Rufous-tailed Hawk (Buteo ventralis): uplist to Vulnerable?

This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2014.

BirdLife species factsheet for Rufous-tailed Hawk

Rufous-tailed Hawk Buteo ventralis is restricted to the lower Andes of Patagonia in southern Chile and Argentina, where it is rare, occurring at naturally low densities. It is currently listed as Near Threatened because it was thought to have a small global population, approaching the threshold for Vulnerable under criterion D1 (<1,000 mature individuals). The population is suspected to be stable despite the fact that the destruction of its habitat is ongoing.

No data is available regarding numbers or densities for this species, and there is no firm evidence of a decline, but its habitat has suffered extensive degradation and some authorities consider that the total population is unlikely to exceed 1,000 individuals (Ferguson-Lees and Christie 2001). The total population is currently placed in the band 250-999 mature individuals, equating to 375-1,499 individuals in total, rounded to 350-1,500 individuals. If this is confirmed, this species would warrant uplisting to Vulnerable under criterion D1 of the IUCN Red List, on the basis that the global population is estimated to be fewer than 1,000 mature individuals. Any evidence of continuing declines in the population could make the species eligible for classification as Endangered under criterion C2a (i or ii) depending on the subpopulation structure.

Further information is required regarding population size, trends and other potential or existing threats, and comments on the proposed uplisting are welcome.

Reference:

Ferguson-Lees, J. and Christie, D. A. (2001) Raptors of the world. Christopher Helm: London.

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  2. Archived 2012-2013 topics: Rufous Crab-hawk (Buteogallus aequinoctialis): uplist to Vulnerable?
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3 Responses to Rufous-tailed Hawk (Buteo ventralis): uplist to Vulnerable?

  1. Heraldo V. Norambuena says:

    1. Distribution

    The Rufous-tailed Hawk (Buteo ventralis) is an endemic raptor which lives in temperate forests from southern Chile and Argentina (Fjeldsa & Krabbe 1990, Bierregard 1995, Trejo et al. 2006), which inhabits wooded areas in both slopes of the Andes Cordillera (Ferguson-Lees & Christie 2001). In Chile, it ranges between the province of Ñuble (Behn 1947) and Tierra del Fuego (36°-55°S, Blake 1977, Araya & Millie 1986, Jaramillo et al. 2003 Pavez 2004), with some occasional records further north of the previous range stated (Philippi 1964, Howell & Webb 1995, Estades 2004). Because of this and the lack of studies into areas with a potential presence of this hawk and the possible confusion alongside other species of the polymorphic Variable Hawk (Geranoaetus polyosoma; Ferguson-Lees & Christie 2001), the exact range of the Rufous-tailed Hawk has not been determined accurately.
    During the past seven years, breeding populations have been identified in forested areas of the Coastal Cordillera and the Intermediate Depression between 37° and 40°S, with most records in Nahuelbuta Cordillera and the Valdivian Coast (Rivas-Fuenzalida et al. 2011, Norambuena et al. 2012). Most recent surveys have uncovered small population points in coastal forest remnants between 35° and 37°S (Constitution-Nahuelbuta). In the Andes, the species have been recorded from 38°S (Tolhuaca National Park) to the south (Rivas-Fuenzalida et al. 2011, Rivas-Fuenzalida et al. in prep.). Based on the discovery of new breeding sites, Rivas-Fuenzalida et al. (in preparation) suggest that the Rufous-tailed Hawk breeding distribution corresponds from the south of Curicó province (34°S) to the south, on the coast, and from the province of Ñuble (36°S) to the south on the Andes.
    We unknown the causes of an apparent absence of the species in the Andes between 34°-36°S, where there are vast forests that seem to be appropriate for the species. In summary, the current distribution of the species in Chile might be stated between 34°-55°S in the Coast Cordillera and between 36°-55°S in the Andes Cordillera, spanning a north-south strip of ca. 2,500 km long and 230 km wide. About the habitat, the distribution is restricted to mountainous areas of middle elevations (0-1,500 m) cords and hills of the Central Valley with the presence of mature forest. The Rufous-tailed Hawk would be absent in vast areas within its range, both in wide areas of the central valley, extensive forest plantations and a major part of the degraded secondary forests, ice fields and mountains. Based on the availability of habitat within their range, we estimated a total breeding distribution area of ca. 368 508 km2.

    2. Population

    Although there is no data about their population size or density, the Rufous-tailed Hawk has been listed as rare and difficult to find throughout its range (Blake 1977, Ferguson-Less & Christie 2001). Jaksic & Jiménez (1986) propose that their population might be rising due to forest reduction, which could also increase the availability of prey. Preliminary data about their diet seems to confirm this perception. In a recent study made in the Ñielol hill, Figueroa et al. (2000) reported that the Rufous-tailed Hawk diet consist on similar proportions of forest birds and grassland birds (24% of all prey consumed respectively) and remains from hares and rabbits. Although a subsequent study confirmed that the species consumed mostly forest species, there were hares detected in their diet (Figueroa et al. 2008) reinforcing the fact that the species can be found in open lands, at least for hunting. However, no evidence of an increase in population is confirmed as a result of forest opening. On the contrary, it has been observed that forest opening reduces the availability of nesting habitat and also increases the vulnerability of the hawks to human persecution (Rivas-Fuenzalida et al. 2011). In addition, aggressive encounters with other species have been observed in open areas or secondary forests (e.g., Geranoaetus polyosoma) and may lead to the displacement of Rufous-tailed Hawk (Rivas-Fuenzalida obs. pers., Norambuena et al. 2012). Furthermore, there are no records about new territories in places where couples have been shot death (Rivas-Fuenzalida et al. 2011). It is likely that low rates of recruitment coupled with high occurrence of human persecution are the reasons of death in adult species, resulting that most young individuals mate with widowed adults, preventing the colonization of new territories. In fact, it has been observed that in several territories, immature individuals (two years old) mate with widowed adults (Rivas-Fuenzalida et al. 2011). Thus it is unlikely a population increase, an expansion of the range of distribution or a recovery in areas where their populations have declined or disappeared. In well-studied areas, such as Nahuelbuta Cordillera (37°-38°S) and the Valdivian Coast (39°-40°S), 32 and 27 sites are known with presence of this raptor, respectively. The density of pairs in known areas was 2.19 pairs/100 km2 in Nahuelbuta and 2.67 pairs/100 km2 in Valdivia.
    Currently only 18 active nests are described, all located between 35°-40°S, which 13 are located in the Coastal Cordillera, three in the Intermediate Depression and two in the Andes Cordillera (Figueroa et al. 2000, Rivas-Fuenzalida et al. 2011, Norambuena et al. 2012, Rivas-Fuenzalida & Asciones-Contreras 2013, Norambuena et al. 2013, Rivas-Fuenzalida et al. in preparation). This hawk would be extremely rare at the northern end of its range (34°-36°S), where ancient forests are highly fragmented, knowing currently only eight territories (Rivas-Fuenzalida et al. in preparation). In the north and center of its distribution range (34°-40°S), this hawk is scarce, there is a current record of 39 breeding territories (adding the published information and that is in preparation). In this area there have been 144 adult individuals in 98 different sites between 2000 and 2013. To the south of the country and southern (40°-55°S) no nests are recorded or any other population data. However, Clark (1986) notes that it is one of the most difficult raptors to observe in Patagonia. It is difficult to make an overall population estimation based on the availability of habitat for breeding, because of the absence of this species in many areas where conditions seem to be suitable. Habitat loss and direct persecution are limiting factors for the presence of this raptor in many areas of its range, particularly on sites disturbed by humans.

    3. Threats

    In a biogeographical scale, the major threat of this hawk is the destruction and alteration of habitat. In fact, most of its range is represented by the Valdivian rainforest ecoregion (35°-43°S) which covered 11.3 million hectares in 1550, an estimation which declined in 2007 to 5.8 million hectares (51% of the original area). This reduction is explained by the conversion of native forests to agricultural grasslands, and since 1974 its replacement by commercial plantations (Lara et al. 2012). About the northern part of its range (35°-39°S), the species has been affected primarily by the replacement of native vegetation to commercial plantations of Pinus spp. and Eucalyptus spp. and agricultural areas too (Lara et al. 2012), meanwhile in the south range (39º-43ºS), it has been affected by the replacement of forest by grasslands and scrub for livestock (Marin et al. 2011, Echeverría et al. 2012, Lara et al. 2012). The southern area of its distribution (43°-55°S) also suffered major product changes made by the colonist’s fire in the late nineteenth and early twentieth century (Armesto et al. 1994). However, the situation of the Rufous-tailed Hawk is unknown in this area. It is possible to say that in recent decades the population has been recovered due to the natural restoration of the forest and low human density in the region.
    At the scale of nesting sites, Rivas-Fuenzalida et al. (2011) reported a high degree of habitat disturbance, including forest operations (clear-cutting and selective logging), vehicular and/or pedestrian movement and presence of pets and domestic labor of local people (extraction of firewood, crops). 50% of nest sites (N = 21) were found to <1 km of permanent human activity sites. In other hand, the remaining sites were located within 1 km from human presence. In a breeding territory located in a mature pine tree where locals demolished the nest and killed the chicks (because adults attacked poultry) the hawks built a new nest in an adjacent tree during the following season (Rivas-Fuenzalida et al. 2011). However, when commercial harvests were planted surrounding the nest tree (which does not cut down), the hawks did not return to reoccupy the nest during the next season (Rivas-Fuenzalida obs. pers.). This suggests that the activity of forest plantation harvesting has a strong impact on the reproductive success of the species.
    Of the total nests recorded (N=18), only two are included within the National System of Protected Areas of the State (SNASPE) or in areas with some degree of protection (Conservation Priority Sites), while the rest is being in private lands (Rivas-Fuenzalida et al. 2011, Rivas-Fuenzalida & Asciones 2013, Norambuena et al. 2013, Rivas-Fuenzalida et al. in preparation). In addition, 19 breeding sites were observed as harassed by local people, being this the main reason of the Rufous-tailed Hawk constant attacks upon many farmers’ poultries (Rivas-Fuenzalida et al. 2011). However, if we add the unpublished recent records, the number of sites where we detected persecution is 43 between 2007 and 2013 and accounted for 52 dead individuals according to the reports from locals.


    References

    Armesto, J., C. Villagrán and C. Donoso. 1994. Desde la era glacial a la industrial: Historia del bosque templado de Chile. Ambiente y Desarrollo 66-72.
    Behn, F. 1947. Contribución al estudio de Buteo ventralis. Boletín de la Sociedad de Biología de Concepción 22:3-5.
    Bierregaard, R. O., Jr. 1995. The biology and conservation status of Central and South American Falconiformes: a survey of current knowledge. Bird Conserv. Int. 5: 325–340.
    Blake, E. R. 1977. Manual of Neotropical birds. Volume 1. Univ. of Chicago Press, Chicago, Illinois, USA.
    Clark, W.S. 1986. What is Buteo ventralis? Birds of Prey Bulletin 3:155-118.
    Echeverría, C., A. Newton, L. Nahuelhual, D. Coomes, J.M. Rey-Benayas. 2012. How landscapes change: Integration of spatial patterns and human processes in temperate landscapes of southern Chile. Applied Geography 32: 822-831.
    Estades, C. F. 2004. Buteo ventralis near Constitución, Maule Region. Bol. Chil. Ornitol. 2004: 38.
    Ferguson-Lees, J. and D.A. Christie. 2001. Raptors of the world. Christopher Helm, London, U.K.
    Figueroa, R.A., J.E. Jiménez, C.A. Bravo, and E.S. Corales. 2000. The diet of the Rufous-tailed Hawk (Buteo ventralis) during the breeding season in southern Chile. Ornitología Neotropical 11:349-352.
    Figueroa, R.A., T. Rivas, and S.E. Corales. 2008. Dieta del aguilucho de cola rojiza (Buteo ventralis) en la Araucanía, sur de Chile. Resúmenes IX Congreso Chileno de Ornitología. 17 pp.
    Fjeldsa, J. and N. Krabbe. 1990. Birds of the high Andes. Apollo Books, Svendborg, Denmark.
    Housse, R. 1925. Avifauna de San Bernando y sus alrededores. Revista Chilena de Historia Natural 29: 141-150.
    Howell, S. and S. Webb. 1995. Noteworthy bird observations from Chile. Bulletin of the British Ornithologists’ Club 115: 57-66
    Jaksic, F.M. and J.E. Jiménez. 1986. The conservation status of raptors in Chile. Birds of Prey Bulletin 3:95-104.
    Jaramillo, A. 2003. Birds of Chile. Lynx Edicions, Barcelona, Spain.
    Lara, A., M.A. Solari, M. Prieto, M.P. Peña. 2012. Reconstrucción de la cobertura de la vegetación y uso del suelo hacia 1550 y sus cambios a 2007 en la ecorregión de los bosques valdivianos lluviosos de Chile (35º – 43º 30´ S). Bosque 33(1): 13-23.
    Norambuena, H.V., V. Raimilla, and J.E. Jiménez. 2012. Breeding behavior of a pair of Rufous-tailed Hawks (Buteo ventralis) in southern Chile. Journal of Raptor Research 46(2): 211-215.
    Norambuena, H.V., S. Zamorano and A. Muñoz-Pedreros. 2013. Nesting of the Rufous-tailed Hawk (Buteo ventralis) on a rocky wall in southern Chile. Revista Brasileira de Ornitologia 21(2): 101-102.
    Pavez, E.F. 2004. Descripción de las aves rapaces chilenas, p. 29-103. In: A. Muñoz-Pedreros, J. R. Rau and J. Yáñez (eds.) Aves rapaces de Chile. Valdivia: CEA Ediciones.
    Philippi-B, R. A. 1964. Catálogo de las aves chilenas con su distribución geográfica. Invest. Zool. Chil. 11:1-179.
    Rivas-Fuenzalida, T., and N. Asciones-Contreras. 2013. Primer registro de nidificación en un acantilado rocoso para el Aguilucho de Cola Rojiza (Buteo ventralis) en el sur de Chile. El Hornero en prensa
    Rivas-Fuenzalida, T., J. Medel, and R.A. Figueroa. 2011. Reproducción del aguilucho colarojiza (Buteo ventralis) en remanentes de bosque lluvioso templado de la Araucanía, sur de Chile. Ornitología Neotropical 22:405–420
    Rivas-Fuenzalida, T., N. Asciones-Contreras, and R.A. Figueroa. Estatus reproductivo del aguilucho de cola rojiza (Buteo ventralis) en el extremo norte de su distribución en Chile. (en prep.)
    Trejo, A., R.A. Figueroa, and S. Alvarado. 2006. Forest-specialist raptors of the temperate forests of southern South America: a review. Revista Brasileira de Ornitologia 14:317-330.

    Researchers:

    Tomás Rivas-Fuenzalida, Red Conservacionista del Patrimonio Natural de Contulmo, Los Canelos #350, Contulmo, Bio-Bío, Chile. peucomapu@gmail.com

    Heraldo V. Norambuena, Centro de Estudios Agrarios y Ambientales, Casilla 164, Valdivia, Chile y Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Casilla 160-C, Concepción, Chile. buteonis@gmail.com

    Javier Medel, Escuela de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. javierantoniomedelhidalgo@gmail.com

    Ricardo A. Figueroa, Escuela de Graduados, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Valdivia. ra_figueroa_rojas@yahoo.com

    Jaime E. Jiménez, Sub-Antarctic Biocultural Conservation Program, EESAT 310B, Department of Biological Sciences, LSA 246E, Department of Philosophy and Religion Studies, EESAT 325F, Institute of Ecology and Biodiversity, jaime.jimenez@unt.edu

    Victor Raimilla, Laboratorio de Ecología, Universidad de Los Lagos, Casilla 933, Osorno, Chile y Centro de Estudios Agrarios y Ambientales, Casilla 164, Valdivia, Chile. phalcoboenus@gmail.com

  2. Andy Symes says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2014 Red List is to pend the decision on Rufous-tailed Hawk Buteo ventralis and keep this discussion open until early 2015, while leaving the current Red List category unchanged in the 2014 update.

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  3. Andy Symes says:

    Recommended categorisation to be put forward to IUCN

    Following further review, there has been no change to our preliminary proposal for the 2014 Red List status of this species.

    This discussion will remain open for further comments and information until early 2015, and the current Red List category will remain unchanged in 2014.

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