Nyctanassa violacea (Linnaeus, 1758)
Bihoreau violacé (French), Pedrete corona clara (Castilian), Yellow-crowned Night Heron (English), Yellow-crowned Night-Heron (English)
The Yellow-crowned Night-Heron ia a small, stocky (but relatively long-necked), mainly nocturnal heron. It typically forages in shallow water, feeding largely on crabs, and roosts during the day in trees or marshes (Sibley 2000). It is more solitary and often more secretive than the somewhat similar and often co-occurring Black-crowned Night-Heron (Nycticorax nycticorax) (Kaufman 1996).
Conservation and Management
At least in North America, Yellow-crowned Night-Heron populations appear to be stable, and in some areas the breeding range has been expanding northward (Kaufman 1996).
The Yellow-crowned Night-Heron feeds mainly at dusk and at night (hence the common name). Although it may also forage during the day, particularly in coastal areas (Kaufman 1996), it is more strictly nocturnal than the sympatric (co-occurring) Black-crowned Night-Heron (Nycticorax nycticorax) and typically spends the day roosting quietly in trees or marshes (Sibley 2000).
Where common, this species may nest in colonies, sometimes with Black-crowned Night-Herons and other herons. The nest is a platform of sticks, often constructed in a tree high above the water, but sometimes low in thickets or mangoves (Kaufman 1996; Martinez-Vilalta and Motis1992).
Based on Dunn and Alderfer 2006: The easy-to-recognize adult Yellow-crowned Night-Heron has a buffy white crown and a black face with white cheeks. In the breeding season, it acquires several long buffy white head plumes that extend down behind its neck. The white-spotted brown plumaged juveniles closely resemble juvenile Black-crowned Night-Herons (Nycticorax nycticorax). Yellow-crowned juveniles can be distinguished by their somewhat grayer upperparts with less conspicuous white spotting; longer neck; stouter, mostly dark bill; and larger eyes. In flight, the Yellow-crowned shows darker flight feathers and trailing edge of the wing and the legs extend farther beyond the tail. For both the Yellow-crowned and Black-crowned Night-Herons, full adult plumage is not acquired until the third year.
The Yellow-crowned Night-Heron favors wooded wetlands, especially swamps, lakes, lagoons, and mangroves; it sometimes nests in wooded suburbs (A.O.U. 1998). It also commonly occurs in shallow tidal waters, as well as along lowland rivers with trees or other heavy cover nearby; it is rarely found in open marshes (Kaufman 1996).
The Yellow-crowned Night-Heron breeds from central Baja California (both slopes), central Sonora, central and northeastern Texas, central Oklahoma, east-central Colorado (rarely), Kansas, southeastern Nebraska, southern and eastern Iowa, southeastern Minnesota, southern Wisconsin, southern Michigan, the lower Ohio Valley, eastern Tennessees, southeastern Pennsylvania, Massachusetts and southern Maine (rarely) south along both slopes of Mexico, the Gulf coast, Bahamas, Antilles, Middle America (including Socorro Island in the Revillagigedo Islands and Isla Maria Madre in the Tres Mafias Islands), and South America (including the Galapagos Islands) on the Pacific coast to extreme northern Peru and on the Caribbean-Atlantic coast to eastern Brazil (A.O.U. 1998).
It winters from central Baja California, central Sonora, the Gulf coast (locally), and coastal South Carolina south throughout the remainder of the breeding range (A.O.U. 1998).
The Yellow-crowned Night-Heron was introduced to Bermuda, where it was formerly considered casual, in the 1970s and has been breeding there since 1979 (A.O.U. 1998).
The Yellow-crowned Night-Heron wanders, at least casually, north as far as central California, southern Arizona, southern New Mexico, Montana, North Dakota, southern Saskatchewan, southern Manitoba, southern Ontario, southern Quebec, southern New Brunswick, Newfoundland, and Nova Scotia, and to Clipperton Island (A.O.U. 1998).
Over much of its extensive distribution, the Yellow-crowned Night-Heron is fairly sedentary (Martinez-Vilalta and Motis1992). In the United States, it may be a permanent resident in southern Florida, but over most of its range in the U.S. it is far less common in winter than in summer, with some birds traveling as far south as Panama and the Lesser Antilles (Kaufman 1996).
Eggs 4-5 (sometimes 2-8), pale blue-green; incubation (21-25 days) and feeding are carried out by both parents (Kaufman 1996). Age at first flight is about 6 weeks (Kaufman 1996).
The diet of the Yellow-crowned Night-Heron includes many crustaceans, especially crabs and crayfish, particularly in coastal areas. It also eats mollusks, frogs, fishes, and insects (Kaufman 1996).
The Yellow-crowned Night-Heron (or a close now-extinct relative) was resident in Bermuda prior to human settlement, but was subsequently largely absent for hundreds of years. In the late 1970s, Yellow-crowned Night-Herons were re-introduced from Florida in an effort to control populations of the land crab Gecarcinus lateralis, which is widely regarded as a pest in Bermuda. A resident breeding population was successfully established and does consume large numbers of the crabs. Subsequent to this heron's establishment on Bermuda, examination of regurgitated pellets confirmed that land crabs comprised approximately 95% of its diet, even in winter, and a reduction of crab holes occurred on lawns and pathways in areas where the birds fed regularly (Wingate 1982).
Evolution and Systematics
Systematics and Taxonomy
The Yellow-crowned Night-Heron was still included in the genus Nycticorax in the 6th edition of the American Ornithologists' Union's Check-list of North American Birds (1983), but based on new research was subsequently moved to the monotypic (i.e, containing just a single species) genus Nyctanassa (A .O.U. 1989: 533).