Honeycreepers

Honeycreepers are 14 living species of birds in the family Drepanididae, which occur only on the Hawaiian and Laysan Islands and nearby islands in the equatorial Pacific Ocean. Unfortunately, a further eight species of honeycreepers have recently become extinct as a result of ecological changes that humans have caused to the habitats of these birds. In addition, at least half of the surviving species of honeycreepers are perilously endangered, as are some of the distinctive subspecies that occur on various islands.

Most species of honeycreepers breed in native forest and shrubby habitats in the Hawaiian Islands. They are resident in those habitats and do not migrate elsewhere during their non-breeding season.

The honeycreepers are small birds, ranging in body length from 4-8 in (11-20 cm). Their bills are extremely varied, depending on the diet of the species. Some honeycreepers have small, thin beaks, ideal for gleaning arthropods from tree foliage. Other species have longer, curved beaks, adaptive to feeding on nectar or on insects deep in bark crevices. The beaks of yet other species are heavier and more conical and are used to feed on plant seeds.

This extreme diversification of species with various bill shapes within such a closely related group of birds is a famous example of speciation. In the case of the honeycreepers, the speciation was driven by natural selection in favor of birds having adaptations favorable to taking advantage of specific ecological opportunities, which occurred in a wide variety on the Hawaiian Islands. Evolutionary biologists consider the adaptive radiation of the Hawaiian honeycreepers to be one of the clearest illustrations of the phenomenon of evolution.

Undoubtedly, all of the many species of honeycreepers evolved from a single, probably quite small founder group that somehow arrived on the Hawaiian Islands by accident in the distant past. Because few other types of birds were present, a variety of ecological niches were unfilled or were utilized by generalist organisms. Under the pervasive influence of natural selection, the original honey-creepers slowly evolved a repertoire of differing bill shapes and other useful adaptations. Eventually, the specialized populations of birds became reproductively isolated. Ultimately, they diversified into different species that were better adapted to feeding and living in specialized ways.

The honeycreepers are also highly variable in color, which ranges from a relatively drab gray to brown, olive, yellow, red, and black. Some species are dimorphic, with the male being larger than the female.

Honeycreepers build their cup-shaped nests in trees. They typically lay two to four eggs, which are incubated by the female. Both of the parents share the duties of raising their babies.