Comparison of faunal equilibrium turnover rates on a tropical island and a temperate island.

Rates of immigration and extinction of bird species on a tropical island, Karkar in the southwest Pacific Ocean, have been estimated from surveys made in 1914 and in 1969. Compared to a temperate-zone island of similar size and isolation (Santa Cruz off southern California), Karkar has a similar extinction rate, but a lower immigration rate expressed as a fraction of the mainland species pool, due to the sedentariness of many tropical forest birds. The probability of extinction is highest for species that are rare (due to narrow habitat requirements, large territory size, competition, recency of colonization, or marginal suitability of habitat), species with "in-and-out" tactics, and populations on small islands.