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MARS Moment: Varied thrush irruption means more birds at Merville’s MARS hospital

James MacKenzie
A varied thrush dines on a berry. An influx of the birds this winter has resulted in more patients at the MARS wildlife hospital. Photo by James MacKenzie

James MacKenzie

Special to Black Press

The varied thrush, a robin-relative with a smart orange and black bib, is unmistakably a bird of the west. Its single toned haunting whistle is reminiscent of summer hikes up the mountain.

Folks around our parts are most likely to spot a few of these skittish but beautiful birds in winter, when they descend from their northern breeding grounds and high elevation haunts to spend the cold season in our low-lying backyards and parks. However, this year was a bit different; varied thrush have been seen in very large numbers this winter, reaching numbers not reported since the late 1980s according to the Comox Valley Christmas Bird Count.

When a volcano blows its lid we call it an eruption, but when sightings of birds like varied thrush explode in numbers, it’s called an irruption. Irruptions happen mostly in northern bird species, like finches, nuthatches, and owls, and are often caused by cyclical food crashes in the north that push birds south. However, a recent study published in the Canadian Journal of Zoology found that reproductive success in the prior breeding season was the main driver for varied thrush irruption events. Whatever is pushing these events, we can be happy to see so many of these beautiful birds than usual.

Unfortunately, an influx of birds in our developed areas means more likelihood for human-wildlife hazards. This winter, our wildlife hospital has had varied thrush admitted as window strike and cat attack patients. What can you do to help? Keep your cats indoors and treat your windows with feather-friendly window decals from our gift shop or explore DIY solutions at

James MacKenzie is the education program co-ordinator at the Mountainaire Avian Rescue Society (MARS) Wildlife Rescue Centre

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