Chondrohierax uncinatus

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Hook-billed Kite
Chondrohierax uncinatus


Status: Lower risk

Population Trend: Stable.

Other Names: Merlion (mirus), Mexican Hook-billed Kite, Mountain-Hawk (mirus), Red-collared Hawk, Red-collared Kite, Regerhinus uncinatus (mirus), Snail Hawk.

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Distribution: Nearctic/Neotropical. Southern UNITED STATES (Texas) and northwestern MEXICO (Sinaloa, Tamaulipas) south through the lowlands of Central America west of the Andes to northwestern PERU and east of the Andes through Amazonia to central PERU, southern BOLIVIA, southern BRAZIL, and northern ARGENTINA; GRENADA. more....

Subspecies: 2 races. C. u. uncinatus: Southern UNITED STATES (extreme southern Texas) south through eastern and western MEXICO (Sinaloa) and CENTRAL AMERICA to COLOMBIA, south to northwestern PERU, east to the GUIANAS and BRAZIL, and south to eastern PERU and eastern BOLIVIA, PARAGUAY, URUGUAY, and northern ARGENTINA; TRINIDAD; C. u. mirus: GRENADA. more....

Taxonomy: The extreme variation in bill size among Hook-billed Kites led earlier taxonomists to believe that there is a large-billed species, megarhynchus, and a small-billed species, uncinatus (Peters 1931). Friedmann (1934) recognized that these morphs are part of the same species, but still regarded the extremely large-billed birds in western South America as a distinct subspecies, immanis. Hellmayr and Conover (1949) pointed out that birds with large bills occur thoughout the range of the species and therefore do not deserve separate taxonomic status, and all recent authorities have accepted this interpretation. Unlike previous authorities, Amadon (1960, 1964) argued that the Cuban Kite, C. wilsonii should be treated as a subspecies of uncinatus. A mitochondrial DNA study by Johnson et al. (2007) showed a large amount of divergence between Cuban and mainland "hook-billed" kites. This supports species status for the Cuban population, which had been the original treatment, based on conspicuous morphological differences. The Grenada population, mirus, shows much less divergence in both genetic and morphological characters from mainland populations, and their separation has been much more recent, according to Johnson et al. (op cit.). more....

Movements: Irruptive or local migrant (Bildstein 2006). Northern populations are at least partially migratory, and there may also be much local wandering throughout the range, probably in response to changing habitat conditions. Stiles and Skutch (1989) suggested that these kites may frequent an area for several months, breed, and then move on. Such behavior would explain the absence of the species at times from known breeding and foraging areas in the Lower Rio Grande Valley of Texas (Brush 2005). Fall migratory movements have been reported from Veracruz, Mexico (Ruelas 2002), Chiapas, Mexico (Gómez de Silva 1999), Belize (Jones 2002, Jones and Komar 2008), Guatemala (Montejo Díaz and Ruelas Inzunza 1997, Eisermann and Avendaño 2006), El Salvador (Jones and Komar 2006), Nicaragua (McCrary and Young 2008), Costa Rica (Porras-Peñaranda and McCarty 2005), and possibly Venezuela (Paulson 1983, Hilty 1999), but the origin(s) and destination(s) of these birds is still unknown (Jones and Komar 2008). Fjeldså and Krabbe (1990) mentioned that this species occasionally migrates in flocks in the Andes, and there is some evidence that it is also a partial austral migrant in Argentina (Formosa and Chaco Provinces) (Contreras et al. 1990, Di Giacomo 2005). In addition, some populations show regular altitudinal movements. more....

Habitat and Habits: Found in lowlands, less commonly to middle elevations, occurring in a wide variety of forest habitats, including wooded freshwater swamps, mangrove swamps, gallery forest, palm forest, montane evergreen forest, deciduous forests, shaded coffee plantations, second-growth, or semi-open areas near water. In northern Mexico and adjacent Texas, it is found in dry acacia thorn woodlands and tropical deciduous forest. It occasionally soars, especially in mid-morning, perhaps for territorial or other social functions, but not for long periods. This species is generally sedentary and sluggish, perching in the middle or even lower branches of trees. It is not particularly shy and can even be tame or curious at times (Brown and Amadon 1968), but it is usually unobtrusive and difficult to find (Brush 2005). Occurs singly, in pairs, or occasionally in family groups of threes or fours. more....

Food and Feeding Behavior: Feeds mostly on terrestrial and arboreal snails, but also occasionally takes frogs, salamanders, lizards, birds, large insects (including caterpillars), and spiders. Takes many snails from tree trunks and branches. Often descends from a perch to the ground to capture land snails or other prey, and may also hover, then glide down, and seize prey (Fjeldså and Krabbe 1990). Smith and Temple (1982) found that bill size is bimodally distributed in many parts of the range and is closely related to the sizes of common tree snails found in a given region. The bill of this kite is not specialized like that of the Snail Kite for piercing snail shells. Hook-billed Kites probably rarely (if ever) feed on adults of large aquatic snails (e.g., Ampullaria, Pulmonaria), the favorite prey of Snail Kites, but there are several reports of them taking young snails of these species, perhaps from tree trunks. more....

Breeding: Hook-billed Kites breed later than other kite species, probably an adaptation to seasonal changes in prey abundance, and eggs hatch at the beginning of the wet season, when snails are most abundant. The nest is a remarkably flimsy, unlined, shallow-cupped platform of small twigs placed in the crotch of a tree or farther out on a horizontal branch, and eggs or young can often be seen through the bottom of the nest. Clutch size is 1-3 eggs (most often 2), which are dull white with heavy spots and blotches of chocolate brown (Kiff 1981) and average 45.4 x 36.0 mm (n = 9) in size. The incubation period is 34-35 days in Guatemala (Vásquez Marroquín et al. 1992), and the nestling period was 38 or 39 days at an Argentine nest (Di Giacomo 2005). Both parents share nest duties, including nest building, incubation, and (to a lesser extent) feeding the young; an incubating bird collected from a nest in Oaxaca, Mexico was a male (Rowley 1984), as were incubating birds in Costa Rica (Orians and Paulson 1969) and Suriname (Haverschmidt 1965). In a Suriname nest, one of two chicks was much larger than the other, which did not survive (Haverschmidt 1964), and this may have been an instance of siblicide. more....

Conservation: Generally regarded as uncommon to locally common throughout its extensive range, but little is actually known of the population status of this unobtrusive species in most regions. The endemic Grenada race (mirus) has been regarded as scarce since its discovery and is classified as Endangered. Ongoing kite surveys on Grenada since 2000 by Peregrine Fund researchers, Russell Thorstrom and Desmond McQueen, have indicated that the total population is between 50 to 75 birds and is presently stable, although ever-threatened by the loss of forested habitat (Thorstrom and McQueen 2008). As a whole, the species is categorized as "Least Concern" by BirdLife International (2007). more....

Important References:
Bierregaard, R.O. 1994. Hook-billed Kite. P. 108 in del Hoyo, J., A.
  Elliott, and J. Sargatal (eds). Handbook of birds of the world. Vol. 2. New
  World vultures to guineafowl. Lynx Edicions, Barcelona, Spain.
Brush, T. 1999. A reclusive, snail-eating raptor of the Lower Rio Grande
  Valley -- the Hook-billed Kite. Texas Birds 1:26-32.
Brush, T. 2005. Nesting birds of the tropical frontier: the Lower Rio
  Grande Valley of Texas. Texas A & M University Press, College Station, TX.
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world. Houghton
  Mifflin, Boston, MA.
Fleetwood, R.J., and J.L. Hamilton. 1967. Occurrence and nesting of the
  Hook-billed Kite (Chondrohierax uncinatus) in Texas. Auk
  84:598-601.
Johnson, J.A., R. Thorstrom, and D.P. Mindell. 2007. Systematics and
  conservation of the Hook-billed Kite including the island taxa from Cuba and
  Grenada. Animal Conservation 10:349-359.
Kiff, L.F. 1981. Notes on eggs of the Hook-billed Kite, Chondrohierax
  uncinatus, including two overlooked nesting records. Bulletin of the
  British Ornithologists' Club 101:318-323.
Lerner, H.R., and D.P. Mindell. 2005. Phylogeny of eagles, Old World
  vultures, and other Accipitridae based on nuclear and mitochondrial DNA.
  Molecular Phylogenetics and Evolution 37:327-346.
Smith, T.B. 1988. Hook-billed Kite. Pp. 102-108 in R.S. Palmer (ed.),
  Handbook of North American birds. Vol. 4. Yale University Press, New Haven,
  CT.
Smith, T.B. 1982. Nests and young of two rare raptors from Mexico.
  Biotropica 14:79-90.
Smith, T.B., and S.A. Temple. 1982. Feeding habits and bill polymorphism
  in Hook-billed Kites. Auk 99:197-207.
Smith, T.B., and S.A. Temple. 1982. Grenada Hook-billed Kites: recent
  status and life history notes. Condor 84:131.
Thorstrom, R., and D. McQueen. 2008. Breeding and status of the Grenada
  Hook-billed Kite (Chondrohierax uncinatus mirus). Ornitologia
  Neotropical 19:221-228.
Whitacre, D.F., and M.A. Vásquez. 2012. Hook-billed Kite. Pp. 48-59 in
  D.F. Whitacre (ed.), Neotropical birds of prey: biology and ecology of a
  forest raptor community. Cornell University Press, Ithaca, NY.
more....

Current Research: Peregrine Fund collaborator and naturalist, Desmond McQueen, continues to conduct surveys of Grenada Hook-billed Kites 2006 to assess the status and distribution of this remnant breeding population.

Sites of Interest:

The Peregrine Fund
Field studies in Grenada.
Xeno-canto
Vocalizations.
Aves de Rapina do Brasil
Species account, with emphasis on Brazil.
VIREO
Hook-billed Kite photos.

Researchers:
Canuto, Marcus
Johnson, Jeff A.
Ruelas Inzunza, Ernesto
Thorstrom, Russell
Zorzin, Giancarlo

Last modified: 7/27/2012

Recommended Citation: Global Raptor Information Network. 2019. Species account: Hook-billed Kite Chondrohierax uncinatus. Downloaded from http://www.globalraptors.org on 17 Nov. 2019