The continental islands have a number of habitats similar to those found on the mainland and it is not surprising to find a wide variety of land birds living on them. Coral cays, on the other hand, have fewer habitats, so their [L3 309 / land bird fauna] is more limited. Many land birds found on the cays are not residents - they are lost, have been blown offshore by storms, or may have made a rest stop during migration.
With 29 species from seven different families, seabirds dominate the coral cays. They are widely found throughout the Great Barrier Reef and of these, 19 species breed there with colonies on at least 78 different islands. The cays of the [M011 / Capricorn Group] are extremely important for breeding and roosting birds. It has been estimated that there are 1.5 million wedge-tailed shearwaters, 500,000 [I007 / black noddies], more than 3,000 each of crested terns and bridled terns and 2,000 each of black-naped terns and roseate terns.
Seabirds have different nesting habits - some nest on [L3 310 / bare sand] or rubble, others need low vegetation, shrubs or [L3 311 / trees]. Therefore, you will find that as a coral cay develops with ecological succession, its bird population changes with the change in vegetation. For example, a sand cay will have only those birds that nest on bare sand, while a [I005 / low wooded island] can support those birds, the birds that need trees and all those in between.
