At Home in the Trees – the Great Blue Heron

December 30, 2012

patience

Great Blue Herons are magnificent looking birds but they can also look quite awkward at times. A heron wading in water, motionless until the moment is right to strike, looks totally in its element. However, these tall, long-legged waders nest (often in colonies) and roost in trees. If you were to design a tree-nesting bird, chances are that you would not come up with a blueprint for a Great Blue Heron. Yet they do just fine, thank you.

taking flight

I worked as a biologist on a province-wide volunteer census of Great Blue Herons several years ago in Ontario. I became quite familiar with Great Blue Heron colonies. Colonies ranged in size from 1 nest (I know, not technically a colony) to over 300 active nests. Most of the large colonies were in hard wood swamps. Wading through these colonies and approaching each tree was quite the experience. (The survey was well-planned and no one entered a colony at a time when birds would desert their young or in a manner that disturbed the birds. ) Great Blue Herons regurgitate food for their young – fish, frogs, carrion, etc. Sometimes they miss and the food falls to the forest floor – as do dead young and excrement. The floor beneath a Great Blue Heron colony (rookery) becomes quite the gross soup of organic materials. Small green duck weed often grew in the same swamp so that my waders were often covered with green, very smelly and very wet slime. And the noise! I strongly suspect that a colony of pterodactyls (if they nested in colonies…who knows?) might look, smell and sound similar to these colonies. Still, I relished my days in the field learning about Great Blue Herons.

while the Ospreys are gone…

Nesting in colonies allows these birds to take advantage of abundant and localized sources of food, such as fish. It also makes them vulnerable, however. Most of the larger Ontario colonies had been active for generations of herons – as long as 50 years or more. Logging can clear out a colony in a season and there may not be another suitable nesting location for miles around. A tornado destroyed most of the nests in one Ontario colony. Heron young may be safer in a nest in the midst of a large number of nests rather than in a solitary nest in the forest. Being a Great Blue Heron young is not a Disney experience. Often the youngest bird in the nest does not make it because it cannot compete with its larger siblings for food.

at home in the trees

I enjoyed traveling Ontario finding and censusing colonies, meeting people who reported colony locations or who were willing to census colonies and of course, working with my field assistants.

closeup of a Great Blue Heron

I see Great Blue Herons now on Kootenay Lake. They are usually solitary birds hunting for fish, small turtles, carrion and other food. They do nest on Kootenay Lake but not in the large colonies that we recorded in Ontario in the 80’s. I like watching them silently and patiently stalk their food. These birds occasionally turn up in winter if the water is not yet frozen and they look oddly appropriate there against a backdrop of snow, dark water and ice.