Yup, I'm officially done with winter. I'm outta here! Me and Mr. Nature Geek are packing our bags and are heading south. We're spending the next two weeks in Costa Rica! (If you thought I was geeking out in Joshua Tree National Park, you just wait.) But before I go, I wanted to get in one last blog post, and what better thing to talk about than migrations? This week, let's cover some migration FAQs:
Why don't all birds migrate?
I was asked this very question just yesterday. Why is it that some birds can tolerate the cold and others can't? The answer is that it's not the cold that drives most birds to migrate, it's a lack of food. Birds that migrate most of time do so because their food becomes scarce or completely absent in the winter. A lack of flower nectar, insects, and fruit, means that the hummingbirds, warblers, and orioles that depend on them must fly south to in order to stay alive. The birds that stick around are those that can always find food to eat. Most of these birds eat seeds or other animals, two kinds of foods that persist in the winter months. Food availability can also vary by region, which affects migrations. For example, while some Canada geese may fly south for the winter, here in Philadelphia, where many waterways remain open and lawns only covered in patchy snow, the geese stick around.
Do any other animals migrate?
Yes, there are many different kinds of animals that migrate! Insects, mammals, fish, amphibians, reptiles, all have representatives that get a move on at some point in their lives. Monarch butterflies have one of the most amazing feats of migration as they fly 3,000 to Mexico to avoid freezing to death. And again, just like with birds, not all migrations are driven by an inability to handle the cold. Caribou of the north and elephants in Africa, one of the last places you'd think of a winter migration, move in order to find food. For elephants, their vegetation doesn't freeze, but rather desiccates during the dry season. Another example, a migration of 1,000 feet to a breeding pond, may not sound like a huge feat to you, but when you're a spotted salamander and everyone wants to make a meal out of you, it's a pretty big deal!
Are all migrations southward?
Migrations occur in all dimensions. The largest migration on the planet occurs in the ocean, where animals that dwell in the deep come to the surface under the safe cover of night in order to feed. In the Rocky Mountains, big horn sheep and mountain goats move from the mountain tops into the valleys in the winter. And salmon are known for their migrations upstream in order to spawn.
What is the longest migration?
That record belongs undeniably to the arctic tern. This bird, hardly more than a foot in length, flies from Greenland to Antarctica in winter and back again in summer. Not only that, but arctic terns don't even fly a straight path between their destinations. Instead, they zigzag in order to take advantage of air currents so that they do not fly into the wind. This makes for a one-way migration of 22,000 miles! And because the arctic tern can live for around 30 years, the amount of flying it does in its lifetime can equal three trips to the moon and back. Fly on little dude, fly on.
I'm thankful that my personal migration to Costa Rica won't take nearly as much time as that of the arctic tern. We all know how hard it is to redeem frequent flyer miles anyway. I shall return in two weeks with stories and photos from a warmer climate so that you can migrate vicariously!