Extinction patterns in the avifauna of the Hawaiian islands


Alison G. Boyer, MSC 03-2020, Department of Biology, University of New Mexico, Albuquerque, New Mexico, 87131. E-mail: aboyer@unm.edu


Through the continuing accumulation of fossil evidence, it is clear that the avifauna of the Hawaiian Islands underwent a large-scale extinction event around the time of Polynesian arrival. A second wave of extinctions since European colonization has further altered this unique avifauna. Here I present the first systematic analysis of the factors characterizing the species that went extinct in each time period and those that survived in order to provide a clearer picture of the possible causal mechanisms. These analyses were based on mean body size, dietary and ecological information and phylogenetic lineage of all known indigenous, non-migratory land and freshwater bird species of the five largest Hawaiian Islands. Extinct species were divided into ‘prehistoric’ and ‘historic’ extinction categories based on the timing of their last occurrence. A model of fossil preservation bias was also incorporated. I used regression trees to predict probability of prehistoric and historic extinction based on ecological variables. Prehistoric extinctions showed a strong bias toward larger body sizes and flightless, ground-nesting species, even after accounting for preservation bias. Many small, specialized species, mostly granivores and frugivores, also disappeared, implicating a wide suite of human impacts including destruction of dry forest habitat. In contrast, the highest extinction rates in the historic period were in medium-sized nectarivorous and insectivorous species. These differences result from different causal mechanisms underlying the two waves of extinction.