Bare-throated Tiger-Heron Tigrisoma mexicanum Scientific name definitions

Bare-throated Tiger-Heron is a medium-sized wading bird of Central America that reaches northwestern South America in Colombia and extreme northwestern Peru. While congeners might be found in more densely vegetated habitats, Bare-throated Tiger-Heron often forages in the open and feeds both on aquatic animals like fish and frogs as well as terrestrial rodents. Overall, the species is long and bittern-shaped with a bit more bulk, in the style of the night-herons.  Juveniles are strikingly barred black and rust throughout their bodies, whereas adults have a gray face with a black crown, spearlike black and yellow bill, grayish upperparts, and rufous underparts; a patch of bare skin on the throat gives the species its common name.

71–81 cm; 1000–1345 g (1 Morales-Pérez, J.E. (1999). Additional bird records for Oaxaca, Mexico. Bull. Brit. Orn. Club. 119(1): 16–25. Close , 2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). Crown and nape black, head-sides grey, black line  from eye to throat, foreneck tawny, hindneck finely barred brown and buff, back dark olive-brown very finely vermiculated buff, flight feather black, and underparts cinnamon with grey thighs. Only <em>Tigrisoma</em> with bare throat , which is bright yellow to orange during breeding, but yellow-green at other times, along with lores and periorbital skin; eyes yellow to silver-coloured; legs and feet dark grey-olive to slate-green; and bill  black with bluish-horn cutting edges and dull yellow mandible. Further separated from T. fasciatum and T. lineatum by black cap and vermiculated brown neck . Some individuals larger , with broader striping, but sexes alike. Iris can be bordered with silver and black. Juvenile boldly barred and spotted cinnamon-buff and fuscous-brown over head, neck and breast, and rest of underparts pale buff broadly barred with brown; upperparts dark brown boldly barred cinnamon, and wings and tail blackish with 4–5 narrow white bars; throat yellow. Second-year acquires uniformly dark slate-coloured remiges with white tips like adult, but has coarser neck barring and duller head-sides (3 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ). Full adult plumage probably acquired in third year of life (3 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ).

Coastal W & E Mexico (from S Sonora and S Tamaulipas) S through Central America to extreme NW Colombia (lower Atrato Valley), with an extremely disjunct population in NW Peru.

Normally found in coastal zones of salt or brackish water, especially mangroves (and is entirely dependent on such habitats in some areas, e.g. NW Peru) (4 Valqui, T. and Walker, B. (2002). Importance of mangrove forests in Peru with notes on Bare-throated Tiger-heron Tigrisoma mexicanum and Rufous-necked Wood-rail Aramides axillaris. Cotinga. 18: 58–61. Close ); also inland , in marshes , swamps of tropical zone, and on freshwater streams and wooded rivers in uplands, typically inhabiting more open habitats than other Tigrisoma. Up to 440 m on Sonora–Sinaloa border (S Mexico), and to 1000 m in Honduras.

Apparently sedentary, but occasionally recorded in the interior of Mexico, e.g. Morelos (5 Urbina-Torres, F. (2000). New distributional information of birds from the state of Morelos, Mexico. Bull. Brit. Orn. Club. 120(1): 8–15. Close ), perhaps principally dispersing immatures, and there is one recent record of a second-year bird in S USA (Texas, Dec 2009–Jan 2010) (3 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ).

Fish (e.g. eels Anguilla anguilla) (6 Winker, K., R. J. Oehlenschlager, M. A. Ramos, R. M. Zink, J. H. Rappole, and D. W. Warner (1992). Avian distribution and abundance records for the Sierra de los Tuxtlas, Veracruz, Mexico. Wilson Bulletin 104(4):699–718. Close ), frogs, crustaceans and insects (flies) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). Recorded eating a small rodent . Generally feeds alone, but forms small flocks at favourable sites. Apparently crepuscular or nocturnal; feeds mainly by remaining motionless and waiting, or by Walking Slowly.

Gives “who, woh, woh, woh” or “howk, howk, howk” on flushing and, in other situations including territory defence, a roaring or booming, double- or treble-noted “ohrr, ohrr, orrr” repeated at 1–2-second intervals while simultaneously raising the neck and bill vertically, but depressing the neck and body feathers, given during evening or at night, especially in breeding season (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ).

Season variable, ranging from Feb–Apr in Panama to May–Aug in El Salvador, but perhaps year-round in Costa Rica (albeit peaking during early rainy season) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), with nestbuilding observed Mar in Belize (7 Piaskowski, V. D., M. Teul, K. M. Williams, and R. N. Cal (2006). Birds of the Sibun riverine forest, Belize. Ornitología Neotropical 17(3): 333–352. Close ) and eggs in late Mar in SE Mexico (Quintana Roo) (8 Lopez-Ornat, A. and Ramo, C. (1992). Colonial waterbird populations in the Sian Ka’an Biosphere Reserve (Quintana Roo, Mexico). Wilson Bull.. 104(3): 501–515. Close ). Normally nests in trees (especially Rhizophora mangroves, but also Ceiba pentandra) (9 Lewis, S.E. and Timm, R.M. (1991). Predation on nestling Bare-throated Tiger-herons by a Great Black Hawk. Ornitol. Neotrop. 2(1): 37. Close , 2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), on horizontal branches 4–15 m over water (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), but also on low branches only 4 m up, in trees on sea cliffs, and once on ground on a cliff ledge c. 50 m above ground (10 Baker, A.J., Aguirre-Barrera, O.A. and White, C.M. (1999). First record of a Bare-throated Tiger-Heron (Tigrisoma mexicanum) nesting on a cliff ledge. Ornitología Neotropical. 10(2): 239–240. Close ); nest is small to large stick platform (c. 150 cm by 25 cm) (10 Baker, A.J., Aguirre-Barrera, O.A. and White, C.M. (1999). First record of a Bare-throated Tiger-Heron (Tigrisoma mexicanum) nesting on a cliff ledge. Ornitología Neotropical. 10(2): 239–240. Close ), usually lined with leaves (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). Clutch 1–3 dull white eggs tinged green, occasionally flecked brown or buff, size (n = 2) 56·6–58·1 mm × 43·5–45·3 mm (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ); chicks  have pale greyish-white down, with white erectile crown plumes. No further information, but nest predators apparently include Buteogallus hawks (9 Lewis, S.E. and Timm, R.M. (1991). Predation on nestling Bare-throated Tiger-herons by a Great Black Hawk. Ornitol. Neotrop. 2(1): 37. Close ).

Not globally threatened (Least Concern). No information available on overall status and population size, and species is difficult to census (like other Tigrisoma). Widespread and fairly common in Honduras in 1960s; supposedly common in Belize, Guatemala and Nicaragua; also in Costa Rica , where 30 pairs breed at Estero Madrigal, but is considered to be declining in Panama due to persecution, wetland drainage and conversion to agriculture (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). However, populations in NW Colombia and NW Peru (4 Valqui, T. and Walker, B. (2002). Importance of mangrove forests in Peru with notes on Bare-throated Tiger-heron Tigrisoma mexicanum and Rufous-necked Wood-rail Aramides axillaris. Cotinga. 18: 58–61. Close ) (the latter apparently isolated by c. 1300 km) are both rather small, although range in the first-named country has recently been shown to be broader than previously suspected (11 Strewe, R. and Navarro, C. (2004). New and noteworthy records of birds from the Sierra Nevada de Santa Marta region, north-eastern Colombia. Bull. Brit. Orn. Club. 124(1): 38–51. Close ). Peruvian population first discovered in late 19th century subsequently went unrecorded again until 1990s, and is largely protected (4 Valqui, T. and Walker, B. (2002). Importance of mangrove forests in Peru with notes on Bare-throated Tiger-heron Tigrisoma mexicanum and Rufous-necked Wood-rail Aramides axillaris. Cotinga. 18: 58–61. Close ).