Collapsing avian community on a Hawaiian island

Abstract

The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua'i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species' ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua'i represents an early warning for the forest bird communities on the Maui and Hawai'i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing.

Keywords: Extinction; Hawai’i forest birds; Kaua’i island; climate change; conservation.

Fig. 1. Population estimates and distributions for native Kaua‘i forest birds.

Population estimates (left panels) are from surveys conducted in 2000, 2005, 2007, 2008, and 2012 across both the interior and exterior portions of the Alaka‘i Plateau (with error bars representing the 95% CI of each estimate). Linear and exponential population change models fitted to the 2000–2012 data are projected from 2013 to 2050 or estimated year of extinction (when abundance is less than 30 individuals, which is a quasi-extinction level). The projections are just one possible outcome of many, assuming that the rate of change is accurate and does not change over the coming decades. Areas of distributional range (right panels) from 1968 through 2012 were determined from presence or absence at count stations and extrapolated across similar elevations and habitats. For ‘apapane, Kaua‘i ‘amakihi, and Kaua‘i ‘elepaio, estimated distributions from 2000 to 2012 were very similar, and only the 2012 range is shown.

Fig. 1. Population estimates and distributions for native Kaua‘i forest birds.

Population estimates (left panels) are from surveys conducted in 2000, 2005, 2007, 2008, and 2012 across both the interior and exterior portions of the Alaka‘i Plateau (with error bars representing the 95% CI of each estimate). Linear and exponential population change models fitted to the 2000–2012 data are projected from 2013 to 2050 or estimated year of extinction (when abundance is less than 30 individuals, which is a quasi-extinction level). The projections are just one possible outcome of many, assuming that the rate of change is accurate and does not change over the coming decades. Areas of distributional range (right panels) from 1968 through 2012 were determined from presence or absence at count stations and extrapolated across similar elevations and habitats. For ‘apapane, Kaua‘i ‘amakihi, and Kaua‘i ‘elepaio, estimated distributions from 2000 to 2012 were very similar, and only the 2012 range is shown.