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Black-crowned Night-Heron

Nycticorax nycticorax ORDER: PELECANIFORMES FAMILY: ARDEIDAE

IUCN Conservation Status: Least Concern

Black-crowned Night-Herons are stocky birds compared to many of their long-limbed heron relatives. They’re most active at night or at dusk, when you may see their ghostly forms flapping out from daytime roosts to forage in wetlands. In the light of day adults are striking in gray-and-black plumage and long white head plumes. These social birds breed in colonies of stick nests usually built over water. They live in fresh, salt, and brackish wetlands and are the most widespread heron in the world.

Birds of North America Online
Yard Map Birds Eye View

At a GlanceHelp

Measurements
Both Sexes
Length
22.8–26 in
58–66 cm
Wingspan
45.3–46.5 in
115–118 cm
Weight
25.6–35.8 oz
727–1014 g
Relative Size
Larger than a Green Heron; smaller and thicker-bodied than a Great Egret.
Other Names
  • Bihoreau à couronne noire (French)
  • Yaboa real, Guanaba, Guaco (Spanish)

Cool Facts

  • The familiar evening sight and sound of the Black-crowned Night-Heron was captured in this description from Arthur Bent’s Life Histories of North American Marsh Birds: “How often, in the gathering dusk of evening, have we heard its loud, choking squawk and, looking up, have seen its stocky form, dimly outlined against the gray sky and propelled by steady wing beats, as it wings its way high in the air toward its evening feeding place in some distant pond or marsh!”
  • Scientists find it easy, if a bit smelly and messy, to study the diet of young Black-crowned Night-Herons—the nestlings often disgorge their stomach contents when approached.
  • Black-crowned Night Heron nest in groups that often include other species, including herons, egrets, and ibises.
  • A breeding Black-crowned Night-Heron will brood any chick that is placed in its nest. The herons apparently don’t distinguish between their own offspring and nestlings from other parents.
  • Young Black-crowned Night-Herons leave the nest at the age of 1 month but cannot fly until they are 6 weeks old. They move through the vegetation on foot, joining up in foraging flocks at night.
  • The oldest Black-crowned Night-Heron on record was 21 years, 1 month old.

Habitat


Marsh

Black-crowned Night-Herons are common in wetlands across North America, including saltmarshes, freshwater marshes, swamps, streams, rivers, lakes, ponds, lagoons, tidal mudflats, canals, reservoirs, and wet agricultural fields. They require aquatic habitat for foraging and terrestrial vegetation for cover. They spend the winter in southern and coastal portions of their breeding range as well as across Mexico and Central America, where they use mangroves, marshes, swamps, lagoons, and flooded rice fields.

Food


Fish

Black-crowned Night-Herons are opportunists feeders that eat many kinds of terrestrial, freshwater, and marine animals. Their diet includes leeches, earthworms, insects, crayfish, clams, mussels, fish, amphibians, lizards, snakes, turtles, rodents, birds, and eggs. They also eat carrion, plant materials, and garbage from landfills. Rather than stabbing their prey, they grasp it in their bills. Black-crowned Night-Herons normally feed between evening and early morning, avoiding competition with other heron species that use the same habitat during the day. They may feed during the day in the breeding season, when they need extra energy for nesting.

Nesting

Nesting Facts
Clutch Size
3–5 eggs
Number of Broods
1 broods
Egg Length
2–2.2 in
5–5.6 cm
Egg Width
1.4–1.5 in
3.6–3.9 cm
Incubation Period
24–26 days
Nestling Period
29–34 days
Egg Description
Greenish-blue.
Condition at Hatching
Mostly helpless, covered with gray and white down, with open eyes.
Nest Description

The male starts building the nest, a platform of sticks, twigs, and other woody vegetation which he collects from the ground (or breaks right off of the trees). Once he has found a mate, the male continues collecting material but passes it to the female, who works it into the nest. Some nests are sturdy, while others are flimsy. They measure 12–18 inches across and 8–12 inches high.

Nest Placement

Tree

The male chooses a nest site in a tree or in cattails—usually in a habitat safe from predators such as on an island, in a swamp, or over water—and then advertises for a female. Black-crowned Night-Herons nest colonially, often with a dozen nests in a single tree. Colonies sometimes last for 50 years or more.

Behavior


Stalking

Black-crowned Night-Herons nest colonially and behave socially all year long. Both males and females vigorously defend feeding and nesting territories, sometimes striking with their bills and grabbing each other’s bills or wings. Night-herons are probably monogamous. The male advertises for a mate with displays that involve bowing and raising the long plume on his head. Both the male and the female incubate the eggs and brood the chicks, greeting each other with calls and raised feathers when switching over duties. The young leave the nest at the age of 1 month and move through the vegetation on foot, forming nocturnal flocks in feeding areas. They learn to fly when they are 6 weeks old, and then disperse widely.

Conservation

status via IUCN

Least Concern

Black-crowned Night-Herons are fairly common and North American Breeding Bird Survey data suggest their populations are stable—although their clumped distributions make it hard to estimate trends precisely. The Waterbird Conservation Plan indicates this species is of moderate concern, with more than 50,000 individuals in North America but a possibly declining population trend. Threats include draining and development of their wetland habitat, and reduced water quality due to contaminated runoff. They are susceptible to accumulating pollutants such as persistent organochlorine pesticides, PCBs, and heavy metals. Colonies of Black-crowned Night-Herons can provide good indications of overall environmental quality, because night-herons forage at the top of food chain, nest in colonies (where they are fairly easy to study), and have a wide distribution. They tolerate disturbances such as traffic, so they are especially useful in revealing environmental deterioration in urban environments.

Credits

Range Map Help

Black-crowned Night-Heron Range Map
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Migration

Resident to medium-distance migrant. Some populations stay in one place year-round, while others disperse short distances of 5–60 miles. Others migrate farther, such as from Massachusetts to Florida and the Caribbean, or from Alberta to Mexico and Cuba. Migrants follow the coast or the Mississippi River flyway.

Find This Bird

Black-crowned Night-Herons are common in wetlands across North America—you just may have to look a little harder than you do for most herons. True to their name, these birds do most of their feeding at night and spend much of the day hunched among leaves and branches at the water’s edge. Evening and dusk are good times to look for these rather stout, short-necked herons flying out to foraging grounds.