Kauai’s Hawaiian Honeycreepers On the Brink of Extinction

honeycreeper

Kauai’s native honeycreeper population is facing extinction. (Photo credit: Sami Sarkis/Photographer’s Choice RF/Getty Images)

New research indicates that six of seven native forest birds found on the island of Kauai in Hawaii are quickly disappearing from the landscape and their range is rapidly contracting. All six of these species are honeycreepers, and four are only found in small, remote locations. The reason for this collapse, as reported in an article in the journal Science Advances, is the spread of avian malaria by mosquitoes. The mosquitoes have been able to expand their territory upward due to climate change and global warming.

Native bird populations are facing other pressures as well. The spread of invasive plants, the incursion of nonnative predators such as rats, and competition by nonnative bird species has also led to a decline in bird populations. However, scientists see the most drastic reduction in native bird populations has been the result of the spread of disease by vectors such as mosquitoes. Research data supports this conclusion. A 2014 study found that the prevalence of disease had more than doubled between 1994-1997 and 2007-2013.

Prior to an increase in global temperatures, mosquitoes kept to the lowlands, where temperatures were warmest. However, as global temperatures have increased, mosquitoes have begun to creep further upward in elevation, to locations where honeycreepers had previously lived undisturbed by such insects. While on other Hawaiian islands, there is steep terrain that is expected to slow the roll of the mosquitoes upwards, on Kauai, there is a flat terrain called the Alakai plateau. Once the mosquitoes–and the avian malaria they carry–make it up that far, the flat terrain makes it easy for disease to spread among the bird populations.

The last field study, conducted in 2012, counted only 468 ‘akikiki and only 945 ‘akeke’e. Conservationists believe that without human intervention, these species could go extinct within the next decade. A captive-breeding program was begun two years ago to rear ‘akikiki and ‘akeke’e eggs and develop a captive population. Scientists are also looking into ways to manage the spread of disease by mosquitoes. Possibilities include releasing infertile male mosquitoes into the population to hopefully suppress population growth; introducing mosquitoes that carry Wolbachia bacteria into the population, which leads to the production of infertile eggs; or introducing genetically modified male mosquitoes that, when bred with wild female mosquitoes, lead to non-viable offspring.

The dire situation on Kauai is worrisome in that the same thing could happen on other Hawaiian islands as well. Though they have different terrain, as temperatures increase, so too will the ability of mosquitoes to increase their territory upward into native bird species’ habitat.

“The close relationship between distribution of disease and temperatures certainly suggests that disease will continue to increase in its distribution on all of the Hawaiian Islands. These forces that are causing these declines on Kauai are expected to reach Maui’s forests and Hawaii forests in the coming decades,” lead author Eben Paxton told a reporter from Yale Environment 360. “The way that we view Kauai is that it’s an early warning system for the rest of the islands. The conservation community concerned about these birds feels that the strategy we develop for Kauai now is going to be applicable to these other islands. If we get it right on Kauai then, I feel pretty good about the prospects of some of the other islands.”

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