ones in nearby mainland southern China. We recovered two well-supported clades within P. reconditus that were not geographically structured with both containing individuals from the same localities across central China. This phylogenetic result corresponded to the ecological niche models that showed expansion from refugia since the last interglacial. This study illustrates the value of using an integrative approach and detailed geographic sampling to help understand the recent diversification of birds in China [Current Zoology 61 （5）： 910-921, 2015].

Exploring novel candidate genes from the Mouse Genome Informatics database: Potential implications for avian migration research

To search for genes associated with migratory phenotypes in songbirds,we selected candidate genes through annotations from the Mouse Genome Informatics database and assembled an extensive candidate-gene library.Then,we implemented a next-generation sequencing approach to obtain DNA sequences from the Painted Bun­ting genome.We focused on those sequences that were conserved across avian species and that aligned with candidate genes in our mouse library.We genotyped short sequence repeats from the following candidate genes:ADRA1d,ANKRD17,CISH and MYH7.We studied the possible correlations between allelic variations occur­ring in these novel candidate migration genes and avian migratory phenotypes available from the published lit­erature.We found that allele variation at MYH7 correlated with a calculated index of speed of migration(km/day)across 11 species of songbirds.We highlight the potential of the Mouse Genome Informatics database in providing new candidate genes that might play a crucial role in regulating migration in birds and possibly in other taxa.Our research effort shows the benefits and limitations of working with extensive genomic datasets and offers a snapshot of the challenges related to cross-species validation in behavioral and molecular ecology studies.

Toward a neurobiology of auditory object perception： What can we learn from the songbird forebrain？

In the acoustic world, no sounds occur entirely in isolation; they always reach the ears in combination with other sounds. How any given sound is discriminated and perceived as an independent auditory object is a challenging question in neu- roscience. Although our knowledge of neural processing in the auditory pathway has expanded over the years, no good theory ex- ists to explain how perception of auditory objects is achieved. A growing body of evidence suggests that the selectivity of neurons in the auditory forebrain is under dynamic modulation, and this plasticity may contribute to auditory object perception. We propose that stimulus-specific adaptation in the auditory forebrain of the songbird （and perhaps in other systems） may play an important role in modulating sensitivity in a way that aids discrimination, and thus can potentially contribute to auditory object perception.

Deafening-induced rapid changes to spine synaptic connectivity in the adult avian vocal basal ganglia

The basal ganglia have been implicated in auditory-dependent vocal learning and plasticity in human and songbirds,but the underlying neural phenotype remains to be clarified.Here,using confocal imaging and three-dimensional electron microscopy,we investigated striatal structural plasticity in response to hearing loss in Area X,the avian vocal basal ganglia,in adult male zebrafinch(Taeniopygia guttata).We observed a rapid elongation of dendritic spines,by approximately 13%,by day 3 after deafening,and a considerable increase in spine synapse density,by approximately 61%,by day 14 after deafening,compared with the controls with an intact cochlea.Thesefind-ings reveal structural sensitivity of Area X to auditory deprivation and suggest that this striatal plasticity might contribute to deafening-induced changes to learned vocal behavior.