BODY CONDITION OF BREEDING VERMILION FLYCATCHERS (PYROCEPHALUS RUBINUS) VARIES BETWEEN AREAS WITH AND WITHOUT CATTLE RANCHING IN CENTRAL ARGENTINA

The body condition of birds may be conditioned by intrinsic (e.g., sex, age, migratory and breeding status) and extrinsic factors, such as anthropic activities (e.g., livestock raising). We describe the biometry and body condition of Vermilion Flycatchers (VEFL) according to sex and age and evaluate which factors best predict their body condition during the breeding season in the Espinal of central Argentina. The study area included “Parque Luro” Provincial Reserve and two nearby private ranches with livestock. We captured and banded VEFL using mist nets between October to February, from 2015 to 2019. We calculated the scaled mass indexes, which relates body mass to biometric measures (culmen, tarsus, and tail length, and wing chord) to choose the best indicator of body condition. As explanatory variables, we used the breeding condition of females in one model, breeding condition of males in another model, and in a final model we used date, year and site, and included all individuals. We banded 93 VEFL that did not vary according to age-dependent body size or reproductive condition. Nevertheless, females weighed more, had higher fat levels and shorter wings than males. The body condition was only explained by breeding site, being smaller in one ranch than the other ranch and the reserve. We highlight the importance of reserves and the need for further research to understand the ecological constraints that South American birds face, to promote their conservation

Future climate change will impact the migration of New World migrant flycatchers (Tyrannidae)

Climate change is reaching several tipping points, likely resulting in habitat shifts at a global scale. Such changes could have serious consequences for migratory species. For instance, climatic changes may impact the distribution of breeding and non-breeding ranges, resulting in longer migration distances for some species. The flycatchers (Tyrannidae) are the largest family of birds in New World. They are small insectivorous birds with different distributions and migratory strategies, including both tropical and temperate species. Here, we aim to map the climatically suitable ranges for Tyrannidae in the future, compare them to their present ranges, and quantify the changes in range size and in migratory distance. We show different impacts on species that breed in the northern vs. southern hemisphere. Furthermore, results suggest that tropical and temperate species would suffer from different stressors. Neotropical austral migrant species would lose part of their breeding ranges, while Nearctic-Neotropical species would need to fly longer distances to reach the same climatic conditions of their current breeding ranges. Because past climate shifts have shaped the evolution of bird migration, these insights are also key for elucidating the mechanisms underlying the evolution and regulation of bird migration, and for conservation planning.conselho nacional de desenvolvimento científico e tecnológic

Short Communications: First tracking of individual American Robins (Turdus migratorius) across seasons

The American Robin (Turdus migratorius) is one of the most widespread, common bird species in North America; yet, very little is known about its migratory connectivity, migration timing, and migratory routes. Using archival GPS tags, we tracked the movements of 7 individual robins from 3 breeding populations in the United States. Four robins captured in Denali National Park and Preserve, Alaska, overwintered in Texas, Nebraska, Oklahoma, and Montana, up to 4,500 km from the capture location. One robin captured in Amherst, Massachusetts, overwintered in South Carolina 1,210 km from the capture location, whereas 2 robins captured in Washington, D.C., spent the entire year within 6 km of their original capture location. Understanding the annual cycle and differences in migration strategies for a species that exhibits large regional variation in movement has the potential to provide novel insights into how conspecific populations respond to current and future heterogeneity in climate and habitat. The regionspecific patterns presented here suggest robins could serve as sentinels of environmental change at a continental scale

Drivers of clutch-size in Fork-tailed Flycatchers (<i>Tyrannus savana</i>) at temperate and tropical latitudes in South America

Many species of birds exhibit a latitudinal gradient in annual reproductive investment, laying more eggs and producing more nestlings at higher latitudes. However, few studies have evaluated the mechanisms that underlie such patterns and such differences in grassland birds specifically. We monitored nests of Fork-tailed Flycatchers (Tyrannus savana) over two breeding seasons at a tropical site in Bolivia (in 2010-11 and 2011-12) and three breeding seasons at a southern temperate site in Argentina (2010-11, 2011-12 and 2012-13), testing two hypotheses explaining variation in clutch-size among populations: the food-limitation hypothesis and the nest-predation hypothesis. Mean clutch-size and mean brood-size were significantly larger at the temperate study site than at the tropical site. Availability of arthropod food per individual bird was significantly higher at the temperate site. There was no relationship, positive or negative, between rates of nest predation and either clutch- or brood-size, and thus no support for the nest-predation hypothesis. We conclude that food availability explains much of the latitudinal variation in clutch-size in this species. We discuss avenues for future research on the mechanisms underlying geographical variation in the life histories of Neotropical birds.Facultad de Ciencias Naturales y Muse

Hacia una interpretación mecanística de la migración de aves en américa del sur

Research to date has demonstrated that bird migration is comprised of highly diverse and plastic behavioural patterns. Our objective is to highlight the importance of studying mechanisms underlying these patterns in austral migrants. We focus on the high incidence of overlap in breeding and non-breeding ranges as a particularly thought-provoking pattern. We then explore the opportunities afforded by partial migration theory to elucidate the mechanisms underlying seasonal range overlap. We propose that a mechanistic understanding of migration in South America will both provide a deeper appreciation of the ecology, physiology and evolution of migratory species in the New World, and improve the scientific foundation for their conservation.La investigación reciente sobre aves migratorias ha demostrado que constituyen un grupo que presenta comportamientos altamente diversos, plásticos y complejos. Nuestro objetivo general es resaltar la importancia de estudiar los mecanismos que generan los patrones que caracterizan la migración de aves en América del Sur. Para ello nos enfocamos en un patrón interesante (la alta incidencia de superposición en la distribución reproductiva y de invernada), analizando las oportunidades ofrecidas por la teoría de migración parcial para dilucidar los mecanismos que producen tal superposición. Proponemos que una comprensión mecanística de la migración de aves en América del Sur no solo proveería una apreciación más profunda sobre la ecología, la fisiología y la evolución de las especies migratorias del Nuevo Mundo, sino que también mejoraría los fundamentos científicos para su conservación

Body condition of breeding Vermillion Flycatchers (Pyrocephalus rubinus) varies between areas with and without cattle ranching in central Argentina

La condición corporal de las aves puede estar influenciada por aspectos intrínsecos (ej., sexo, edad, comportamiento migratorio y reproductivo) y extrínsecos, como la presencia de actividades antrópicas (ej., ganadería). En este trabajo se describe la biometría y la condición corporal del churrinche, según el sexo y la edad, y se establecen los factores que las condicionan durante la época reproductiva en la provincia fitogeográfica del Espinal del centro de Argentina. El área de estudio comprendió la Reserva Provincial Parque Luro y dos estancias privadas ganaderas aledañas. Se capturaron y anillaron churrinches empleando redes de niebla entre octubre y febrero, desde 2015 a 2019. Se calcularon índices de masa escalada, el cual relaciona la masa corporal con medidas biométricas (largos de culmen, tarso y cola y cuerda de ala) para escoger el mejor predictor de la condición corporal. Como variables explicativas se emplearon en un modelo el estado reproductivo de las hembras; en otro, el estado reproductivo de los machos y en otro la fecha, el año de la temporada y el sitio, contemplando todos los individuos. Se anillaron 93 churrinches que no difirieron según su edad en sus medidas biométricas, ni características de condición corporal, ni condición reproductiva. Sin embargo, las hembras presentaron mayor masa y niveles de grasa y tenían el ala más corta que los machos. La condición corporal del churrinche solo fue explicada por el sitio reproductivo, siendo menor en una de las estancias con ganadería, con respecto a la otra estancia y a la reserva. Se resalta la importancia de las áreas protegidas naturales para mantener a las poblaciones de aves y la necesidad de estudios futuros que establezcan los mecanismos que modulan la condición corporal de las aves migratorias australes del neotrópico para promover su conservación.The body condition of birds may be influenced by intrinsic (e.g., sex, age, migratory and breeding status) and extrinsic factors, such as anthropic activities (e.g., livestock raising). We described the biometry and body condition of Vermilion Flycatchers (VEFL) according to sex and age, and evaluated which factors best predict their body condition during the breeding season in the phytogeographic province of Espinal in central Argentina. The study area included Parque Luro Provincial Reserve and two nearby private ranches with livestock. We captured and banded VEFL using mist nets between October and February, from 2015 to 2019. We calculated scaled mass indices, which relates body mass to biometric measures (culmen, tarsus and tail lengths, and wing chord) to choose the best indicator of body condition. As explanatory variables, we used the breeding condition of females in one model, breeding condition of males in another model, and in a final model we used date, year, and site, and included all individuals. We banded 93 VEFL that did not vary according to age-dependent body size or reproductive condition. Nevertheless, females weighed more, had higher fat levels, and shorter wings than males. Body condition was only explained by breeding site, being smaller in one ranch than at the other ranch and the reserve. We highlight the importance of protected nature reserves to maintain bird populations and the need for further research to establish the mechanisms that modulate the body condition of Neotropical austral migrant birds to promote their conservation.Fil: Rebollo, María Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Sarasola, José Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencia Exactas y Naturales. Departamento de Recursos Naturales. Centro para el Estudio y Conservación de Aves Rapaces; ArgentinaFil: Jahn, Alex. Indiana University; Estados UnidosFil: Cereghetti, Joaquín. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentin

Speciation Associated with Shifts in Migratory Behavior in an Avian Radiation

Gómez-Bahamón et al. show that speciation is associated with changes in migratory behavior in fork-tailed flycatchers (Tyrannus savana). Divergence occurred through loss of migratory behavior of a single lineage. This mode of speciation likely occurred across New World flycatchers (Tyrannidae).Fil: Gómez Bahamón, Valentina. Field Museum of Natural History; Estados Unidos. Investigación Para la Conservación En El Neotrópico; Colombia. University of Illinois; Estados Unidos. Universidad de los Andes; ColombiaFil: Márquez, Roberto. University of Chicago; Estados UnidosFil: Jahn, Alex. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Miyaki, Cristina Yumi. Universidade de Sao Paulo; BrasilFil: Tuero, Diego Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Laverde, Oscar. Universidad de los Andes; Colombia. Pontificia Universidad Javeriana; ColombiaFil: Restrepo, Silvia. Universidad de los Andes; ColombiaFil: Cadena, Carlos Daniel. Universidad de los Andes; Colombi

Follow the Rain? Environmental Drivers of Tyrannus Migration across the New World

Predictable seasonal changes in resources are thought to drive the timing of annual animal migrations; however, we currently understand little about which environmental cues or resources are tracked by different migratory bird species across the planet. Understanding which environmental cues or resources birds track in multiple migratory systems is a prerequisite to developing generalizable conservation plans for migratory birds in a changing global environment. Within the New World, climatic differences experienced by Nearctic–Neotropical migratory (NNM; i.e. breed in North America and spend the nonbreeding period in the Neotropics) and Neotropical austral migratory (NAM; i.e. breed and spend the nonbreeding period wholly within South America) bird species suggest that their migratory strategies may be shaped by unique selective pressures. We used data gathered from individuals fitted with light-level geolocators to build species distribution models (SDMs) to test which environmental factors drive the migratory strategies of species in each system. To do so, we evaluated whether temperature, precipitation, and primary productivity (NDVI) were related to the seasonal distributions of an NNM (Eastern Kingbird [Tyrannus tyrannus]) and NAM species (Fork-tailed Flycatcher [T. savana]). Both Eastern Kingbird and Fork-tailed Flycatcher locations were positively correlated with high precipitation during their nonbreeding seasons. Eastern Kingbird locations were positively correlated with both NDVI and temperature during their breeding season and both pre- and post-breeding migrations. Fork-tailed Flycatcher locations were positively correlated with both temperature and precipitation during both migrations, but only temperature during the breeding season. The value of extending the application of geolocator data, such as in SDMs, is underscored by the finding that precipitation was such an important predictor of the nonbreeding distributions of both types of migrants, as it remains unclear how global climate change will affect wet–dry cycles in the tropics

U‐Pb dating of a remagnetized Paleozoic limestone

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95119/1/grl5536.pd

On the chirality of quark modes

A model for the QCD vacuum based on a domainlike structured background gluon field with definite duality attributed to the domains has been shown elsewhere to give confinement of static quarks, a reasonable value for the topological susceptibility and indications that chiral symmetry is spontaneously broken. In this paper we study in detail the eigenvalue problem for the Dirac operator in such a gluon mean field. A study of the local chirality parameter shows that the lowest nonzero eigenmodes possess a definite mean chirality correlated with the duality of a given domain. A probability distribution of the local chirality qualitatively reproduces histograms seen in lattice simulations.Comment: RevTeX4, 5 figures, 14 page