Explore the vast range of titles available.

Songbirds, which rely heavily upon acoustic communication, employ a variety of strategies to reduce the degree to which their songs are masked by other sounds within the environment. One such strategy is to make active adjustments to song timing to avoid temporally overlapping other environmental sounds. While playback studies in many different songbird species have demonstrated that territorial males avoid overlapping conspecific songs in that context, there is comparatively little known about how such behavior varies across contexts. For example, there is relatively little information on avoidance of overlapping in naturalistic interactions (e.g., countersinging) among conspecific singers; likewise, few studies have assessed the degree to which males avoid overlapping heterospecific songs. Songbird researchers have also explored possible communicative functions of song overlapping, most notably the idea that overlapping conveys information related to aggression. The objectives of the present study were to compare song overlapping across contexts and to assess the relationship between song overlapping and physical responses to conspecific playback in the Hermit Thrush (Catharus guttatus). Degree of song overlapping in response to conspecific (n = 29) and heterospecific playback (n = 31), as well as during naturally occurring countersinging (n-21 pairs), was compared to chance levels. Avoidance of overlapping occurred in all 3 contexts, although to a lesser degree in response to heterospecific playback. Comparison of physical responses to song overlapping during conspecific playback revealed no association, aligning with recent studies in other species indicating that song overlapping is not an aggressive signal. Instead, the avoidance of song overlapping appears to be an important tool for decreasing the risk of acoustic interference posed by both conspecific and heterospecific songs. Received 27 February 2023. Accepted 28 December 2023.

The Aztec Thrush (Ridgwayia pinicola) is an understudied species. Many aspects of its basic biology are unknown, including its food and foraging preferences. Here, we describe observations of Aztec Thrush consuming fruits of the tree Ilex hrundegeeana and flowers of the bromeliad Tillandsia hourgaei in the pine-oak forest of the highlands of Jalisco in western Mexico. These observations provide information about the diet of this species and its possible ecological role in regenerating and structuring processes of this forest. Received - June 2021. Accepted I October 2021.

Species of the genus Morishitium Witenberg, 1928 are parasites of the body cavity, air sacs, and lungs of birds. At least 14 species are considered valid, but molecular confirmation of their status is lacking. Here, we provide the first molecular data on Morishitium dollfusi isolated from their type host Pica pica, compared them with previously reported molecular data from Morishitium polonicum isolated from their type and paratype hosts, Turdus merula and Turdus philomelos, and performed extensive measurements of 511 individuals of Morishitium spp. across a broad host spectrum, at multiple infection intensities, and year-round. We analyzed the molecular phylogenetics of Morishitium spp. adults isolated from bird hosts of Czech origin and provide comparative measurements of the analyzed specimens. Based on the molecular examination of morphologically identified specimens of M. dollfusi and M. polonicum (CO1, ND1, and ITS2 markers), we propose synonymization of Morishitium dollfusi (Timon-David, 1950) with Morishitium polonicum (Machalska, 1980) (isolates of European origin). The three markers were either identical (CO1, ITS2) or formed haplotypes shared by the two species (ND1). Morphological analyses revealed a continuum of key identification features for the two above-named species, although we used specimens matching the original descriptions and isolated them from the type hosts. Therefore, Morishitium polonicum is a junior synonym of Morishitium dollfusi. Attention is needed regarding the status of East Asian isolates identified previously as M. polonicum (or M. polonicum malayense). The molecular analysis revealed that these isolates form a distinct clade, and further research is needed to produce data allowing the likely separation of the malayense clade as a separate species.

We tracked 47 Wood Thrushes (Hylocichla mustelina) using radio telemetry over 2 breeding seasons in Virginia, USA. Here we present 2 noteworthy observations from this effort. First, we recorded one adult male with synchronous tail replacement in post-breeding molt during tracking from the early breeding season until the fall migration. Synchronous tail molt is seldom documented in Passeriformes and may have consequences for behavior and habitat use during this period of reduced mobility. Second, we recorded a widower male providing parental care by feeding young for nearly the entire nestling period. These observations highlight both the vulnerability of the Wood Thrush immediately following the breeding season and its potential reproductive resilience in the case of mate loss. Received 19 May 2019. Accepted 30 July 2020.

Migratory landbirds are in decline across North America as factors like habitat loss and climate change pose significant challenges across the annual cycle. Migration is a period of especially high mortality as birds must navigate new landscapes to find suitable foraging habitat and deal with ecological barriers, predation, and competition along the way. Stopover sites where birds can rest and refuel are crucial for successful migration. Refueling performance is linked to a variety of factors including season, migratory distance, habitat quality, and body condition upon arrival. Here, we used plasma triglyceride to investigate how season, progression of season (ordinal day), and breeding latitude influenced the stopover refueling performance of 7 migratory songbird species during fall and spring migration at an inland site in the Connecticut River Valley in western Massachusetts. We found that Swainson's Thrushes (Catharus ustulatus) and White-throated Sparrows (Zonotrichia albicollis) had greater refueling performance in spring, while Gray Catbirds (Dumetella carolinensis) showed increased refueling performance in fall, suggesting that birds refuel differently at the same site and experience different pressures between seasons during migration. Progression of season did not influence refueling performance for most species in either season, but in fall the refueling performance of Gray Catbirds increased as the season progressed, while the refueling performance declined as the fall season progressed for Ycllow-rumped Warblers (Setophaga coronata). We used stable isotopes to examine how breeding latitude influenced refueling performance for a subset of Gray Catbirds and found that, contrary to our expectations, Gray Catbirds nearer to their breeding destination in spring had greater refueling performance, suggesting that birds may try to improve their body condition directly before arriving at their breeding grounds to increase their reproductive competitiveness. Our results show that refueling performance of songbirds passing through inland stopover sites varies across species and can be influenced by a variety of factors including season and breeding latitude.

Microfilariae (MF) are the immature stages of flarial nematode parasites and inhabit the blood and dermis of all classes of vertebrates, except fish. Concurrent ingestion of MF and arboviruses by mosquitoes can enhance mosquito transmission of virus compared to when virus is ingested alone. Shortly after being ingested, MF penetrate the mosquito's midgut and may introduce virus into the mosquito's hemocoel, creating a disseminated viral infection much sooner than normal. This phenomenon is known as microfilarial enhancement. Both American Robins and Common Grackles harbor MF--that is, Euflaria sp. and Chandlerella quiscali von Linstow (Spirurida: Onchocercidae), respectively. We compared infection and dissemination rates in Culex pipiens L. mosquitoes that fed on birds with and without MF infections that had been infected with West Nile virus (WNV). At moderate viremias, about 10 (7) plaque-forming units (pfu)/ml of blood, there were no differences in infection or dissemination rates among mosquitoes that ingested viremic blood from a bird with or without microfilaremia. At high viremias, >[10.sup.85] pfu/ml, mosquitoes feeding on a microfilaremic Grackle with concurrent viremia had significantly higher infection and dissemination rates than mosquitoes fed on viremic Grackles without microfilaremia. Microfilarial enhancement depends on the specific virus, MF, and mosquito species examined. How virus is introduced into the hemocoel by MF differs between the avian/WNV systems described here (i.e., leakage) and various arboviruses with MF of the human filarid, Brugia malayi (Brug) (Spirurida: Onchocercidae) (i.e., cotransport). Additional studies are needed to determine if other avian species and their MF are involved in the microfilarial enhancement of WNV in nature.

Tarsiger indicus (Vieillot, 1817), the White-browed Bush Robin, is a small passerine bird widely distributed in Asian countries. Here, we successfully sequenced its mitogenome using the Illumina Novaseq 6000 platform (Illumina, San Diego, CA, USA) for PE 2 × 150 bp sequencing. Combined with other published mitogenomes, we conducted the first comprehensive comparative mitogenome analysis of Muscicapidae birds and reconstructed the phylogenetic relationships between Muscicapidae and related groups. The T. indicus mitogenome was 16,723 bp in size, and it possessed the typical avian mitogenome structure and organization. Most PCGs of T. indicus were initiated strictly with the typical start codon ATG, while COX1 and ND2 were started with GTG. RSCU statistics showed that CUA, CGA, and GCC were relatively high frequency in the T. indicus mitogenome. T. cyanurus and T. indicus shared very similar mitogenomic features. All 13 PCGs of Muscicapidae mitogenomes had experienced purifying selection. Specifically, ATP8 had the highest rate of evolution (0.13296), whereas COX1 had the lowest (0.01373). The monophylies of Muscicapidae, Turdidae, and Paradoxornithidae were strongly supported. The clade of ((Muscicapidae + Turdidae) + Sturnidae) in Passeriformes was supported by both Bayesian Inference and Maximum likelihood analyses. The latest taxonomic status of many passerine birds with complex taxonomic histories were also supported. For example, Monticola gularis, T. indicus, and T. cyanurus were allocated to Turdidae in other literature; our phylogenetic topologies clearly supported their membership in Muscicapidae; Paradoxornis heudei, Suthora webbiana, S. nipalensis, and S. fulvifrons were formerly classified into Muscicapidae; we supported their membership in Paradoxornithidae; Culicicapa ceylonensis was originally classified as a member of Muscicapidae; our results are consistent with a position in Stenostiridae. Our study enriches the genetic data of T. indicus and provides new insights into the molecular phylogeny and evolution of passerine birds.

The European Birds Directive (2009/147/EC) mandates that migratory game birds “are not hunted during their period of reproduction or during their return to their rearing grounds”. For each huntable species, the study of the onset of the reproductive phase is important in order to plan the hunting season. The purpose of this study was to evaluate the development of the fattening status and reproductive activity of the song thrush. To achieve this goal, the chemical and fatty acid compositions of the pectoral muscle were analyzed in relation to the fattening status of the birds. In addition, reproductive status was evaluated through anatomical and pathological examinations of tissues and the assessment of sex steroid profiles. The results showed that the fattening statuses and fatty acid profiles of the song thrush increase from December to February, corresponding with low ambient temperatures and the approach of spring migration. The change in fatty acid profile may also be related to their diet, which switches from insectivorous to vegetarian, during the winter. The sex hormone profiles and histological examination show that both male and female song thrushes were in a reproductive quiescence phase during the period under consideration. In this study, we aimed to evaluate the development of the fattening condition and the reproductive status of the song thrush from December to February. For this purpose, the chemical and fatty acid compositions of the pectoral muscle were analyzed in relation to the fattening state of the birds. Moreover, their reproductive activity was evaluated via the anatomical and pathological examination of tissues and through the assessment of sex steroid profiles. One hundred ninety-five thrushes captured by local hunters during the 2018–2019 and 2019–2020 hunting seasons in different provinces of the Apulia region in Italy were used. The first step was the measurement of bird body mass, and the amount of subcutaneous body fat was estimated visually. During post-mortem examinations, the pectoral muscle was excised and used for chemical and fatty acid analysis and a hormone assay, respectively. Moreover, ovaries and testicles were evaluated to determine the degree of maturation and thus the reproductive status of the birds. The results regarding fattening status and fatty acid profile confirmed that in January–February, thrushes change their diet, increasing their intake of oleic acid, likely to better cope with low temperatures and prepare for long-distance migration. In both male and female thrushes, the concentrations of sex hormones confirmed a phase of reproductive quiescence from December to February, which was also confirmed through histological examination of the gonads.

Urbanization drastically alters natural ecosystems and the structure of their plant and animal communities. Whereas some species cope successfully with these environmental changes, others may go extinct. In the case of parasite communities, the expansion of urban areas has a critical effect by changing the availability of suitable substrates for the eggs or free-larval stages of those species with direct life cycles or for the range of hosts of those species with complex cycles. In this study we investigated the influence of the degree of urbanization and environmental heterogeneity on helminth richness, abundance and community structure of rufous-bellied thrushes (Turdus rufiventris) along a rural-urban gradient in the metropolitan region of Porto Alegre, State of Rio Grande do Sul, Brazil. This common native bird species of southern Brazil hosts 15 endoparasite species at the study region. A total of 144 thrushes were collected with mist nets at 11 sites. The degree of urbanization and environmental heterogeneity were estimated by quantifying five landscape elements: buildings, woodlands, fields, bare lands, and water. Landscape analyses were performed at two spatial scales (10 and 100 ha) taking into account home range size and the potential dispersal distance of thrushes and their prey (intermediate hosts). Mean parasite richness showed an inverse relationship with the degree of urbanization, but a positive relationship with environmental heterogeneity. Changes in the structure of component communities along the rural-urban gradient resulted from responses to the availability of particular landscape elements that are compatible with the parasites' life cycles. We found that the replacement of natural environments with buildings breaks up host-parasite interactions, whereas a higher environmental (substrate) diversity allows the survival of a wider range of intermediate hosts and vectors and their associated parasites.