Have you ever seen a great blue heron nest or rookery? Find out where, when, and how these magnificent birds mate and raise their young.
If you spend any time around water in North America, chances are good that eventually you’ll spot a great blue heron. Standing as high as 4 feet tall, these birds are icons of the wetlands and are often seen foraging in the shallows for food. They’re usually solitary creatures, but when breeding and nesting season rolls around, that behavior changes dramatically. Here’s what to know about great blue heron courtship rituals, rookeries, and “parenting.”
Mating Behavior of Great Blue Herons
These majestic herons start mating in late winter or early spring — usually by February or March, depending on the location. Pairs are monogamous throughout the season, but they look for new mates each year with elaborate courting displays.
Males arrive at the nesting grounds first, staking out a site. Then, they put on a show. Sitting on the nest site, a male stretches his head to the sky and bows it low, clicking his bill and showing off for prospective mates. When a female approaches, the two perform a series of displays including clapping their bills together and stretching their necks in unison.
Great Blue Heron Nests
The display continues as nest-building begins. Males bring sticks to the females, who accept them with stretches and bill clapping before placing them carefully into the nest. These nests can take up to two weeks to build, as the female creates a platform as well as a cup-shaped nest lined with soft items like pine needles, moss, grasses, and leaves.
As you might expect for such large birds, these are large nests. They stretch at least 20 inches across. Because some great blue herons reuse nest sites, those nests can become substantial over time. Some are as long as 4 feet across and several feet deep.
Rookeries: Communal Nesting
For most of the year, great blue herons are solitary. With that said, they almost always nest in large colonies, known as a rookery (or sometimes a heronry). Rookeries can include anywhere from 50 to 500 pairs nesting together. Though they can nest on or near the ground, these herons are more likely to be found raising young up to 100 feet high in the treetops.
Heron rookeries are located on or near water; you might spot them near lakes, swamps, mangroves, or other wetlands. They may be made up of great blue herons alone, or they could include other wading and water birds like little blue herons, tricolored herons, cormorants and anhingas, wood storks, and more. A rookery is a noisy, active place, with adults coming and going and baby birds clamoring for food. (Up close, they can also be rather stinky.)
How Great Blue Herons Raise Their Young
The female heron lays two to six pale blue eggs over several days. Incubation takes nearly a month, with males and females taking turns sitting on the eggs. Newly-hatched heron chicks are gangly and covered in soft gray down, and they weigh about as much as a tennis ball. They have voracious appetites, and both parents are kept busy feeding them with regurgitated fish, crustaceans, frogs, or insects. After the first month, parents switch to whole fish, rodents, frogs, and more.
It takes a while for these nestlings to grow to their full size — about two and a half to three months. They begin to fledge when they’re around two months old, stretching their wings and hopping around in the nest and on branches nearby. After they build enough strength in their wing muscles, the young birds take flight and begin their lives as one of the largest water birds in North America.
READ ON: How to identify a green heron
Sources
- Cornell Lab of Ornithology, “Great Blue Heron: Life History,” “Bird Cams FAQ: Great Blue Heron Nest“
- National Audubon Society, “Field Guide: Great Blue Heron“
