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The genus Phalcoboenus of caracaras is
a New World group that is comprised of four medium
size species, mainly scavenger birds of prey.
The four species are linked mainly to vegetation
free zone along the Andean-patagonian axis, from
Ecuador south to the southern end of South America
(Vuilleumier 1970, 1991). The Striated Caracara
(Phalcoboenus aus...
Citations
... chimango), during the Middle Pleistocene, about 2 Mya (Fuchs, Johnson, and Mindell 2012). The southernmost species, P. australis, diverged roughly 0.6 Mya (Fuchs, Johnson, and Mindell 2012) and present a disjunct distribution restricted to islands in the Fuegian archipelago and the Islas Malvinas/Falkland Islands (IM/FI) (Balza, Lois, and Raya Rey 2017;Balza et al. 2022;Marín et al. 2006;Reeves, Crofts, and Bildstein 2018) (Figure 1). These archipelagos have a markedly different biogeographical history. ...
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 present.
Taxon
Phalcoboenus australis .
Methods
We used RAD sequencing to assess genetic diversity, population structure and to model demographic history through descriptive and hypothesis‐based evolutionary methods.
Results
We found evidence of two independent lineages: one inhabiting the Fuegian archipelago and the other one occurring in the Islas Malvinas/Falkland Islands, with the latter presenting higher genetic diversity and evidence of finer‐scale population structure. The best supported demographic scenario places the divergence time of these lineages during the last glacial period (ca. 50,000 years ago), with the occurrence of gene flow during the first 27,000 years after their divergence. Recent demographic modelling supports the general pattern of increasing genetic variability as landmasses were uncovered following the glacial period (i.e., the Fuegian archipelago) in contrast with a decrease in genetic diversity associated to island fragmentation (i.e., in the Islas Malvinas/Falkland Islands).
Main Conclusions
We propose that post‐glacial sea level rise and the subsequent isolation across the submerging Patagonian Shelf have driven population fragmentation and recent genetic structure in this species. Our findings advocate for recognising the two identified divergent lineages as distinct conservation units. We highlight the intricate interplay of ecological factors, glacial cycles and population dynamics in shaping the evolutionary trajectory of this unique and threatened raptor species in southern South America.
... El carancho austral (Phalcoboenus australis, Gmelin 1788), es un caracara endémico de las islas e islotes del extremo sur de la Patagonia y del archipiélago de Malvinas (Strange, 1996;Marín et al., 2006;Birdlife International, 2024). Actualmente está catalogado a nivel global como especie "Cercana a la Amenaza" y a escala nacional como especie En peligro (Aves Argentinas & Ministerio de Ambiente y Desarrollo Sustentable de la Nación, 2017; Birdlife International, 2024). ...
Las invasiones biológicas, especialmente en islas, son una causa importante de pérdida de biodiversidad. Aunque su impacto suele ser negativo para la biota nativa, depredadores como las aves rapaces pueden beneficiarse de la incorporación de presas invasoras en su dieta. Para comprender este tipo de interacciones los estudios tróficos son fundamentales, sobre todo antes de realizar acciones de control sobre las invasoras. El carancho austral (Phalcoboenus australis) es una rapaz insular, endémica del sur de Argentina y Chile, que se asocia durante la época reproductiva a colonias de aves marinas. El objetivo de este trabajo fue investigar la ecología trófica del carancho austral en la isla Observatorio durante la época reproductiva, centrándose en el uso de presas introducidas como el conejo de Castilla (Oryctolagus cuniculus) y la rata (Rattus sp.), y comparándolo con el sitio estudiado previamente en bahía Franklin. Mediante análisis de isótopos estables (AIE) de sangre de los pichones y análisis de egagrópilas de los nidos, se caracterizó la dieta de los individuos reproductivos de isla Observatorio y se la comparó con la de los de bahía Franklin. En dos días de trabajo de campo (17 y 18 de diciembre de 2021) se censó a los pares reproductivos en la isla (16 nidos activos). Se tomaron muestras de sangre de 17 pichones de 14 nidos y se recolectaron 102 egagrópilas de 13, junto a muestras de tejido de presas potenciales. Se registró el consumo de especies invasoras en el 69% de los nidos muestreados de isla Observatorio, y el nicho isotópico de los pichones fue hasta más de seis veces mayor que el de los de bahía Franklin, en la que no se detectaron presas introducidas. El principal componente de la dieta en isla Observatorio fue el pingüino magallánico (Spheniscus magellanicus), posiblemente facilitado por la depredación de lobos marinos (Otaria flavescens) sobre los pingüinos, registrada en la bibliografía y en los días de trabajo de campo. El AIE permitió
inferir que la mayor amplitud en el nicho isotópico de los pichones de isla Observatorio por sobre los de bahía Franklin estuvo dada por la inclusión de conejo y rata enriquecidos en 15N. La inclusión
de invasoras en la dieta de los pichones tiene implicancias en las acciones de manejo a realizar y probablemente también en la dinámica poblacional del carancho austral. El control con rodenticidas debería realizarse con especial cuidado, debido al peligro de envenenamiento secundario de los caranchos, sabiendo que se alimentan de las invasoras. Es posible que el subsidio de las invasoras aumente la densidad de nidos y la supervivencia invernal de la especie en isla Observatorio, por lo que es recomendable que futuros trabajos profundicen en esas líneas.
... The species is known to be present on the island for a long time, as the holotype was collected in 1775 in this site (Strange 1996). Most breeding populations occur in the Malvinas/Falkland archipelago (Reeves et al. 2018), and other breeding sites in the Fuegian archipelago include Franklin Bay (Isla de los Estados), Goffré Island, Noir Island, Diego Ramírez islands and Mitre Peninsula (Tierra del Fuego Main island) (Clark 1984;Parera et al. 1997;Marín et al. 2006;Cursach et al. 2012;Balza et al. 2017). We counted 15 breeding territories and found 10 active nests of Striated Caracara, containing a total of 15 chicks. ...
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 to update the status of the main seabird colonies and the most abundant avian terrestrial predator at Observatorio and Goffré Islands during the breeding season. In only 4.5 km², the islands would harbour ~ 90,000 breeding seabirds. Seabird colonies occupied different areas of the islands and varied in their population status, with Imperial Shags (Leucocarbo atriceps) showing an increase and Southern Giant Petrels (Macronectes giganteus) a decrease according to the last surveys. Magellanic Penguin (Spheniscus magellanicus) population estimations also suggest a decrease but the last survey was based on total, and not on occupied nest sites. We recorded and assessed one new breeding species: The globally near-threatened Striated Caracara (Phalcoboenus australis), which has an important breeding population of around 15 territorial pairs at Observatorio Island. These islands appear to be an important regional bird site and future studies would determine their trends and threats, especially those related with invasive species.
... The striated caracara (Phalcoboenus australis, hereafter "caracara") is a near threatened bird of prey restricted to islands in southern South America (BirdLife International, 2018;Frere et al., 1999;Marín et al., 2006;Reeves et al., 2018). During the breeding season, they associate with seabird colonies, breeding in their proximity and feeding on eggs, chicks, adults, and carcasses (Catry et al., 2008;Liljesthröm et al., 2008;Strange, 1996). ...
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, we examined intraspecific variation in the trophic niche of a resident population of striated caracara (Phalcoboenus australis) on Isla de los Estados (Staten Island), Argentina, using pellet and stable isotope analyses. While this raptor specializes on seabird prey, we assessed this population's potential to forage on terrestrial prey, especially invasive herbivores as carrion, when seabirds are less accessible. We found that the isotopic niche of this species varies with season, age, breeding status, and, to a lesser extent, year. Our results were in general consistent with classic predictions of the optimal foraging theory, but we also explore other possible explanations for the observed pattern. Isotopic niche was broader for groups identified a priori as opportunistic (i.e., nonbreeding adults during the breeding season and the whole population during the nonbreeding season) than it was for individuals identified a priori as selective. Results suggested that terrestrial input was relatively low, and invasive mammals accounted for no more than 5% of the input. The seasonal pulse of rockhopper penguins likely interacts with caracara's reproductive status by constraining the spatial scale on which individuals forage. Niche expansion in spatially flexible individuals did not reflect an increase in terrestrial prey input; rather, it may be driven by a greater variation in the types of marine prey items consumed.
... The most southerly distributed of all birds of prey, the relatively little-studied Striated Caracara (Phalcoboenus australis) is a medium-sized raptor (approximately 1.5-2.0 kg) with a global, island-restricted breeding range of 30,000 to 46,000 km 2 on the Fuegian regions of Argentina and Chile and outer islands in the Falkland Islands (Islas Malvinas; Ferguson-Lees and Christie 2001, Marín et al. 2006, Birdlife International 2017. Striated Caracaras, which lay up to 4-egg clutches and feed largely on carrion, typically breed in association with seabird colonies (Strange 1996, Woods 2017. ...
... These surveys, which encompassed 54 islands, resulted in an estimated Falklands population of 500 pairs (Woods and Smith 1999). An additional 18 islands surveyed in November 2006 (Woods 2007) suggested that breeding numbers were stable overall, although there were small, local increases on several islands visited in both 1997-1998and 2006-2007(Woods 2007. The surveys suggested that breeding Striated Caracaras are locally numerous on several outer islands in the Falklands, principally the northern and western parts of the archipelago, north and west of the main island of West Falkland, and on outer islands off the southern coast of the main island of East Falkland (Strange 1996, Woods andWoods 1997; Fig. 1) with much smaller numbers nesting on West Falkland itself ( Fig. 1). ...
... The population estimate for 1963-1965 (approximately 40 islands), was 450 pairs, and for subsequent surveys in the 1980s was 337 pairs (approximately 58 islands; Strange 1996). In 1997-1998and 2006, population estimates were 500 and 520 pairs (approximately 54 and 18 islands), respectively Smith 1999, Woods 2007). In addition, an estimated 85 breeding pairs inhabited New Island during the austral summer of 2006-2007(Catry et al. 2008. ...
We conducted surveys of breeding pairs of the endemic and globally "Near Threatened" Striated Caracara (Phalcoboenus australis) on 79 outer islands in the Falklands archipelago (Islas Malvinas) during the austral-summer breeding seasons of 2013-2014 and 2014-2015. A total of 354 breeding pairs (defined as pairs with evidence of egg-laying), or an archipelago-wide adult breeding population of at least 0.05 birds/km² was recorded. An additional 477 probable breeding pairs also were found. The distribution of breeding pairs remains similar to that found during surveys in the 1990s and 2000s. Grand Jason, Steeple Jason, New Island, Beauchêne Island, and Bird Island, the five islands with the highest numbers of breeding pairs, accounted for half of the total breeding population. "Vegetationally pristine" islands with dense areas of tussac grass (Poa flabellata) and high densities of small burrowing seabirds-namely Bird Island, Saddle Island, and Beauchêne Island-supported the highest densities of breeding pairs. Eighty percent of all pairs occurred on National Nature Reserves or on privately owned nature sanctuaries. Our surveys suggest that sustained protection of key breeding sites is critical for the long-term conservation of this species. We recommend that populations of Striated Caracaras at Tierra del Fuego also be surveyed and that the global population status of the species be reassessed.
... Striated caracaras are relatively large, stocky, and inquisitive scavenging and predatory birds of prey (Falconiformes). The species breeds in close proximity to seabird colonies, where individuals feed themselves and their developing young on seabird eggs and nestlings, and on dead and dying adult seabirds [12,[15][16][17]. Striated caracaras take marine and terrestrial invertebrates [12] and placentas and carrion of terrestrial livestock and marine mammals [15,18]. ...
... Striated caracaras are relatively large, stocky, and inquisitive scavenging and predatory birds of prey (Falconiformes). The species breeds in close proximity to seabird colonies, where individuals feed themselves and their developing young on seabird eggs and nestlings, and on dead and dying adult seabirds [12,[15][16][17]. Striated caracaras take marine and terrestrial invertebrates [12] and placentas and carrion of terrestrial livestock and marine mammals [15,18]. ...
Background
The extent to which seasonal changes in food availability affect small-scale movements in free-ranging populations of birds of prey is relatively little studied. Here we describe a seasonal “micro-migration” of a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands in response to seasonal changes in the availability of seabird carcasses. We banded more than 450 individuals on Saunders Island, deployed archival and satellite GPS data loggers on 17 individuals, and monitored movements within and between two feeding areas on Saunders Island, a “marine-subsidized” site near seabird colonies and an anthropogenic “human-subsidized” farm site 16 km to the southeast.
Results
During 67 observation days between 2010 and 2015, resightings of 312 banded caracaras were greater at the marine-subsidized site during austral summer than winter, and the total daily resightings varied significantly between spring versus summer, summer versus winter, autumn versus spring, and autumn versus winter. Resightings were higher at the human-subsidized site in austral winter than summer and the total daily resightings varied significantly across all bi-seasonal comparisons. Resightings indicated that at least 12 of 197 birds (6.1%) moved between the human- and marine-subsidized sites at least once during the same winter, 15 of 335 birds (4.5%) did so in spring, none of 164 birds did so in summer, and 16 of 297 birds (5.4%) did so in autumn. Individuals fitted with archival GPS data loggers at the marine-subsidized site in summer maintained highly localized 95% kernel core areas (0.55 ± 0.12 km² [mean ± SD]), whereas those at the human-subsidized site in winter maintained larger 95% kernel core areas (3.8 ± 4.6 km²). Two of 6 satellite-tagged individuals that summered at known caracara breeding colonies 80 km WNW of Saunders Island were subsequently resighted in winter at the human-subsidized site.
Conclusion
Our results suggest that seasonal shifts in food resource availability drive seasonal micro-migrations in a farm-island population of striated caracaras, and that farm sites can be critical in providing nutritional resources for caracaras when naturally occurring marine-subsidized resources become less available. Our results have important implications for striated caracara spatial ecology and conservation, as increased winter survival could improve the status of this globally Near-Threatened population.
... The species is classified as Near Threatened (IUCN 2015) with an extant population of ,2,500 mature individuals. They reside mostly on Staten Island (Isla de los Estados) in the Fuegian region and in the Malvinas/Falkland Islands (BirdLife International 2013), with fragmented breeding records in southern Chile (Marín et al. 2006). The species is largely associated with seabird breeding colonies (i.e., Rockhopper Penguins [Eudyptes chrysocome], Black-browed Albatross [Thalassarche melanophris]). ...
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 breeding output of a population of Striated Caracaras in Franklin Bay, Staten Island, Argentina. We found one of the lower breeding density values reported for this species, although this population is associated with one of the biggest colonies of Rockhopper Penguins. The main material used for the construction of Striated Caracaras' nests was tussac grass, though only half of nests were placed in grassland. The spatial pattern for nest sites corresponds with global and local clustering. All successful Striated Caracaras' nests were at least 250 m from the nearest neighboring nest, were generally closer to the colony of Rockhopper Penguins than failed nests, and had more Rockhopper patches around them. Breeding success was 0.73 successful nests/active nests, productivity was 1.27 ± 1.01 young/active nest, and brood size was 1.75 ± 0.71 young/successful nest. The presence of invasive wild goats and red deer is proposed as a factor that could be restricting nest site availability in the study area.
... The genera Falco (Kleinschmidt 1929;Reynolds 1934;Bullock 1949;Torres 1970;Araya et al. 1974;Schlatter 1976;Araya and Millie 1998), Caracara (Reynolds 1934), and Milvago (Jaksic et al. 2002) can be found from Arica to Magallanes regions. Among Phalcoboenus, P. megalopterus is the most widely distributed species occurring from the extreme north (Hellimayr 1932) south to Magallanes (Jaksic et al. 2002); P. albogularis (Vuilleumier 1985, Cursach et al. 2009) has been sighted once in the central area of Chile, and P. australis is limited to the extreme south (Reynolds 1934, Drouilly 1968, Collar 1986, Marín et al. 2006. ...
... Nesting data on P. megalopterus in Chile are limited to a monograph by Housse (1937), who presumed the species would nest in the rich vegetation areas of the mountains. In general, falcons begin nesting in early spring, laying between 2 and 4 eggs, with an incubation period of 15 to 20 days (Housse 1934, Housse 1935, Housse 1936a, Morrison and Phillips 2000, Díaz and Armesto 2003, Marín et al. 2006. Raimilla et al. (2014) described cooperation in care and nursing in P. australis. ...
Eight species of falcons (Falconidae) have been recorded in Chile. To date, all relevant studies considered birds of prey in general, with no specific focus on this family. Based on a comprehensive review of the literature, an updated report is presented on the state of knowledge of falcons in Chile. This data set comprises a total of 165 studies published from 1915 to 2015. Scientific productivity was lowest in 1945-1955 and highest in 2005-2015, with a steady increase since 1985. However, the focus of research in Chile is biased towards two species: Milvago chimango and Falco sparverius. Two administrative regions, Santiago Metropolitan Region and Araucanía, were the most studied whereas Arica, Tarapacá, and Antofagasta regions accounted for fewer than 1% of the studies. Faunistic studies (including abundance) were the most common research topic. It is suggested that the lack of knowledge regarding species in the genus Phalcoboenus may negatively affect the conservation status of these species, and believed that the lack of preference for certain research topics, such as systematics and natural history, are the result of historical factors including the decrease of field biology and perhaps a biased interest of the researchers. Finally, this review highlights the paucity of information on falcons and provides a framework for directing future research.
... En las Islas Malvinas, Isla de los Estados e Islas de Año Nuevo se concentraría al menos el 65% de la población global (BirdLife International 2013). En el continente es raro y si bien se conocen registros para el sur de Chile hasta los 51°S, su reproducción ha sido confirmada en muy pocas localidades, generalmente aisladas entre sí (Meiburg 2006, Marín et al. 2006. En Chile se encuentra al menos presente en el Parque Nacional Cabo de Hornos y las Reservas de las islas Guarello, Noir, Almagro y Diego Ramírez (Chebez 2008). ...
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) es una rapaz endémica del sur de Argentina y Chile, que se encuentra principalmente en islas y normalmente se asocia, durante la época reproductiva, a colonias de aves y mamíferos marinos. El objetivo general de este estudio es aumentar el conocimiento sobre el estado actual de la población y la biología reproductiva del carancho austral en Bahía Franklin, Isla de los Estados, Tierra del Fuego. Se buscaron e identificaron los nidos activos de la especie en el área de estudio durante noviembre y diciembre de 2014. Se realizaron análisis espaciales de patrones de puntos globales, globales ponderados y locales; se modelaron las variables, en relación a su presa principal, que explican la presencia de los nidos; se evaluó el éxito reproductivo y la productividad y se tomaron datos sobre las características de los sitios nido para luego comparar los datos obtenidos con la información disponible en bibliografía. Se encontró un total de 16 nidos activos en el área de estudio, que corresponde con una densidad de 1.43 parejas/km2, el valor más bajo encontrado hasta ahora para la especie. Los nidos se encontraron generalmente de forma agregada.. Las variables que mejor explicaron la presencia de los nidos fueron la cercanía a la colonia de pingüino penacho amarillo (Eudyptes chrysocome) y la visibilidad de la colonia desde el nido. Todos los nidos, excepto dos, estuvieron asociados exclusivamente (en términos de cercanía) con parches de E. chrysocome. El 100% de los nidos accesibles estaban construidos en su mayor parte con fibras de pasto tussock (Poa flabellata) aunque sólo la mitad de los nidos estuvo construida asociada al pastizal de tussock. Para n=11 nidos, el éxito reproductivo aparente fue de 0.73 y la producción total fue de 1.27 ± 1.00 pichones. Existieron diferencias significativas en el éxito reproductivo en función de la distancia al nido de carancho austral más cercano: los nidos que fracasaron en la incubación fueron también los más cercanos entre sí. La dinámica reproductiva de esta especie aparenta ser diferente en el área de estudio a lo que se observa en las Islas Malvinas, donde existen las únicas poblaciones estudiadas de P. australis. Allí, los nidos se disponen de forma regular a la menor distancia posible de la colonia de aves marinas y la mayoría de los nidos están en el suelo. La disposición en núcleos agregados de los nidos, así como observaciones de las características de los sitios de nidificación encontrados, hacen suponer que la densidad reproductiva en esta área está limitada por la escasa disponibilidad de sitios aptos para la construcción del nido. Se propone que la presencia de dos herbívoros introducidos, la cabra (Capra hircus) y el ciervo colorado (Cervus elaphus), están afectando negativamente a la densidad de parejas reproductivas de P. australis, al disminuir la abundancia del pasto tussock y ramonear y pisotear en los alrededores de la colonia de E. chrysocome. Se propone un modelo en el cual además estas especies son un recurso alimenticio importante para P. australis durante el invierno en forma de carroña, ya que en ese momento del año las colonias de aves marinas se encuentran ausentes, y que la reducción en la mortalidad que esto conllevaría, produciría una mayor abundancia total de individuos de P. australis, lo que redundaría en mayor competencia intraespecífica y menor reclutamiento poblacional.
