Yellowstone Natural History: Great Blue Herons

It’s a special treat in Yellowstone National Park to see Great Blue Herons wading in one of the Park’s many waterways.

Described as statue-like in poise and composure, a Great Blue Heron will walk the waters, neck curved to a strikingly sinuous S, until—whap!—it’s got a trout or a frog. And with a gulp the fish is gone; the heron moves on, a living artwork in the scenery.

It’s equally impressive seeing these large birds soar or, even better, alight on a waterway.

Although Great Blue Herons are by no mean unique to Yellowstone, they’re still a marvelous surprise to see in places like the Hayden Valley or along the Madison River.

Basic Facts

• Scientific name: Ardea herodias.
• Most common and largest heron in North America.
• Distinguished by their long bills and blue cap and wing feathers.
• Body is slate-gray and white.
• Both male and female Great Blue Herons measure 38-54 inches long.
• Wingspan: 65.7-79 inches.
• Weigh 74 to 88 ounces.
• Great Blue Heron necks can bend to a sinuous S shape, making them more aerodynamic and better at striking at prey.

Habitat

• Live in both freshwater and saltwater habitats.
• Great Blue Herons will also forage in grasslands and farm fields.
• Often forage alone.
• Live in breeding colonies, often found two to four miles from favorite feeding areas.
• Colonies often found in isolated swamps or islands, near forest-bound lakes and ponds.
• Great Blue Herons will defend their territories with a specialized stance—head thrown back, beak skyward, wings outstretched.
  

Diet

• Strike at a variety of prey.
• Fish is a staple of diet.
• Other prey includes amphibians, reptiles, insects—even small mammals and other birds.

Hunting

• Great Blue Herons have two assets when it comes to hunting: strong mandibles and dagger-like bills.
• These come in handy with larger fish, who often get shook around with spine-breaking force before a heron feeds.
• Great Blue Herons have another advantageous adaptation: specialized chest feathers that can be used to wash fish slime and oils from their feathers.
• Finally, heron eyes contain a large percentage of rod-type photoreceptors, enabling them to hunt day and night.

Range/Migration

• Great Blue Herons will build nests from available materials, sometimes using unguarded or abandoned nests.
• Males will present their nest to a female, who can decide whether to build her portion.
• Females will weave a platform and nest cup, lining it with pine needles, dry grass, mangrove leaves, moss, and other materials.
• Nest building can take anywhere from three days to two weeks.
• A finished nest measures an average of 20 inches across.
• Some nests used year after year will become more elaborate over time, widening and deepening.
• A mature Great Blue Heron nest can measure upwards of four feet across and three-and-a-half feet deep.

Courtship

• Courtship is elaborate, taking place in a colony of nesting pairs.
• Number upwards in the hundreds and even thousands.
• Displays include ritualized greetings, stick transfers and nest relief ceremony.
• Great Blue Herons will erect plumes and “clapper” bill tips to attract females.
• Herons are seasonally monogamous but choose different mates through their lives.
  

Reproduction

• Great Blue Herons lay two to six eggs.
• One to two broods per year.
• Eggs measure two-and-a-half to three inches long and two inches wide.
• Coloring: pale blue.
• Incubate for 27-29 days.
• Great Blue Herons will nest for 49-81 days.

Blue and White

• A variety of Great Blue Heron, called the “great white heron” is found exclusively in southern Florida, the Yucatan Peninsula, and the Caribbean.
• Known to overlap—blue and white great heron hybrids are called “Wurdemann’s herons.”
• Wurdemann’s herons have the body of a Great Blue Heron with a white heron’s head and neck coloring.