When the petrel sea bird feeds, its feet patter on the surface of the water. It almost looks as if the bird is walking on water. There is a story in the bible about St. Peter walking on water. Hundreds of years ago someone familiar with that story named the bird after St. Peter. At least that's what I've been told.
Petrels are a type of pelagic bird—they live on the open sea, flying to land only to breed. Non-pelagic birds fly close to shore; seeing them is a sign that land is nearby. If you can't tell a pelagic bird from a non-pelagic one, you'll be sorely disappointed if you're lost at sea and encounter petrels. You might think you are close to land when in fact it's no where in the vicinity of your boat.
Because they fly for long periods of time, petrels have thin legs. Their legs can't support their weight very well, which is one reason stay at sea except when they need to breed.
Petrels—and other pelagic birds—drink sea water. You or I would die if we drank that much salt. How do these birds survive? They have a specially built bill that has nostril tubes for blowing out salt. If you look closely, you can see the saline dripping out of the tubes.
When I was in Antarctica recently, I saw 10 different varieties of petrels. They appeared soon after we crossed the Antarctic convergence zone, circling the ship while we were in open waters. One of my favorites is the Cape Petrel. It has the most amazing pattern on its wings. It almost looks stenciled on its back.
Photos copyright Glen Gould.