great blue heron

Great Blue Heron

Ardea herodias


The Great Blue Heron is a large grey bird with a long neck, long legs, short tail, and a long, thick, bill. Its back, belly, and wings are bluish-grey in color, and the neck is reddish-grey. There is a white stripe on the crown of the head and there are black feathers extending from the back of the head. Males and females are similar in appearance.


The Great Blue Heron is the largest heron in North America. It measures 36-55 inches (91-140 cm) from head to tail and has a wingspan of 66-79 inches (167-201 cm). A typical Great Blue Heron weighs 4-8 lbs (2-3.5 kg).



Great Blue Herons primarily eat small fish, although they may also eat shrimp, crabs, insects, and small birds, mammals, reptiles, and amphibians if they are available. The Great Blue Heron at Cosley Zoo receives a daily diet of fish.


Great Blue Herons build their nests in trees, where they are safe from predators. They breed in colonies which can contain up to 500 nests each. Males gather sticks and bring them to the females, who then use the sticks to build the nests. The female lays 3-6 pale blue eggs in a clutch (group of eggs). Both parents incubate the eggs for a total of about 28 days until they hatch. After hatching, both parents feed the chicks by regurgitating their own food. Chicks fledge (leave the nest) about 2 months after hatching. Great Blue Herons typically mate once per breeding season.

Shelter and Space Needs

Great Blue Herons are found throughout North America. Great Blue Herons from the northern part of the country, including Illinois, migrate to Central or South America for the winter. They are found in a variety of habitats including marshes, bogs, swamps, and lake edges. A Great Blue Heron’s habitat requires calm, slow-moving water that the bird can stand in to hunt for food.

Life Expectancy

About half of the Great Blue Heron population dies before reaching one year of age, since they are most vulnerable when they are young. Birds that make it past this point can live to be up to 15 years of age.

Relationship With Man

Birdwatchers often delight in watching these graceful birds, which also help to control fish and insect populations. The population control they provide makes them an important part of healthy freshwater ecosystems.

Fun Facts