Origin, paleoecology, and extirpation of bluebirds and crossbills in the Bahamas across the last glacial–interglacial transition

Abstract

On tropical islands, extensive extirpation of birds and other vertebrates occurred during the Holocene, following human arrival. Much less is known about pre-Holocene extirpation on islands. We focus on two species (Eastern bluebird Sialia sialis and Hispaniolan crossbill Loxia megaplaga) that were lost in the Bahamas to changes in sea level (becoming higher), land area (getting smaller), climate (becoming warmer and wetter), and habitat (loss of pine grassland) that took place during the last glacial–interglacial transition, many millennia before peopling of the islands. While volant, the bluebird evolved a short wing in the Bahamas, whereas the crossbill retained a similar morphology to the surviving population on Hispaniola. Each major glacial–interglacial shift reconfigured the resident Bahamian flora and fauna.