Akeke‘e or Kaua‘i Akepa. Photo by Lucas Behnke

The breeding season for some of Kaua‘i’s rarest forest birds is well underway, and this year protection efforts by the Kauaʻi Forest Bird Recovery Project will get a boost from a grant by Club 300, according to a news release by the state Department of Land and Natural Resources.

The Swedish organization pledged $5000 to help KFBRP deal with invasive mosquito and plant species in the Alakaʻi Plateau. Non-native plants such as ginger, create areas of standing water where mosquitos can breed. Those introduced mosquitos carry avian malaria which can be fatal for native birds.

KFBRP Project Coordinator Dr. Cali Crampton said, “Avian malaria is a serious threat to forest birds. The disease is spread by mosquitos. Our researchers have been finding mosquito larvae in pools created by invasive plants like Himalayan ginger”.

Native birds evolved in the absence of mosquitoes and they have few defenses against mosquito-borne illnesses. Avian malaria can kill them in just 24 hours. Crampton added, “Controlling mosquitos is key to saving our native forest birds from extinction”.

An ‘akeke‘e perches on an ‘Ohi‘a tree in Kaua‘i’s upper forest. ‘Akeke‘e have experienced a 98 percent decline in population in the interior of its range during 2000-2012. Photo courtesy of Robby Kohley

Before Western contact, there were no mosquitos in the Hawaiian Islands. Mosquitos are thought to have first arrived on a ship that docked in Lahaina on Maui in 1826 and dumped bilge water into a swamp there. The water contained mosquito larvae. Recent research by KFBRP and partners suggest that weeds make the mosquito problem worse because they slow down streams, creating standing water. Then, the invasive plants shade the pools, so they never dry out. That creates the perfect breeding ground for mosquitos.

The presence of weeds in the delicate Alakaʻi ecosystem also reduces food availability for forest birds, which rely on native plants such as ōhi’a lehua to survive. Birds which are poorly nourished are more likely to die from disease. Work by KFBRP and Colorado State University suggest that Puaiohi, a fruit eating native thrush, does not eat the fruit of most non-native plants. This species is disappearing from weed-infested parts of its range. Similarly, ‘akekeʻe forages for insects and nests only in ōhia lehua, a native canopy tree, which cannot regenerate in heavily weed-infested areas. Non-native vegetation is also less suitable for nesting.

The island of Kauaʻi has lost five of its native birds in recent decades and those that survive are restricted to the Alakaʻi Plateau, a small area of pristine forest at high elevation. In addition to avian malaria, remaining birds are at risk from introduced predators, such as rats and feral cats, and habitat destruction.

Population estimates and distributions for the akeke‘e. On the left panel, linear and exponential population change models fitted to the 2000 to 2012 data are projected from 2013 to 2050 or estimated year of extinction. Areas of distributional range are shown on right panel from 1968 to 2012. Red is 2012, green is 2005-2008, and purple is 1968-1973. Graphic image courtesy of Paxton et al 2016

Weed removal is good for people too. The forest provides humans with free ecosystem services such as flood water storage, filtration, and fertilization for fields downstream. Invasive plant species upset the delicate balance of the system and can contribute to flooding and other environmental problems on the island. Since mosquitos are not native to Hawaii, they are not an integral part of the food chain, so there is no downside to removing them; in fact, there might also be benefits to human health as mosquitoes can vector many human diseases.

Crampton said, “Removing invasive species from this fantastic forest area is a win on so many different fronts and involves many partners. We’re delighted to be able to expand our work this year with the help of Club 300 and welcome the international recognition that this grant brings of the importance of Kauaʻi’s native birds”.


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