The Majestic Great Blue Heron
If you spend time at our parks, you may have spotted the majestic great blue heron gliding or perching near water. The largest of the North American herons, blue herons have long legs, a slender throat and a powerful, dagger-like bill. Their immense size and iconic blue-grey colouring make them hard to miss. Despite their size, these herons surprisingly choose to nest in trees.
Tree Nesters
Great blue herons nest in large trees such as pine and cottonwood, typically within 10 kilometres of their foraging habitat. They build their nests with sticks from the ground, as well as with sticks from nearby shrubs, trees and unguarded abandoned nests.
They mainly nest in trees, but also nest on:
- Bushes
- The ground
- Artificial nest platforms
- Duck blinds
- Channel markers
The Art of Nest Building
Males gather nesting material and present it to the female, who then weaves the sticks into a platform and saucer-shaped nest cup. The female may fill the nest with dry grass, pine needles, reeds, moss or small twigs.
Nests can range from a simple platform that is only 50 centimetres wide to more elaborate structures up to 1.2 metres across and one metre deep. It can take anywhere from three days to two weeks to build the nest. Herons may use the more elaborate nests over multiple years.
Herons are colonial nesters. Some colonies can have hundreds of individual nests. Herons build nests anywhere from five to 75 metres off the ground and they usually have multiple nests per tree. One tree can have 10 nests! During the breeding season, mates are typically monogamous, but they don’t mate for life, finding new partners each year and beginning the nest building process anew.
Other Tree Nesting Herons
There are other herons that nest in trees as well, such as green herons (Butorides virescens), great egrets (Ardea alba), and black-crowned night herons (Nycticorax nycticorax).
Ground nesting herons such as American bitterns and least bitterns build their nests in thick stands of bulrushes and cattails. Sometimes they will nest on dry ground in grassland areas with tall herbaceous plants.
Appearance and Behaviour
Habitat
The great blue heron is the most common heron in Canada, spanning from coast to coast in the southern region. They are the largest heron species in North America, standing at approximately one metre tall with a wingspan of one to two metres.
This species lives in many freshwater and saltwater habitats, including southern wetlands and northern boreal forests.
Diet
Fish make up most of their diet, but they also eat a range of other foods such as insects, amphibians, small mammals, reptiles and birds. Although they are expert fishers, there have been cases of great blue herons choking themselves to death by trying to swallow fish that are too large to fit down their long, s-shaped throats.
Monitoring Great Blue Herons
Surprisingly, monitoring reports have observed herons nesting near eagle nests. Bald eagles (Haliaeetus leucocephalus) are predators of heron nestlings however, they are also very territorial. These clever birds have learned that nesting close to an eagle’s nest improves their breeding success, as the eagle defends its territory against other eagles.
Coming across a heron colony is a rare and spectacular site. If you come across a heron colony, please keep your distance. If people come too close, they may easily disturb nesting herons and cause them to abandon their young. Remember to bring your birding gear, like binoculars or a camera, to get a closer look from afar the next time you visit our parks!
Learn more about birding spots at our parks.
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By Stephanie Donison, Natural Heritage Assistant.