On 18 April 2014, Eric and I enountered a nice gathering of Pigeon Guillemots (Cepphus columba) — at one point Eric counted 23 individuals.
Some guillemots were displaying in the water. In the photo below, look for the bird with its head feathers raised (its head looks "puffy" relative to the others) and its tail held upright.
Occasionally one or two birds would take off and fly up to an offshore rock where it looked like they were investigating possible nesting sites.
The image below shows one guillemot in flight, with its white wing patches and bright red feet. But there's another guillemot in the picture that's barely visible because it's tucked away in a crevice. Can you spot it?
The second guillemot is in the upper right corner of the picture (see red circle below, highlighting the bird peeking out of the crevice and looking to the left).
A few fun facts: The males probably choose the nest site. They defend a territory of about 1-4 square meters around the nest entrance. The females lay 1-2 eggs, usually some time between mid-May and mid-June. Females and males will incubate the eggs for ~30 days. It will take ~40 days for the young to fledge (after being brought many fish by both parents).
And if you're wondering about those red feet — it's possible they're used in courtship displays.
[All facts from The Birds of North America account by Peter J. Ewins, 1993.]