Ixobrychus is a genus of bitterns, a group of wading bird in the heron family Ardeidae. It has a single representative species in each of North America, South America, Eurasia and Australasia. The tropical species are largely resident, but the two northern species are partially migratory, with many birds moving south to warmer areas in winter. The Ixobrychus bitterns are all small species, their four larger relatives being in the genus Botaurus. They breed in large reedbeds, and can often be difficult to observe except for occasional flight views due to their secretive behaviour.
copyright: D. DesJardin
Yellow-crowned Night Heron has blue grey body plumage. Head pattern is black and white. Adult has black head with creamy to buff crown and forehead, and broad white auricular stripe. In breeding plumage, we can see 2 to 6 elongated, black and white occipital feathers. It has broad pointed wings and squared tail. Neck and underparts are pale grey. Upperparts are blue grey with dark brown feathers, with pale edges. Flight feathers are blackish, and it has grey under wings. Yellow-crowned Night Heron has thick and heavy blackish bill, sometimes greenish yellow below at base. Lores are greyish yellow. Eyes are amber to red in adults. Legs are yellow, becoming pinkish red in breeding plumage. Both sexes are similar, with female somewhat smaller. Juvenile has greyish plumage, finely spotted with buff on upperparts. Eyes are paler than adults, yellow to amber. Legs are greenish yellow. Juvenile reaches adult plumage at about two years of age.
Yellow-crowned Night Heron lives in mangroves and coastal areas. It is found in open beaches, but also in freshwater marshes and wooded swamps and thickets.
Yellow-crowned Night Heron feeds mainly on crustaceans, but also fish, amphibians, aquatic insects, snails, and sometimes small snakes. It may eat young birds fallen from the nest. The yellow-crowned night-heron eats many foods common to all wading birds but is unique among the ardeids in that it specializes on crustaceans, crayfishes being its principal food item. Parents feed young mostly crayfishes, after fledging immature birds adopt adult diet.
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Yellow-crowned Night Heron is mainly nocturnal, but sometimes it searches for food among roots of mangroves at all hours of the day. It follows the riversides and captures both aquatic and terrestrial animals. It searches for prey in tidal creeks and tide pools, wading in shallow water, or standing and waiting for food. It walks with elegance, slowly, picking prey up from the ground, appearing to do it with little concern. After feeding, it rests in the middle of an island, standing in a crouching posture. Yellow-crowned Night Heron defends itself strongly, with its claws and the bill. It is a solitary bird, and it may nest singly or in loose colonies. It is monogamous. Courtship displays include circle flights used in territorial defence.
The yellow-crowned night-heron is probably seasonally monogamous but little is known about its breeding behavior. This species has been described as solitary, to highly colonial, but usually is seen in small conspecific groups, on the fringes of larger heronries or nesting singly. It is not known if males arrive on breeding grounds before females and courtship is not described.
Yellow-crowned Night Heron nests in trees, but sometimes on the ground. This species nests in colonies, located in dense vegetation. They avoid areas with insufficient cover. When they nest in low vegetation, they nest closer to the ground, and in groups with other herons. Nest may be located at about 2.5 meters , but also in trees from 3 to 8 meters. Nest is a platform made with dry sticks, in loose manner, and also with some weeds and a scanty lining of fibrous roots. Both sexes participate in nest construction. Female lays 2 to 4 pale blue green eggs. Incubation lasts about 21 to 25 days, by both parents. Chicks are fed by both parents, with regurgitated food on the first days. Young remain at nest until they are able to fly (about 25 days), but they leave it to follow adults along shores. They may climb on branches to hide if threatened. This species produces one brood per season, sometimes two.
Generally fairly sedentary. Majority of northern population of nominate violaceus migrates to Caribbean and Central America, occurring South to Grenadines and Panama respectively. Leaves colonies in September, returning in March. Subspecific range overlap considerably due to effects of post-breeding dispersal.
Range: North America, Latin America : East USA to Peru and East Brazil