Ever wondered what bird migration looks like across the entire Western Hemisphere? Well, thanks to the visionaries at the Cornell Lab of Ornithology, now we know:
The gif is kind of hypnotizing, and definitely fun to watch. But what exactly are we looking at?
The dots are showing 118 different species of birds as they travel between their breeding and wintering grounds in North, Central, and South America. The routes are based off of millions of eBird observations from 2002 to 2014, mapped out and analyzed by Cornell scientists in a recent paper in Proceedings of the Royal Society B. (A numbered key for all the species is available.)
By blending all the birds’ trajectories into one animation, the researchers were able to pick out four major migration patterns: clockwise, counterclockwise, intersecting, and transoceanic. They found that most species choose a clockwise loop that takes them over water and land (come September, watch how a big mass of dots leaps off the East Coast and into the ocean, before arching back over the tip of South America). Though this may seem like a detour, it’s actually the fastest track for birds, since it lets them ride some powerful tailwinds to their destinations. The clockwise migrators—Black-billed Cuckoos, Cape May Warblers, and Veerys, to name a few—tend to mix things up, too. They fly wide in fall, and take a more inland path in spring (see how fewer dots are venturing over the Atlantic in the first half of the year). Meanwhile, species that stick to a straighter route—Brown-chested Martins, Crowned Slaty Flycatchers, and Rusty Blackbirds are three examples—use the same itinerary to and from their breeding grounds. To test this trend, just pick a dot and follow it from start to beginning. If it moves along a steady slope—and doesn’t make you dizzy—then you’ve probably chosen an "intersecting" bird.
Finally, notice how a lot of the straight shooters are funneling through the Yucatan? That's because they're sidestepping geographic obstacles, like the Sierra Madre Mountains. Knowing that this bottleneck exists is really important: It can help us pinpoint where a big chunk of species are resting during migration, so we can make sure those habitats are up to snuff. And to state the obvious—it shows us that the isthmus is a top-notch birding spot.
Wow . . . all that from citizen science—and one very nifty gif.