Explore the vast range of titles available.

The failure of breeding attempts is a major hindrance to bird reproduction, making nest site choice under strong selective pressure. Urbanization may offer lower risk of nest predation to certain bird species, but the impact of using anthropogenic structures as nesting sites on parental fitness is seldom studied. We studied the effect of anthropogenic substrates and brood parasitism by the shiny cowbird Molothrus bonariensis on the nest success of a Neotropical songbird, the pale‐breasted thrush Turdus leucomelas. We monitored 263 nesting attempts between 2017 and 2020 to estimate daily survival rate (DSR), which represents the probability of a given nest surviving until the next day. DSR was modelled as a response variable in function of substrate type (plants as ‘natural' or human buildings as ‘artificial') and brood parasitism as fixed factors, using as covariates year, a linear and a quadratic seasonal trends. Additionally, we tested the effect of these same explanatory variables on the number of fledglings per nest using a generalized linear mixed‐effects model. Most nests (78.7%) were placed in artificial substrates and apparent nest success (i.e. the percentage of nesting attempts that produced at least one thrush fledgling) was higher in artificial (50.2%) than in natural substrates (37.5%). DSR was higher for nests in artificial than in natural substrates regardless of cowbird parasitism, whereas the number of fledglings per nest was higher both in artificial substrates and for nests without cowbird parasitism. We highlight that nesting in buildings significantly increases parental fitness in pale‐breasted thrushes, which may favor their settlement in cities and potentially drive the evolution of this breeding behavior in urban birds.

Do all birds' sex chromosomes follow the same canonical one-way direction of evolution? We combined cytogenetic and genomic approaches to analyze the process of the W chromosomal differentiation in two selected Passeriform species, named the Pale-breasted Thrush Turdus leucomelas and the Rufous-bellied thrush T. rufiventris . We characterized the full catalog of satellite DNAs (satellitome) of T. leucomelas , and the 10 TleSatDNA classes obtained together with 16 microsatellite motifs were in situ mapped in both species. Additionally, using Comparative Genomic Hybridization (CGH) assays, we investigated their intragenomic variations. The W chromosomes of both species did not accumulate higher amounts of both heterochromatin and repetitive sequences. However, while T. leucomelas showed a heterochromatin-poor W chromosome with a very complex evolutionary history, T. rufiventris showed a small and partially heterochromatic W chromosome that represents a differentiated version of its original autosomal complement (Z chromosome). The combined approach of CGH and sequential satDNA mapping suggest the occurrence of a former W-autosomal translocation event in T. leucomelas , which had an impact on the W chromosome in terms of sequence gains and losses. At the same time, an autosome, which is present in both males and females in a polymorphic state, lost sequences and integrated previously W-specific ones. This putative W-autosomal translocation, however, did not result in the emergence of a multiple-sex chromosome system. Instead, the generation of a neo-W chromosome suggests an unexpected evolutionary trajectory that deviates from the standard canonical model of sex chromosome evolution.

The avian life cycle is composed by a progressive sequence of life history stages (LHS). Changes in energy expenditure and exposure to stressors at different LHS require corresponding changes in behavior, physiology, and morphology. Variation in hematological parameters, such hematocrit (Hct), hemoglobin (Hb), and heterophil to lymphocyte ratio (H/L ratio), can have permissive, stimulatory, and preparative actions to help maintain homeostasis through different LHS. Few studies have examined differences in these parameters among different LHS in free‐living birds, with most of them restricted to temperate zones. We collected blood samples and measured hematological parameters every week for over a year from a population of a common resident bird species in southeastern Brazil, the pale‐breasted thrush Turdus leucomelas. Hematocrit and hemoglobin concentration were highest during the onset of the reproduction and lowest during molt. Furthermore, H/L ratios were higher at the end of the reproduction, indicating that the breeding season could be the most stressful period of the year for this population of thrushes. There was no difference between sexes for any hematological parameter at any LHS. These results show that there is a permissive physiological effect for Hct and Hb to facilitate LHS transitions and that reproduction could be the most stressful event for this species. Lastly, these results mirror those from temperate species despite distinct environmental differences between these regions.

Movement is a key spatiotemporal process that enables interactions between animals and other elements of nature. The understanding of animal trajectories and the mechanisms that influence them at the landscape level can yield insight into ecological processes and potential solutions to specific ecological problems. Based upon optimal foraging models and empirical evidence, we hypothesized that movement by thrushes is highly tortuous (low average movement speeds and homogeneous distribution of turning angles) inside forests, moderately tortuous in urban areas, which present intermediary levels of resources, and minimally tortuous (high movement speeds and turning angles next to 0 radians) in open matrix types (e.g., crops and pasture). We used data on the trajectories of two common thrush species (Turdus rufiventris and Turdus leucomelas) collected by radio telemetry in a fragmented region in Brazil. Using a maximum likelihood model selection approach we fit four probability distribution models to average speed data, considering short-tailed, long-tailed, and scale-free distributions (to represent different regimes of movement variation), and one distribution to relative angle data. Models included land cover type and distance from forest-matrix edges as explanatory variables. Speed was greater farther away from forest edges and increased faster inside forest habitat compared to urban and open matrices. However, turning angle was not influenced by land cover. Thrushes presented a very tortuous trajectory, with many displacements followed by turns near 180 degrees. Thrush trajectories resembled habitat and edge dependent, tortuous random walks, with a well-defined movement scale inside each land cover type. Although thrushes are habitat generalists, they showed a greater preference for forest edges, and thus may be considered edge specialists. Our results reinforce the importance of studying animal movement patterns in order to understand ecological processes such as seed dispersal in fragmented areas, where the percentage of remaining habitat is dwindling.

Selection of safe nest sites is a first step toward improving the chances of breeding successfully. Reusing old nests can save time and energy for breeding birds, but nest reuse is rare among opencup nesting songbirds and the factors contributing to this behavior and its consequences for reproductive output remain little known. We studied an urban population of Pale-breasted Thrushes (Turdus leucomelas) in southeastern Brazil to determine whether nest reuse (1) was more likely after a successful nesting attempt both within and between breeding seasons, (2) affected the number of fledglings in the next nesting attempt, (3) reduced the chances of nest parasitism by Shiny Cowbirds (Molothrus bonariensis), and (4) was associated with earlier initiation of nests at the beginning of breeding seasons and shorter re-nesting intervals within breeding seasons. We monitored 266 nests from 2010 to 2019 and obtained data on 130 re-nesting events by individually marked birds. Nest reuse was more frequent after successful nesting attempts within breeding seasons. New nests were more likely to be parasitized by cowbirds, which had a negative effect on the number of fledglings per clutch. Reusing nests allowed earlier initiation of breeding at the start of breeding seasons, but did not shorten re-nesting intervals within seasons. Nest reuse by Pale-breasted Thrushes followed the win-stay lose-switch strategy and corroborated the time-saving hypothesis. Our results suggest that nest reuse may increase the fitness of Pale-breasted Thrushes by reducing the likelihood of cowbird parasitism. La selección de sitios seguros para la anidación es un primer paso hacia el incremento en la probabilidad de una reproducción exitosa. La reutilización de nidos viejos puede ahorrar tiempo y energía para las aves en la reproducción, pero la reutilización de los nidos, entre las especies passeriformes con nidos de copa abiertas, es poco frecuente y los factores que contribuyen a este comportamiento y sus consecuencias para la reproducción son poco conocidas. Estudiamos una población urbana de Turdus leucomelas en el sureste de Brasil para determinar si la reutilización de los nidos (1) era más probable después de un intento de anidación exitoso, umero de tanto dentro de la misma temporada como en diferentes temporadas de reproducción, (2) afecta el número de pichones en el siguiente intento de anidación, (3) reduce la probabilidad de ser parasitado por Molothrus bonariensis y (4) estuvo asociado con una iniciación más temprana de los nidos al inicio de las temporadas de reproducción e intervalos de re-anidación más cortos dentro de la misma temporada. Monitoreamos 266 nidos desde 2010 hasta 2019 y obtuvimos datos de 130 eventos de re-anidaci on por individuos marcados. Los nidos nuevos fueron parasitados por Molothrus bonariensis con mayor probabilidad, lo cual a su vez tuvo un efecto negativo sobre el número de pichones en la nidada. La reutilización de los nidos permitió una iniciación más temprana de la reproducción al inicio de la temporada reproductiva, pero no redujo los intervalos de reanidación dentro de la misma temporada. La reutilización de nidos por Turdus leucomelas siguió la estrategia quedarse-ganar cambiar-perder y corrobora la hipótesis de ahorro de tiempo. Nuestros resultados sugieren que la reutilización de los nidos puede incrementar la aptitud en Turdus leucomelas mediante la reducción de la probabilidad de parasitismo por Molothrus bonariensis.

Plasmodium spp. are haemosporidian protozoans that alternate their live cycles between bloodsucking Culicidae dipterans and vertebrate hosts (mammals, reptiles, and birds). In birds, these parasites are the causative agents of the so-called avian malaria, a disease associated with considerable declines and extinctions in the avifauna in different geographical regions. In this work, we applied a multidisciplinary approach, light microscopy and cytochrome oxidase b (cyt b) gene sequence analysis, for characterization of Plasmodium spp. found in association with wild birds of the genus Turdus, collected in Atlantic forest fragments of southeastern Brazil. From the total 90 analyzed birds, 58 (47 Turdus rufiventris, 9 Turdus leucomelas, 1 Turdus albicollis, and 1 Turdus flavipes) were positively infected with Plasmodium unalis, a haemosporidian that was previously detected in Turdus fuscater in Colombia and in penguins in Brazil, but has never been found in association with these Turdus species of this present work. Moreover, all 7 new sequences of P. unalis cyt b gene clustered into a monophyletic clade with previously characterized P. unalis sequences with a mean genetic divergence of 1.6% and with a maximum divergence of 3.1%, indicating for a high degree of intraspecific polymorphism within this parasitic species. Together, our data highlight the existence a high degree of intraspecific variation within P. unalis and highlight the importance of integrative taxonomy to an accurate identification and characterization of avian haemosporidian parasites.

According to the enemy release hypothesis (ERH) the spread of invasive species will be facilitated by release from their enemies as they occupy new areas. However, the ERH has rarely been tested by comparing populations of native (non-invasive, long established) species with expanding or shifting ranges, to the same species as invasive in another area. We tested the ERH with respect to blood parasite levels (prevalence and intensity of Plasmodium spp. and Haemoproteus spp.) of (a) two closely related, widely distributed species of thrush (Turdus leucomelas and T. merula), and (b) an invasive sparrow (Passer domesticus) whose range has expanded from the Old World to the New World since the 18th century. A total of 158 birds were sampled in Portugal and 99 in Brazil. All bird species were parasitized, and 55% of the individuals collected were parasitized, and the mean intensity of infection was of 28 parasites per 10,000 erythrocytes. We assessed whether differences in levels of infection (prevalence and intensity) were due to site (tropical/New World and temperate/Old World) or host species. The ERH was supported: Passer domesticus and Turdus merula had higher levels of parasitism in the Old World than in the New World. Thus, P. domesticus seems to be benefitting from its \"recent\" range expansion, compared to T. leucomelas, through ecological release from its native parasites and because the parasites of the recently invaded area seem to be infesting native species instead. Resumo: De acordo com a hipótese da liberação do inimigo (HLI), a disseminação de espécies invasoras será facilitada pela liberação de seus inimigos ao ocuparem novas áreas. No entanto, a HLI raramente é testada comparando-se as populações de espécies nativas (não invasivas, estabelecidas há muito tempo) que apresentam expansão ou alteração de habitats, com populações das mesmas espécies em habitats que foram invadidos. Testamos a HLI com relação aos níveis de parasitas no sangue (prevalência e intensidade de Plasmodium spp. e Haemoproteus spp.). De (a) duas espécies estreitamente relacionadas e amplamente distribuídas de Turdus (Turdus leucomelas e T. merula), e (b) um pardal invasor (Passer domesticus) cujo alcance se expandiu do Velho Mundo para o Novo Mundo desde o século 18. Um total de 158 aves foram amostradas em Portugal e 99 no Brasil. Todas as espécies foram parasitadas e 55% dos indivíduos foram parasitados, sendo que a intensidade média da infecção foi de 28 parasitas por 10.000 eritrócitos. Avaliamos se as diferenças nos níveis de infecção (prevalência e intensidade) foram devidas ao local (tropical/Novo Mundo e temperado/Velho Mundo) ou espécies hospedeiras. A HLI foi corroborada: Passer domesticus e Turdus merula apresentaram valores mais elevados de parasitismo no Velho Mundo do que no Novo Mundo. Assim, P. domesticus parece estar se beneficiando de sua expansão \"recente\" em comparação com T. leucomelas, através da liberação ecológica de seus parasitas nativos porque os parasitas da área recentemente invadida parecem infestar espécies nativas.

A new coccidian species (Protozoa: Apicomplexa: Isospora) is described parasitizing white-necked thrushes Turdus albicollis Vieillot, 1818; rufous-bellied thrushes Turdus rufiventris Vieillot, 1818; pale-breasted thrushes Turdus leucomelas Vieillot, 1818; and yellow-legged thrushes Turdus flavipes Vieillot, 1818 from 3 different localities in Brazil. Isospora sabiai n. sp. has oocysts that are subspherical to ellipsoidal, 20.9 × 18.6 μm, with smooth, delicate, bilayered wall, ∼1.1 μm thick. Micropyle inconspicuous or imperceptible. Oocyst residuum absent, but small polar granules rounded or comma-shaped are present. Sporocysts are elongate ellipsoidal to reniform, 16.5 × 9.2 μm. The Stieda body is knob-like. Sub-Stieda body rounded to conical, sometimes homogeneous with the Stieda body. Sporocyst residuum is present, usually as a cluster of numerous granules. Sporozoites are vermiform with 2 refractile bodies. The oocysts and sporocysts of I. sabiai n. sp. are uniform in the proportionality of width on length, but exhibited different patterns of size associated with each host species; therefore, an ecological discussion is introduced aimed at associating these morphometrical patterns of the oocysts with the habits of the different species of thrushes. This is the seventh isosporoid coccidian reported from New World turdids.

Habitat alteration can disrupt host-parasite interactions and lead to the emergence of new diseases in wild populations. The cerrado habitat of Brazil is being fragmented and degraded rapidly by agriculture and urbanization. We screened 676 wild birds from three habitats (intact cerrado, disturbed cerrado and transition area Amazonian rainforest-cerrado) for the presence of haemosporidian parasites (Plasmodium and Haemoproteus) to determine whether different habitats were associated with differences in the prevalence and diversity of infectious diseases in natural populations. Twenty one mitochondrial lineages, including 11 from Plasmodium and 10 from Haemoproteus were identified. Neither prevalence nor diversity of infections by Plasmodium spp. or Haemoproteus spp. differed significantly among the three habitats. However, 15 of the parasite lineages had not been previously described and might be restricted to these habitats or to the region. Six haemosporidian lineages previously known from other regions, particularly the Caribbean Basin, comprised 50-80% of the infections in each of the samples, indicating a regional relationship between parasite distribution and abundance.

One of the least known aspects of the biology of diurnal birds is their nocturnal behavior, which limits our knowledge on their circadian cycles and total home ranges. We studied the nocturnal behavior of the Pale-breasted Thrush (Turdus leucomelas) in a suburban area in Brazil to investigate the relationship between the night roost and diurnal home range (DHR). Birds returned every night to the same roosts in tall trees with dense canopy. In contrast to their nesting habits, birds did not use buildings as nocturnal roosts. In 4 of 9 cases, night roosts were completely outside the DHR. When they were inside the DHR, night roosts were not close to the core area of the DHR. Our results, together with data for a few other bird species, show that considering nocturnal roosting behavior is essential for a more accurate estimate of home ranges of diurnal birds.