SPECIES RICHNESS ON THE NONDISTURBED NORTHWESTERN

An examination of selected ecological variables on the 18 low, sandy, non- disturbed islands of the northwestern Hawaiian Islands, and the vascular plants and birds, primarily seabirds, occurring there shows that species richness on low, sandy, oceanic islands is influenced by ecological diversity and is affected by variables similar to those on high, rocky islands. Species richness of vascular plants on these islands can be predicted by means of stepwise regression on the basis of area of vegetation, and to a lesser extent, elevation. In turn, variation in numbers of breeding species of seabirds, total species of seabirds, and total species of birds on these same islands can be predicted on the basis of number of species of vascular plants, and to a lesser extent, area of the island. Ecological diversity, although poor in quality, is of prime importance in regulating use of low, sandy, oceanic islands by any seabird. Although terrestrial birds use islands for obtaining food and for nesting whereas seabirds use islands only as a nesting and roosting place, species of terrestrial birds and sea- birds on islands are associated with similar ecological variables.