Cocoi Heron Ardea cocoi Scientific name definitions

The largest of the South American herons, the Cocoi Heron is a gregarious heron of South America away from the high Andes, from eastern Panama south to central Argentina and Chile. While likely a resident in most of its range, a few vagrant records (notably Trinidad and the Falkland Islands) suggest movements by at least some birds. In many parts of its range, the Cocoi Heron is the most common and easy to see heron, as it forages in the open, and occupies a large range of habitats where there is water. The Cocoi Heron can often be seen in along rivers, streams, marshes, or even agricultural waterways as it forages for fish, frogs, and other similarly-sized animals by standing or walking slowly near or in shallow water. The large size; long, all-white neck; and black cap make this bird distinctive throughout its range. Though young birds may appear similar to the closely related Great Blue Heron (Ardea herodias), they always show the distinctive dark cap that comes down below the eye.

95–127 cm; 1900–2100 g (1 Graves, G. R., and R. L. Zusi (1990). Avian body weights from the lower Rio Xingu, Brazil. Bulletin of the British Ornithologists' Club 110(1): 20–25. Close , 2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). Black on head more extensive than on A. cinerea and A. herodias , reaching to below eye, but sometimes with paler forecrown and long head plumes; mainly grey over upperparts and wings, with black shoulder patch visible at rest, and largely white underparts including neck , thighs and undertail, except black belly; bill dull yellow, slightly paler below and with blackish base (becoming bright yellow, with reddish tinge in breeding season), legs and feet black (dusky pink in breeding season), and eyes usually yellow, with blue lores. Additional differences in adult plumage from A. herodias include the paler neck and black on underparts. Juvenile  generally greyer, especially on neck, with buff-streaked underparts, thighs and undertail, and duller black cap, paler forecrown and no plumes (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ).

• Great Egret x Cocoi Heron (hybrid) Ardea alba x cocoi
• Great Blue x Cocoi Heron (hybrid) Ardea herodias x cocoi

Most of South America excluding Andes, from E Panama S to Aysén (Chile) and Chubut (Argentina).

Very variable; any kind of wetland, including mangroves, swamps, lake shores, rivers , small streams (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), flooded pastures and estuaries; absent from arid coasts and dense forest, though does occur in marshy areas surrounded by forest. Normally in lowlands, but straggles up to at least 2550 m in Cochabamba and Tarija, Bolivia, and 2210 m in Imbabura, N Ecuador (3 Santander G., T., Terán, K., Mueces, T., Lara, A., Llumiquinga, C. and Guevara, E.A. (2011). Registros inusuales de aves costeras en lagunas Altoandinas de Ecuador. Cotinga. 33: 105–107. Close ).

Generally sedentary, though birds in extreme S of range probably migrate N during winter and considered to be more frequently encountered on coast of NW Peru (where generally rare) in summer or during El Niño events (4 Valega, R.C. (2007). Avifauna of a relict mangrove forest in San Pedro, dpto. Piura, Peru. Cotinga. 27: 42–47. Close ). Also some post-breeding dispersal; occasionally reaches Strait of Magellan and L Kami in far S, and is reasonably regularly recorded in Santa Cruz province, Argentina (5 Imberti, S. (2003). Notes on the distribution and natural history of some birds in Santa Cruz and Tierra del Fuego provinces, Patagonia, Argentina. Cotinga 19:15–24. Close , 6 Darrieu, C. A., A. R. Camperi, and S. Imberti (2008). Avifauna (non Passeriformes) of Santa Cruz province, Patagonia (Argentina): annotated list of species. Revista del Museo Argentino de Ciencias Naturales 10:111–145. Close ). Non-breeding vistor to Trinidad mainly Dec–Ju1, and very rare on Tobago, where just five records in last 15 years (7 Kenefick, M., Restall, R. and Hayes, F.E. (2011). Birds of Trinidad & Tobago. Second edn. Christopher Helm, London. Close ). Recorded just once (Feb 1925) on La Plata I, off W Ecuador (8 Ortiz-Crespo, F. I., and P. Agnew (1992). The birds of La Plata Island, Ecuador. Bulletin of the British Ornithologists’ Club 112(2):66–73. Close ) and on Laje dos Santos I, 40 km off coast of São Paulo, SE Brazil (9 Campos, F.R., Campos, F.P. and Jesus Faria, P. (2007). Trinta-réis (Sternidae) do Parque Estadual Marinho da Laje de Santos, São Paulo, e notas sobre suas aves. Rev. Bras. Orn. 15(3): 386–394. Close ). Accidental visitor to Falklands (mostly in Feb–May and Sept) (10 Woods, R. W. (1988). The Birds of the Falkland Islands. Anthony Nelson, Oswestry, England. Close , 11 Gregory, P. (1994) Notes on new and scarce birds in the Falkland Islands 1988–1990. Bulletin of the British Ornithologists' Club 114: 12–20. Close ) and Gough I, as well as on Fernando de Noronha.

Fish (e.g. Menticirrhus littoralis, Synbranchus marmoratus, Mugil curema) (12 Vooren, C. M., and A. Chiaradia (1990). Seasonal abundance and behaviour of coastal birds on Cassino Beach, Brazil. Ornitologia Neotropical 1(1–2):9–24. Close , 13 Gonçalves de Oliveira, T.C. and Araujo Monteiro Filho, E.L. (2009). Comportamento de imersão parcial do corpo de Ardea cocoi (Ciconiiformes: Ardeidae) durante estratégia de captura na região de Cananéia, litoral sul de São Paulo. Atualidades Orn.. 149: 18-19. Close ), frogs, aquatic insects (both adults and larvae) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ); in coastal Brazil occasionally eats dead or dying animals, including crabs (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ); in Peru takes mostly large fish 20–30 cm long. Passive feeder , most prey taken when Standing; in Chile mostly feeds by night, in Argentina often by day. Once observed briefly landing on sea, apparently to feed, around fishing boats (14 Browne, P.W.P. (2003). Feeding behaviour of herons at sea off the coast of south-east Brazil. Cotinga. 19: 81-82. Close ). Usually solitary and territorial, but occasionally feeds in large groups, e.g. 100–200 birds feeding in Lagoa do Peixe, Brazil, in Jan 1974, as water receded, and will join concentrations of other waterbirds, especially if food is abundant, sometimes pirating food from species such as Wood Storks (Mycteria americana) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ) and even young Magnificent Frigatebirds (Fregata magnificens) (13 Gonçalves de Oliveira, T.C. and Araujo Monteiro Filho, E.L. (2009). Comportamento de imersão parcial do corpo de Ardea cocoi (Ciconiiformes: Ardeidae) durante estratégia de captura na região de Cananéia, litoral sul de São Paulo. Atualidades Orn.. 149: 18-19. Close ), as well as foraging in association with tucuxis (Sotalia fluviatilis guianensis) in shallower waters (13 Gonçalves de Oliveira, T.C. and Araujo Monteiro Filho, E.L. (2009). Comportamento de imersão parcial do corpo de Ardea cocoi (Ciconiiformes: Ardeidae) durante estratégia de captura na região de Cananéia, litoral sul de São Paulo. Atualidades Orn.. 149: 18-19. Close ).

Poorly described, but has characteristic “rraahbm rraabb” call, typical of other large grey herons (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ).

Season: Jul in Surinam, Aug–Nov in SE Brazil and Argentina, Oct in Uruguay (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), and eggs laid second and third weeks of Aug, colony abandoned between early Nov and late Jan in SC Chile (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ); egg-laying period can be prolonged even within same colony, e.g. early Sept to late Oct at one Argentine site (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ). Colonial; colonies sometimes large (up to 400–600 pairs in Surinam) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ) and may be mixed, e.g., in Venezuela with Ardea alba, Maguari Storks (Ciconia maguari) and Jabirus (Jabiru mycteria) (17 González, J.A. (1996). Breeding biology of the Jabiru in the southern llanos of Venezuela. Wilson Bull.. 108(3): 524-534. Close ), in NE Argentina with Egretta thula, Ardea alba, Nycticorax nycticorax and Anhinga (Anhinga anhinga) (18 Parera, A. and Bosso, A. (1996). Descripción de una colonia mixta de aves acuáticas en Laguna Iberá, Corrientes, Argentina [Description of a mixed waterbird colony at Laguna lberá, Corrientes Province, Argentina]. Hornero. 14: 81–84. Close ), and in SC Chile with A. alba and Neotropical Cormorant (Phalacrocorax brasilianus) (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ). Nest  of reeds and twigs, lined with grass, mean size 92·2 cm × 72·3 cm × 45 cm (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ), and situated in trees, bushes (even cacti) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ) or in Zizaniopsis reedbeds, where may be just 30–40 cm above water level, but typically in 20–25 m-tall trees (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), although nests at Chilean colony, in Salix babilonica, were all 3·2–5·1 m above ground, and situated within 2–26 m of adjacent pair (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ) (4–67 m between neighbouring nests of conspecifics in Argentine colony, wherein nests were just 85–116 cm above water surface) (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ). Nest construction period c. 7 days (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). Clutch 2–5 sky blue eggs (speckled paler) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ) in Argentina (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ), size 51–76 mm × 34–50 mm (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close , 15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ), mass 64·8–96·1 g (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ), but 2–4 chicks  in Brazil. Incubation c. 25–29 days (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close , 16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ); downy chick is grey-white with darker cap (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ); fledging period c. 55 days (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ). At Chilean colony, of 64 eggs monitored, 55 hatched (88% hatching success, versus 81% in Argentine colony) (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ), 90% of nests produced at least one young and 47% of chicks that hatched ultimately fledged, with mean number of young fledged 1·7/nest (range 1–3) (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ); at Argentine colony, most chick mortalities occurred during first two weeks of life, with starvation (70%) and predation (30%) to blame (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ). At nests in Argentina, young fed varied diet, e.g. beetles (Callichthys sp., Hoplosternum sp.), small fish (Hoplias malabaricus, Symbranchus marmoratus) (15 González-Acuña, D., Figueroa R., R.A., González, A., Barrientos, C., Ardiles, K. and Moreno, L. (2008). Biología reproductiva de la Garza Cuca (Ardea cocoi) en el centro-sur de Chile [Breeding biology of the White-necked Heron (Ardea cocoi) in south-central Chile]. Ornitología Neotropical. 19(4): 485–493. Close ) and small mammals (e.g. Myocastor coypus), in one study, analysis of contents suggested diet was 64% mammals, 45% fish, 18% birds (including young of own species, i.e. heterocannibalism) and 18% insects and arachnids, with insects (Tropisternus sp.), fish (Odontesthes argentinensis) and small mammals (Ctenomys talarum) numerically most important (58% of total number of prey consumed) (16 Pretelli, M.G., Josens, M.L. and Escalante, A.H. (2012). Breeding biology at a mixed-species colony of Great Egret and Cocoi Heron in a Pampas wetland of Argentina. Waterbirds. 35(1): 35–43. Close ). Few other data, although nest predators include Southern Caracaras (Caracara plancus) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ).

Not globally threatened (Least Concern). Widespread in lowland S America, especially in C & S parts of the continent (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ). In early 1970s breeding population of Surinam estimated at 2500 pairs, but slumped to 300–500 pairs in 1980s. Common but not abundant in Argentina; generally common in Chaco zone; census of R Paraguay in Jan 1984 yielded 4000 birds. Common in Darién, Panama (although no evidence of breeding in this region) (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ), and along Caribbean coast of Colombia; scarce or absent along arid Pacific coast from Guayaquil (Ecuador) to Valparaiso (Chile), and uncommon on coasts of NE Brazil (19 Girão, W., Campos, A.A. and Albano, C. (2009). Evidência da garça-moura Ardea cocoi (Ciconiiformes: Ardeidae) no estado do Ceará, Brasil. Atualidades Orn.. 152: 23-24. Close ). Only significant conservation issue is loss of wetland habitats, although the species’ wide range should be sufficient insurance against all but the most wholesale of changes (2 Kushlan, J. A., and J. A. Hancock (2005). The Herons. Oxford University Press, Oxford, UK. Close ).