Figure 22.13 Effects of island area and isolation on bird species richness. In the South Pacific, researchers examined the number of birds living on islands that were various distances from New Guinea. On islands of a similar distance from New Guinea, large islands contained more bird species than small islands. On islands of a similar area, islands near to New Guinea contained more bird species than islands far from New Guinea.

Data from R. H. MacArthur and E. O. Wilson, An equilibrium theory of insular zoogeography, Evolution 17 (1963): 373–387.