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Ardea herodiasgreat blue heron

By Robert Naumann

Geographic Range

Great blue herons can be found in the Nearctic and Neotropical regions. During the spring and summer, they breed throughout North and Central America, the Caribbean, much of Canada and the Galapagos. Some populations migrate to Central and South America during the winter months, but do not breed there. Several small populations breed in the southern hemisphere, including the Galapagos Islands and coastal Venezuela. (Ferguson, 1998)

Habitat

Great blue herons always live near sources of water, including rivers, lake edges, marshes, saltwater seacoasts, and swamps. They usually nest in trees or bushes that stand near water, breeding at elevations of up to 1,500 m. They tend to avoid marine habitats along the east coast and instead live inland. (Ferguson, 1998)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • coastal
  • Range elevation
    1500 (high) m
    4921.26 (high) ft

Physical Description

Great blue herons are the largest herons in North America. They stand approximately 60 cm tall and are 97 to 137 cm long. They weigh 2.1 to 2.5 kg. They have long, rounded wings, long bills that taper to a point at the end, and short tails. They also have very long necks and legs. The bills are a yellowish color and the legs are green. Great blue herons have gray upper bodies, and their necks are streaked with white, black and rust-brown. They have grey feathers on the back of their necks with chestnut colored feathers on their thighs. The males have a puffy plume of feathers behind their heads and also tend to be slightly larger than females. (Ferguson, 1998)

  • Sexual Dimorphism
  • male larger
  • Range mass
    2100 to 2500 g
    74.01 to 88.11 oz
  • Range length
    97 to 137 cm
    38.19 to 53.94 in

Reproduction

Great blue herons generally have one mate per breeding season.

Great blue herons typically breed from March to May in the northern part of their range and November through April in the southern part of their range. Females lay between 2 and 7 pale blue eggs. Birds living further north tend to have more eggs. Both parents incubate the eggs, which means that the parents take turns sitting on the nest to keep the eggs warm until they hatch. The eggs hatch after 26 to 30 days of incubation. After living in the nest for about 2 months, the babies (called chicks) are ready to fledge, which means they are old enough to leave the nest and survive on their own. Herons become sexually mature when they are about 22 months of age. (Ferguson, 1998)

  • Breeding interval
    Great blue herons breed once yearly.
  • Breeding season
    Breeding occurs from March to May in northern parts of their range and November to April in southern parts of their range.
  • Range eggs per season
    2 to 7
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    30 (high) days
  • Average time to hatching
    27 days
  • Range fledging age
    60 to 81 days
  • Average age at sexual or reproductive maturity (female)
    22 months
  • Average age at sexual or reproductive maturity (male)
    22 months

Both parents care for and feed the chicks until they are ready to leave the nest. The largest chicks receive the most food. (Ferguson, 1998)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan / Longevity

The oldest wild great blue heron was said to be 23 years old, but most do not live so long. The average lifespan for a great blue heron is around 15 years. As with most animals, they are most vulnerable when they are young. More than half (69%) of the great blue herons born in one year will die before they are a year old.

  • Range lifespan
    Status: wild
    24.5 (high) years
  • Average lifespan
    Status: wild
    15 years
  • Average lifespan
    Status: wild
    294 months
    Bird Banding Laboratory

Behavior

Great blue herons are mainly active in the mornings and at dusk when fishing is best. They are solitary predators, preferring to hunt alone. However, they do often breed in groups called colonies, and during the day they will sleep with flocks of over 100 other herons. Great blue herons are also extremely territorial and will aggressively defend their nests.

Communication and Perception

Great blue herons are relatively quiet compared to other related species. They release a soft "kraak" when they are disturbed in flight. Other heron calls include a "fraunk" when they are disturbed near their nests which usually lasts about 20 seconds, and an "ar" when they are greeting other members of their species. These herons are known to have up to 7 different calls. They also snap their bills together and use complicated body movements in courtship displays.

Food Habits

Great blue herons fish in both the night and the day, with most of their activity occurring around dawn and dusk. Herons use their long legs to wade in shallow water and their sharp "spearlike" bills to catch their food. Great blue herons' diet consists of mainly fish, but also includes frogs, salamanders, lizards, snakes, birds, small mammals, shrimps, crabs, crayfish , dragonflies, grasshoppers, and many other aquatic insects. Herons locate their food by sight and usually swallow it whole. Herons have been known to choke on prey that is too large. (Ferguson, 1998)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • terrestrial non-insect arthropods
  • aquatic crustaceans

Predation

Northwest crows and common ravens have been reported eating heron eggs. Eagles, racoons, bears, turkey vultures, and red-tailed hawks prey on the young birds and sometimes even the adults. Birds will abandon a colony where they have been living after a predator has killed an adult or chick in the area. (Ferguson, 1998)

Ecosystem Roles

Great blue herons control fish and insect populations in many different habitats. They are also an important source of food for the animals that prey on them.

Economic Importance for Humans

Economic Importance for Humans: Positive

Great blue herons are a delight to watch and are important members of healthy, freshwater ecosystems.

Economic Importance for Humans: Negative

People who create and stock fish ponds may find that their expensive fish are being eaten by great blue herons. This can be prevented by installing bird netting or using decoy herons to scare the birds away. (Ferguson, 1998)

Conservation Status

This is the most well-known and most widespread heron in North America. Human interference with the heron primarily involves destruction of habitat. Many herons are also killed each year due to collisions with utility wires. Great blue herons are protected by the United States Migratory Bird Treaty Act.

Other Comments

Great blue herons have up to 7 known subspecies. One interesting subspecies is the great white heron (Ardea herodias occidentalis), with mostly white plumage, that lives mainly in Florida and the Carribbean. (Ferguson, 1998)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Robert Naumann (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

crepuscular

active at dawn and dusk

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Hancock, James and James Kushlan. 1984. The Herons Handbook. Harper and Row Publishers Inc.

Terres, John K. The Audubon North American Encyclopedia of North American Birds. 1980. Alfred A Knopf Inc.

Ferguson, P. 1998. "The Dreaded Predator" (On-line). Accessed 16 May 2000 at http://www.ponddoc.com/WhatsUpDoc/Predators/DreadPred.html.

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