It’s the middle of winter holidays, and every family has their rituals. Whether you’re roasting chestnuts on an open fire or bundling up and heading out into the rain or snow, everyone has their own way of enjoying (or at least making the most of) the colder weather. With the COVID-19 pandemic, even “snowbirds” have been staying close to home in the winter months. But the non-human summer residents of Mayne Island have no such inhibitions. Among other creatures, there are birds, bats, and baleen whales that frequent Mayne in the summer but are absent every winter. Which begs the question: Where did they go?
Although there are many species that journey far and wide and cross Mayne Island in their travels, a few outstanding migrations are worth taking note of. From a hummingbird that weighs less than a nickel to a whale longer than a bus, a diversity of animals travel thousands of kilometers every year as the seasons change. The hoary bats, rufous hummingbirds, humpback whales, and turkey vultures of Mayne Island are spending this winter somewhere toasty warm.
Migration Patterns
Before we jump into the amazing feats of migratory critters, let’s start with the basics: What is migration, and why do animals do it?
Animal migration is the movement of animals from one place to another, often over long distances. It’s usually initiated by changes in season or the climate of a place. Animal migrations are cyclical and involve a return trip. In many cases, migrations bring animals back and forth between feeding and breeding grounds. Other animals migrate so they can remain in a consistent climate (eg. going south for the winter to avoid freezing temperatures in the northern hemisphere).
Hoary Bats: When Solitary Creatures Converge
Hoary bats are natural social distancers, enjoying a solitary lifestyle during their northern summers. They have lots of space to spread out: hoary bats have the largest distribution of any bat species in the Americas. They have been documented in every province and territory in Canada and are found as far south as Argentina. These large bats spend the summers foraging in open areas and roosting alone in tall trees. Once the weather begins to turn and insects become scarce, they link up with other hoary bats in groups that can be hundreds strong and travel south for the winter.
The migration patterns of hoary bats are poorly understood, but the ones from BC likely fly upwards of 1000 km, ending up in southern USA and northern Mexico. During their long migrations they fly at an average of 20 km per hour, at heights of up to 2.4 km above ground. They replenish their energy stores by stopping to hunt along the way. The journey is perilous: Each year hundreds of thousands of migratory bats are killed by wind turbines. Measures can be taken to reduce mortalities, such as stopping the turbines when wind speeds are low (and barely any energy is generated, anyway) during peak migration periods.
Once they reach their southern destinations, the activities of the hoary bat are shrouded in mystery. Some may continue to hunt insects in these warmer areas where food is plentiful. In a single meal, they can consume 40% of their body weight! Others might spend part of their winter hibernating. When spring comes back around, the bats return to BC, where the Conservancy watches for them during our bat surveys.
Rufous Hummingbird: Massive Journey, Tiny Wings
When you’re looking at migration length compared to body size, the rufous hummingbird’s Alaska to Mexico journey is hard to beat! This tiny critter beats its 5 cm long wings to travel an astonishing 6,300 km twice a year. In the late summer and early fall, they move down the Rocky Mountains towards the west coast of Mexico. They tend to travel on their own, at approximately 40 km/hr. Unlike the hoary bats previously mentioned, rufous hummingbirds fly low to the ground while migrating.
Why migrate south? Hummingbirds have the highest metabolic rate of any animal on earth, and can eat up to half of their body weight in sugar each day. When northern food sources begin to dwindle with the colder weather, they migrate towards Mexico to eat nectar from flowers, as well as small insects and spiders. Winters are spent in southern Mexico, where they are known to frequent the pine-oak forests of Guerrero.
Humpback Whales: No Eating in the Bedroom
Humpback whales are known around the world for their annual migrations, with some individuals traveling well over 4500 km one way. In the waters off BC’s coast, humpbacks spend the summers eating massive amounts of krill and small, schooling fish in nutrient rich, productive zones. By this time of the year, we still see occasional humpbacks circling Mayne Island, but many have moved towards warmer waters to breed.
Most of the humpback population that feeds around southern BC migrates to Mexico and Central America. From approximately December to March each year, these whales gather in subtropical and tropical waters to mate and give birth. There are very few observed instances of humpbacks eating in their breeding grounds: they live off of their own fat, stored up from months of feeding. Pregnant females are the first to arrive at and last to leave the feeding grounds each year, as they need extra fat reserves to survive the migration. Interestingly, grown offspring are often found at the same breeding and feeding grounds as their mothers.
Life in the breeding grounds is chaotic. Males compete for females by two seemingly incongruous means: singing and fighting. All the whales in the North Pacific Ocean sing the same song, and they do it without having vocal chords! The song is made by pushing air through their nasal cavities, and can be heard by other whales thousands of kilometers away. Lactating females avoid each other in the breeding grounds, and groupings of whales are constantly shifting. Mother-calf pairs are often seen with a third whale, normally a male. Other groups usually consist of one female and several males. Females become pregnant every two to four years, and pregnancies last about a year. Calves nurse for about three months in the warm breeding grounds and can grow 0.5 m each month in preparation for the long trip to the feeding grounds.
Turkey Vultures: Gone Before Thanksgiving
Have you ever been to East Sooke Park in the early fall? If you have, you’ve likely seen mass amounts of turkey vultures soaring on rising currents of warm air, or “thermals,” overhead. The turkey vultures that frequent the hilltops of Mt. Parke and Vulture Ridge on Mayne Island are likely to be found there with others from across the Gulf Islands and Vancouver Island, each waiting for their turn to cross the Strait of Juan de Fuca. Unlike the previously mentioned rufous hummingbirds who constantly beat their wings to fly, turkey vultures primarily soar on thermals to get from one point to another. They must sometimes wait for weeks for the right conditions to travel across an open area, like the Strait. Despite their dependency on thermals, they can reach heights of 6 km above ground and fly over 300 km per day.
Once they’ve made it to the Olympic Peninsula, these bald birds continue to travel south towards Venezuela. Due to their dependency on thermals, they only fly after the sun has been up for a few hours. Like many species, turkey vultures eat very little during their migration, stopping to feed only if an unexpected opportunity arises. Once they reach Venezuela, they spend the winter months feeding on carrion and soaring on thermals provided by the warmer climate.
Next time you see a turkey vulture or any of our other migratory species, take a moment to appreciate the arduous journey they have made to get here! It’s humbling to think of the places these animals have seen, and to share a space with them for part of the year. They remind us that animals need continuous habitats to survive and thrive, not just isolated patches of nature in public parks and marine protected areas.
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