Great blue herons are majestic birds you can see around Will County’s marshes, rivers, ponds and lakes — basically anyplace with still or slow-moving, shallow water. Keep an eye out for them this spring as they hunt, pair up with mates and build nests for their young.
Spotting a great blue heron
These birds are easy to identify. Just look for the large grayish-blue bird with black stripes above its eyes. How tall are you? Great blue herons can reach 4 1/2 feet tall. When they spread out their wings, their wingspan can reach 5 1/2 feet from one wingtip to the other. How does your arm span compare?
Despite their size, great blue herons are very light, tipping the scales at between 4 1/2 pounds and 8 pounds. They have their hollow bones to thank for that. If they had solid bones like we do, they would never get off the ground to fly. They would just be too heavy.
Words to know
Fray: To unravel or become worn at the edges.
Majestic: Showing impressive beauty or dignity.
Preen: To straighten and clean feathers with a beak.
Wooed: To seek the favor or attention of someone or something.
One of their coolest features are special chest feathers. These feathers continue to grow and fray, turning into a soft, powdery down. Think about your most loved stuffed animal or favorite sweater that gets super soft from all that use. What’s the point of these feathers? They act as a napkin! Great blue herons use the special chest feathers to remove slime and oils from their other feathers as they preen, or clean, themselves.
The heron hunting method
Great blue herons spend up to 90% of their waking time hunting, so they know what they are doing. Standing almost perfectly still, they scan shallow water for food. They move slowly, stalking prey through the water, deliberately picking up their long feet.
Then, when the moment is perfect, they throw their long, S-shaped neck forward and pierce a fish with their incredibly pointed bill. A few sharp shakes later and the fish’s spikes are broken. The great blue heron can swallow their dinner whole. Yum!
In addition to fish, they eat small mammals, birds, frogs, salamanders, turtles, snakes, crayfish and insects with a quick snap of their bills. They are not picky and eat whatever is in striking distance. Because their eyes are adapted to see in the dark, great blue herons can hunt day and night.
Building a home
From March through May, great blue herons are deep in nesting season. They like to nest high up in trees, but they will also nest on the ground, in bushes or on structures like duck blinds or human-made platforms. They settle with other herons in colonies called rookeries. There can be up to 500 nests in one rookery!
Males find a spot first and dance to attract a mate. Wooed by calls, wing flaps and head thrusts, females weave together a platform- or saucer-shaped nest from the sticks males bring. She lines it with pine needles, mosses, reeds, dry grasses and small twigs. After between three days and two weeks, the work is done. Nests can get to be 4 feet across, especially when the pair opt to spruce up an old nest from last year.
Each pair has one clutch of three to six eggs. After about 28 days, the eggs will hatch. Parents will usually stick together for the season, but often find new mates the following year.
These birds value their space and are shy. If you get too close, they will warn you off with a couple squawks and a few flaps of their wings. Then they will usually fly away. They will even abandon their nesting grounds when people get too close. If you come across a great blue heron nest, back away slowly and stay far away.
This nesting behavior is why Lake Renwick Heron Rookery Nature Preserve is closed to the public March 1 through the middle of August. Structures that look a little like pirate ships were built on islands in the middle of the lake so herons, egrets and cormorants can nest. We don’t want to stress out parents and young herons during this time.
You can still watch the colony through mounted scopes at Lake Renwick Preserve’s Copley Nature Park access. Or check out the Forest Preserve District of Will County’s event calendar to see when it is open for special public programs and guided bird viewings.
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