For many people, the Cape Petrel will be one of the first birds they see while crossing the Drake Passage. Often the ship is followed by a dozen or so of these nicely coloured birds. They are easy to identify by their black (or actually more dark brown) and white checkered pattern on their upper wings.
We often get the question why do these birds (and others) follow ships? They likely try to feed on things that are usually just under the surface of the water which is brought to the surface by the propellor of the ship. Another reason is that she ship creates some wind, which they can use again to get uplift which they need to fly. Another reason could be that they have learned that boats often are connected with food as many of the ships in these waters are fishing vessels where they can feed on the discards.
I always like to think there is a fourth reason, which is that for birds that typically spent most of their time at the open ocean, which makes a ship a nice change of scenery for a while. But that might be an over-anthropomorphic thought from me.
Cape Petrels are found all around Antarctica, on subantarctic islands and can be found all around the Southern Ocean and the southern parts of the Atlantic and Pacific oceans.
There are two subspecies of the Cape Petrel. The one seen in the Drake Passage is of the nominate subspecies and has a bit more white on the uppersides as the australis subspecies, which can be found around Australia and New Zealand.