Data from: Multiple reversals in bill length over 1.7 million years in a Hawaiian bird lineage

Evolutionary change has been documented over geological time but reversals in morphology, from an ancestral to a derived state and back again, tend to be rare. Multiple reversals along the same lineage are even rarer. We use the chronology of the Hawaiian Islands and an avian example, the Hawaiian honeycreeper amakihi (Hemignathus spp.)lineage, which originated on the oldest main island of Kauai 1.7 million years ago, to examine process of sequential reversals of bill length. We document three single reversals and two multiple reversals of bill length on six main islands from oldest to youngest, consistent with the phylogeny of the lineage. Longer bills occur on islands with endemic species, including phylogenetically relevant outgroups, that may compete with or dominate the amakihi. On islands without those species, the amakihi had shorter bills of similar length. Both types of reversals in this lineage integrate microevolutionary processes with macroevolution in the adapative radiation of Hawaiian honeycreepers.