If you look up the trunk of many of the larger trees within the Sea to Sky corridor you’ll see some large fist-sized holes. These holes are a result of the interactions of two important forest species. The pileated woodpecker ( Dryocopus pileatus ) – pileated refers to its distinctive red crest of head feathers – and the carpenter ant ( Camponotus pennsylvanicus ). They have a remarkable relationship and both are essential parts of a healthy forest.
These ants live in colonies chewed out of dead or decaying trees. You can see the sawdust they’ve pushed out of their nest at the base of the tree. They don’t eat the wood; they just use it to build nests and tunnels. This is bad news if it’s in your house, but good news for the forest because chewing the wood starts the process of recycling the nutrients into the next generation of trees. Each colony will contain as many as 10,000 ants.
Carpenter ants mostly hunt for food at night because they’re so big that they are easily seen by daytime predators, like birds. They "farm" aphids for honeydew, eat insects, dead animals, seeds and fruit. They are important in controlling the populations of pest insects, like the spruce budworm and tent caterpillars.
When the weather gets cold, the carpenter ants clump together in their nests and avoid freezing to death by producing glycerol, a kind of internal anti-freeze. This is the time they are most vulnerable to predation by the pileated woodpecker.
The pileated woodpecker, North America’s largest woodpecker and one of six woodpecker species likely to be seen around the Pemberton, Whistler and Squamish areas, loves to eat carpenter ants. It catches the ants with a long, sticky, barbed tongue. This amazing tongue also protects the pileated woodpecker from knocking itself out when hammering on trees by acting as the skull’s shock absorber. If we were to hit our heads on a tree as hard as a pileated woodpecker does, we’d be knocked unconscious. But all the hammering does wear its bill down, thus it continuously grows throughout the bird’s life.
The pileated woodpecker doesn’t migrate from our local area in the winter. Instead, it hunts for concentrated masses of hibernating ants and spends up to a month excavating a single hole to get to the sleeping ant colony where it can take its time eating every last one of them, a much needed protein and fat feast. The holes left behind are important habitat for other birds and mammals that use them for nesting sites.
So the next time you’re out on the trail, in the forest or even in your own backyard look up, way up, and see if you can spot the telltale holes in the tree trunks. Think about the remarkable relationship that resulted in them.
Monthly Bird Walk – The next bird walk will take place Saturday, Aug. 7th. Join Whistler experts in the monthly update of our feathered locals and migrants.
Written by: Dan McDonald