Black-crowned
Night Heron
Common name:
Black-crowned night-heron
Class: Aves
Order: Ciconiformes
Family: Ardeidae
Genus: Nycticorax
Species: Nycticorax nycticorax
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photo M. Noonan |
Taxonomy/ description
The Black-crowned Night Heron has a stocky body,
with a short neck and legs. Adult night heron’s have a distinctive
coloring, with a black cap and upper back, gray wings, rump and
tail, and a white to pale gray underbelly. Its bill is stout and
black, and its eyes are red. For most of the year, the legs of an
adult night heron are yellow-green, but by the height of the
breeding season, they turn pink. The eyes of the juvenile
black-crowned night heron are yellowish or amber, and the dull gray
legs lack the colorful pigmentation of those of the adult. The
juvenile also has a brown head, neck, chest and belly streaked with
white. The wings and back are darker brown, though the tips of the
feathers have large white spots.
Habitat/ diet
The black-crowned night heron is found across North America from
Washington through Quebec, south through coastal Mexico, as well as
locally in Central America and the Caribbean. Some winter as far
north as Oregon and the New England states.
Most colonies of
black-crowned night herons are associated with large wetlands. They
inhabit a variety of wetland habitats such as swamps, streams,
rivers, marshes, mud flats and the edges of lakes that have become
overgrown with rushes and cattails. The black-crowned night heron’s
diet consists mainly of fish, though it also eats as leeches,
earthworms, and insects. It also eats crayfish, mussels, squid,
amphibians, lizards, snakes, rodents, birds, eggs, carrion, plant
materials, and garbage and refuse at landfills.
Black-crowned
night-herons are usually solitary foragers, and strongly defend
their feeding territory. The night heron prefers to feed in shallow
waters, where it grasps its prey with its bill instead of stabbing
it. A technique called 'bill vibrating,' which is opening and
closing the bill rapidly in water, creates a disturbance which may
lure prey. Evening to early morning are the usual times it feeds,
but when food is in high demand, such as during the breeding season,
it will feed at any time of the day.
photo M. Noonan
Behavior/ reproduction
Black-crowned night herons are social at all times of the year,
associating with other species of herons frequently. In the winter,
it roosts communally. It is also a migrating species. The fact that
this night heron feeds throughout the night means that it avoids
competition with day herons which use the same habitat. Feeding
sites are used repeatedly. Black-crowned night herons defend both
feeding and nesting territory. Also, their young can be aggressive,
regurgitating or defecating on human intruders.
Black-crowned Night Herons are thought to be monogamous. Pair
formations are signaled by males becoming aggressive and performing
snap displays, in which they walk around in a crouched position,
head lowered, snapping their bills together or grasping a twig. The
snap display is then followed by the advertisement display,
sometimes called the stretch, snap-hiss, or song and dance display,
to attract females. In this display a male stretches his neck out
and bobs his head, and when his head is level with his feet, he
gives a snap-hiss vocalization. Females that come near the
displaying male are rejected at first, but eventually a female is
allowed to enter his territory. Mating usually takes place on or
near the nest, and begins the first or second day after the pair is
formed. There is one brood per season. Black-crowned night herons
nest colonially, and often there can be more than a dozen nests in
one tree. The nest is built near the trunk of a tree or in the fork
of branches. The eggs are laid at 2 day intervals, beginning 4-5
days after pair formation. Incubation, which lasts 24-26 days, is
carried out by both adults. After 2 weeks, the young leave the nest.
By 3 weeks, they can be found clustered at the tops of trees if they
are disturbed. By Week 6-7 they fly well and depart for the feeding
grounds. Adult black-crowned night herons do not recognize their own
young and will accept and brood young from other nests. The young
have a tendency to regurgitate their food onto intruders when
disturbed.
Where to see them in WNY
One good place to find the Black-crowned night-heron is on the
Swallow Hollow Trail at the Iroquois National Wildlife Refuge. From
the parking lot, take the trail heading to the left. Be sure to
begin looking once you reach the earthen dike; emergent marshes like
this one are great habitats for these birds. |