A native bird that was common across the Hawaiian Islands 100 years ago could become extinct by 2100, according to a new study by the U.S. Geological Survey.

The red honeycreeper or iiwi could disappear unless action is taken to reduce bird diseases such as avian malaria in its habitat, the agency warned Tuesday.

The iiwi (Drepanis coccinea) was once found from sea level to 6,000 feet in elevation along the slopes of Hawaii’s volcanoes but is now mainly found in high-elevation forests where the climate is too cold for mosquitoes.

It flies to lower elevations seeking its preferred food, the nectar of flowering plants.

But the bird’s range of movement has put it at risk of contracting diseases, as it flies into areas where temperatures are higher and mosquitoes carrying avian malaria are plentiful, the study said.

Eben Paxton, the study’s co-author, said that “with avian disease widespread at low and mid-elevation of the islands, these movements from disease-free high elevations to areas where disease occurs could lead to their extinction.”

He said scientists are conducting a study to see if they can use a naturally occurring bacteria as birth control to reduce or even eliminate the nonnative mosquito, which was introduced in 1826. Rooting pigs create holes where standing water can accumulate to become mosquito breeding pools.

Since the early 1990s, scientists have been fencing off areas from cattle and pigs and reforesting high-elevation areas at Hakalau Forest National Wildlife Refuge with flowering native trees and shrubs that have nectar sought by the iiwi.

Paxton said the reforestation has created habitat for many birds, although it hasn’t stopped the iiwi from continuing to seek nectar from trees and shrubs at lower elevations, where mosquitoes are plentiful.

Scientist estimate the number of iiwi at 605,418 statewide, including 543,000 on Hawaii island.

Stable or declining populations of the iiwi have been found on the windward side of Hawaii island, while the population has been strongly increasing on the Kona side, including Hakalau National Park, according to the U.S. Fish and Wildlife Service.

Only a few individual birds have been sporadically detected on Oahu, Molokai and west Maui in recent decades.

Scientist fear that with global warming, the mosquito-free forests between 5,000 and 6,000 feet elevation will continue to narrow, increasing the iiwi’s vulnerability to avian malaria.