The swallow-tailed gull is endemic to the Galapagos and can be seen all around the archipelago. They prefer the areas with the warmer water at the eastern islands. When they are not breeding, they travel long distances and feed out in the sea as far south as Peru and Chile.
They make their nests on the rocks and cliff areas in the shoreline of most islands. Females lay 1 egg that hatches after 35 days. They spend about 3 months with their parents before they are independent.
They have several vocalizations, most of which are to communicate with others in the colony. They can warn other individuals when intruders are near the nesting sites.