Isla Seymour is a 1.9-sq-km island with a dry landing. A rocky 2.5km trail encircles some of the largest, most active seabird-breeding colonies in the islands. Frigates and blue-footed boobies are the main attractions and there is always some kind of courtship, mating, nesting or chick-rearing to observe. You can get close to the nests – there is always at least one pair of silly boobies that builds their nest in the middle of the trail. Sea lions and land and marine iguanas are common; occasional fur seals, lava lizards and Galápagos snakes are seen, too.
Mosquera is a tiny island (about 120m by 600m) between Baltra and Seymour. There's no trail, but visitors land on the beach to see (or swim with) the sea lions. Keep your distance – males are territorial and may charge or swim into you if you get too close to females or young.