Image credit: Olaf Oliviero Riemer, Creative Commons

Species of the Week: great grey owl

Each week, One Earth’s “Species of the Week” series highlights a relatively unknown and fascinating species to showcase the beauty, diversity, and remarkable characteristics of our shared planet Earth.

In the snowy, desolate regions of the Northern Hemisphere, across Canada, Siberia, and dipping into the Mongolian steppe, massive wings soar silently over the frozen landscape. The great grey owl is known by many names, cinereous owl, spectral owl, Lapland owl, spruce owl, bearded owl, sooty owl, and the ominous, ‘Phantom of the North.’ Piercing yellow eyes sunk deep into their grey and white facial plumage adds to their mysterious nature. Deep, rhythmic whoos heard across the otherwise silent forest complete this haunting picture. However, despite the personification and lore of the locals, great grey owls are mostly non-aggressive and provide essential pest control to their ecosystem. 

Great grey owls are the world's largest species of owl by length. Their bodies can weigh up to 1,900 g (4.19 lb), measure 84 cm (33 in) long, but their wingspan can exceed 1.52 m (5 ft). As with most owl species, females are slightly larger than males. Both genders have grey feathers with white patterned bars streaking through them. Their large round heads have a distinct circular pattern surrounding their eyes and below their bright, yellow beak is a pure white tuff or "bow-tie."

The great grey owl is the flagship species of the Sayan Montane Conifer Forests ecoregion, located in the Sayan Mountain Conifer Forests, Alpine Meadows & Steppe bioregion (PA36).

These large facial feathers focus sound and allow the great grey owl to be an alpha predator in their ecosystem. Mainly hunting at night and near dawn and dusk, these birds wait at a low listening spot like a stump, tree limb, or fence post. They can hear prey moving beneath 60 cm (2.0 ft) of snow and upon locating, will swoop down and then plunge into the drift. Their diet relies upon available small rodents like mice and gophers with the occasional hare, mole, shrew, and weasel. Great grey owls play an important role in their environment by controlling these small animal populations. 

Benefitting from other species in the forest, great grey owls do not build their own nests but rather use abandoned ones. Breeding occurs from March to May and four eggs are typically laid. Owlets hatch after 30 days and spend 2 to 3 weeks in the nest. After this time, the young jump or fall from the nest to explore their world, and then the white, fuzzy young must use beak and feet to climb back into trees. Finally, they learn to fly after an additional 1 to 2 weeks, and by winter they are on their own. 

The abundance of food affects the number of eggs a female lays and in years when small mammal populations are very low the great grey owl may not attempt nesting. Drought, deforestation, and global temperature rise also keep the great grey owl from mating as food and habitat become scarce. Luckily, the great grey owl population is healthy and not currently threatened by extinction. Conservation efforts like the Mother Tree Project in British Columbia and the Snow Leopard Conservancy in Eastern Eurasia indirectly help protect the great grey owl and its ecosystem. This proves once again that our planet is a shared one and helping one species protects many more and ultimately, even us humans. 

The great grey owl is the flagship species of the Sayan Montane Conifer Forests ecoregion, located in the Sayan Mountain Conifer Forests, Alpine Meadows & Steppe bioregion (PA36).