Species Profile

Scientific name: Nyctanassa violacea

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Current Status: In Pennsylvania, the yellow-crowned night-heron is listed as state endangered and protected under the Game and Wildlife Code. Nationally, they are not listed as an endangered or threatened species. All migratory birds are protected under the federal Migratory Bird Treaty Act of 1918.

Population Trend: Yellow-crowned night-herons (Nyctanassa violacea) are one of the state's rarest nesting birds. They are rare, regular visitors or residents in the Piedmont region of southeastern Pennsylvania (all or parts of Bucks, Northampton, Lehigh, Berks, Lebanon, Lancaster, Dauphin, York, Adams and Cumberland counties), where they breed locally. In the coastal plain area along the Delaware River near Philadelphia, they are rare, irregular visitors. They are accidental visitors elsewhere in the state, particularly in late summer following the breeding season. Currently, the only known breeding site is in an urban setting in Dauphin County. Nests were once also found along Conestoga and Little Conestoga creeks in Lancaster County, Conodoquinet Creek in Cumberland County, Bellevue Park in Dauphin County (as recently as 2011) and Kiwanis Lake in York County. Surveys in the 1990s counted not more than eight to 12 nests in any year in the state. Yellow-crowned night-herons were first listed as threatened species in 1990 because of their limited population and restricted range. They were downgraded to endangered in 1999 because of their small and vulnerable population.

Identifying Characteristics: Adults are medium-sized, 22 to 28 inches in length from bill tip to tail tip, gray with a black head and whitish cheek patch and crown. Eyes are red and legs yellowish, except during courtship when they turn coral pink to scarlet. Their name identifies a distinguishing characteristic – the yellowish crown, or top of the head. Immature birds are brown, finely spotted and streaked with white buff. Yellow-crowned night-herons have a more slender profile than the similar black-crowned night-heron (Nycticorax nycticorax) and a slimmer, longer-looking neck. They also have longer legs than their cousins so the entire foot extends past the tail when it is in flight. The juveniles have narrow, sharply defined streaks on their neck and breast. Night herons are considered crepuscular and nocturnal, being more active in early morning and evening, and at night.

Biology-Natural History: Pennsylvania lies at the northern edge of this species' breeding range, which is mainly in the southcentral United States and parts of Central and South America. Yellow-crowned night-herons nest singly or in small groups in the lower reaches of the Susquehanna River. Adults will return to the same nest tree for decades. A typical clutch contains three or four pale bluish-green eggs. Nesting starts as early as April. By mid-summer, most young have fledged. Yellow-crowned night-herons predominantly eat cray-fish, but will eat other invertebrates if crayfish are not abundant. Crayfish are a major part of this bird's diet in Pennsylvania, however.

Preferred Habitat: This bird feeds mainly along small, shallow streams. It nests in brush or trees, usually sycamores, found on islands or along streams. Most nests found in recent years are along the Susquehanna River and its tributaries in suburban and urban areas of Cumberland and Dauphin Counties. Yellow-crowned night-herons seem more tolerant of human activities than other herons and will nest in neighborhoods with a park-like setting. They are known to nest within 100 yards of houses and roads and may place their nest over a roof or driveway, which can cause conflicts with humans. 

Reasons for Being Endangered: As a breeding bird, the combination of rarity, tendency to nest in small groups, and nesting near human dwellings makes this species particularly vulnerable to local habitat disturbance or loss. The largest nesting colony known in Pennsylvania, representing more than half the state's known breeding population, was on a small Susquehanna River island, located offshore of the Governor's residence. It subsequently moved to the mouth of the Conodoquinet Creek, but human disturbance dispersed the colony. Degradation of water quality, along with loss of the primary food source – crayfish – is an ever-present threat. Yellow-crowned night-herons, like so many birds that dwell near human dwellings, require some tolerance and understanding from the people who share their environment.  

Management Practices: As a Pennsylvania endangered species, nesting colonies are protected through the Pennsylvania Natural Heritage Program and the Environmental Review process. Colonies are monitored through the Pennsylvania Game Commission Colonial Waterbird Program. Studies on habitat requirements and disturbance tolerance are needed to better understand factors limiting this population. Education and outreach programs can help to garner community support for this rare bird. Watershed protection efforts to reduce polluted runoff will greatly benefit this, and other, waterbird species.

Sources:
McWilliams, G. M. and D. W. Brauning. 2000. The Birds of Pennsylvania. Cornell University Press, Ithaca, New York.

Shutsky, R. M. 1992. Yellow-crowned Night-Heron (Nycticorax violaceus). Pages 62-63 in Atlas of Breeding Birds in Pennsylvania. (D. W. Brauning, ed.) University of Pittsburgh Press, Pittsburgh, PA.

Watts, Bryan D. 1995. Yellow-crowned Night-Heron ( Nyctanassa violacea), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.

Suggested Further Reading:
Crossley, G. J. (Compiler). 1999. A Guide to Critical Bird Habitat in Pennsylvania: Pennsylvania Important Bird Areas Program. Pennsylvania Audubon Society, Harrisburg, PA

Hancock, J. and H. Elliot. 1978. The Herons of the World. Harper & Row, Publishers, New York, NY. p. 124-128.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Search for "yellow-crowned night-heron."

Pennsylvania Audubon. 2005. Important Bird Area Conservation Plans. Pennsylvania Audubon Society, Harrisburg, PA.

Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission. 2005. Pennsylvania Wildlife Action Plan, version 1. Harrisburg, Pennsylvania.