Isla Isabela, More than Boobies

Isla Isabela

Lago Crater

Male Frigate-bird

Female Frigate-bird

Young Frigate-bird in Flight

Isla Isabela is a birdwatcher’s paradise offering many species in addition to the ever present population of boobies. The island is literally covered with birds. One of the cruising guidebooks suggests looking for the flocks of circling birds to find this incorrectly charted Island. In addition to the variety of boobies, the island is also home to Great Frigate-birds, Magnificent Frigate-birds, Sooty Terns, Brown Noddies, and Heermann’s Gulls. It seemed eerie walking across the island while so many birds stared down at us from every tree-top and frigate-birds flew about overhead – it was as if we were in a scene from Jurassic Park. The island is actually a result of prehistoric volcanic activity, and the caldera of this extinct volcano is located in the middle of the island. The caldera has since filled with water and is called Lago Crater. Frigates, which are related to the Pelican, look rather prehistoric. They are a long-winged, fork-tailed bird with a hooked bill. Interestingly, frigates can’t walk very well and do not swim, so are essentially aerial creatures. Having the largest wingspan (85 inches) to body weight ratio of any bird, they are able to stay aloft for more than a week, landing only to roost or breed. The only other bird known to spend days and nights on the wing is the Common Swift. Male frigates are all-black and have a scarlet throat pouch (gular pouch) that is inflated like a balloon during the breeding season to attract a mate. Females are black, but have a white breast and a blue eye-ring, while immature birds have a white head and white under-parts. Nests are constructed in low trees and a single egg is laid each breeding season. Both parents take turns feeding for the first three months, after which the mother feeds the young for another eight months. Since it takes so long to rear a chick, frigate-birds do not breed every year. It is typical to see juveniles as big as their parents waiting to be fed. When youngsters sit waiting for endless hours in the hot sun, they assume an energy-efficient posture - their head hangs down and they sit so still that they appear to be dead. When the parent returns, however, they wake up and the hungry juvenile plunges its head down the parent’s throat and feeds. Because frigates produce very little oil, they are unable to land or take off from the water so their food source is caught in flight, snatching prey from the beach or ocean surface with their long, hooked bills. Sometimes frigates rob chicks from other seabirds, earning the nickname, Man of War birds. We also saw Brown Pelicans and Heermann’s Gulls strutting along the beach. Adult Heermann’s Gulls have a medium gray body and a red bill with a black tip. In the breeding season the head is white and in non-breeding season the plumage is a dusky gray. After breeding, the bird colonies disperse to central California and south as far as Guatemala, and less commonly north as far as British Columbia. Heermann’s Gulls sometimes pirate prey from other seabirds, particularly Brown Pelicans with whom they keep company. We also enjoyed seeing the numerous iguanas and lizards on the island, scurrying over rocks and hiding in the underbrush. Visiting Isla Isabela is a wonderful stop for boaters, but the island is exposed to wind and ocean swell with a rocky irregular bottom that tends to "eat" anchors. It has been suggested that boaters secure a rope to the boat end of the anchor chain so it can quickly be cut loose in case of bad weather or in case the anchor becomes lodged in the rocks.