Alex E Jahn

Smithsonian Institution · Migratory Bird Center

There are six species of flamingos in the world, all under pressure from human activities in their wetland habitats. Obtaining global population estimates for flamingos is challenging because of their broad geographical range, nomadic movements, capacity for long-distance flight, and the complexity of international monitoring. Two species, the Ande...

Supplementary material of the article: Cueto, V.R., C.A. Gorosito, G. Brown & A.E. Jahn. 2024. En route activity of Chilean Elaenia, a long-distance migratory bird in South America. Journal of Ornithology: on line, november 2024 – DOI: 10.1007/s10336-024-02237-1

The logistics of measuring activities that occur at fine temporal scales, such as short stopovers that last a few hours, has proven very challenging when studying small migratory birds. Here, we deployed multi-loggers equipped with an accelerometer and thermometer on Chilean Elaenias (Elaenia chilensis) to evaluate their activity patterns while the...

The logistics of measuring activities that occur at fine temporal scales, such as short stopovers that last a few hours, has proven very challenging when studying small migratory birds. Here, we deployed multi-loggers equipped with an accelerometer and thermometer on Chilean Elaenia (Elaenia chilensis) to evaluate their activity patterns while they...

Food selection is a key aspect of a bird's life history strategy, so understanding how birds respond to variation in food abundance is relevant to evaluating their general ecology and survival, and also the potential consequences of the degradation of environments impacted by livestock. We studied the dietary ecology of Vermilion Fly-catchers (VEFL...

The Altillanura is a unique ecosystem within the Colombian Llanos, characterized by well-drained savannas and extensive riparian forests. The Altillanura harbors a rich assemblage of species, largely understudied and currently under threat by large-scale and unplanned agribusiness. Moreover, the number of public protected areas in the Colombian Lla...

Understanding how diet and life history strategies interact is important for exploring constraints of available nutrition on energetically expensive life history events in wild animals (i.e., reproduction, annual migration, molt). Previous research on migratory birds breeding in the Northern Hemisphere has demonstrated trophic niche shifts from inv...

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 (Tyrann...

Morphology is closely linked to locomotion and diet in animals. In animals that undertake long-distance migrations, limb morphology is under selection to maximize mobility and minimize energy expenditure. Migratory behaviours also interact with diet, such that migratory animals tend to be dietary generalists, whereas sedentary taxa tend to be dieta...

Resumen La condición corporal puede influir en diferentes procesos fenológicos que, a su vez, pueden ser desempeñados diferencialmente según la edad y sexo de los individuos. Presentamos la biometría, condición corporal, estado reproductivo y muda de la tijereta sabanera (Tyrannus s. savana), un migrante austral del Neotrópico. En La Pampa, Argenti...

Resumen • 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 condi-ción corporal del churrinche, según el sexo y la edad, y se estable...

South America is home to the highest diversity of birds on the planet, yet we still understand relatively little about their seasonal movements, or even which species are migratory. During two consecutive years, we used satellite transmitters to study the movement ecology of 10 individual Snail Kites (Rostrhamus sociabilis) captured in southern Bra...

Bird migration patterns are changing worldwide due to current global climate changes. Addressing the effects of such changes on the migration of birds in South America is particularly challenging because the details about how birds migrate within the Neotropics are generally not well understood. Here, we aim to infer the potential effects of future...

Aproximadamente la mitad de las especies de aves conocidas realizan desplazamientos migratorios y se estima que cada año se movilizan alrededor de 50 billones de individuos. No hay duda que semejante “movimiento” ha llevado al ser humano a tratar de entender cómo y porqué se produce este fenómeno. En este artículo comentamos los resultados que hemo...

As earth-bound, bipedal creatures, our view of the world contrasts sharply with that of the miniature winged beasts we call songbirds, capable of crossing vast oceans, deserts, and mountains numerous times during their fast-paced lives. Unsurprisingly, the journeys of songbirds, as well as those of larger birds such as storks defied the comprehensi...

Synopsis Sonations are sounds that animals produce with structures other than the vocal apparatus for communication. In birds, many sonations are usually produced with modified flight feathers through diverse kinematic mechanisms. For instance, aeroelastic fluttering of feathers produces tonal sound when airflow exceeds a threshold velocity and ind...

Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozen...

Migratory animals move up to thousands of kilometers every year [1]. Losses of migration (i.e., migratory drop-offs) occur when individuals of a migratory species stop migrating and establish founder sedentary populations, a phenomenon documented in birds [2, 3, 4, 5] and butterflies [6]. In theory, losses—and also gains—of migration might promote...

Currently classified as Vulnerable by BirdLife International, this species, the southernmost in distribution of the four bellbirds, is much sought-after for the commercial cagebird trade. Bare-throated Bellbird is endemic to the Atlantic Forest of eastern Brazil south to northeastern Argentina and eastern Paraguay. While the nearly all-white male s...

Little is known about the age at which many Neotropical bird species first attempt to breed. We evaluated the breeding condition of 515 adult and subadult males and females among four species of Turdus thrushes (T. nigriceps, T. chiguanco, T. amaurochalinus and T. rufiventris) in Tucumán, Argentina during three breeding seasons (2015 to 2018). We r...

Bajo un escenario de selección intersexual, los beneficios que el sexo selectivo obtiene al aparearse con individuos "preferidos" del sexo opuesto pueden ser: un mayor cuidado parental, un mejor territorio o que su descendencia herede los caracteres preferidos. Aparearse con individuos preferidos puede resultar en descendencia con un mayor éxito re...

Bird migration in South America is highly diverse, with some species migrating solely within the tropical latitudes, others migrating between tropical wintering grounds and south-temperate breeding grounds, and yet other migrating within south-temperate latitudes of the continent. Until recently, bird migration in South America was virtually ignore...

• Identifying the processes that determine avian migratory strategies in different environmental contexts is imperative to understanding the constraints to survival and reproduction faced by migratory birds across the planet. • We compared the spring migration strategies of Fork‐tailed Flycatchers (Tyrannus s. savana) that breed at south‐temperate...

Scientists have long been trying to understand why the Neotropical region holds the highest diversity of birds on Earth. Recently, there has been increased interest in morphological variation between and within species, and in how climate, topography, and anthropogenic pressures may explain and affect phenotypic variation. Because morphological dat...

Scientists have long been trying to understand why the Neotropical region holds the highest diversity of birds on Earth. Recently, there has been increased interest in morpho- logical variation between and within species, and in how climate, topography, and anthropogenic pressures may explain and affect phenotypic variation. Because morphological d...

Species co-occurrence in local assemblages is shaped by different processes at different spatial and temporal scales. Here we focus on historical explanations and examine the phylogenetic structure of local assemblages of the Furnariides clade (Aves: Passeriformes), assessing the influence of diversification rates on the assembly and species co-occ...

The White-throated Kingbird (Tyrannus albogularis) is a widespread species in north-central South America, where it inhabits a variety of open to semi-open habitats. The breeding biology of the species is almost unknown. We describe the reproduction of the species based on 34 nests found in southeastern Brazil and eastern Bolivia since 2004, and eg...

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 large body of research has shown how avian morphology is shaped by specific behavioral repertoires and life history traits. Yet, the majority of such research has been conducted on birds breeding at north-temperate latitudes. We tested the hypothesis that functional wing traits of Fork-tailed Flycatchers (Tyrannus savana), which migrate within So...

Species co-occurrence in local assemblages is shaped by different processes at different spatial and temporal scales. Here we focus on historical explanations and examine the phylogenetic structure of local assemblages of the Furnariides clade (Aves: Passeriformes), assessing the influence of diversification rates on the assembly and species co-occ...

An organism's life history strategy is made up of a suite of physiological, behavioral, and ecological traits, which vary at both the interspecific and intraspecific levels in accordance with selective pressures operating on individuals. For birds, 2 primary ecological factors have been proposed to explain intraspecific and interspecific variation...

We reviewed the occurrences and distributional patterns of migratory species of birds in Brazil. A species was classified as migratory when at least part of its population performs cyclical, seasonal movements with high fidelity to its breeding grounds. Of the 1,919 species of birds recorded in Brazil, 198 (10.3%) are migratory. Of these, 127 (64%)...

en For migratory birds, early arrival at breeding areas has many benefits, such as acquisition of better territories and mates. This strategy has been found in numerous species breeding at north‐temperate latitudes, but has not been yet reported for intra‐tropical migratory species. We evaluated the relationship between arrival date, initiation of...

Songbirds must annually undergo two energetically demanding but important activities: breeding and feather molt. Due to the high energetic investment that each demands, these two events are generally not carried out simultaneously. However, substantial variation in the level of annual reproductive investment among populations may result in variatio...

South America is home to some of the largest, most diverse grasslands on the planet, providing critical habitat for numerous plants and animals and vital resources for millions of people. Yet, at the dawn of the 21st Century, South America's grasslands are experiencing rapid, widespread and unprecedented impacts from activities such as pesticide us...

Few details are available on the migration (rates, routes, dates) of Neotropical austral migrant birds, which breed and migrate wholly within South America. Only one long-distance austral migrant breeds in the South American temperate forest biome: the White-crested Elaenia (Elaenia albiceps chilensis). However, the migratory dates, routes, and win...

Fork-tailed Flycatchers (Tyrannus s. savana) breed from central to southern South America from September to January, migrating to northern South America to spend the non-breeding season. However, little is known of the migratory routes, rate, and timing of migration of those that breed in Brazil. In 2013, we attached light-level geolocators to bree...

Understanding the annual cycle of migratory birds is imperative for evaluating the evolution of life-history strategies and developing effective conservation strategies. Yet, we still know little about the annual cycle of migratory birds that breed at south-temperate latitudes of South America. We aged, sexed, and determined the progression and int...

Aproximadamente la mitad de todas las especies conocidas de aves realizan desplazamientos migratorios, que son movimientos estacionales entre los lugares en que nidifican y se reproducen, en el verano, y aquellos en que pasan el invierno. Se estima que cada año se movilizan por esa causa alrededor de 50 mil millones de individuos. Actualmente la mi...

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...

Little is known about the timing of migration, migration routes, and migratory connectivity of most of the >230 species of birds that breed at south temperate latitudes of South America and then migrate toward the tropics to overwinter. We used light-level geolocators to track the migration of 3 male and 3 female Fork-tailed Flycatchers (Tyrannus s...

Descriptions of intra- and interspecific variation in migratory patterns of closely related species are rare yet valuable because they can help assess how differences in ecology and life-history strategies drive the evolution of migration. We report data on timing and location of migration routes and wintering areas, and on migratory speed and phen...

For a migratory bird, the costs and benefits of utilizing a given migratory strategy vary according to the biotic (e.g., physiology) and abiotic (e.g., weather) constraints it experiences throughout the year. In the New World, closely related species migrate to breeding grounds located across a wide range of latitudes, from northern North America t...

Over 250 bird species migrate wholly within South America, many of which spenddifferent parts of their annual cycle in different countries. We attached light-level geolocatorsto individual migrant flycatchers of the genus Tyrannus in Santa Cruz Department, Bolivia(twelve White-throated Kingbirds, T. albogularis) and Buenos Aires Province, Argentina...

Resumen. – Fidelidad al sitio reproductivo y no-reproductivo de once especies de migrantes australes del Neotrópico. – Existe muy poca información sobre los patrones de fidelidad al sitio de los migrantes australes del Neotrópico, que migran dentro de América del Sur. Anillamos aves migratorias en tres sitios de América del Sur, uno ubicado en el t...

We describe partial migration of passerine birds across temperate latitudes in the New World. Owing to lower climatic seasonality near the coast of North America, the proportion of partial migrants at high latitudes in North America should be lower when excluding coastal records. We detected a 10% decrease in the proportion of partially migratory s...

Research on Nearctic-Neotropical migratory birds in Colombia has strengthened in the last decade although most work has been centered on boreal migrants. Achievements are reflected in recent publications, in the studies presented at national ornithology conferences, and in the publication of the National Plan for Conservation of Migratory Species....

Little is known about the relationship between seasonal food availability and the foraging strategies of insectivorous Neotropical birds. We studied a population of Tropical Kingbirds (Tyrannus melancholicus), a primarily insectivorous species, in eastern Bolivia to examine relationships between rainfall, food availability, and foraging strategies...

1. Little is known about mechanisms that drive migration of birds at tropical latitudes. Because most migratory bird species in South America have populations that are present year-round, partial migration (in which only some individuals of a given population migrate at the end of the breeding season) is likely to be common, providing an opportunit...

We attempted to distinguish spring passage migrant Tropical Kingbirds (Tyrannus melancholicus) from resident conspecifics where they overlap in South America. Migrant males at our Bolivian study site had significantly less tail feather molt and longer wing chords than resident males. Migrant females had significantly longer wing chords, less flight...

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences...

Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical g...

Understanding how home range size varies across seasons can provide insights into how birds respond to changes in resource levels. Yet, seasonal variation in home range size of most Neotropical birds is poorly understood. We recorded locations of color-banded Tropical Kingbirds during four years at a site comprised of cerrado woodland, humid forest...

Many migrant birds that breed in North and South America overwinter in the tropics of South America. Yet their exact distribution, micro-habitat use, and threats to survival on their win-tering grounds are still poorly understood. Although many use secondary habitats, others require habitats such as native grasslands that are under intense threat o...

La migración de las aves en América de Sur ha sido documentada desde el período colonial, pero los problemas con su denominación aún permanecen sin resolver. En este trabajo se revisa la confusión pasada y actual sobre la manera de llamar a las aves que migran latitudinalmente dentro de América del Sur y se sugiere un término alternativo simple y g...

Bird migration in South America has been documented since the colonial period, although the problem with its denomination remains unresolved. The objectives of this paper are to first review the past and current confusion regarding terminology for birds that do latitudinal migration within South America and second to suggest a simple and general al...

We studied the bird community at a site in the Gran Chaco of Bolivia composed principally of gallery forest bordering the Parapeti River within a larger landscape of dry thorn forest. We present the first detailed analysis of local avian community diversity across seasons and habitats for the bolivian chaco, utilizing both observational and mist-ne...

Bird migration in South America has been documented since the colonial period, although the problem with its denomination remains unresolved. In this paper we review the past and current confusion regarding terminology for birds that migrate latitudinally within South America and suggest a simple and general alternative term. Having a general term...

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 pa...

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 pa...

Austral migrant birds were banded during austral fall (March–April) and spring (October–November) in the Chaco of Santa Cruz, Bolivia. The Tyrannidae was the most common family captured in terms of number of species and total individuals. The difference in capture numbers between the austral spring and fall seasons was the greatest for the Fuscous...