Bihoreau violacé

Identification

The yellow-crowned night heron is a rather stocky wading bird, ranging from 55 to 70 cm (1 ft 10 in – 2 ft 4 in) and from 650 to 850 g (1.43–1.87 lb), the females being a little smaller than the males. The yellow-crowned night heron has a wingspan ranging from 101 to 112 cm (3 ft 4 in – 3 ft 8 in). The neck, slim when extended, exposes its large head (compared to its body), with a large and heavy bill.<p>The body and back are a smooth grey-blue, with a black scaled pattern on the wings. The long legs are yellow and turn coral, pink or red during courtship. The most characteristic part of the yellow-crowned night heron is the head: black and glossy, with white cheeks and a pale yellow crown going from the bill, between the eyes and to the back of the head, giving the bird its common name. Such colours make the face appear striped in a horizontal black-white-black-white pattern. Long, thin, white feathers grow to the back of the crown during mating season. The bill, also black, is thick and deeply set under the eyes which are dark orange or red.<p>Like all herons, the yellow-crowned night heron flies with long, slow purposeful wing beats. It can be found gliding over water with its legs easily visible, extended straight below the tail, unlike the black-crowned night heron, whose legs can barely be seen in flight.<p>It takes about three years for yellow-crowned night herons to acquire the full physical appearance of adults. Before that, the young birds show signs of immaturity such as a brownish body, an overall greyish head, drab colors and spots and streaks on their plumage.<p>Although the adults are easy to tell apart, juvenile yellow-crowned night heron can look very similar to juvenile black-crowned night heron. Yellow-crowned juveniles tend to stand straighter and have heavier bills and longer legs, and their spots and streaks are finer than those of the black-crowned.

Taxonomie

Being a heron, the yellow-crowned night heron is related to egrets and bitterns (the family Ardeidae), and, more distantly, to pelicans and ibises (the order Pelecaniformes). The night herons are usually considered to have separated from the day herons (such as the great blue heron or the green heron).<p>Various classifications recognize five subspecies, but little is known as to how much they are integrated together and how much their geographic range varies. Their body size decreases from north to south, and the shape of their bills varies geographically, depending on the size of the crustaceans they eat in different regions.<p>A related heron, the Bermuda night heron, was endemic to Bermuda, but became extinct following human colonization.

Nom scientifique

Nyctanassa violacea

Autorité

(Linnaeus, 1758)

Ordre

Pélécaniformes

Famille

Ardéidés

Genre

Nyctanassa

Répartition et habitat

The yellow-crowned night heron looks for shallow water to live in: marshes, wooded swamps, and lakeshores for inland populations, and thickets, mangroves and cliff-bound coasts for coastal populations. It can also be found in areas that don't always have enough water, but that get flooded on a regular basis. Its habitat is closely linked to that of the crustaceans that make for most of its diet, and it tolerates fresh water, brackish water and saltwater.<p>Another important habitat factor is nesting sites. The yellow-crowned night heron needs bushes or trees to build nests, although it will use rock ledges where vegetation is unavailable (for example, on cliffs).<p>Unlike the black-crowned night heron, the yellow-crowned does not mind living near humans and can be found in wooded neighborhoods, nesting on rooftops and driveways. Such cohabitation may not go smoothly and can create conflicts with humans. The yellow-crowned night heron is found exclusively in the Americas, and its distribution depends closely on food (mainly crustaceans) availability.<p>It winters where the climate allows for year-round crab activity: tropical and subtropical regions, south Florida, the Gulf Coast (Louisiana to Alabama), and the eastern Texas coast. It is also found in Mexico, Central America, Galápagos Islands, the Caribbean and northern South America (south to Peru and Brazil in coastal regions) where generally resident.<p>From 1925 to 1960, the yellow-crowned night heron spread northward for reasons still not clear. Today, in addition to its winter and year-round range, it can be found in the south-east inland of the United States during breeding season and additional isolated breeding colonies have been recorded even farther inland, all the way to the northern border of the United States.<p>Different subspecies and populations have different migratory behaviour. Subspecies and populations that are insular or live in warmer areas are confirmed to be sedentary. The tropical subspecies and populations migrate, but to an extent that is still unclear for lack of data. The migratory behaviour of the yellow-crowned night heron has changed with its expansion north: one subspecies (Nyctanassa violacea violacea) migrates to the northern limits of its range, moving north and west after breeding. Birds observed outside of the normal range are usually first-years or strays.<p>Migration occurs in mid-March in lower latitude, and from mid-March to April in higher latitude.

Migration

Migrateurs complets

Comportement

Mode de migration: Migrateurs complets.

Conservation

Tendance de la population: stable.

Tendance de la population

stable