Friday, January 9, 2009

Colourful keystone character.

Northern Flicker.

Northern Flickers make a mess of suet cages. They swing about, flapping clumsily, bashing the suet cake to bits with their big bills. More ends up on the ground than in their gizzard. Not to worry though, juncos, sparrows, finches, towhees and others rush to snap up the crumbs. The flicker is thus, indirectly, a provider of winter food for other birds.

This unintended charity is not out of character for our colourful friend. It is, after all, a woodpecker, and many woodpeckers are considered keystone species—species vital to their ecological communities because their activities provide the ecological needs (foraging or nesting habitat, food, etc.) for many other species. They are primary cavity nesters (i.e., they create the holes), whose abandoned nests will then be used by other species (secondary cavity nesters).

Although the Pileated Woodpecker is a much larger bird and among woodpeckers creates the largest nest cavities, which may then be adopted by the widest diversity of secondary cavity nesters-- including Western Screech Owl, Flammulated Owl, Northern Saw-whet Owl, Boreal Owl, Northern Hawk Owl, Vaux’s Swift, Barrow’s Goldeneye, Common Goldeneye, Wood Duck, Hoary Bat, Silver-haired Bat and Northern Flying Squirrel-- it isn’t considered the key-most keystone woodpecker in this part of the continent.

That honour goes to the Northern Flicker (despite its penchant for, as I have previously reported, pummelling the roof of our house). Although providing nests for a lesser size-range of secondary cavity nesters (excluding the larger, tree-dwelling ducks), the flicker is a more important keystone species by virtue of its commonness and widespread range. Its list of nest inheritors includes Bufflehead, Hooded Merganser (which are both small ducks), Northern Pygmy-owl, Western Screech Owl, Flammulated Owl, Northern Saw-whet Owl, Boreal Owl, Northern Hawk Owl, Mountain Bluebird, Western Bluebird, American Kestrel and Northern Flying Squirrel. Impressive.

Something to think about as they swing around, flailing and prodding with that hefty tree-battering bill, sending chunks of suet, seed and fruit to the ground below. The juncos, sparrows, finches, towhees are happy, and sooner or later, I'm hoping, a Varied Thrush will be happy too. Which will make me happy.

References on cavity nesters and keystone species:

Aubry, K.B. and C. M. Raley. 2002. The Pileated Woodpecker as a keystone habitat modifier in the Pacific Northwest. USDA Forest Service Gen. Tech. Rep. PSW-GTR-181. 2002.

Fenger, M., T. Manning, J. Cooper, S. Guy and P. Bradford. 2006. Wildlife & Trees in British Columbia. Lone Pine Publishing. 336 pp.

1 comment:

Anonymous said...

I don't think there is a more spectacular sight than a pileated at my suet cage.