Males typically arrive first at breeding grounds from their winter territories in the Southeast United States or South America, staking out nests or assembling new ones. A few days later, the females arrive, launching the males into bouts of frenzied exhibitionism. There's a lot at stake, for unlike geese, loons and some other large birds, many great blue herons choose new mates and nest sites each season. Courting herons put these adornments to good use, flashing them in displays aimed to impress prospective mates, strengthen existing pair bonds or keep other herons away from the nest. Throughout the colony, birds stretch and snap their necks, clatter bills, ruffle feathers or slowly flap around in ceremonial flight.
Sticks are the currency of the colony.
The birds fight over them and depend on them for successful nesting. Inside a finished nest, a female lays two to five pale blue or greenish blue eggs, which rest in a shallow indentation lined with pine needles, moss, grass or other soft material. Males and females share incubation duties, which last a month, then spend about two months feeding and brooding their growing young. Despite the parents' hard work, many hatchlings die, falling to predators or toppling out of nests during storms or after taking a wrong step. Also, the smallest and youngest nestlings often starve or are pushed from the nest by larger and more aggressive siblings.