ash grey and streaked with buff. The neck and upper body surface are pale brownish with a little ash grey tinge on the neck. Compared to the adult, the crown is duller and the under-tail coverts have a dusky streaking. Juveniles also lack the long plumes and occipital crest typical of the adult. Despite the paler colouration, the downy chick already shows the contrast between the dark head and pale neck typical of the adult. Similar species At the southernmost extent of its range (e.g., Colombia and Panama), the cocoi heron sometimes overlaps in range with the closely related and similarly sized great blue heron (A. herodias). The cocoi is distinguished by a striking white neck and solid black crown, but the duller juveniles are more easily confused. Distribution and habitat The cocoi heron occurs throughout much of South America except in the Andes and in some parts of Argentina. It is native in Argentina, Panama, Suriname, Colombia, Venezuela, Bolivia, Brazil, Chile, Ecuador, French Guiana, Guyana, Paraguay, Peru and Uruguay. Overall, the cocoi heron is notably widespread and ranges from Central America to the mainland shores on the Strait of Magellan, but is rarely found further south than Chubut in Argentina. It has an estimated extent of occurrence of 20600000 km2. It inhabits the wetter parts of the Chaco and occurs as a vagrant in the Falkland Islands, Saint Helena, Ascension Island and Tristan da Cunha. It is a regular, non-breeding visitor to Trinidad and Tobago. The habitat comprises almost any body of water or wetland away from dense forest; including lake shores, swamps, rivers and estuaries. Gallery forest, grassland and beaches have also been reported to be suitable feeding grounds. Pastures appear to be disfavoured probably because these habitats harbour a large proportion of insects, which are less favoured as prey than fish and mammals. In the Falkland Islands, the habitat appears to comprise small streams. In one study in the Parana river, water with aquatic vegetation was found to be the most preferable, followed by open waters, with the lowest preference for beaches. This heron is found at elevations up to 2550 m above sea level. Ecology Feeding This heron feeds primarily on fish measuring over long; with mammals, amphibians and sometimes insects also being consumed. Fish species consumed include whitemouth croaker, wolf fish, various Leporinus species up to 200 mm long and streaked prochilod. This heron has