Mating occurs between March and May. Males select nesting sites and then perform courtship displays to attract a female. Mature herons pair up and nest and raise young. Mated pairs typically are monogamous only for the year.
Great blue heron females lay two to seven eggs that are pale blue in color. Eggs hatch within 26 to 30 days. Young fledge in 2 months. Both adults care for young.
Nesting by herons tends to be colonial. Groups of nesting herons are called rookeries. Most species of herons nest in trees or near water.
Herons are migratory birds that tend to fly north in the spring. Herons feed mostly during the day or at dusk; black-crowned night-herons and yellow-crowned night-herons feed mostly at dusk or night. Depending on species, herons hunt alone but group hunting can occur. Foraging areas can be several miles from nesting sites.
Herons prefer wetlands that have slow moving or standing fresh water with tall trees nearby. Herons will feed in brackish waters as well.
Herons primarily feed on animals associated with aquatic environments, including fish, crustaceans, lizards, and frogs.