Ulises Balza

National Scientific and Technical Research Council | conicet · CADIC - Centro Austral de Investigaciones cientificas

Optimal foraging theory predicts an inverse relationship between the availability of preferred prey and niche width in animals. Moreover, when individuals within a population have identical prey preferences and preferred prey is scarce, a nested pattern of trophic niche is expected if opportunistic and selective individuals can be identified. Here,...

Breeding outcome in birds can be influenced by both intrinsic and extrinsic factors, and these may contribute differentially to each stage of the breeding cycle. Island raptors are relatively threatened species that rely on simplified food webs and usually co-occur with invasive species. Here, we studied a population of Striated Caracara (Phalcoboe...

As global biodiversity is rapidly declining due to habitat loss, it is important to determine how to protect it. The policies of many conservation agencies are still prioritizing the preservation of a single large habitat area (SL) versus several small areas of the same size (SS), despite empirical support favouring SS. However, to date, while many...

Aim To understand the influence of Andean uplifts and glacial cycles on South American biodiversity, we delve into the population genetics and evolutionary history of a unique subantarctic island raptor specialised in exploiting marine food webs. Location Islands in Tierra del Fuego and Malvinas/Falklands. Time period Last glacial period to the p...

Monitoring of endangered raptors is challenging for species that live on remote systems such as islands. Here, we present the insights of an analysis combining various sampling techniques to monitor the endangered Striated Caracara (Phalcoboenus australis) populations in the subantarctic region. We complement traditional banding and monitoring of n...

Marine Protected Areas (MPAs) are crucial for conserving marine biodiversity, and assessing the effectiveness of boundaries in protecting marine species is essential. In the Southwest Atlantic Ocean, four MPAs have been created. In this study we evaluate the use of these MPAs by Southern Rockhopper Penguins (Eudyptes chrysocome) that nest at Isla d...

The Sooty Shearwater (Ardenna grisea) is a species facing global decline, nesting on southern hemisphere islands, and migrating to the northern hemisphere during the non-breeding season. Historical groundwork on Wollaston Island in Chile suggested a possible dispersion of breeding grounds along the seaward fringe of the Fuegian islands, including I...

To date no spatially explicit account of a contact zone or putative hybrid zone for the White-throated and Mountain Caracaras is available. Here, we estimate the location and extent of the contact zone between these two species and provide evidence of putative hybrids, aiming to highlight the ecological importance of northern Patagonia for evolutio...

The Sooty Shearwater ( Ardenna grisea ) is a species facing global decline, nesting on southern hemisphere islands, and migrating to the northern hemisphere during the non-breeding season. This study confirms the species ́ breeding presence on Isla de los Estados in the Fuegian archipelago, Argentina. Additionally, we present a preliminary evaluati...

The IUCN Red List of Threatened Species is an extinction risk assessment tool that has guided species conservation over the last five decades. However, as wildlife scientists and conservationists, we argue that its influence on the global conservation agenda can hinder effective species conservation efforts. Here, we review the limitations of the R...

The Argentinian Ministry of Environment has approved the translocation of 45 guanacos from Southern Patagonia to the Pampas region, a distance of 1500 km, as the initial phase toward future translocations into a National Park located in the Chaco region, another 1600 km further North. This decision raises concerns about the technical and ethical as...

‘Rewilding’ is a nature conservation strategy gaining prominence worldwide. Established in the Northern Hemisphere, rewilding initiatives have increasingly been proposed in Argentina, but their relative merits, feasibility of implementation and accountability have lacked adequate analysis and discussion. Recently, 125 scientists and practitioners w...

Density estimations are not independent from the methodology used. Factors than can influence density estimation in seabirds include spatial arrangement, colony dynamics and history over time. As burrow nesting seabirds, Spheniscus penguins´ numbers are not easily assessed with methods such as aerial surveys. There are at least five methods being u...

En los últimos años se han desarrollado en Argentina distintas intervenciones relacionadas con el rewilding (o re-asilvestramiento), abarcando una variedad de especies (e.g., grandes carnívoros, ungulados, psitácidos) y ecorregiones (e.g., Chaco Húmedo y Seco, Estepa Patagónica). El reasilvestramiento es definido como una estrategia aplicada en el...

Las rutas y el tráfico de vehículos asociado tienen un fuerte impacto sobre la fauna silvestre en todo el mundo. Los grandes carnívoros son particularmente susceptibles a la mortalidad por colisiones vehiculares, especialmente las especies con grandes áreas de acción como el aguará guazú. El objetivo de este trabajo es analizar los movimientos de t...

Mercury pollution is a serious global environmental issue and the characterization of its distribution and its driving forces should be urgently included in research agendas. We report unusually high mercury (Hg) concentrations (>5 μg/g) along with stable isotopes values in feathers of southern rockhopper penguins (Eudyptes chrysocome) from colonie...

This paper provides data on a newly discovered colony of Magellanic penguins Spheniscus magellanicus in the southwest Atlantic Ocean. A new settlement was found while conducting southern rockhopper penguin Eudyptes chrysocome studies in the San Juan de Salvamento colony in Staten Island, Argentina. The colony holds 88 breeding pairs. While the orig...

Based on the latest phylogeny of raptors produced by Mindell et al. (2018) and the occurrence of white rump patches following Ferguson-Lees & Christie’s (2001) and the Handbook of Birds of the World (2022) accounts, we performed ancestral state reconstructions and phylogenetic logistic regression to assess the phylogenetic signal of white rump pres...

La influenza aviar es una enfermedad aguda y altamente transmisible en aves domésticas y silvestres. Puede transmitirse también de aves a mamíferos, incluyendo a las personas. Los contagios a personas ocurren mayormente en contextos específicos de contacto muy estrecho y/o ambientes muy contaminados. Estos contagios a personas han ocurrido esporádi...

En los tiempos que corren nos hemos acostumbrado a ver las redes sociales plagadas de afirmaciones y propuestas a viva voz de ONG y empresas con responsabilidad social empresarial sobre estrategias para la conservación de la biodiversidad. Últimamente, más que nunca, estas propuestas están apoyadas por instituciones del Estado argentino, que las ha...

Continental islands are often sites of low diversity and endemism, as well as important areas for the protection of bird populations, especially seabirds. On Isla Observatorio and the Año Nuevo Islands, in the Southwestern Atlantic, the latest assessment of avifauna dates from more than 20 years ago. In this study, we use a combination of methods t...

The striated caracara (Phalcoboenus australis) is an endemic species of the islands of southern Argentina and Chile, and inhabits mainly grasslands where seabirds breed. On Isla de los Estados and the Año Nuevo islands (IDLE), they coexist with invasive alien species such as red deer and goats. The aim of this work is to study whether the populatio...

Muchos ejemplos de importantes procesos ecológicos provienen de sistemas insulares. Esto se debe a su espacio y biodiversidad acotados, y a que usualmente se conoce con detalle su historia geológica y de conexión con continentes. Sin embargo, en Argentina todavía existe un conocimiento rudimentario sobre las aves que dependen parcial o totalmente d...

Mercury is a widely available pollutant associated with negative effects on wildlife, especially top predators. Here, we characterized the mercury concentrations in feathers of Striated Caracara Phalcoboenus australis on Isla de los Estados (Argentina). With feather mercury levels averaging 26.3 mg/kg, this population has the highest mean feather m...

Los movimientos que realizan los individuos son relevantes para diversos procesos demográficos. Los individuos jóvenes, debido a su mayor movilidad, son claves para la conectividad entre poblaciones, y estudiarlos resulta fundamental para entender las dinámicas poblacionales. El carancho austral (Phalcoboenus australis) es una especie no migratoria...

Organic waste in garbage dumps serves as an easily obtained food subsidy for many species globally, with a variety of both positive and negative effects on animals' reproductive and health parameters. However, in some regions, such as southern Patagonia, this phenomenon remains unstudied. In Ushuaia, Tierra del Fuego province, Argentina, seven spec...

Stable isotopes raw data. Corrected δ15N, δ13C and C/N ratio is reported.

In this note we report three new specimens of Abrothrix (Angelomys) xanthorhina from Isla de los Estados, southernmost Argentina, which are representative of the nominal form Akodon llanoi Pine, 1976. These are the first voucher specimens since the species description, more than four decades ago. In addition, we provide morphometric data for these...

Abstract Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connect...

Introducción: El guayacán real (Guaiacum sanctum; Zygophyllaceae) de Mesoamérica y las Antillas está amenazado en gran parte de su área de distribución. Evaluamos si una población de G. sanctum en el Parque Nacional Palo Verde en Costa Rica es viable a largo plazo. Métodos Usando dos estudios demográficos, uno en 1997 y otro en 2017, estimamos las...

In this comment, we outline our own experience in almost 10 years of educational talks using birds of prey as ambassadors of their wild populations in the large metropolis of Buenos Aires, Argentina. Based on the ideas settled in the Bekkessy et al. (2018) paper, we account for our discursive change over the years, from a sustained development-base...

Several species of raptors that breed in North America migrate to the southern hemisphere during the non-breeding period. The Broad-winged Hawk (Buteo platypterus) is one of them, and its wintering distribution reaches the north and central part of South America, although there are published records for the species in Argentina and southern Brazil....

Understanding how environmental factors modulate foraging is key to recognizing the adaptive value of animal behavior, especially in ectothermic organisms such as ants. We experimentally analyzed the effect of rain on the foraging of leaf-cutting ants, a key ant group that is commonly found in rainy habitats. Specifically, we experimentally discrim...

The Striated Caracara (Phalcoboenus australis) is a poorly known raptor associated with seabird colonies, restricted to the islands of southern South America, and with an estimated extant population of <2,500 mature individuals. We evaluated the number of breeding pairs, described the characteristics and spatial pattern of nest sites, and estimated...

Las poblaciones de las mayoría de las aves rapaces son vulnerables y se encuentran amenazadas a nivel global por una serie de características ecológicas comunes: baja productividad y densidades, altos requerimientos de espacio y recursos, vulnerabilidad a compuestos químicos y modificación de su hábitat. El carancho austral (Phalcoboenus australis)...