HISC eNews Vol. 3, No. 4

The magnificent red-tailed tropicbird in flight is only one of several seabird species found on Hawaii’s offshore islands. Their chicks are often victims of predation by invasive species, such as ants and rats. –Photo by Eric VanderWerf

Aloha Kakou,

The birds that first inhabited the Hawaiian Islands arrived by chance, surviving flight over thousands of miles of open ocean. From these early ancestors flourished and evolved an array of bird species that adapted to our unique environment–free of threats and, eventually, found nowhere else on Earth. That all changed when humans began to populate the Islands with their ensuant intrusion into natural habitats, bringing with them mammals, mosquitoes and other invasive species. Over time, many Hawaii birds became extinct and are now known only from archaeological and cultural records. Presented here are some of today's greatest threats, and some potential threats, to Hawaii birds.

Patrick Chee

Invasive species, alien flora and fauna, destroy native forests, spread disease, and kill Hawaii birds. Since the arrival of the first humans to the Hawaiian Archipelago, more than half of the islands’ 140 native bird species have become extinct. Today, 31 Hawaii bird species are endangered—one third of the nation’s endangered birds.

Rats, ants, mosquito-borne diseases, ungulates, cats, a plant fungus called guava rust, and the strawberry guava are the most damaging. Not yet in Hawaii, potential threats include the brown treesnake, red imported fire ant and avian influenza.

The rat, likely among the first wave of invasive species in Hawaii, continues rampant broad-scale impacts on forest, open country, and wetland and sea birds.

Offshore islands, many of them Hawaii State Seabird Sanctuaries, host thousands of magnificent seabirds. Rats attack nesting seabirds, their eggs and their fledglings, including the wedge-tailed shearwater (uau kani), brown booby (a), Bulwer’s petrel (ou), white-tailed tropicbird (koae kea) and the red-tailed tropicbird (koea ula).

On several offshore islets grow some of Hawaii’s most diverse and intact coastal plant communities. They feed on young plants and on seeds of rare and vulnerable native plants, such as the lama tree, loulu palm and pua ala shrub.

With the goal to restore habitats and aid the recovery of species damaged by rodents, state and federal agencies use rodenticides to help restore seabird and native plants.

Since the 18th century, at least 47 ant species capable of impacting ground and tree-nesting bird populations have invaded the islands. Ants lower a chick’s hatching success by attacking its eyes or devouring its foot webbing.

July 2009

Hawaii Invasive Species Council grants have funded research into the control of invasive ants. HISC now funds an invasive ant coordinator for the Hawaii Department of Agriculture who works on preventing the entry of new invasive ant species to Hawaii, such as the red imported fire ant and the further spread of ants already present, such as the little fire ant.

Mosquitoes arriving in the water barrels of ships carried bird pox and bird malaria. Today, many remaining native forest birds can only survive in forests above altitudes where these mosquitoes thrive.

Ungulates—the pig, goat, sheep, axis deer and even wild cow—contribute to the destruction of native habitats. The omnivorous pig is probably the most damaging ungulate. It spreads exotics, such as strawberry guava and Himalayan blackberry and overturns the native hapuu tree fern to get at its starchy central stem. It also roots and wallows, creating breeding habitats for mosquitoes.

The feral cat is one of the worst invasive species impacting native wildlife in Hawaii. Feral and free-ranging cats are found at all elevations and in all habitats, where they kill rare and endangered birds, such as the Hawaiian goose (nene), Hawaiian honeycreeper (palila), and Hawaiian petrel (uau). DLNR’s Division of Forestry and Wildlife has joined the national Cats Indoors! campaign.

A notorious rust fungus, Puccinia psidii, native to Brazil, where it is found on guava, is spreading through the transport of plants and cut flowers to other areas of the world. The fungus exists in several strains, which can attack and seriously damage other plant species in the myrtle family, such as the ohia, which comprises 80% of Hawaii’s native forests and provides vast watersheds and essential habitat for most Hawaiian forest birds and plants. Hawaii is finalizing regulatory measures to prevent additional strains of guava rust from South America, Florida and California.

Strawberry guava is found intruding on watershed forests, stifling biodiversity and crowding out native habitats of birds, such as the endangered Hawaiian petrel. A proposed biocontrol insect, tested for 15 years, would reduce plant vigor and fruit production but not kill strawberry guava. Environmental assessment is still underway.

The brown treesnake preys on adult birds, their eggs, and their young. It is not yet established in Hawaii, but since 1981, eight brown treesnakes have been found there, all associated with the movement of civilian and military vehicles or cargo from Guam. If the brown treesnake establishes a breeding colony in Hawaii, scientists say many more remaining birds would be wiped out.

The brown treesnake is now the subject of a cooperative program to control snake populations on Guam and prevent its spread throughout the Pacific Rim.

“In the last 40 years alone we may have lost 10 forest bird species-an astonishing rate of one every four years,” said Scott Fretz, DOFAW wildlife program manager. “The task of battling invasive species and recovering native birds in Hawaii is enormous. Without a big increase in dedicated funds we will continue to be limited in what we can do.”

The endangered Hawaiian petrel, or uau, in its fragile habitat on Hii Ridge on the island of Lanai. The conservation measures needed to preserve and maintain existing habitat is significant to its survival. –Photo courtesy Lanaihale Project