The Great Blue heron is a tall and statuesque bird when wading in the water seeking its prey, and it is graceful and swift when flying with its slow deep wing beats. It is one of the most majestic wild birds in North America. This stately bird has subtle blue-gray plumage and often stands motionless while it scans for prey or it wades belly deep using long, deliberate steps. It can strike rapidly to capture its prey.
Great Blue herons live in neoarctic and neotropical regions. In spring and summer, this species breeds throughout Central and North America, southern Canada, the Caribbean and the Galapagos. They occur in many habitats including mangrove and salt marsh swamps, freshwater swamps and marshes, estuaries, coastal lagoons, ditches, riverbanks, flooded fields, and lake edges.
These birds are active mainly in the mornings and during dusk when the fishing is best. A great blue heron is a stalk-and-strike hunter that locates its prey by sight and so it needs to hunt during daylight. They hunt alone but often breed in rookeries, sleeping at night amongst flocks of more than 100 other herons. They are extremely territorial and defend their nests aggressively. They are mostly migratory, though some populations in the southern United States stay in one area year-round. Northern populations move to the south of the United States, or to Central or South America, as they cannot catch fish when the water is frozen. They are a relatively quiet species and make a soft "kraak" if disturbed in flight or "fraunk" if disturbed near their nest. Their greeting to others of their species is an "ar" sound. They use up to 7 different sounds.
Great Blue herons are carnivores (piscivores), they eat mainly fish, but also frogs, salamanders, snakes, lizards, young birds, small mammals, crabs, shrimp, crayfish, dragonflies, and grasshoppers, as well as many aquatic invertebrates.
Great Blue herons usually have one mate for the duration of the breeding season and then will choose a new mate in the following year, which means they exhibit a serial monogamous mating system. Males perform courtship displays in order to attract a female, including flight displays and posturing with their feathers fluffed up. The birds in the north of their range breed from March until May and November to April in the south. Males often arrive first at the breeding grounds and most of them will choose an existing nest for the season. However some males, mostly younger ones, will make a new nest. These herons nest in trees near water, though nests are also located in bushes and sometimes on the ground. Nesting is in colonies with 5 to 500 nests, an average per colony of 160 nests. 3 to 7 eggs are laid and incubation is shared by both parents, for about 28 days. The young remain in the nest for around 9 to 10 weeks. The chicks start to climb on branches near the nest at the end of week 7, and at week 9 they are able to make short flights. They become sexually mature at about 22 months old.
The Great Blue heron is abundant and widespread, and at species level is not subjected to any major threats. However, some populations, especially those in small areas near the coast, are vulnerable to such localized impacts as habitat destruction, human persecution and disturbance, pollution.
The Heron Conservation resource estimated Great Blue heron populations of more than 35,000 birds in the 1970s along the east and south North American coast, but now the nesting population just in Louisiana numbers over 10,000 individuals and has been increasing. There are about 1,500 birds in south Florida. Little data is available for its inland range; in Quebec over 12,000 pairs; In Ontario 13,000 pairs and in Illinois 5,000 pairs. Overall the population is likely to number 100,000 to 250,000. According to the All About Birds resource, a continental population of the Great Blue heron is around 83,000 breeding birds. Overall, currently this species is classified as Least Concern (LC) and its numbers today are Increasing
Due to their diet, this species controls fish and insect populations across a range of habitats. They may also affect predator populations (crows, ravens, eagles, raccoons, bears), as items of prey.