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yellow-crowned night heron

Nyctanassa violacea

What do they look like?

Yellow-crowned night-herons are medium-sized wading birds, weighing between 650 and 800 g. This species is about 55 to 70 cm in length, from the tip of their bill to the end of their tail, with a wingspan of about 1.1 m. Males and females look very similar, although males are slightly larger. Adult yellow-crowned night-herons have a slate-gray body with a black head, a white streak across both cheeks, and a yellowish crown and plumes. Their bill is black, broad, and stout. Their legs are orange-to-yellow, and their eyes are noticeably red. The feathers of their wings and back have black centers and are edged in light gray, which makes their wings look scaled. Immature yellow-crowned night-herons have different plumage from adults. Juvenile herons are grayish brown across their body and head, with fine white speckles throughout their body. They lack the yellow crown and plumes, but have the red eyes. Their bill and legs are black. Immature yellow-crowned night-herons look similar to juvenile black-crowned night-herons; however, when they fly the feet and part of the legs of yellow-crowned night-herons extend beyond their tail, whereas the feet and legs are barely visible in black-crowned night-herons. Juvenile yellow-crowned night-herons slowly develop adult plumage after several years of molting. (Audubon, 1937; Bull and Farrand, 1994; Riegner, 1982; Watts, 2011)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Range mass
    650 to 800 g
    22.91 to 28.19 oz
  • Range length
    55 to 70 cm
    21.65 to 27.56 in
  • Average wingspan
    1.1 m
    3.61 ft

Where do they live?

Yellow-crowned night-herons (Nyctanassa violacea) are small, semi-nocturnal wading birds that live in freshwater and coastal areas throughout North and South America, especially the southeastern United States, Central America, and northern South America. In North America, their range has increased northward and they can now be found from southern New England, south to Florida, and west to Texas. They are also found further inland along the Mississippi and Minnesota Rivers. Further south, their range includes the coasts of Mexico and Central America, to northern Brazil and Peru. This species is also found on Caribbean islands like the Bahamas, Puerto Rico, Cuba, and the Lesser Antilles. Their breeding grounds are mostly in inland areas of the northern half of their United States range. Their wintering range is in coastal areas of Central and South America. (Audubon, 1937; Bent, 1963; Bull and Farrand, 1994)

What kind of habitat do they need?

Yellow-crowned night-herons live in two major habitat types. In inland areas, they are found in freshwater wetlands, wooded swamps, and marshes. They are also commonly found in freshwater lowlands and other areas that often flood. Along the coast, yellow-crowned night-herons live in salty thickets, lagoons, mangrove forests, and rocky, cliff-bound coasts. They have even been seen on dry islands in the Caribbean Sea, where they have little fresh water. Yellow-crowned night-herons are found in these habitats because they mostly eat aquatic prey. This species builds nests at different heights, from a few meters above the water, to tree branches 12 m above the ground. (Audubon, 1937; Bent, 1963; Bull and Farrand, 1994; Laubhan and Reid, 1991; Laubhan, et al., 1991)

  • Range elevation
    0 to 730 m
    0.00 to 2395.01 ft

How do they reproduce?

Yellow-crowned night-herons are a pair-bonding species that nests either alone or in colonies of four to five nearby nests. When in colonies, pairs build nests on separate trees. Pairs form either during migration or early in the breeding season on the breeding range. Once a pair is formed, the male and female work together to build a nest, but play different roles. The male usually collects materials for the nest and the female stays at the nest site and builds the nest. Where they nest and what they use for nesting can vary depending on their habitat. Nests usually include a platform of sticks with a lining of leaves or needles. In freshwater habitats, oak branches and pine needles are the most common materials used to build nests, though mangrove materials are often used in salty conditions. Herons breeding farther inland in freshwater habitats tend to nest in the upper canopy, away from the center of the tree. In coastal areas, the nests are usually closer to the water, possibly because there are few tall trees available. Low nests are especially common in mangrove swamps. (Bagley and Grau, 1979; Bent, 1963; Laubhan, et al., 1991; Watts, 2011)

While forming pairs and building nests, yellow-crowned night-herons communicate with stretch displays and flight activities. Flight activities involve in-flight behaviors like pursuit, circle flight, and wing flapping, which is used to let mates and other colony members know about breeding activities, like nest building and egg laying. Stretch displays involve a rapid up and down extension of their neck, with their head and bill kept horizontal. They use these displays to communicate with their mates. Yellow-crowned night-herons breed once a year, from early spring to early summer. Pair bonding and nesting occurs from early March to April and the eggs hatch after two to three weeks of incubation. Yellow-crowned night-herons usually have one brood per season, including three to five oval, pale blue-green eggs. If the nest is lost early in the breeding season, they may have a second brood. After hatching, the chicks grow quickly for five weeks and fledge in about their sixth to eighth week. Even after fledging, the juveniles often stay near the nest for a couple more weeks and receive food from their parents and learn how to forage through observation. So, the complete breeding season can end as late as July, when the juveniles have grown and learned enough to survive on their own. (Afkhami and Strassmann, 2007; Audubon, 1937; Bagley and Grau, 1979; Bent, 1963; Bull and Farrand, 1994; Laubhan and Reid, 1991; Watts, 2011)

  • How often does reproduction occur?
    Yellow-crowned night-herons breed once per year.
  • Breeding season
    These birds breed from early spring to mid-summer.
  • Range eggs per season
    3 to 5
  • Range time to hatching
    2 to 3 weeks
  • Range fledging age
    6 to 8 minutes
  • Range time to independence
    10 to 11 weeks
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Yellow-crowned night-herons invest largely in their young. Both males and females care for their offspring, from building the nest to helping the offspring after they fledge. The parents build and defend the nest together, males collect the materials and females build the nest. After the eggs are laid, both parents incubate them, they place one foot on either side of the eggs and lower their body on top. When the eggs hatch, both parents feed their young. One parent leaves the nest to forage and regurgitates the food into the nest for the young to eat. Throughout nest building and offspring care, both the male and female defend the nest and their young. The defending heron stands still or walks toward intruders while thrusting their head forward and vocalizing or snapping their bill. When eggs or young are present, the adults face in opposite directions almost 75% of the time they are together at the nest, which helps them watch for threats. With time, the nestlings slowly lift their heads, stand, walk, flap their wings, and fly. However, even when the juveniles fledge about six to eight weeks after hatching, they return to the nest for a couple more weeks for food. During this time, juveniles learn important skills from their parents, especially how to forage. (Bagley and Grau, 1979; Laubhan and Reid, 1991)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • male
      • female
  • pre-hatching/birth
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning

How long do they live?

There is little information available about the lifespan of yellow-crowned night-herons in the wild or in captivity. However, the transition from juvenile to adult plumage takes about two years. Banding stations in the United States have records of a banded individual that was six years and three months old. This means the species likely lives at least four to six years. (Bent, 1963; Bird Banding Laboratory, 2013; Watts, 2011)

How do they behave?

Outside of breeding, the behaviors of yellow-crowned night-herons are split into two categories: general and foraging. When they are not foraging, adult herons walk slowly through the shallow waters of wetlands, swamps, and coastal thickets and rarely enter deep waters. When they fly, their feet and legs can be seen beyond the end of their tail. Yellow-crowned night-herons flap their wings slowly as they fly. Preening is a common and important behavior for this species. Adults preen themselves and one another, especially after foraging. Foraging behavior involves a slow, stalking motion as night-herons search for prey in shallow water. Once they find prey, they strike quickly and use their wide, stout beak to crush the prey in their mouth. Larger prey tends to be handled longer and dropped more often. Although they live in colonies, they mostly forage alone. A large group of herons in one area may mean there is a good amount of food available. Adults and juveniles spend about the same amount of time doing general and foraging behaviors. Adults are better foragers than juveniles, who learn from the adults by observation. (Audubon, 1937; Bagley and Grau, 1979; Bent, 1963; Bull and Farrand, 1994; Laubhan and Reid, 1991; Laubhan, et al., 1991; Watts, 2011)

Home Range

During the breeding season, adults maintain and protect territories that are at least as large as the nest and nearby area. While breeding, adults forage as far as 15 to 20 meters from the nest. There is little information about the range and territories of the species during migration and wintering. (Audubon, 1937; Bagley and Grau, 1979; Bent, 1963; Bull and Farrand, 1994; Laubhan and Reid, 1991; Laubhan, et al., 1991; Watts, 2011)

How do they communicate with each other?

Yellow-crowned night-herons communicate through sight, sound, and touch. These herons use physical displays mostly for reproduction and nest defense. They perform a greeting ceremony when they approach the nest and a stretch display when they build the nest. The forward display is used to defend the nest against intruders. Yellow-crowned night-herons also communicate by preening, feather ruffling, head scratching, and bill clappering. Adults have six major call types. The most common is the “scaup” call, which is a loud, high-pitched quawk sound. It is usually used when a yellow-crowned night-heron is startled or leaving the colony. There are three calls linked to breeding: the “whoop” call during a stretch display, the “huh” call during pair formation, and the “yup, yup” call during the greeting ceremony. The “ahhh, ahhh” call is more aggressive and used when an intruder is in their nest area. The “squawk” call and the “bill snap” are also aggressive and used for the forward display. (Bagley and Grau, 1979; Bull and Farrand, 1994; Watts, 2011)

What do they eat?

Yellow-crowned night-herons mostly eat aquatic prey. Over 80% of their diet is made up of crayfish and crabs, especially fiddler crabs, marsh crabs, and green crabs. Their wide, stout beak is good for crushing crustaceans. Herons found in inland areas eat mostly crayfish, while coastal herons mostly eat crabs. They also eat other aquatic prey such as mussels, snails, aquatic worms and insects, leeches, amphibians (both frogs and tadpoles), and small fish such as eels and pipefish. This species also hunts lizards, snakes, small mammals, and young birds that fall out of their nest. Yellow-crowned night-herons have been seen foraging at all hours of the day. They forage alone by walking slowly through the wetland or coastal thicket and stalking for prey in the water. The herons select prey by sight, at least partly by size. They spend more time handling larger prey and are more likely to drop them. Juveniles have a more diverse diet and are not as good at capturing prey as adults. In big groups, juveniles are often outcompeted for food by adults. (Audubon, 1937; Bent, 1963; Martínez, 2004; Riegner, 1982; Watts, 2011)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • aquatic crustaceans

What eats them and how do they avoid being eaten?

Adult yellow-crowned night-herons have no direct predators, but humans sometimes hunt them for game and food. American crows often eat yellow-crowned night-heron eggs from nests. (Audubon, 1937; Bent, 1963; Laubhan and Reid, 1991; Watts, 2011)

  • Known Predators
    • American crows (Coruvs brachyrhynchos)

What roles do they have in the ecosystem?

Yellow-crowned night-herons impact their ecosystem as predators. They prey on crayfish, crabs, small fish, snakes, insects, lizards, young birds, and small mammals. However, they usually specialize in crustacean prey and have big impacts on crab and crayfish populations. Other than human hunting, adults of this species are not usually preyed upon. Outside of predation, yellow-crowned night-herons are an intermediate host of the eastern equine encephalomyelitis (EEE) virus. (Bent, 1963; Hassan, et al., 2003; Laubhan, et al., 1991; Martínez, 2004; Riegner, 1982; Watts, 2011)

Do they cause problems?

Like any large bird, yellow-crowned night-herons can bite, but are rarely aggressive to humans. Usually, yellow-crowned night-herons quietly sneak away from humans and return when the area is undisturbed. This species can also transfer diseases. Yellow-crowned night-herons are an intermediate host of the eastern equine encephalomyelitis (EEE) virus, or sleeping sickness, which is common in the southeastern United States. Yellow-crowned night-herons receive the virus from mosquitoes. The virus can then be transmitted to a wider range of mosquito species that then transmit the virus to horses and humans, which are dead end hosts. Because the EEE virus causes mortality in horses and seizures or death in humans, the presence of yellow-crowned night-herons can have a negative effect on humans by transmitting the virus. (Bent, 1963; Hassan, et al., 2003)

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings
    • carries human disease

How do they interact with us?

Outside of game hunting, yellow-crowned night-herons have no major positive effects on humans. (Bent, 1963; Watts, 2011)

  • Ways that people benefit from these animals:
  • food

Are they endangered?

Yellow-crowned night-herons are sometimes hunted for food. However, none of this hunting has caused a severe threat to its population. In fact, their breeding range has been expanding northward in recent decades. (Bent, 1963; Bull and Farrand, 1994; Watts, 2011)

Some more information...

Contributors

Frank Stabile (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

Afkhami, M., J. Strassmann. 2007. Adult yellow-crowned night-herons face in opposite directions at the nest. The Wilson Journal of Ornithology, 119: 747-749.

Audubon, J. 1937. The Birds of America. New York: The Macmillian Company.

Bagley, F., G. Grau. 1979. Aspects of the yellow-crowned night-heron reproductive behavior. Proceedings of the Colonial Waterbird Group, 3: 165-175.

Bent, A. 1963. Life Histories of North American Marsh Birds. New York: Dover Publications.

Bird Banding Laboratory, 2013. "Yellow-crowned night-heron" (On-line). United States Geological Survey. Accessed October 23, 2013 at https://www.pwrc.usgs.gov/BBL/longevity/Longevity_main.cfm.

Bull, J., J. Farrand. 1994. National Audubon Society Field Guide to Birds: Eastern Region. New York: Chanticleer Press.

Hassan, H., E. Cupp, G. Hill, C. Katholi, K. Klingler, T. Unnasch. 2003. Avian host preference by vectors of eastern equine encephalomyelitis virus. American Journal of Tropical Medicine and Hygiene, 69: 641-647.

Laubhan, M., F. Reid. 1991. Characteristics of the yellow-crowned night-heron nests in lowland hardwood forests of Missouri. Wilson Bulletin, 101: 486-491.

Laubhan, M., D. Rundle, B. Swartz, F. Reid. 1991. Diurnal activity and foraging success of yellow-crowned night-herons in seasonally flooded wetlands. Wilson Bulletin, 103: 272-277.

Martínez, C. 2004. Food and niche overlap of the scarlet ibis and the yellow-crowned night-heron in a tropical mangrove. Waterbirds, 27: 1-8.

Riegner, M. 1982. The diet of yellow-crowned night-herons in the eastern and southern United States. Colonial Waterbirds, 5: 173-176.

Watts, B. 2011. "Yellow-crowned Night-heron (Nyctanassa violacea)" (On-line). The Birds of North America Online. Accessed October 23, 2013 at http://bna.birds.cornell.edu/bna/species/161.

 
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Stabile, F. 2014. "Nyctanassa violacea" (On-line), Animal Diversity Web. Accessed July 19, 2018 at http://www.biokids.umich.edu/accounts/Nyctanassa_violacea/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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