Summary

Did you know?

Great Blue Herons have been known to choke to death when trying to swallow a fish that is too large.

State Ranking Justification

Great Blue Herons are considered a local and common breeder in upstate New York. The second Breeding Bird Atlas reported 478 confirmed breeding blocks (McGowan and Corwin 2008) representing breeding in 55 of 62 counties. The number of confirmed breeding blocks has doubled since the first Breeding Bird Atlas (Andrle and Carroll 1988 and McGowan and Corwin 2008). While populations appear to be stable, habitat loss still poses a threat to this species. At this time, New York Natural Heritage tracks rookeries with greater than 50 active nests. Most rookeries in New York have fewer than 50 active nests.

Short-term Trends

It appears that there has been an increase in Great Blue Heron rookeries between the first Breeding Bird Atlas (1980-1985) and the second Breeding Bird Atlas 2000 (2000-2005) with the number of confirmed breeding blocks increasing from 212 to 478 blocks (Andrle and Carroll 1988, McGowan and Corwin 2008). Great Blue Herons continue to nest in nearly all of New York State excluding the Coastal Lowlands (McGowan and Corwin 2008). Breeding Bird Survey analysis indicates a slight delcine of 0.7% per year between 1980 and 2006 (Sauer et al. 2007).

Long-term Trends

Great Blue Heron populations decreased during the late 1800s and early 1900s, mostly due to shooting and habitat loss. Breeding populations along the Coastal Lowlands were eliminated in New York. Populations most likely started to rebound with the recovery of beaver populations in the state. Beaver activities resulted in flooding of lowlands that provided additional nesting and foraging habitat for Great Blue Herons. A five-year study conducted with the Federation of New York Bird Clubs (currently known as the New York State Ornithological Association) to assess Great Blue Heron populations found that 41 rookeries were active for at least one year during the study period. Aerial surveys of 110 rookeries that were reported by various scientific organizations and scientists were conducted between 1972 and 1981. These surveys concluded that Great Blue Heron nesting abundance likely increased since the mid-1960s (Andrle and Carroll 1986). Breeding Bird Survey analysis indicated a population increase of 1.4% per year from 1966 to 2006 (Sauer et al. 2007).

Conservation and Management

Threats

One of the more significant threats faced by Great Blue Herons is the loss of habitat. New York State has lost over half of its wetlands since colonization (Tiner 1984 cited in NatureServe 2003). More recently, losses of wetlands in the Lake Plains portion of the state have been offset as agricultural lands revert back to wetlands, although net losses of wetlands in the Hudson Valley continue. Equally important, the quality of remaining habitat is often degraded by fragmentation, exotic plants, and nutrient enrichment (Riexinger, personal communication, October 31, 2003). During the late 1800s many species of herons were persecuted for their feathers, although Great Blue Heron populations were not as damaged by this as other heron species (Cornell Lab of Ornithology 2003). While this practice no longer continues, shooting in some areas may still pose a threat to this species.

Conservation Strategies and Management Practices

Efforts should be made to maintain the quantity and quality of habitats where Great Blue Herons are breeding as well as nearby areas that are used for foraging. Great Blue Herons usually need several areas to forage, in order to support a rookery.

Habitat

Habitat

Typically, Great Blue Heron habitat includes freshwater and brackish marshes that are near lakes, rivers, bays, lagoons, ocean beaches, fields, or meadows. Nests tend to be high in the trees of swamps and wooded areas.

Associated Ecological Communities

• Brackish tidal marsh (guide)
  A marsh community that occurs where water salinity ranges from 0.5 to 18.0 ppt, and water is less than 2 m (6 ft) deep at high tide. The vegetation in a brackish tidal marsh is dense and dominated by tall grass-like plants.
• Common reed marsh
  A marsh that has been disturbed by draining, filling, road salts, etc. in which common reed (Phragmites australis) has become dominant.
• Estuarine common reed marsh
  A tidal marsh dominated by non-native reedgrass (Phragmites australis). Estuarine reedgrass marshes may become established in tidal freshwater, brackish, and salt marsh settings. Establishment usually follows alteration of the original marsh through impacts such as dredging, ditching, or impounding water.
• Floodplain forest (guide)
  A hardwood forest that occurs on mineral soils on low terraces of river floodplains and river deltas. These sites are characterized by their flood regime; low areas are annually flooded in spring, and high areas are flooded irregularly.
• Freshwater intertidal mudflats (guide)
  A sparsely vegetated community characterized by low rosette-leaved aquatics. This community occurs on exposed intertidal mudflats where the water is fresh (salinity less than 0.5 ppt). This community is best developed where mudflats are nearly level so that broad expanses are exposed at low tide. The plants are completely submerged in 0.9 to 1.2 m (3 to 4 ft) of water at high tide and they are usually coated with mud.
• Freshwater intertidal shore (guide)
  A community of the intertidal gravelly or rocky shores of freshwater tidal rivers and creeks, sometimes occurring at the base of cliffs. The vegetation may be very sparse.
• Freshwater tidal marsh (guide)
  A marsh community that occurs in shallow bays, shoals, and at the mouth of tributaries of large tidal river systems, where the water is usually fresh (salinity less than 0.5 ppt), and less than 2 m (6 ft) deep at high tide. Typically there are two zones in a freshwater tidal marsh: a low-elevation area dominated by short, broadleaf emergents bordering mudflats or open water, and a slightly higher-elevation area dominated by tall grass-like plants.
• Impounded swamp
  A swamp (with at least 50% cover of trees) where the water levels have been artificially manipulated or modified, often for the purpose of improving waterfowl habitat. Red maple is a characteristic tree. Often there are many standing dead tree trunks. Purple loosestrife and duckweed may become dominant in the understory.
• Perched swamp white oak swamp (guide)
  A swamp that occurs in a shallow depression on a forested hillside where the water table is locally perched above the surrounding groundwater level. The water level fluctuates seasonally; the swamp may be flooded in spring and nearly dry by late summer. The dominant tree is swamp white oak, which may form a nearly pure, open canopy stand in areas that are permanently saturated.
• Red maple-blackgum swamp (guide)
  A maritime, coastal, or inland hardwood swamp that occurs in poorly drained depressions, sometimes in a narrow band between a stream and upland. Red maple and blackgum are often codominant or blackgum may be the dominant tree. Pitch pine may occur on drier hummock islands in pine barrens settings.
• Red maple-hardwood swamp (guide)
  A hardwood swamp that occurs in poorly drained depressions, usually on inorganic soils. Red maple is usually the most abundant canopy tree, but it can also be codominant with white, green, or black ash; white or slippery elm; yellow birch; and swamp white oak.
• Silver maple-ash swamp (guide)
  A hardwood basin swamp that typically occurs in poorly-drained depressions or along the borders of large lakes, and less frequently in poorly drained soils along rivers. These sites are characterized by uniformly wet conditions with minimal seasonal fluctuations in water levels. The dominant trees are usually silver maple and green ash.

Range

New York State Distribution

Currently, breeding Great Blue Herons occur throughout the state excluding the Coastal Lowlands where it is a nonbreeding summer visitor. The last known breeding record from the Coastal Lowlands was on Gardiners Island during the late 19th century (Levine 1998). Most Great Blue Herons leave New York for the winter, but some stay where open water persists. Usually, they can be found along the coast and more rarely along the shores of the Great Lakes when open water is present.

Global Distribution

Great Blue Herons breed from southeastern Alaska across southern Canada to Nova Scotia and south to southern Mexico, the Greater Antilles, the Virgin Islands (St. Thomas and Anegada), islands off coastal Venezuela, and on the Galapagos. Non-breeding birds are found from southeastern Alaska, the central United States, and southern New England south to northern South America (mainly to northern Colombia and northern Venezuela). During the winter in the Unites States, the highest densities occur along the lower Colorado River, around the Great Salt Lake, and near Aransas National Wildlife Refuge on the Texas coast (Root 1988). They are known to wander widely outside their usual range; they have been reported a few times as far as Hawaii. Some subadults may spend the summer in their non-breeding range.

Best Places to See

• Iroquois National Wildlife Refuge (Orleans County)
• Lower Schodack Island (Rensselaer County)

Identification Comments

Identifying Characteristics

Great Blue Herons are large, gray-blue birds with long brownish or green legs and long "s"-shaped necks. They measure 97-113 centimeters (38-54 inches) in height. Their wingspan is between 167 centimeters (66 inches) and 201 centimeters (79 inches) and they can weigh 2100-2500 grams (74.12-88.25 ounces). Great Blue Herons have a white forehead with a black stripe that extends above the eye and a white foreneck streaked with black. The bill is thick and yellowish. Eyes are yellow. During the breeding season, adults have ornate plumes on their head, neck, and back. Non-breeding adults do not have ornate plumes and their bill is more yellow. Sexes are similar. Juveniles have a black crown without ornate plumes. Great Blue Herons typically nest in colonies, also known as heronries or rookeries, but can also be solitary nesters. Nests vary in size from 0.5 meters (19 inches) across to 0.9-1.2 meters (3-4 feet) across. They build their nest out of sticks and line the shallow depression with fine twigs, moss, pine needles, or grass. The birds continue to add materials to the nest during incubation through rearing their young. Nests are usually 7.6-30.5 meters (25-100 feet) off the ground. Eggs are a dull, pale blue. The clutch size is typically 2-6 eggs. The Great Blue Heron call is a deep, hoarse croak ("frahnk, frahnk, frahnk").

Best Time to See

Great Blue Herons are usually present in New York year-round, but are more abundant during their breeding season from mid-April through the end of July. Generally, they tend to be crepuscular, but they can also be active during the day and night. They can be found near areas with open water usually standing still in the more shallow areas. Winter distribution is more restricted than during other seasons and varies from year to year depending on the severity of the winter weather and availability of open water.

Similar Species

• Little Blue Heron (Egretta caerulea) (guide)
  Little Blue Herons are smaller and more slender than Great Blue Herons. They are also a uniform gray color and lack plumes on the head. Their bill is dark with a bluish base unlike herons whose bill is a yellowish color.
• Tricolored Heron (Egretta tricolor) (guide)
  Tricolored Herons are more slender, have white plumes on the head, and a white belly that contrasts with the dark chest.
• Sandhill Crane (Grus canadensis)
  The Sandhill Crane is larger than the Great Blue Heron, has a shorter bill, a red cap, and bushy feathers on the rump. Also, Sandhill Cranes are found in fields rather than aquatic areas.

Great Blue Heron Images

Taxonomy

Great Blue Heron
Ardea herodias Linnaeus, 1758

• Kingdom Animalia
  • Phylum Craniata
    • Class Aves (Birds)
      • Order Pelecaniformes (Pelicans and Cormorants)
        • Family Ardeidae (Herons, Bitterns, and Egrets)

Additional Resources

References

Allen, H. 1991. The great blue heron. NorthWord Press, Inc. 175 pp.

American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.

Andrle, Robert F. and Janet R. Carroll, editors. 1988. The atlas of breeding birds in New York State. Cornell University Press. 551 pp.

Bull, John. 1974. Birds of New York State. Doubleday, Garden City, New York. 655 pp.

Cornell Lab of Ornithology. 2003. All about birds [web application] Copyright 2003. Available http://www.birds.cornell.edu/programs/AllAboutBirds/BirdGuide/Great_Blue_Heron.html. (Accessed: March 28, 2005).

DeMauro, M. M. 1993. Colonial nesting bird responses to visitor use at Lake Renwick heron rookery, Illinois. Natural Areas Journal 13:4-9.

Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1992. Birds in Jeopardy: the Imperiled and Extinct Birds of the United States and Canada, Including Hawaii and Puerto Rico. Stanford University Press, Stanford, California. 259 pp.

Fleury, B. E., and T. W. Sherry. 1995. Long-term population trends of colonial wading birds in the southern United States: the impact of crayfish aquaculture on Louisiana populations. Auk 112:613-632.

Gibbs, J. P. 1991. Spatial relationships between nesting colonies and foraging areas of great blue herons. Auk 108:764-770.

Levine, E. 1998. Bull's birds of New York State. Comstock Publishing Associates, Ithaca, NY.

McGowan, K.J. and K. Corwin, eds. 2008. The Second Atlas of Breeding Birds in New York State: 2000-2005. Cornell University Press, Ithaca, NY. 688 pp.

McNeil, R., R. Benoit, and J.-L. Desgranges. 1993. Daytime and nighttime activity at a breeding colony of great blue herons in a nontidal environment. Can. J. Zoool. 71:1075-1078.

NatureServe. 2003. NatureServe Explorer: An online encyclopedia of life [web application]. Version 1.8. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer. (Accessed: January 26, 2004).

New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.

Palmer, R. S. (editor). 1962. Handbook of North American birds. Vol. 1. Loons through flamingos. Yale University Press, New Haven. 567 pp.

Parker, J.E. and G.R. Maxwell. 1969. Selected maintenance behavior in a Great Blue Heron colony on Ironsides Island, New York. Kingbird 19:192-199.

Payne, R. B., and C. J. Risley. 1976. Systematics and evolutionary relationships among the herons (Ardeidae). Univ. Michigan Mus. Zool., Misc. Publ. No. 150. 115 pp.

Powell, G.V.N. 1987. Habitat use by wading birds in a subtropical estuary: implications of hydrography. Auk 104:740-749.

Pratt, H. D., P. L. Bruner, and D. G. Berrett. 1987. A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press, Princeton, New Jersey. 409 pp. + 45 plates.

Root, T. 1988. Atlas of wintering North American birds: An analysis of Christmas Bird Count data. University of Chicago Press. 336 pp.

Sauer, J.R., J.E. Hines, and J. Fallon. 2007. The North American breeding bird survey, results and analysis 1966-2006. Version 10.13.2007. US Geological Survey, Patuxent Wildlife Research Center, Laurel, MD.

Spendelow, J. A. and S. R. Patton. 1988. National Atlas of Coastal Waterbird Colonies in the Contiguous United States: 1976-1982. U.S. Fish and Wildlife Service, Biological Report 88(5). x + 326 pp.

Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.

Tiner, R.W. 1984. Wetlands of the United States: current status and recent trends. U.S. Fish and Wildlife Service. Newton Corner, MA. 59 pp.

Links

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• NatureServer Explorer

About This Guide

Information for this guide was last updated on: December 10, 2008

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Ardea herodias. Available from: https://guides.nynhp.org/great-blue-heron/. Accessed December 8, 2023.