The frigate bird is instantly recognizable, with their large red sac and forked tail. Although you might only catch a glimpse of the sac while they're resting while the fork might only be seen during flight.
The Galapagos is home to a large number of these birds, many of which reside there throughout the year. You'll most likely see them around any of Floreana, Genovesa, or San Cristobal Islands, but there is an evergreen colony on North Seymour, the small island to the north of Baltra.
While hiking on North Seymour we had the opportunity to witness a male Frigate perform a mating dance, trying to attach the attention of a lovely female. After about 10 minutes she yawned and flew away. Obviously he needed some work on his routine. Not the best picture: