Great blue heron
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The great blue heron (Ardea herodias) is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America, as well as far northwestern South America, the Caribbean and the Galápagos Islands. It is occasionally found in the Azores and is a rare vagrant to Europe. An all-white population found in south Florida and the Florida Keys is known as the great white heron. Debate exists about whether these white birds are a color morph of the great blue heron, a subspecies of it, or an entirely separate species.<ref name="fws">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="sibleyguides">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
TaxonomyEdit
The great blue heron was one of the many species originally described by Carl Linnaeus in his 18th-century work, Systema Naturae.<ref>Template:Cite book</ref> The scientific name comes from Latin {{#invoke:Lang|lang}}, and Ancient Greek {{#invoke:Lang|lang}} (Template:Transliteration), both meaning "heron".<ref name=job>Template:Cite book</ref>
The great blue heron's niche in the Old World is filled by the congeneric grey heron (Ardea cinerea), which is somewhat smaller (Template:Convert), and sports a pale gray neck and legs, lacking the brown hues of the great blue heron. The great blue heron forms a superspecies with the grey heron which also includes the cocoi heron of South America, which differs in having more extensive black on the head and a white breast and neck.
The five subspecies are:<ref name=hbw/>
| Image | Subspecies | Distribution |
|---|---|---|
| File:Great Blue Heron (9012933612).jpg | A. h. herodias
Linnaeus, 1758 |
most of North America, except as below |
| File:Blue Heron, Lake Sammamish State Park.jpg | A. h. fannini
Chapman, 1901 |
the Pacific Northwest from southern Alaska south to Washington; coastal |
| File:Ardea herodias 2 - Hilton Head.jpg | A. h. wardi
Ridgway, 1882 |
Kansas and Oklahoma to northern Florida, sightings in southeastern Georgia |
| File:Tier Wasservogel weiß Everglades Florida USA.jpg | A. h. occidentalis Audubon, 1835 | southern Florida, Caribbean islands, formerly known as a separate species, the great white heron |
| File:Galápagos Inseln, Ecuador (13895209521).jpg | A. h. cognata
Bangs, 1903 |
Galápagos Islands |
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DescriptionEdit
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The great blue heron is the largest heron native to North America. Among all extant herons, it is surpassed in size only by the goliath heron (Ardea goliath) and the white-bellied heron (Ardea insignis). It exhibits a minor degree of sexual dimorphism; males are slightly larger than females, but otherwise the sexes are not easily outwardly distinguishable. It has head-to-tail length of Template:Convert, a wingspan of Template:Convert, a height of Template:Convert, and a weight of Template:Convert.<ref name = "CRC">Template:Cite book</ref><ref name="HBW">Template:Cite book</ref><ref>Cornell Lab of Ornithology</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In British Columbia, adult males averaged Template:Convert and adult females Template:Convert.<ref name="Simpson, K 1984">Template:Cite thesis</ref> In Nova Scotia and New England, adult herons of both sexes averaged Template:Convert,<ref name= Quinney/> while in Oregon, both sexes averaged Template:Convert<ref>Template:Cite journal</ref> Thus, great blue herons are roughly twice as heavy as great egrets (Ardea alba), although only slightly taller than them, but they weigh only about half as much as a large goliath heron.<ref>Template:Cite book</ref>
Notable features of great blue herons include slaty (gray with a slight azure blue) flight feathers, red-brown thighs, and a paired red-brown and black stripe up the flanks; the neck is rusty-gray, with black and white streaking down the front; the head is paler, with a nearly white face, and a pair of black or slate plumes runs from just above the eye to the back of the head. The feathers on the lower neck are long and plume-like; it also has plumes on the lower back at the start of the breeding season. The bill is dull yellowish, becoming orange briefly at the start of the breeding season, and the lower legs are gray, also becoming orangey at the start of the breeding season. Immature birds are duller in color, with a dull blackish-gray crown, and the flank pattern is only weakly defined; they have no plumes, and the bill is dull gray-yellow.<ref name=hbw>Template:Cite book</ref><ref name="sibley">Template:Cite book</ref><ref name=ng>Template:Cite book</ref> Among standard measurements, the wing chord is Template:Convert, the tail is Template:Convert, the culmen is Template:Convert, and the tarsus is Template:Convert.<ref>Blake, Emmett Reid (1977). Manual of Neotropical Birds, Volume 1. University Of Chicago Press, Template:ISBN</ref><ref>Proceedings of the United States National Museum, Volume 42.</ref> The heron's stride is around Template:Convert, almost in a straight line. Two of the three front toes are generally closer together. In a track, the front toes, as well as the back, often show the small talons.<ref>Murie & Elbroch, Peterson Field Guide to Animal Tracks, pg. 334 (2005)</ref>
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The subspecies differ only slightly in size and plumage tone, with the exception of A. h. occidentalis, native to South Florida, which also has a distinct white morph, known as the great white heron (not to be confused with the great egret, for which "great white heron" was once a common name).<ref name="fws" /> The great white heron differs from other great blues in bill morphology, head plume length, and in having a total lack of pigment in its plumage. It averages somewhat larger than the sympatric race A. h. wardi and may be the largest race in the species. In a survey of A. h. occidentalis in Florida, males were found to average Template:Convert and females average Template:Convert, with a range for both sexes of Template:Convert.<ref name="CRC" /> This is mainly found near salt water, and was long thought to be a separate species. Birds intermediate between the normal morph and the white morph are known as Würdemann's heron; these birds resemble a "normal" great blue with a white head.
The theory that great white herons may be a separate species (A. occidentalis) from the great blue heron has again been given some support by David Sibley.<ref name="sibleyguides" />
Similar speciesEdit
The "great white heron" could be confused with the great egret (Ardea alba), but is larger, with yellow legs as opposed to the great egret's black legs. The reddish egret (Egretta rufescens) and little blue heron (Egretta caerulea) could be mistaken for the great blue heron, but are much smaller, and lack white on the head and yellow in the bill. At the southernmost extent of its range (e.g., Colombia and Panama), the great blue heron sometimes overlaps in range with the closely related and similarly sized cocoi heron (A. cocoi). The cocoi is distinguished by a striking white neck and solid black crown, but the duller juveniles are more easily confused. More superficially similar is the slightly smaller grey heron, which may sometimes appear as vagrants on the northern coasts of North America. The grey heron (which occupies the same ecological niche in Eurasia as the great blue heron) has very similar plumage, but has a solidly soft-gray neck. Erroneously, the great blue heron is sometimes referred to as a "crane". Herons and cranes are easiest to differentiate in flight; cranes hold their necks straight when flying, but herons bend theirs into an S shape.
Distribution and habitatEdit
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The great blue heron is found throughout most of North America, as far north as Alaska and the southern Canadian provinces in the summer. In winter, the range extends south through Florida, Mexico, and the Caribbean to far northwestern South America (regular in Colombia and Venezuela, accidental elsewhere in South America). Birds east of the Rocky Mountains in the northern part of their range are migratory and winter in the coastal areas of the Southern United States, Central America, or northern South America. From the Southern United States southwards, and on the lower Pacific coast, they are year-round residents.<ref name="hbw" /> However, their hardiness is such that individuals often remain through cold northern winters, as well, so long as fish-bearing waters remain unfrozen (which may be the case only in flowing water such as streams, creeks, and rivers).
The great blue heron can adapt to almost any wetland habitat in its range. It may be found in numbers in fresh and saltwater marshes, mangrove swamps, flooded meadows, lake edges, or shorelines. It is quite adaptable and may be seen in heavily developed areas as long as they hold bodies of fish-bearing water.
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Great blue herons rarely venture far from bodies of water, but are occasionally seen flying over upland areas. They usually nest in trees or bushes near water's edge, often on islands (which minimizes the potential for predation) or partially isolated spots.<ref name="usgs">Short, Henry L. and Cooper, Robert J. (1985). Habitat suitability index models Great blue heron. Biological report 82(10.99). Washington, DC : Western Energy and Land Use Team, Division of Biological Services, Research and Development, Fish and Wildlife Service</ref>
It has been recorded as a vagrant in England,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Greenland, Hawaii, and the Azores.<ref name="hbw" />
The great white heron is unique to South Florida, including Great White Heron National Wildlife Refuge in the Florida Keys.<ref name="fws" />
BehaviorEdit
DietEdit
The primary food for the great blue heron is fish. While they can prey on various sizes of fish from small fingerlings to large adult fish, measuring Template:Convert in length and weighing around Template:Convert, small to medium-sized fish around Template:Convert are usually preferred.<ref name="Baird">Baird, Spencer Fullerton, Thomas Mayo Brewer, and Robert Ridgway. The water birds of North America. Vol. 1. Little, Brown,, 1884.</ref><ref>Forbes, L. Scott. "Feeding behaviour of great blue herons at Creston, British Columbia." Canadian journal of zoology 65.12 (1987): 3062-3067.</ref> Primary prey fish is variable based on availability and abundance. In Nova Scotia, 98% of the diet was flounder.<ref name="Quinney">Quinney, T. E. and P. C. Smith. 1979. Reproductive success, growth of nestlings and foraging behaviour of the Great Blue Heron (Ardea herodias herodias L.). contract rept. No. KL229-5-7077. Can. Wildl. Serv. Ottawa.</ref> In British Columbia, the primary prey species are sticklebacks, gunnels, sculpins, and perch.<ref name="Butler, R 1991">Butler, R. 1991. Habitat selection and time of breeding in the Great Blue Heron (Ardea herodias). PhD Thesis. Univ. of Brit. Col. Vancouver.</ref> California herons were found to live mostly on sculpin, bass, perch, flounder, and top smelt.<ref>Hom, C. W. 1983. Foraging ecology of herons in a southern San Francisco Bay saltmarsh. Colonial Waterbirds 6:37-44.</ref><ref>Stickley Jr, Allen R., et al. "Impact of great blue heron depredations on channel catfish farms." Journal of the World Aquaculture Society 26.2 (1995): 194-199.</ref><ref>Hodgens, Lynn S., Steven C. Blumenshine, and James C. Bednarz. "Great blue heron predation on stocked rainbow trout in an Arkansas tailwater fishery." North American Journal of Fisheries Management 24.1 (2004): 63-75.</ref>
Besides fish, it is also known to feed on a wide range of prey opportunistically. Amphibians such as leopard frogs, American bullfrogs, toads and salamanders are readily taken, as well as reptiles such as small turtles, snakes and lizards.<ref name="hbw" /><ref name="ADW" /><ref name="UWI">{{#invoke:citation/CS1|citation |CitationClass=web
}}</ref> They can take on sizeable snakes, including water snakes Template:Convert in length.<ref name="Baird" /><ref>Elliot L, Gerhardt C, Davidson C (2009) The frogs and toads of North America: a comprehensive guide to their identification, behavior and calls. Mariner Books, Boston</ref><ref>Sutton, George Miksch. "Great blue heron swallows large snake." The Auk 63.1 (1946): 97-99.</ref> Aquatic crustaceans (such as crayfish, shrimp and crabs), grasshoppers, dragonflies and aquatic insects are taken as supplementary prey.<ref name="hbw" /><ref name="ADW" /><ref name="UWI" /> They also prey on small mammals including shrews, rats, ground squirrels, and moles.<ref name="hbw" /> One study in Idaho showed that from 24 to 40% of the diet was made up of voles. Remains of muskrats (Ondatra zibethicus) and long-tailed weasels (Mustela frenata) was also found in pellets during the study.<ref>Collazo, J. A. 1979. Breeding biology and food habits of the Great Blue Heron at Heyburn State Park, Benewah County, Idaho. Master's Thesis. Univ. Idaho, Moscow.</ref> There are reports that great blue heron prey on both young and adults of eastern cottontails (Sylvilagus floridanus).<ref>Cintra-Buenrostro, Carlos E., and Jessica E. Cifuentes-Lujan. "PREDATION OF EASTERN COTTONTAIL RABBIT (SYLVILAGUS FLORIDANUS) BY GREAT BLUE HERON (ARDEA HERODIAS)." TEXAS ORNITHOLOGICAL SOCIETY 52 (2019): 17.</ref><ref>Paul C. Palmer, Great Blue Heron Kills and Carries Off an Eastern Cottontail Rabbit, Department Of History, Texas A&I University, Kingsville, Texas 78363</ref> Though not often, birds such as black rails (Laterallus jamaicensis), phalaropes, American dippers (Cinclus mexicanus), pied-billed grebes (Podilymbus podiceps) and chicks of marsh terns (Chlidonias) are also taken.<ref name="hbw" /><ref>Parker, Michael S. "Opportunistic predation by a great blue heron on an american dipper." The Wilson bulletin (Wilson Ornithological Society) 105.4 (1993): 698-699.</ref><ref>Stolen, ERIC D. "Great Blue Heron eating a Pied-billed Grebe." Florida Field Naturalist 29.3 (2001): 87.</ref>
- Le Grand Heron.jpg
Eating a small fish
- Mouthfull Heron.jpg
Eating a large sunfish
- Blue Heron and two toed amphiuma (6074193002).jpg
Eating a two toed amphiuma
- Great blue heron eating a snake (94629).jpg
Eating a brown water snake in Florida
- Snake Snack (15669784882).jpg
Eating a garter snake
- GreatBlueHeroneatingturtle08.jpg
Eating a hatchling common snapping turtle
- Great Blue Heron imported from iNaturalist photo 134213334 on 3 December 2024.jpg
Eating a California ground squirrel
- Great Blue Heron and Gopher (50909452786).jpg
Eating Botta's pocket gopher
- Great Blue Heron imported from iNaturalist photo 285096808 on 3 December 2024 (cropped).jpg
Eating a duck
- Fishing bird Chippokes Plantation State Park Virginia (16448378679).jpg
Eating a swimmer crab
Herons locate their food by sight and usually swallow it whole. They have been known to choke on prey that is too large.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Wolf, B. O. and S. L. Jones. 1989. Great Blue Heron Deaths Caused by Predation on Pacific Lamprey. Condor 91:482–484.</ref> They are generally solitary feeders. Individuals usually forage while standing in water, but also feed in fields or drop from the air, or perch, into water. Mice are occasionally preyed on in upland areas far from the species' typical aquatic environments.<ref name="usgs" /> Occasionally, loose flocks gather to feed, and may be beneficial since they are able to locate schools of fish more easily.<ref name="usgs" />Template:Multiple image As large wading birds, great blue herons are capable of feeding in deeper waters, and thus are able to harvest from niche areas not open to most other heron species. Typically, the great blue heron feeds in shallow waters, usually less than Template:Convert deep,<ref name="usgs" /> or at the water's edge during both the night and the day, but especially around dawn and dusk. The most commonly employed hunting technique of the species is wading slowly with its long legs through shallow water and quickly spearing fish or frogs with its long, sharp bill. Although usually ponderous in movements, the great blue heron is adaptable in its fishing methods. Feeding behaviors variably have consisted of standing in one place, probing, pecking, walking at slow speeds, moving quickly, flying short distances and alighting, hovering over the water and picking up prey, diving headfirst into the water, alighting on water feet-first, jumping from perches feet-first, and swimming or floating on the surface of the water.<ref name="usgs" />
BreedingEdit
This species usually breeds in colonies, in trees close to lakes or other wetlands. Adults generally return to the colony site after winter from December (in warmer climes such as California and Florida) to March (in cooler areas such as Canada). Usually, colonies include only great blue herons, though sometimes they nest alongside other species of herons. These groups are called a heronry (a more specific term than "rookery"). The size of these colonies may be large, ranging between five and 500 nests per colony, with an average around 160 nests per colony. A heronry is usually relatively close, usually within Template:Convert, to ideal feeding spots.<ref name="usgs"/> Heronry sites are usually difficult to reach on foot (e.g., islands, trees in swamps, high branches, etc.) to protect from potential mammalian predators. Trees of any type are used when available. When not, herons may nest on the ground, sagebrush, cacti, channel markers, artificial platforms, beaver mounds, and duck blinds. Other waterbirds (especially smaller herons) and, occasionally, even fish and mammal-eating raptors may nest amongst colonies.<ref>Custer, T. W., R. G. Osborn, and W. F. Stout. 1980. Distribution, species abundance, and nesting-site use of Atlantic Coast colonies of herons and their allies. Auk 97:591-600.</ref><ref>Ryser, Jr., F. A. 1985. Birds of the Great Basin. Univ. Nevada Press, Reno.</ref>
Although nests are often reused for many years and herons are socially monogamous within a single breeding season, individuals usually choose new mates each year.<ref name="ReferenceA">Butler RW. The Great Blue Heron. In Birds of North America (ed: Poole and Gill), No. 25</ref> Males arrive at colonies first and settle on nests, where they court females; most males choose a different nest each year.<ref name="ReferenceA"/> Great blue herons build a bulky stick nest. Nests are usually around Template:Convert across when first constructed, but can grow to more than Template:Convert in width and Template:Convert deep with repeated use and additional construction.<ref>Andrle, R. F. 1988. The Atlas of Breeding Birds in New York State. Cornell Univ. Press, Ithaca, New York.</ref> If the nest is abandoned or destroyed, the female may lay a replacement clutch. Reproduction is negatively affected by human disturbance, particularly during the beginning of nesting. Repeated human intrusion into nesting areas often results in nest failure, with abandonment of eggs or chicks. However, Vancouver B.C. Canada's Stanley Park has had a healthy colony for some years right near its main entrance and tennis courts adjacent to English Bay and not far from Lost Lagoon.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The park's colony has had as many as 183 nests.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The female lays three to six pale blue eggs, which can measure from Template:Convert in length and Template:Convert in width, though the smallest eggs in the above sample may have been considered "runt eggs" too small to produce viable young. Egg weights range from Template:Convert.<ref>Bent, A. C. 1926. Life histories of North American marsh birds. U.S. Natl. Mus. Bull. 135.</ref> One brood is raised each year. First broods are laid generally from March to April.<ref>Brandman, M. 1976. A quantitative analysis of the annual cycle of behavior in the Great Blue Heron (Ardea herodias). PhD Thesis. Univ. Calif. Los Angeles.</ref><ref>Vermeer, K. 1969. Great Blue Heron colonies in Alberta. Can. Field-Nat. 83:237-242.</ref> Eggs are usually laid at two-day intervals, incubated around 27 days, and hatch asynchronously over a period of several days.<ref name="ReferenceA"/> Males incubate for about 10.5 hours of each day, while females usually incubate for the remainder of each day and the night, with eggs left without incubation for about 6 minutes of each hour.<ref name="ReferenceA"/>
The first chick to hatch usually becomes more experienced in food handling and aggressive interactions with siblings, so it often grows more quickly than the other chicks.<ref name=ADW>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Both parents feed the young at the nest by regurgitating food. Parent birds have been shown to consume up to four times as much food when they are feeding young chicks (about 4300 kJ/day) than when laying or incubating eggs (about 1200 kJ/day).<ref name="ReferenceA"/> By the time they are 45 days old, the young weigh 86% of the adult's mass.<ref>Quinney, T. E. 1982. Growth, diet, and mortality of nestling Great Blue Herons. Wilson Bull. 94:571-577.</ref> After about 55 days at the northern edge of the range (Alberta) and 80 days at the southern edge of the range (California), young herons take their first flight.<ref name="ReferenceA"/> They return to the nest to be fed for about another three weeks, following adults back from foraging grounds, and are likely to gradually disperse away from their original nest over the course of the ensuing winter.<ref name="ReferenceA"/> Young herons are not as successful at fish capture as adults, as strike rates are similar, but capture rates are about half that of adults during the first two months after fledging.<ref name="ReferenceA"/>
PredationEdit
Predators of eggs and nestlings include turkey vultures (Cathartes aura), common ravens (Corvus corax), and American crows (Corvus brachyrhynchos). Red-tailed hawks (Buteo jamaicensis), American black bears (Ursus americanus), and raccoons (Procyon lotor) are known to take larger nestlings or fledglings, and in the latter predator, many eggs.<ref name="Simpson, K 1984"/><ref>Lopinot, A. C. 1952. Raccoon predation on Great Blue Herons. Auk 68:235.</ref><ref>Hjertaas, D. G. 1982. Great Blue Herons and raccoons at Nicolle Flats. Blue Jay 40:36-41.</ref><ref>Foss, E. 1980. A black bear in a Great Blue Heron colony. Murrelet 61:113.</ref> In exceptional case, a young Harris's hawk (Parabuteo unicinctus) killed a subadult great blue heron.<ref>Woodward, H. D., & Trussell, R. W. (2003). Lone Harris's Hawk kills Great Blue Heron. Journal of Raptor Research, 37(1), 85-86.</ref> Adult herons have few natural predators and are rarely preyed upon due to their large size and sharp beak, but bald eagles (Haliaeetus leucocephalus) are known to attack great blue herons at every stage of their lifecycle from in the egg to adulthood.<ref name = Baird/><ref>Forbes, L. S. 1987. Predation on Great Blue Herons: is it important?. Colonial Waterbirds 10:120-122.</ref><ref>Kelsall, J. P. and K. Simpson. 1980. A three-year study of the Great Blue Heron in southwestern British Columbia. Proc. Colonial Waterbird Grp. 3:69-74.</ref> And less frequently, golden eagles (Aquila chrysaetos) and great horned owls (Bubo virginianus) are known to take adults.<ref>Olendorff, R. R. (1976). The food habits of North American golden eagles. American Midland Naturalist, 231-236.</ref><ref>Houston, C. Stuart, Dwight G. Smith and Christoph Rohner. 1998. Great Horned Owl (Bubo virginianus)', The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/372</ref> There is a single report that a large bobcat (Lynx rufus) managed to subdue and kill an adult great blue heron.<ref>Monson, Gale. “Great Blue Heron Killed by Bobcat.” The Wilson Bulletin, vol. 63, no. 4, 1951, pp. 334–334. JSTOR, http://www.jstor.org/stable/4158020. Accessed 5 Feb. 2023.</ref> Using its considerable size and dagger-like bill, a full-grown heron can be a formidable foe to a predator. In one instance, during an act of attempted predation by a golden eagle, a heron was able to mortally wound the eagle, although it succumbed to injuries sustained in the fight.<ref>Santy, D. 1964. A recollection of an encounter between a Golden Eagle and a Great Blue Heron. Blue Jay, 22: 55.</ref> When predation on an adult or chick occurs at a breeding colony, the colony can sometimes be abandoned by the other birds. The primary source of disturbance and breeding failures at heronries is human activities, mostly through human recreation or habitat destruction, as well as by egg-collectors and hunters.<ref name="Butler, R 1991"/><ref>Simpson, K., J. N. M. Smith, and J. P. Kelsall. 1987. Correlates and consequences of coloniality in Great Blue Herons. Can. J. Zool. 65:572-577.</ref>
In art and logosEdit
John James Audubon illustrates the great blue heron in Birds of America, Second Edition (published, London 1827–1838) as Plate 161. The image was engraved and colored by Robert Havell's London workshops. The original watercolor by Audubon is in the collection of the New-York Historical Society.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The great blue heron (with its color changed to orange) is the basis of logos for the Delmarva Shorebirds minor league baseball team from the team's 1996 inception.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Great white herons feature prominently in the logo for the Major League Soccer club Inter Miami CF.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ReferencesEdit
Further readingEdit
External linksEdit
- Audubon's Great Blue Heron – Close-ups from Plate 161, Birds of America
- Great Blue Heron - Ardea herodias - USGS Patuxent Bird Identification InfoCenter
- Great Blue Heron Species Account – Cornell Lab of Ornithology
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