Wilson's Storm-Petrel: The Water Walker
What’s the most ubiquitous bird you can think of? Even the least outdoorsy of us have crossed paths thousands of times with European Starlings, House Sparrows, and Rock Pigeons. Anyone with a yard has likely been visited by American Robins, and, in the case of those with feeders, American Goldfinches.
What if I told you there was one bird—an amazing bird—whose global population is estimated at a mind-blowing 30 million, but that most people have never even heard of, let alone seen? Well, uh, there is one. That’s why I’m writing this.
It’s called a Wilson’s Storm-Petrel, and it’s got more chutzpah in its weird little beak than the rest of those common species put together. (One word: Naricorn. More on that in a minute.)
Named after Alexander Wilson, the “Father of American Ornithology,” Wilson’s Storm-Petrels live their entire lives out on the open sea. Unless you take a dedicated pelagic seabirding trip (which you should, sometime), your best chance to see one is onboard a whale-watch boat off the East Coast. There are actually lots of different birds out there on the oceans, birds that never come to land but to breed (and even then it’s usually on remote, rocky islands). Like the more familiar albatrosses and shearwaters, storm-petrels cover huge distances of ocean to find their food. Unlike those large birds, though, Wilson’s Storm-Petrels are no bigger than a swallow.
For such a small bird to make a life out there on the rough seas requires some special modifications, and Wilson’s Storm-Petrels have a couple nifty ones, including, yes, the naricorn, a bony tube that covers the bird's nostrils. This mythological-sounding adaptation serves a number of important purposes, including keeping the dang salt out of the eyes, and it's shared by other seagoing species known together as “tubenoses.” (The decision to label the group "tubenoses" rather than "naricorns" does seem like a bit of a missed branding opportunity. Then again, ornithologists have never been known for their marketing skills.)
Back to the salt: A life spent on the ocean does not, obviously, involve a lot of fresh water. In order to whet their whistles without curing their little bodies from the inside out, storm-petrels and other tubenoses have developed glands above their bills that secrete excess salt. The naricorns serve to then direct the salty secretions away from the bird’s eyes and feathers, keeping them clean and tidy.
Naricorns also help storm-petrels smell out food on the landmark-less open ocean. Unlike mammals, few of the world’s birds use smell to find prey—vultures (mmm, rotting meat) and tubenoses are among the few exceptions. Storm-petrels scour the sea for krill, fish, squid, and other small sea goodies, and once they pick up the scent they zigzag back and forth through the odor trail to find the source.
When they find food, Wilson’s Storm-Petrels get to show off their special party trick. These birds are too small to dive, so they have to wait for their food to get close enough to the surface to pick off.
So they walk on water.
Okay, maybe they don’t actually walk on water. But when they aim themselves into the wind and sort of hover in one place, touching their feet to the water’s surface in a gentle, bouncing dance, that sure is what it looks like. Encountering a flock of Wilson’s Storm-Petrels in one of these balletic performances is an amazing experience for a pelagic birder—well worth the early morning wake-up and queasy stomach.
Why Wilson’s Storm-Petrels walk on water is a little uncertain. It might be to help keep their place over the food, but it might have a trickier purpose. Unlike most storm-petrel species, which have entirely black legs and feet, Wilson’s Storm-Petrels have high-contrast yellow webbing between their toes. It’s thought that by dipping their feet into the water the birds might actually be attracting prey to the commotion, essentially fishing with their feet.
Though its methods might seem unorthodox to us land-lubbers, the foot-fishin’, sea-drinkin’ Wilson’s Storm-Petrel has done pretty well for itself—it's likely the most numerous of all seabirds, thriving across the globe, in all oceans except the Arctic. So grab some Dramamine and a few ginger snaps and go find some yourself.