Black-crowned Night-Heron

Nycticorax nycticorax

(c) Glen Tepke
  • ARDEIDAE
  • Herons, Bitterns, Egrets
  • Ciconiiformes
  • Guanaba, Yaboa real
  • Bihoreau gris
Introduction
Squatting on the water's edge, the Black-crowned Night-Heron is a short-legged, able fisher.
The genus name "Nycticorax" means night-croaker; fittingly, the bird is often heard at dusk as it flies overhead with a harsh "quork!" Breeding on every continent except Australia and Antarctica, the Black-crowned Night-Heron is the second most widespread heron in North America.
Appearance Description
On average, Black-crowned Night-Herons are 25 inches long and weigh 1.9 pounds, with a wingspan of 44 inches. With its short neck folded, the stocky Black-crowned Night-Heron has a hunched appearance. The adult's medium grey under-parts contrast with a black back, mantle, and crown. A white plume adorns the nape. The face is light grey fading to white around the large, red eyes and forehead. The stout legs, usually yellow-green, become pinkish at breeding time. Easily confused with Yellow-crowned Night-Herons, juvenile Black-crowneds are mostly grayish brown, liberally streaked and dotted with white, and distinguished by a black and yellow bill.  
Range Map
Courtesy Kenn Kaufman
Range Distribution
The Black-crowned Night-Heron breeds across most of the United States, except for the Appalachian Mountains into Maine, the upper Great Lakes, and the arid northern plains. The birds' breeding range extends into south central Canada and northeast along the St. Lawrence River. Most winter coastally on the Atlantic from New England through Florida, around the Gulf Coast, and on the Pacific from southern Oregon south. Black-crowned Night-Herons occur throughout most of South America outside the central Amazon watershed.
 
A legend for the range map to the right can be found here.
Habitat
Black-crowned Night-Herons are wetland habitat generalists, thriving on fresh and saltwater habitats alike. The birds use marshes, swamps, estuaries, lagoons, and mudflats, as well as altered wetlands, such as canals, flooded fields, human-made islands, and aquaculture sites, often foraging within vegetated cover. Small islands near marshes and wooded or brushy swamps provide breeding sites.
Feeding
A still and patient predator, the Black-crowned Night-Heron has an omnivorous diet. This nocturnal forager uses vegetated wetlands to ambush small fish (carp, eel, minnows, shad, and shiners), crayfish, fiddler crabs, small snakes, mice, rats, chicks of other wading birds, insects (beetles, crickets, grasshoppers, and dragonflies), and even some plant matter. In shallow water, the Black-crowned Night-Heron may lure prey by vibrating its bill.
Reproduction
Black-crowned Night-Herons nest in colonies of mixed species. As early as December in Florida, males establish territories with bill snapping, twig shaking, and the construction of a loose platform. Males attract females with a "stretch display"—an exaggerated bow that accentuates the white plumed head. The male gathers twigs and passes them to the female, who constructs a shallow nest in a tree, shrub, or on the ground, and lines it with roots and grasses. For 24 to 26 days, both parents incubate three to five greenish eggs, then brood, feed, and defend the grayish hatchlings.
 


Black-crowned Night-Heron hatchlings feed on regurgitated food from the adults. Within ten days they can clamber out of the nest to avoid predators. After about three weeks, young birds exhibit defense mechanisms, include regurgitation. Depending on age differences, food availability, and brood size, siblings may attack each other. Black-crowned Night-Herons fledge in 6 to 7 weeks and may form small flocks near foraging areas, where they still beg for food from adults. Later they disperse outside the breeding area.

Migration

Black-crowned Night-Herons disperse after breeding, and this movement blends into fall migration which continues through October. Using routes along both coasts and the Mississippi River valley, most herons withdraw from the northern breeding range, but may be permanent residents south of the Carolinas.

  • 2,015,000
  • unknown
Population Status Trends
With a few important, regional exceptions, most Black-crowned Night-Heron populations have been increasing since the 1960s. Increases are most significant in scattered locations like Louisiana, the southern Atlantic coast, many parts of California, and the Dakotas. Regional losses appear widespread and difficult to reverse in southern Florida, southern Minnesota, southeastern Pennsylvania, the St. Lawrence River, the Gulf Coast of Texas, and central Wisconsin. The Black-crowned Night-Heron is listed as "endangered" in Indiana and Pennsylvania, "threatened" in Kentucky, Maine  and New Jersey, a "species of greatest conservation need" in Maryland and New York, and a "species of special concern" in Michigan and Wisconsin.
Conservation Issues
Heron plumes could once fetch $32 per ounce. But the end of the feather trade in the early 1900s, along with the control of DDT in the 1980s, helped stabilize and then increase Black-crowned Night-Heron populations. Recently, the herons have benefited from the spread of aquaculture and islands created by dredging in Texas, Florida, New Jersey, and the Great Lakes. Where their presence is deemed a threat, farm managers can obtain permits to kill and repulse herons with noise makers, like night-heron distress calls. For this species and other wading birds, chemical threats such as insecticides and waste pits at oil refineries may kill up to two million birds per year.
 
Black-crowned Night-Herons occasionally pose threats to other nesting species. Given their omnivorous diet and nocturnal habits, they may enter colonies of ground-nesting species such as gulls, terns, and Piping Plovers, and cause considerable mortality to eggs and probably chicks, as well. Control measures are sometimes deemed necessary where Black-crowned Night-Herons threaten other endangered species
 
Despite this heron's success, many regional populations suffer from long-term declines. Pennsylvania's recent listing of this species as "endangered" cited ongoing habitat loss, perilous population levels, and abandonment of colonies. With over 56% of Pennsylvania's wetlands destroyed, its game commission cites habitat loss as a primary culprit and protects colonies at key locations like the Sheets Island Archipelago, now designated one of Audubon's Important Bird Area.
What You Can Do
Join a nature walk with a local bird club or a state Audubon chapter. Look for Black-crowned Night-Herons in early fall, when the birds have dispersed and are easier to find along the edges of ponds, canals, and marshes.
 
Attend a festival where Black-crowned Night-Herons are often seen, such as California's Morro Bay Winter Bird Festival (Martin Luther King, Jr. weekend each year) , or the Sullys Hill Birding and Nature Festival (June 14-17, 2007) near Devil's Lake, North Dakota.
 
Go online to monitor state and federal designations of waterbirds as "endangered," "threatened," or "species of special concern." Most states provide listings and management plans for birds and critical wetlands. Visit the Pennsylvania Game Commission's site for one such example.
 
For more actions you can take, including Audubon activities, please visit our resources page.
More Information
Visit our resources page for more information about this species.
Natural History References
Davis, W. E., Jr. 1993. Black-crowned Night-Heron (Nycticorax nycticorax). In The Birds of North America, No. 74 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
 
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
 
Medeiros, M. J., E. E. Emond, and B. J. Ploger. "An Unusual Type of Sibling Aggression in Black-Crowned Night Herons." Condor 102:2 (March-April, 2000) 438-440.
 
Noble G. K., M. Wurm, and A. Schmidt. 1938. "Social Behavior of the Black-Crowned Night Heron." Auk 55 (January) 7-40.
 
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, Results and Analysis 1966 - 2005. Version 6.2.2006. USGS Patuxent Wildlife Research Center, Laurel, MD.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York. 2000.
Conservation Status References
"Black-crowned Night-Heron." Endangered Species. Pennsylvania Game Commission. 22 February 2006.
 
Dahl, T. E. 1990. Wetlands: Losses in the United States 1780s to 1980s. U. S. Department of the Interior, Fish and Wildlife Service. Washington, D. C. 13 pages.
 
Davis, W. E., Jr. 1993. Black-crowned Night-Heron (Nycticorax nycticorax). In The Birds of North America, No. 74 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
 

 

"Migratory Bird Mortality: Many Human Caused Threats Afflict Our Bird Populations."  Fact Sheet. U.S. Fish and Wildife Service, Division of Migratory Bird Management. January 2002.
 
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, Results and Analysis 1966 - 2005. Version 6.2.2006. USGS Patuxent Wildlife Research Center, Laurel, MD.
 

Sibley, David Allen. 2000. The Sibley Guide to Birds.New York. Alfred A. Knopf,