It was a chilly evening in the winter of 2008. I was crossing the railroad tracks on the way home from work when I suddenly found myself in the middle of a flock of perhaps 2,000 birds.
I had inadvertently startled a huge flock of birds that had recently irrupted!
We don’t live in a particularly active tectonic zone, so there should be no confusion between an irruption of birds and a volcanic eruption (although Jasper apparently did have an earthquake 44 years ago). In bird-nerd terms, an irruption is a sudden change in numbers of a bird population, almost always in response to food.
Irruptions take place when there is a food shortage where the birds currently are, and there is an abundance of food where they are headed. These movements can be from high altitude to low, from east to west, from north to south…pretty much any way you can think of. Irruptions are sort of like migrations, except that migrations occur between breeding grounds in the summer and warmer places to spend the winter. Migrations occur like clockwork, while irruptions can take place at any time—something that can be regular, or not very regular at all.
The Bohemian lifestyle
In terms of Jasper irruptions, the first birds you might think of are the Bohemian Waxwings. These social birds arrive in big noisy flocks almost every winter to feast on the bounty of mountain ash berries that Jasper’s ornamental trees usually provide.
According to Webster’s, a bohemian is an artist living an unconventional lifestyle. I like to think of our Bohemian Waxwings as unconventional artists that specialize in creating art on our parked cars (their palette leans heavily to red). You may have noticed that in some years, we have waxwings by the thousands for much of the winter, but in other years hardly any show up, and if they do, it’s only for a few weeks. This inconsistency is tied closely to the berry crop – when the berries run out, the waxwings get the heck out of Dodge.
For the love of conifers
Another Jasper bird that irrupts (but not regularly) is the White-winged Crossbill. These oddball finches specialize in eating the seeds from conifer trees, most often white spruce, or tamarack. As the name suggests, the tips of their bills are actually crossed, a feature which enables them to pry open conifer cones to get at the seeds within. Crossbills are completely dependent on cone crops. They will travel (irrupt!) at any time of the year and in any direction—anywhere they can get conifer seeds! They will also breed at any time of year, again in response to food abundance. Crossbills don’t arrive in massive numbers like the Waxwings, so look for smaller flocks at the tops of big spruce trees, or on the roads picking up gravel. The males are red and black, while the females are yellow and grey. Both have white wing bars.
The year everything turned rosy
The mother of all Jasper irruptions happened on that winter in 2008, and it only happened once (at least as far as I know; perhaps some long-time Jasperites can correct me). In that year, something like 5,000 Grey-crowned Rosy Finches descended on Jasper and spent the entire winter dominating bird feeders and stripping our maple trees of their seeds. They would also hang out on the railroad tracks, where they would hoover up spilt grain. Rosy Finches are birds of the alpine—they hold the North American record for high altitude breeding, on the slopes of Denali in Alaska. They do however, descend to lower elevations in winter. In 2008, they hung around Jasper from January until mid-April, and then returned to their high alpine breeding grounds, never to be seen again (at least not in large numbers…the odd one will show up). If you want to see one in the summertime, small numbers can be found pretty reliably at the top of the Jasper SkyTram.
Grey-crowned Rosy Finches are a beautiful bird—a rich chestnut brown with rosy wing bars and a grey crown with a black forehead. Let’s hope they return someday for a second irruption!
Mark Bradley // email@example.com