For the Birds
The rapid decline of the Hawaiian honeycreepers and the people fighting to stop it
Editor-in-Chief Peter Holden Chao
Photos by Elizabeth Lough
The biology department at UH Hilo received a $25,000 donation from Hawaiʻi Forest & Trail, a local tour company aimed at natural history and conservation, in an effort to prevent the rapid decline of the Hawaiian honeycreepers. These birds are found only in Hawaiʻi and include colorful species such as the ‘iʻiwi, the palila, the ‘amakihi, the ʻakiapōlāʻau, and many others. These native birds have been greatly affected by the spread of avian pox and malaria, vectored by Culex quinquefasciatus, a non-native mosquito.
“The ‘iʻiwi is one of the Hawaiian honeycreepers, which is a group of birds that evolved in Hawaiʻi. They are endemic to Hawaiʻi and they evolved from a single genetic colonizer to Hawaiʻi several million years ago. From that single genetic colonization, over 60 different species of birds evolved, which is the world’s best example of the evolutionary process in birds. It surpasses Darwin’s finches in the Galapagos,” said Hawaiʻi Forest & Trail Founder, Josh Pacheco. “That family of bird has also had the most extinctions of any group of birds in modern times. We’ve lost a lot of those birds, a majority of them, and the ones we have left, many of them are endangered.”
The mosquito was introduced to Hawaiʻi in 1826, but it took time for people to notice vector borne diseases. “We’re one of the only places where mosquito borne disease is the primary cause of decline in birds. Very few places in the world have no native mosquitos. This is one of the few places where mosquitos never made it on the entire planet, because we're so isolated in the middle of the ocean here,” said Dr. Patrick Hart , professor and chair of the UH Hilo Biology Department.
“There were these big waves of die-offs in birds and nobody knew why exactly,” continued Hart. “It looks like the pox, and the visible skin lesions they get. People were describing pox like lesions on the birds, so we knew that it was here then, but they had no clue about avian malaria. Now it’s known to be probably the biggest threat to the remaining honeycreepers we have.”
“Over half of those [honeycreepers] have gone extinct, and more than half of the remaining ones are endangered or critically endangered, so there’s just a handful left that aren’t critically endangered,” said Hart. “We’ve got projections of populations and they are all just declining to zero within 20 to 40 years.”
“A lot of it’s related to elevation. The older islands aren’t as tall as the younger islands. Maui and the Big Island have elevations above the range that these mosquitos generally go, but O‘ahu and Kaua‘i do not. Their highest peaks are below the range of these mosquitos,” said Hart. “There’s a really good chance that were going to lose all of our native birds from Kaua‘i, or at least most of the rest of the honeycreepers in the next 20 years because of avian malaria.”
Hart continued, “There’s been a lot of work, a lot of monitoring done recently, and we’re watching the populations crash before our very eyes. There’s a couple species crashing on Maui as well. Even though it’s a really tall island there still seems to be that with global warming, mosquitoes seem to be moving up in elevation. The birds are forest birds. Each island has a tree line, the mosquitos are coming up but the birds can’t go any higher. The mosquitos are making the zone that they can inhabit narrower and narrower. We’re really afraid that we’re going to lose, in our lifetime, most of the remaining native Hawaiian birds.”
It is the efforts of Assistant Professor of Biology, Dr. Jolene Sutton’s lab, that are looking to halt the population decline by manipulating strains of wolbachia, an endosymbiont bacteria present in half of all insects, including the Culex quinquefasciatus, the mosquito responsible for the transmission of avian malaria. “What we want to do with the wolbachia is use it in a birth control technique,” said Sutton. “If we can import and then establish in our lab a Culex with different wolbachia, then the idea is that when we release those males, only the males, into the wild, so that there are more of those males then wild males, it is our lab reared males that get to mate with all of the females.”
Sutton continued, “The females have one strain of wolbachia, and the males have a different strain of wolbachia and that’s incompatible. They will produce eggs, but the eggs won’t hatch. That’s our goal: to actually get the mosquito population down when it comes to wolbachia.”
“What we do in the lab is we collect mosquitos from the wild and they naturally have wolbachia and so in the lab we clear them. We use antibiotics to get rid of the wolbachia and we try to give them a different strain of wolbachia. There's a couple of different ways people have done this and there's a couple different ways we are trying this,” said Sutton. “One of those ways is to raise your mosquito colonies in the lab and these don't have wolbachia in them. When they lay eggs, the eggs have to be fresh, laid like 20 minutes ago kind of fresh. We collect them and we line them up on a microscope slide and we have a very fine needle that inject a mixture into each egg one by one and that mixture contains wolbachia. In our lab what were trying to do is to take wolbachia from a different kind of mosquito that’s also here in Hawaiʻi and inject that into the mosquito that were interested in, the one that vectors avian malaria.”
“This particular method has also been used with good success in other places as well. It’s a tried and true method, this wolbachia, it just hasn’t been used here before,” said Sutton. “Our inspiration is we’ve got these introduced mosquitos here in Hawaiʻi, no mosquitos are native here, and this one mosquito vectors avian malaria and avian pox, and those two diseases, particularly malaria, have massive impacts on native bird populations.” Sutton continued, “With the climate warming, and mosquitos moving up, the parasite that actually causes avian malaria is able to complete its life cycle because the temperatures are warmer at higher elevations.”
“There’s a parasite, that when a mosquito bites a bird that has avian malaria, it ingests the blood, and at the same time it ingests this parasite. This parasite is called plasmodium. When a mosquito goes and bites another bird, it infects that bird with plasmodium that causes avian malaria,” said Sutton. “It infects different parts of the body. The first place it gets into is the blood, and the symptoms it causes are fatigue. The birds are very tired just like people when they get malaria.” The disease bursts their red blood cells, the body is unable to transport oxygen, the birds become anemic and for some of these birds, they perish.
“If they can make it past a month or so, I think they’re okay, but generally they don’t,” said Hart. “There are a couple birds that seem to be evolving tolerance. They can actually get bit by an infected mosquito and have been known to be able to survive, like the Hawaiʻi ‘Amakihi in Lower Puna and we think the ‘Apapane, one of the red birds, seems to have some tolerance. A lot of them still die, but some within the population survive.”
When asked about how she felt about the population of the Hawaiian honeycreepers, Dr. Jolene Sutton, assistant professor of biology at UH Hilo, said, “I feel very hopeful as well as very concerned. The reason that I am hopeful is because we can do something about mosquito borne diseases here in Hawaiʻi. The technology already exists. I’m concerned that we might not do it fast enough.”
Sutton’s lab already has Culex colonies, the mosquito that vectors avian malaria, that have been cleared of wolbachia. “The fastest way to infect them with a different strain of wolbachia is to import a mosquito of the same species, with a different strain of wolbachia and mate them to the ones we have in the lab. If we can take a female Culex mosquito that has a different strain of wolbachia and breed her with our lab colonies, we would have here in Hawaiʻi, a Hawaiʻi strain of Culex, with a different strain of wolbachia and we could be ready to start testing in the lab, the birth control effects, and quickly be ready to move to field trials.”
Sutton continued, “What’s holding us back right now, is we put in a permit application, we submitted it in December, an import permit application. We’re waiting on that. If people told their senators and legislation that they wanted us to be able to import mosquitoes, we could be moving much faster. The same species is already here and we would import it into the lab. We have wolbachia in our mosquitoes, we get bitten by mosquitoes that have wolbachia all the time. The wolbachia that we want to import is in a mosquito that also bites people, so it’s right there. It’s so close. I almost hate this term, but it the lowest hanging fruit that I can envision. We need this import permit. If we could have that, I could be ready to start trials in the lab on the birth control effects in two months.”
Sutton emphasized the need for people to talk to their legislators, “Knock on your legislator’s door, call them up, go to the meetings. Right now there is a lot of talk amongst officials and senators about mosquito borne diseases. Bills are in the works about mosquito borne diseases and mosquito control. Getting out and supporting those kinds of bills and being very vocal about it is something I would like to see a lot more of.”
“All of the native bird species are only found in Hawaiʻi and now they’re in really small populations, that’s one of the things that makes them so special,” said Sutton. “You just cannot go anywhere else in the world and see a Palila.”