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Mountain migrations


In their search for berries, black bears are Whistler’s most popular mountain migrants. Photo by Liz Barrett.

Hearing the word “migration,” you might think about birds flying great geographical distances. However, there are other kinds of animal migrations like the ones that happen every year in Whistler—altitudinal journeys up and down mountains. Just like humans that escape the heat and busyness of the valley during hot summer days, other animals are also always looking to improve their living condition.


Our most popular mountain migrants are black bears. They start each spring by feeding in snow-free valleys but then journey up mountains looking to feed on berries, which ripen at higher elevations as temperatures warm up throughout the summer. To prepare for hibernation, a black bear needs to eat 20,000 calories per day, which is equal to 36 kilograms or 78 pounds of berries. 


A favourite food of black bears is black huckleberries (Vaccinium membranaceum), which ripen as late as September near tree line. Even higher on the mountain in the alpine, the berry bushes are dwarfed but still an important food for bears. Dwarf blueberry (V. caespitosum) is a common alpine berry and less common is blue-leaved blueberry (V. deliciosum).


But for bears to enjoy large and plentiful berries, the flowers of Whistler’s berry plants first need to be visited by insect pollinators. Even though some fruit can pollinate without the aid of insects and other animals, they will produce a much less abundant crop. Insects are another kind of mountain migrant, with many feeding on the pollen or nectar of flowers as they bloom higher and higher on the mountain.

 

With insects moving higher on the mountain, whatever feeds on insects will also move higher. Many birds feed primarily on insects so will follow them up the mountain in the summer. One example is the mountain chickadee that feeds on alpine insects and spiders during warm months, then often moves to lower elevations during colder months.

 

Another mountain migrant in a class all its own is the American dipper—North America’s only truly aquatic songbird. Right now, these adventurous thrill-seekers of the songbird world are up in the mountains. They feed on insects in fast-flowing mountain rivers and streams, diving in and out of pools, braving waves, waterfalls, and whitewater. When alpine rivers freeze or dry up, this little charcoal-grey bird will be back down in the valley. True to its name, dippers are easy to identify by their odd habit of bobbing (or dipping) up and down while looking for food.


The way everything in nature is interconnected is utterly amazing—to realize that a 400-pound black bear is entirely dependent on tiny insect pollinators for survival! This is especially true in Whistler since black bears here have little (if any) access to fish for food. (Note that all life on Earth would be in trouble if insects disappeared, but that is a topic for another article.)


Hope you have fun exploring Whistler’s amazing natural surroundings. If you enjoy the alpine, you might consider yourself a kind of mountain migrant as well!


Written by: Kristina Swerhun


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