Birds Not Mosquitoes project partners Chris Farmer, Luka Zavas, and Ryan Monello discuss a modern mosquito-control technique to save Hawaii’s forest birds from imminent extinction. This project is the first time this technique has been used to protect animals. Hosted by Jeri Stoller. A production of Park Science magazine, Winter 2023 issue (December 29, 2023), https://www.nps.gov/subjects/parkscience.
[PODCAST INTRODUCTION, WITH MUSIC: Welcome to Park Science Podcast, a podcast of Park Science magazine that highlights milestones and contributions to science made by parks and programs of the National Park Service. Find our podcast series as well as the full Park Science magazine online at nps.gov/parkscience.]
CHRIS: This generation of conservationists, this generation of outreach people, this generation of everybody, are ones who can make a difference. If we make that difference, if we enact these solutions, we can save these birds.
JERI: I’m Jeri Stoller, and I’m going to tell you a story about birds and mosquitoes. Hawaiian honeycreepers are a group of small native forest birds found only in Hawaii. Historically, there were more than 50 species of honeycreepers. But now there are only 17, and many of them are nearing extinction. A big cause of their decline is avian malaria[1], which causes these colorful birds to weaken and die.
Avian malaria is a disease carried by mosquitoes, but mosquitoes may also be part of the solution. Scientists are working to breed incompatible male mosquitoes that can mate with female mosquitoes and prevent them from having offspring. Birds Not Mosquitoes[2] is a multi-agency partnership working to protect native Hawaiian honeycreepers from extinction. I talked to some of the people working on this project to find out more. [SOUND OF BIRDS SINGING]
JERI: Can we start by each of you introducing yourself and your role in Birds Not Mosquitoes?
CHRIS: Hi, I am Dr. Chris Farmer. I am with the American Bird Conservancy. I am Hawaii program director. I am based on the island of Hawai`i, and I do a lot of different things with Birds Not Mosquitoes. I’ve been here since the beginning and was one of the people, along with the National Park Service, that helped to create and organize the entire effort.
LUKA: Aloha, my name is Luka Zavas. I live on the island of O‘ahu. I'm from the east side in ʻĀhuimanu. I also work for the American Bird Conservancy as the outreach manager for the Birds Not Mosquitoes partnership.
JERI: When did scientists start to notice a decline in honeycreepers?
CHRIS: I'm sure the scientists and the people on the islands observed, because when the Europeans arrived, they brought so many non-native species, including mosquitoes and avian malaria, that many, many species got wiped out. We lost so many of our species. We have about a third of our native avifauna left. Everybody was noticing this. The first paper that is in the scientific literature that talks about this, that did a really good study, looking at the relationship between mosquitoes, avian malaria, and the honeycreepers, was in the late 60s, 1968.
LUKA: Prior to that, when you go through the nūpepa, the newspapers written in traditional ʻŌlelo Hawai`i, there are articles from early as 1871 noticing the decline in birds, so the sounds disappearing. And even though they didn't have a reason or why it was happening, but it was just a drastic loss in our avifauna was noticeable even from back then before we could actually put a pulse on why the declines were happening.
JERI: If these birds have been declining for so long, why are we focusing on it right now?
RYAN: The issues we're dealing with today really came to the forefront around 2017. That's Ryan Monello. He works for the National Park Service as the program manager of the Pacific Island Network Inventory and Monitoring Division[3]. He's also a biologist.
RYAN: And that was brought about by collaborative work that was done between the My Forest Bird Recovery project[4] and the National Park Service, where we monitor these forest bird populations every five years. And I'll use forest birds and honeycreepers interchangeably. So it included Haleakalā National Park as well as other really important nature reserves that exist on East Maui.
And we surveyed all of them together and then did a joint report and found that kiwikiu, which are the Maui parrot bills, were below 200 in population size, and so that's extremely concerning. We thought they were closer to 500. And over the prior decade, they had declined to less than 200 individuals. And the ʻākohekohe, which is also referred to as the Maui crested honeycreeper, was below 2,000 individuals. But the ʻākohekohe actually has a smaller range than the kiwikiu, so both of these species are just really on the forefront of the next birds that could potentially go extinct.
JERI: Those are significant declines.
RYAN: At the same time, partners in Kauaʻi, so the Kauaʻi Forest Bird Recovery Project, and they were working with USGS [U.S. Geological Survey] and others, were finding very similar trends in Kaua‘i and dramatic declines in some of the endemic species that occurred there. And real concern about their long-term persistence. So really, the alarm was raised around 2017. People have been worried about it for a while, but I think what changed was it looked like things were happening on the landscape much faster than we anticipated.
JERI: How did you collect data on how many birds were in an area?
RYAN: Yeah. So the bird surveys consist of point counts. And so bird surveyors go out on established routes. What they'll do is they'll go out and they periodically stop at different points along the transect. And they do these same transects each time and mostly by sound in Hawaii. Because you rarely see these birds in the wet rainforests that they tend to occur in, or even the drier forests, they're hard to see. You can estimate how far away they are, and then what species you're hearing. But then you can take that data and when you analyze it, you can estimate the density of the birds in the area as well as extrapolate it out to population sizes. And so that's how we can get to knowing the approximate number of individuals we still have out on the landscape.
JERI: So surveyors stop at points along a route and listen to the bird song. Then they record how many they hear. From this you can estimate how many birds are in the area. Why are the birds declining?
RYAN: So the primary reason is avian malaria, and avian malaria is an introduced disease in Hawaii, and southern house mosquitoes are the vector of avian malaria. They are what transmit avian malaria to the birds, and that is also an introduced species. So we're dealing with two introduced species that both transmit and cause the disease. Well, until 2017, they hadn't really been recognized as invading these uppermost elevations, because they're cold intolerant—malaria in particular can only survive and reproduce if temperatures are on average above a certain amount each year.
And so these higher elevations where the birds were still living, and what we called a refugia essentially, had not been invaded by the mosquitoes, nor the disease really, yet. And so what's happened more in the last decade is that the mosquitoes and avian malaria have started to make incursions into these upper elevation areas that used to be too cold for them. And now they can’t support it, so these birds are contracting the disease. And they have no resistance to it, because they evolved in isolation of it in Hawaii and lost all their potential resistance that maybe their ancestors had to prevent malaria.
And so now when this new disease comes in—and this is not uncommon—when you find in certain island environments different things like this happening, these species are completely vulnerable to it. And so that's the primary source. There are other reasons for decline. For example, introduced predators and loss of habitat. Right now, in the areas where we're working and most concerned about in the Park Service are areas that are still really good habitat. Upper elevation tend to be cooler but are now being invaded, at least in pulses at a frequent enough occurrence to where these birds are getting infected and dying of it, and that's causing population declines.
JERI: If conditions don’t improve, what will happen to the birds?
RYAN: And so overall, we expect, for example, with kiwikiu and ʻākohekohe, which both occur in the upper elevations forests of Haleakalā, we probably have somewhere in the order of two to 10 years before they go extinct, roughly.
JERI: Why are these birds so important, Luka?
LUKA: They have a biocultural relationship with Hawaii, and so when I talk to folks about them, I first like to start off with like you have to imagine five to six million years ago when the islands of Kauaʻi and Ni‘ihau, which are the oldest islands in the main Hawaiian islands that we live on today, but at that time, they were just newly birthed out of the sea. So these were like brand spanking new islands, and these birds, the Hawaiian honeycreepers, their ancestor, came at that time and from there, adaptive radiation, you know, from different relationships that these birds have built with the different plant species that made it also here to Hawaii.
Insects that were here too and created these like intricate relationships that helped one another evolve. So some of the plants now have flowers that mimic the beak of the bird, and so they must be pollinated by that bird, or they must have their seeds dispersed by that bird, or have their, like, twigs cleaned by a certain honeycreeper because of the way that it, like, pecks out and acts like a dentist of the forest and keeps the forest from being too overburdened with insects and such. And so those are the great biological relationships that these birds have with these plant species.
That abundance is what Hawaiians saw when they first then came to Hawaii. I just try to imagine what it sounded like, because it really was a bird paradise. As we humans are like, just fascinated by the facts that birds can fly, that they can get their little bodies off the ground, up into the air. And that association was really valued. Because the Hawaiians they came, they saw these relationships, they watched and learned how these relationships interacted one another as they learned how to insert themselves into this island ecosystem and build a life for themselves.
JERI: What did these birds mean to the people who lived there?
LUKA: So the islands are kind of split. So there's the Wao Akua, which is the realm of the gods. And then there's like, middle sections that are like...there's like a Wao Kanaka which is then or where the people are living. And so they saw that these Hawaiian honeycreepers that they lived from seashore all the way up to the tops of the mountains, were flying between the Wao Kanaka or the place of the people to the place of the gods. So these birds became like messengers of the gods. They became different body forms of the gods, representations of the gods.
JERI: How did Hawaiians show their connection to the birds? Their feathers were incorporated into ‘ahu ’ula, so ‘ahu ’ula are the capes, the feather capes. Mahiole are the feathered helmets. And then you have kāhili, which are the standards, and then the lei hulu. And each one had different meanings behind them. But if you think that, like the mahiole has over 200,000 different feathers in it, that means that generations of families were going out and collecting those feathers and planning of how they’re getting created, and so their loss is really that loss in that story.
So for generations, you know, you knew when you saw this bird or this product that not only were you looking at all the hours and love and intention that was put into creating it by the person who made it but also all the hours and time it took for the people to go out and collect it. And then also the hours and time it took for each of those birds to, like, grow their feathers and become, you know, alive and generations. And then being able to see that these feathers are also connected all the way back to that first ancestor of the Hawaiian honeycreeper that came. And so that genealogical story that is held within those are starting to get cut off.
JERI: What were some of the first ideas that scientists had to save these birds?
CHRIS: You know, we've watched the honeycreepers vanish from the lowlands and start to decline. And you know all the scientists working on them have been noticing this over decades. And there's been intensive work by the National Park Service, by the State Division of Forestry and Wildlife, by others like ABC and other organizations involved here. And we've done a lot of different things. We've done fencing to get out the ungulates, the non-native things like pigs and goats that destroy the habitat. We have done predator removal; we have reforested; we have worked incredibly hard. Everybody in Hawaii is so committed for conservation and worked so hard to restore and protect the native species that are left.
And one of the things that's become painfully obvious over the last decade or so is that the one thing that we can't really address at the landscape scale, is mosquitoes. There's not a fence. There's not a way to protect them. You could have small aviaries where the captive propagation programs can protect small numbers of these birds. But we've tried to do some things, pig wallows in some places where the pigs destroy the habitat, knock down the hāpu‘u ferns and make perfect little breeding pools. If you reduce those, you reduce numbers of mosquitoes. If you find where they're breeding, you can treat them with larvicide and get rid of the larvae, but we can't do a broad-spectrum insecticide like something like DDT that people have heard about, or some of the other insecticides that are more recent.
CHRIS: With the forest that we're talking about the birds, but also where people get their water from, and there's also lots of endangered insects. And so if you spray these insecticides up there, you would wipe out the entire ecosystem, and you destroy it that way. So you wouldn't be able to protect anything. And so there was no good, successful, landscape-scale approach to solving mosquito problem. It’s something that we've known about for decades, and it's been scary.
But with the decades of research and millions of dollars into human health, the Hawaiian conservation, they're able to build upon that and find this tool, the incompatible insect technique that allows us to implement something that has been tested and tried for human health and works on those mosquitoes and deploy it for conservation. So that is what we are working on with the Birds Not Mosquitoes project is a way of doing that tool at the landscape scale in Hawaii to protect the remaining forest birds.
LUKA: Another question people ask is like, "Oh, if we get rid of mosquitoes, how is that going to affect Hawaii?” Because in some places, mosquitoes are important for like pollination and some birds do eat mosquitoes as part of their diet. Well, in Hawaii, they only got here like 200 years ago, and in that time, they haven't become important or the sole, you know, pollinator or food source for anything. Our ʻōpeʻapeʻa or bat may eat mosquito if it happens to fly in front of their mouth, but nobody is reliant upon it. And so if we were to get rid of all of them, like actually be able to eradicate them from the islands, we would only see benefits, no negative environmental cascades of a missing piece.
JERI: Ryan, how does the incompatible insect technique work to reduce mosquitoes?
RYAN: Yeah. So the way that incompatible insect technique works that we're using is that we have southern house mosquitoes on the landscape that occur in Maui. They're non-native, but they're a wild population that exists there, and they're what are causing the problems. Insects throughout the world, about 50 percent of insects, roughly, carry a naturally occurring bacteria that's called Wolbachia. And when you look at those mosquitoes that are on the ground in Maui, the males and the females when they mate either don't have Wolbachia, or they have the same type of Wolbachia in general, and that allows them to successfully reproduce.
But if you can take a male that has a different type of Wolbachia bacteria, it's a different strain. Same bacteria, but it's just a different strain, and you put it in a male mosquito and it tries to mate with a female mosquito that has a different strain of Wolbachia, then you can find situations where their eggs do not hatch. Essentially it ends the potential for offspring.
JERI: So when males and females with a different kind of Wolbachia mate, their eggs don’t hatch. How do you know what kind of Wolbachia the mosquitoes have?
RYAN: You have to test different strains of Wolbachia to see which ones will work. And so we've done that, working with our partners. This is being done through a cooperative agreement with The Nature Conservancy and Verily Life Sciences. So we're using the same species of mosquitoes from Hawaii, and they are then reared with a different strain of Wolbachia bacteria in them.
And then you separate out the males and the females, and then you release the males in the wild with the wild females, and you release so many that they overflood the female population. And so females generally are only going to breed with male mosquitoes that have a different Wolbachia type is the idea. And it basically causes the population to crash if you can get a high enough overflooding ratio.
And so this is being done around the world in different urban areas for human health concerns. And we're now looking to apply this to this situation we have in Maui. It would be the first time it's done for natural resource or conservation reasons.
JERI: How does releasing more mosquitoes affect people?
RYAN: It's really important for people to understand that we've come a really long way in terms of the technology we use to separate males and female mosquitoes, and so when we release those mosquitoes, we're releasing male mosquitoes, and the potential for error is only one in 900 million. Importantly, the male mosquitoes that are released, male mosquitoes do not bite people. So even if you were standing in the middle of one of these releases and you had thousands of mosquitoes that were suddenly in the area where you're at, you wouldn't experience any more bites.
CHRIS: There's a lot of concern that this is a genetically modified organism or some sort of GMO, and it is very much not. There's no change to any of the genome of either the bacteria or the mosquito.
JERI: What step in the process for implementing the incompatible insect technique are you at now?
RYAN: Yeah. So it's pretty exciting. To this point, we have both, and I say “we” as a group, Birds Not Mosquitoes, as well as our partners, such as Verily Life Sciences, have figured out how to successfully breed the mosquitoes in captivity in mass, which is tricky in and of itself to get done, so they could produce the number of mosquitoes that need to be produced. They have successfully transinfected mosquitoes in the lab with a Wolbachia that is not compatible with the mosquitoes that occur on the landscape naturally. And then we have taken those mosquitoes and done some initial trials to determine how long they live, how far they travel, and how well they're going to be transported from where they're being produced in California to Hawaii.
And so we've completed all that. It's gone well. And so now we are preparing our plans to implement this at a landscape level. So ideally, starting in mid-November, we will start treating approximately 3,000 acres both on and off Park Service lands in key conservation areas for these birds, where we can distribute the male mosquitoes. And then what we aim to see is suppression in the wild mosquitoes of those landscapes.
JERI: How long do you expect this project to take? RYAN: There's pros and cons with it, so one of the drawbacks of it is you have to keep doing it indefinitely until you have another tool. But on the whole, we can't stop doing it. That can also be seen as, you know, positive. Because, essentially, if for some reason you needed to reverse what we're doing on the landscape, we could just stop releasing incompatible male mosquitoes, and things would go back to how they were. JERI: Do you expect honeycreepers to return to past population sizes?
RYAN: Right now our primary goal is to preserve the ones that we have and prevent further declines and stabilize them. Everyone working on this would absolutely love to see range expansions and population increases into the future. Right now, we're in such a critical state that our entire goal is to simply prevent them from going extinct on the landscape and maintain a viable population.
LUKA: And I just want to add that this project IIT is, you know, is aiming to suppress mosquitoes, not eradicate them. So I also like to think of this as a, like, not the answer to our mosquito problem or to our bird problem. This is our “let's give us some time” answer. By releasing these incompatible males and ensuring that the critical habitats, not even like the expansive habitat these birds could be in but just like these tiny, core critical habitats, are oases of spaces where they can be safe. So that we have time to talk about what are next steps, as both the community and as conservationists, of, you know, what does mosquito control in the future look like?
And then also that, you know, mosquito control isn't the only thing the birds need. The birds still need rat control. The birds still need, you know, fences to be put up. The birds still need habitat restoration. A kind of, like, success in conservation as a whole that we did really good conservation for our birds, folks, all around, would that be I have an ʻiʻiwi singing outside of my door in Waikīkī.
We won't see those level successes in the near future. I'm thinking maybe like my sons might be able to see that, or his children might be able to see that. But that is the island, that is the vision that we are all working towards, and that is like I would say that's when I would like pop out a bottle of champagne and be, like, I was successful kind of thing is when we can see something like that.
JERI: Thank you Luka, Ryan, and Chris, and good luck with this project. I’m Jeri Stoller. Thanks for listening.
[PODCAST CONCLUSION, WITH MUSIC: This has been Park Science Podcast. Catch up on more podcasts and articles at nps.gov/parkscience.]
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Credits: Bird sounds: Daniel Lane, XC27366. Accessible at https://xeno-canto.org/27366. CC BY-NC-SA 3.0; Brooks Rownd, XC122341. Accessible at http://www.xeno-canto.org/122341. CC BY-NC-SA 3.0.
Podcast length: 23 minutes and 47 seconds
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About the author: Jeri Stoller is a Scientists in Parks intern with the National Park Service’s Pacific West Region Inventory and Monitoring Division.
[1] https://www.usgs.gov/diseases-of-terrestrial-wildlife/avian-malaria
[2] https://www.birdsnotmosquitoes.org/
[3] https://www.nps.gov/im/pacn/index.htm
[4] https://kauaiforestbirds.org/]
