The yellow-crowned night heron ( Nyctanassa violacea) is a stocky wading bird. While most herons' diets consist mainly of fish, the yellow-crowned night heron feeds almost exclusively on crustaceans, which accounts for its greater population in coastal areas.
Habitat and Distribution
Yellow-crowned Night Herons breed in and near wetlands primarily in the southeast United States, in areas of abundant crustaceans. Although concentrated on the southern Atlantic Coast, they are regularly found inland as far north as Ohio, Wisconsin, and Minnesota, and sometimes appear in Michigan and Ontario.
This species is found in freshwater wetlands, wooded swamps, and marshes and commonly found in freshwater lowlands and other areas that regularly flood, mangrove forests, and rocky, cliff-bound coasts. They live in two major habitat types.
After the breeding season many individuals disperse to the north and west before migrating to wintering grounds. Wintering areas include the Gulf and Atlantic Coasts. They withdraw from most of northern and inland breeding range in winter, some migrants going as far south as Panama and Lesser Antilles. In late summer, a few wander far to north. Strays from western Mexico reach southwestern United States.
Nesting Habitat
Their breeding habitat includes barrier islands, coastal lowlands, inland lowlands, forests with open understories, mangroves, and edges of lagoons. On islands with limited vegetation, they may nest on rock ledges. In coastal areas they forage along the edges of tidal marshes, tide pools, calm beaches, and lagoons. Inland, they forage along shallow creeks, rivers, ponds, lakes, and swamps, and occasionally on lawns, plowed fields, and other upland sites. The species was introduced into Bermuda in a successful attempt to bring land crabs under control there.
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Physical Characteristics
The yellow-crowned night heron ( Nycticorax violaceus) averages about 25 ounces in weight and is about 22-28 inches long. Their wingspan is a little less than four feet. The length ranges 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 body and back are a smooth grey-blue, with a black scaled pattern on the wings. In flight, feet extend much farther past tip of tail.
It has long yellow to orange legs and a gray body. They have a black head, black bill, red eyes, white cheek patch, and a yellowish-white crown. The 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.
There is little difference in the physical appearance of males and females, though males are slightly larger.
Juvenile night-herons have distinctly different plumage from adults. They lack the yellow crown and plumes, but have the red eyes. Their legs and feet are black.
It takes about three years for yellow-crowned night herons to acquire the full physical appearance of adults. Although the adults are easy to tell apart, juvenile yellow-crowned night heron can look very similar to juvenile black-crowned night heron. The legs and feet are barely visible in black-crowned night-herons.
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Diet and Foraging Behavior
Yellow-crowned Night Herons eat mostly aquatic prey. The yellow-crowned night heron's diet consists mainly of crabs and crayfish. They will also eat fish, eels, mussels, frogs, tadpoles, aquatic insects, snails, and small snakes.
Yellow-crowned Night Herons feed primarily on freshwater and saltwater crustaceans, including marsh crabs, fiddler crabs, ghost crabs, mole crabs, mud crabs, blue crabs, lady crabs, green crabs, rock crabs, and toad crabs. In inland areas they feed almost exclusively on crayfish.
They also eat smaller amounts of earthworms, leeches, marine worms, centipedes, snails, mussels, insects, scorpions, frogs, tadpoles, marine fish, freshwater fish, small snakes, turtles, young birds, and small mammals. They may forage any time of the day and night, although it prefers the night to feed the young. The feeding schedule near coast probably influenced by tides.
Standing still or walking slowly, they forage within several feet of the water’s edge, separated from other foraging individuals by about 15 feet. When within striking distance of prey they lunge with their bills, swallowing smaller animals whole. They grab larger crabs by the legs or pincers and shake them apart, then swallow the pieces whole or use their bills to break them further. Larger prey items tend to be handled longer, but dropped more often. The stout bill seems to be an adaptation for feeding on hard-shelled crustaceans. The species was introduced into Bermuda in a successful attempt to bring land crabs under control there.
Foraging Techniques
Night-herons search for prey in the shallow water. It selects prey visually, either stalking it or standing and waiting for it to come within reach.
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When hunting crayfish, the heron stands at the entrance of the burrow, always facing the sun so its shadow is not cast over the entrance of the burrow, which would alert the crawfish. It can also choose an alternate pattern of walking slowly towards prey with its body bent and its head retracted, then standing and waiting before walking slowly again, sneaking up effectively on unsuspecting crabs. Once close enough, it lunges with its bill.
Small prey are swallowed whole while larger prey (for example, a large crab), it will try to dismember in order to eat the body first and the legs last, or to jab it straight through the body.
Diet Variation
The yellow-crowned night heron is a crustacean-feeding specialist whose diet consists mostly of crabs in coastal areas and crayfish in inland areas.
Adults have a more diverse diet and are less efficient at prey capture than adults. This is more true when food is abundant and the herons forage in flocks.
Nesting Behavior
Yellow-crowned Night Herons nest near or over water in trees such as pine and oak-as high as 60 feet or more off the ground-or on lower vegetation such as mulberry, myrtle, hackberry, and mangrove. On islands with limited vegetation, they may nest on rock ledges. The male chooses the location, and the pair may start several nests before completing one. They nest alone or in colonies of up to several hundred pairs, sometimes with other heron species.
The nest, a platform of sticks with a slight hollow in the center, can measure more than 4 feet across. The male and female build it together as part of their pair bonding. Initially, the male carries sticks to the female, who begins the nest. Later, both gather and place materials on the nest. Where possible, they strip sticks from the limbs of dead trees rather than gathering them from the ground. Sticks can be up to about 20 inches long and an inch thick. The twig nest is sometimes lined with leaves, vines, or Spanish moss. The building process averages about 10 days.
Nest Placement is near or over water in trees such as pine and oak-as high as 60 feet or more off the ground-or on lower vegetation such as mulberry, myrtle, hackberry, and mangrove. On islands with limited vegetation, they may nest on rock ledges. The male chooses the location, and the pair may start several nests before completing one. They nest alone or in colonies of up to several hundred pairs, sometimes with other heron species. The twig nest is sometimes lined with leaves, vines, or Spanish moss. The building process averages about 10 days.
Nesting Facts
- Clutch Size: 2-6 eggs
- Egg Length: 1.8-2.2 in (4.6-5.7 cm)
- Egg Width: 1.2-1.5 in (3-3.7 cm)
- Incubation Period: 24-25 days
- Nestling Period: 30-43 days
- Egg Description: Pale bluish green.
- Condition at Hatching: Helpless, covered in white or pale gray down, with eyes open after 1 day.
General Behavior
Yellow-crowned Night Herons usually walk slowly, using a bent-over posture when foraging, and fly with slow wingbeats. Courting Yellow-crowned Night Herons perform display flights, along with a neck-stretching display: the male slowly raises and then quickly retracts his head while fanning his long shoulder plumes. The female will sometimes reciprocate.
They form socially monogamous pairs, and some maintain their bonds from year to year. Pairs may nest close together, but both adults and young defend the site from intruders, lunging and jabbing with their bills while squawking. Older young may peck or trample younger siblings and even push them out of the nest.
Conservation Status
Yellow-crowned Night Herons are fairly numerous, but their population trends are hard to assess because nesting birds can be hard to see during large standardized surveys. The North American Breeding Bird Survey identified no statistically significant change in their population between 1966 and 2019, although trends suggest a decline.
Partners in Flight estimates the global breeding population at 400,000 and rates them 12 out of 20 on the Continental Concern Score, indicating a species of relatively low conservation concern. Historically, Yellow-crowned Night Herons were hunted as food or for their plumes.
Like all wetland birds, they are vulnerable to habitat loss or degradation. In residential areas where herons nest over houses, roads, and driveways, people sometimes disturb nesting birds on purpose to drive them away.