On just about any given day you can find 'i'iwi, among the more charismatic species of Hawaiian honeycreepers, flitting around Hosmer's Grove, just past the entrance to Haleakala National Park. These energetic little bursts of red flit from tree to tree feeding on the nectar of ohia flowers and the occasional spider or insect.
Once abundant on all islands from sea level up into the mountains, these brilliant birds are now rarely seen lower than 5,000 feet. Below that elevation, avian malaria, a bird disease transmitted by mosquitoes, has decimated Hawaiian honeycreepers. Today, even the birds subsisting in the high-mountain pockets of habitat are threatened - not only by invasive plants and animals, but also by climate change.
Avian malaria is not new in Hawaii. Migratory birds carrying malaria regularly visited Hawaiian shores - but before mosquitoes were introduced, the disease had no way to infect resident bird populations. In 1826, sailors on the whaling ship Wellington dumped barrels of mosquito-infested water into a Lahaina canal. That marked the beginning of the end for low- and mid-elevation native honeycreepers.
An adult ‘i‘iwi sips nectar from flowers in Waikamoi. The birds used to be abundant on all islands from the ocean to the mountain but today these birds are rarely seen lower than 5,000 feet elevation due to avian malaria.
FOREST and KIM STARR photo
Since then, mosquito-born diseases have caused two major waves of extinction in Hawaiian honeycreepers. Native forest birds have shown scant resistance to foreign diseases. Those that survive inhabit forests above the "mosquito line," where neither mosquitoes nor the diseases they carry can thrive. In cooler temperatures, avian malaria can't reproduce fast enough to infect birds. Thus the largest populations of 'i'iwi dwell in the cloud forests of East Maui and Hawaii; the birds are increasingly rare or nonexistent on islands without tall mountains. 'i'iwi have vanished from Lanai and only a few remain on Molokai and West Maui. With a warming climate, the remnants of disease-free habitat may shrink or disappear.
And Hawaii is heating up. Each decade since 1975, minimum nighttime temperature has increased an average of almost one degree Fahrenheit. Nighttime temperature is the determining factor in estimated elevational range of avian malaria. Over the last 50 years, the mosquito line has steadily marched up the mountain, from 2,000 feet in the late 1960s to nearly 5,000 feet today.
Climate change may affect our native birds in other ways. Summer storms are predicted to become more frequent, creating more habitat for mosquitoes during their optimum breeding season, increasing their density and the likelihood of transmission of avian malaria. Meanwhile, overall rainfall may decrease, compromising the health of the native Hawaiian rainforest and the inhabitants that rely on it.
The i'iwi is not the only bird likely to be chased out of remaining habitat by avian malaria and climate change. In Hawaii, all of our non-migratory birds, such as the Maui crested honeycreeper, or akohekohe, Maui parrotbill, or kiwikiu, and the apapane, face the same danger. These species are unique among the world's creatures; they exist nowhere else on earth. Many of them are highly significant to the Native Hawaiian culture and all play critical roles in their natural environments. Their loss would be devastating.
In response to concerns raised about the 'i'iwi's perilous situation, the U.S. Fish and Wildlife Service is proposing to list the 'i'iwi as federally threatened or endangered, with climate change noted as a factor in its decline.
How can you help? Support efforts to address the causes of climate change. Work to protect the remaining natural areas that shelter 'i'iwi. And take a trip to Hosmer's Grove to witness just how spectacular these winged treasures are.
* Lissa Fox Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia'i Moku, "Guarding the Island," is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island's environment, economy and quality of life.