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.
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.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
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.
Great blue herons are a delight to watch and are important members of healthy, freshwater ecosystems.
Positive Impacts: ecotourism
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.
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.
Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; aquatic crustaceans
Primary Diet: carnivore (Piscivore )
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.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
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.
Range elevation: 1500 (high) m.
Habitat Regions: temperate ; tropical ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams; coastal
Wetlands: marsh ; swamp
Other Habitat Features: riparian
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.
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.
Range mass: 2100 to 2500 g.
Range length: 97 to 137 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
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.
Known Predators:
Great blue herons generally have one mate per breeding season.
Mating System: monogamous
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.
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.
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.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average eggs per season: 4.
Both parents care for and feed the chicks until they are ready to leave the nest. The largest chicks receive the most food.
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)
