Recovery on a Wing and a Prayer: Birds Face Habitat Loss, Disease, Alien Species

If a poster child exists for Hawai`i’s endangered species, it most likely has a beak. While plenty of invertebrates and plants are acknowledged as imperiled, the birds are Hawai`i’s calling card when it comes to charismatic megafauna.

And the news from the frontline in the battle to protect the rarest of these rare birds is decidedly mixed, according to reports presented at the 2007 Hawai`i Conservation Conference, held in Honolulu in July.

“That’s the best news I’ve heard yet,” said David Burney, conservation director of the National Tropical Botanical Garden, at the conclusion of the presentation by Michelle Reynolds on how a reintroduced population of Laysan teal (Anas laysanensis) were faring at Midway Atoll. Others in the audience clearly shared Burney’s enthusiasm for the translocation project described by Reynolds, a researcher with the USGS in Volcano.

Since Western contact, the Laysan teal, also called the Laysan duck, had been known only from Laysan Island, a tiny, 1,000-acre patch of high land in the Northwestern Hawaiian archipelago, some 900 miles northwest of Honolulu, and Lisianski Island, about 150 miles northwest of Laysan. The ducks were extirpated from Lisianski after multiple ship wrecks introduced mice that devoured much of the island’s plant cover. On larger Laysan, the teal hung on, despite a plague of rabbits that felled less fortunate species, including the Laysan rail, the Laysan millerbird, and the Laysan honeycreeper. By 1911, the population was down to just 11 individuals. It has made a comeback of sorts, but the little duck was vulnerable as a small, isolated population whose adult members were estimated to fluctuate between 300 and 600 adults for most of the last 40 years.

Until recently, the duck was thought to have been found only in the northwestern islands, where it was particularly adapted to the conditions found at Laysan. One of the mainstays in the ducks’ diet is the brine fly from a hypersaline lake in the middle of the island. For many people acquainted with the ducks only through photos, the image of the open-mouthed ducks chasing clouds of the tiny flies is what first comes to mind whenever the ducks are mentioned. With such hypersaline lakes (more than three times saltier than the ocean) being rare, bird experts believed opportunities for translocating the birds to other islands, in hopes of increasing the odds of the species’ survival, were limited.

Then, in recent decades, Laysan teal bones were discovered on most of the main Hawaiian islands, at elevations ranging from the coast up to 5,000 feet. The bird that had been thought to be highly specialized was, in light of these discoveries, recast as a generalist, inhabiting environments ranging from coastal wetlands to high forests. Furthermore, the discoveries challenged the notion that the Laysan teal depended on the hypersaline lake and brine flies. No hypersaline lakes exist in the main Hawaiian islands, except for one created by salt-making Hawaiians on Kaua`i.

As the 2004 recovery plan for the Laysan teal states, “the relevance of current habitat use is difficult to interpret when a species has declined to a single remnant population. It is important to consider the possibility that some aspects of the ecological conditions on Laysan may not be ideal for this species.”

In October of that year, the first wave of Laysan teal descended on Midway Atoll’s Sand Island, and on Eastern Island the following year. Thousands of volunteer hours had gone into preparing the island for the birds’ arrival. Alien species of plants were removed, native grasses planted, and freshwater seeps excavated. (Actually, the Midway project is the second translocation experiment for the teal: in 1967, 12 adults were released at Pearl and Hermes reef. Within a few months, all had disappeared.) The researchers selected 20 juveniles to translocate after monitoring the Laysan Island population to ensure that the relocated flock represented as much genetic diversity from Laysan as possible. Reproductive trends were monitored as well, so that birds to be relocated would be removed during a period of population growth rather than decline. A year later, 22 more birds, most of them juveniles, were ferried to Midway.

The results have been phenomenal. According to Reynolds, the Midway Laysan teal have had much better breeding success than those at Laysan. Juvenile females have begun breeding at much younger ages, and the average clutch size (7 eggs) at Midway is nearly twice that at Laysan (3.8 eggs). Although a few of the released birds have died or disappeared – one apparently having been attacked by an angry albatross – the Midway population as a whole is thriving. Over the next couple of years, even more birds may be ferried from Laysan to Midway to maximize genetic diversity. According to Reynolds, whether that can be done depends on funding and the population dynamics of the Laysan birds themselves, since translocations occur only during years when the Laysan population is on the rise.

And after Midway? The Fish and Wildlife Service is looking to other sites, including Lisianski. Before the first bird can set its webbed feet on that island, however, some habitat restoration work needs to be done – most critically, restoring freshwater seeps like those filled in when plant cover was lost.

In any case, said Holly Freifeld, a bird expert with the service, no decision has been made as to what the next translocation site will be. “We need to get the interested parties together to discuss what needs to be done,” she said.

Sophisticated computer modeling has allowed biologists and others to predict what will happen to endangered species under a wide range of circumstances. Kirsty Swinnerton, a biologist with the Maui Forest Bird Recovery Project, and colleagues Eric Vanderwerf and David Leonard took advantage of these computing advances to predict what might happen to the endangered Maui parrotbill (Pseudonestor xanthrophrys).

The parrotbill population hovers around 500 individuals, all of which are found in remote areas of the East Maui rainforest. For small birds, they are relatively long-lived, with one known to be at least 13 years old. Breeding pairs raise at most one chick per year, and juveniles can hang around the nest well after they’re fledged, which Swinnerton suspects can “depress reproduction” even further.

Like the Laysan teal, the habitat historically occupied by the parrotbill may not be optimal, but rather the only habitat available after deforestation, alien species, disease, and other ravages of modern times pushed it out of areas that were more hospitable.

Swinnerton and her colleagues punched the parrotbill’s vital stats into a computer model to determine just how long the species could survive if nothing were done. Under a do-nothing scenario, the time to extinction could be somewhere between 20 and 40 years – probably closer to 20, Swinnerton reported. If rats were controlled and nesting success rose to 50 percent from the present 32 percent, the parrotbill would buy a little time (roughly 4 years), but would still go extinct. Even if nest success increased to 75 percent, Swinnerton said, the species would last only another half-century. But improvements in nesting success in the birds’ current range may be unlikely. Heavy rains, high winds, and frequent storms on the windward slopes can affect survival of young, and are also associated with nest abandonment

If a second population were established at Kahikinui, on the dry, leeward slopes of Haleakala where the parrotbill was much more abundant in prehistoric times, that alone would increase the mean time to extinction by 66 years, Swinnerton said.

Work has already started on preparing about 480 hectares of state-owned land at Kahikinui for eventual occupation by parrotbills. But it may be years before the welcome mat can be rolled out for the bird. After more than a century of cattle grazing, logging, and other landscape-scarring activities, restoring the koa forests of the past will take some time.

Scott Fretz, wildlife biologist with the state Division of Forestry and Wildlife, says that the state is working with other landowners in the Leeward Haleakala Watershed Partnership to attempt to bring back the forests above the 3,500-foot elevation. “From Kaupo to Ulupalakua Ranch is the core area we’re focusing on.”

The plan is to work outward from the best of the remnant forest, he said. The state land, part under management of the Department of Hawaiian Homelands, part managed by DOFAW, includes some of the best habitat. DOFAW is putting in a fence laterally across the 3,500-foot contour, stretching three miles between land to be acquired by Haleakala National Park, to the east, and DHHL, to the west. “We need our partners on both sides to have their fences join up with ours, so we can restore across that larger landscape,” he said.

The DHHL land accounts for some 9,000 acres, DOFAW land for roughly 4,000, and Park Service land to Kaupo consists of another 9,000 or so acres, for a total of more than 20,000 acres.

The forest restoration, Fretz said, “is a long-term solution to parrotbill recovery – 20 years, 50 years, 100 years. While remnant forest can be found in some of the area, much of it is very degraded, to the point where little or no forest is left. To restore that could take 50 years or more.”

“We don’t know enough about how parrotbills live in this kind of forest to say how many can persist there now or 10 or 20 years from now. Right now, the main task is to breed a sufficient number of parrotbills, and the captive propagation program is doing that. Then we can start pilot reintroduction projects, as was done with the palila on Mauna Kea. We can put birds out there, in a small amount of core forest, to develop methods and monitor them.”

But scrubbing up the habitat is just one element of any translocation project. Swinnerton elaborated on the difficulties in an email to Environment Hawai`i: “Reintroduction and translocation of small passerines in general is a relatively new field, and there are not many templates to follow. The Maui parrotbill is a particularly complex species because it has a highly specialized foraging technique and the juvenile associates with its parents in a family group for up to one year (and sometimes longer) after leaving the nest.

“Currently, the captive-breeding program is being developed to investigate the potential of captive birds for reintroduction, and the field research that the Maui Forest Bird Recovery Project is doing will give us the information we need to develop translocation protocols – for example, do we translocate single birds or family groups, adults or juveniles? We don’t yet know whether we will reintroduce captive birds or translocate wild birds, but possibly a combination of both might work, as has been done with the palila.”

E `imi wale no i ka lua o ka `uwa`u `a`ole e loa`a.
(Seek as you will the burrow of the `uwa`u, it cannot be found.)

Even in ancient times, the Hawaiian petrel, `ua`u (Pterodroma sandwichensis), was tough to find, as this `olelo, or Hawaiian proverb, suggests. Although the Hawaiians hunted the bird for food, not until more modern times did its population crash, thanks to introduced black rats, mongooses, and cats.

In recent years, the largest population of `ua`u was thought to be on Haleakala, where about 1,000 burrows have been counted. Kaua`i is now thought to support an even larger population, with smaller populations elsewhere.

Jay Penniman, who works with the state Department of Land and Natural Resources’ Division of Forestry and Wildlife, and DOFAW colleagues Fern Duvall and Christine Costales have lately been focusing attention on the Lana`i population. Near the summit of Lana`ihale, the vegetation consists largely of thick, matted stands of native `uluhe fern. The ferns make it difficult for humans to find the petrel burrows, but feral cats seem to have no problem, Penniman said. Examination of feline scat has confirmed that the cats prey on the birds. To date, 12 cats have been trapped, but many more continue to threaten the petrels, Penniman said.

In addition, rats pose a problem to the petrels, whose fat chicks are left unguarded weeks at a time as their parents forage thousands of miles in search of squid, crustaceans, and fish. Penniman is hopeful that the Environmental Protection Agency will soon clear the way for aerial broadcast of rat poison, making it possible to control rat populations on a meaningful scale.

Other measures Penniman and his colleagues have undertaken include outlining a perimeter fence with white tape, making it visible to the night-flying petrels (23 percent of the known deaths of the birds have been caused by flying into fences, he said). Finally, Sheila Conant, one of Hawai`i’s premier ornithologists (and a dog trainer of equal renown), is training one of her precocious border collies to search for petrel burrows.

The endangered koloa, or Hawaiian duck (Anas wyvilliana), is found nowhere else in the world. The mallard (Anas platyrhynchos) is ubiquitous.

When the two get together, as they seem to be doing with alarming frequency, the result is a fertile hybrid. Experts now fear that such interbreeding poses a serious threat to the koloa’s existence as a unique species.

Kimberly Uyehara, Andrew Engilis Jr., and Michelle Reynolds presented the results of their research into this problem in a poster displayed at the conservation conference.
The problem does not come from mallards that make it to the islands on their own. Such “migratory” mallards, occasionally found in the islands, “are rare, not in breeding condition, and do not pose a threat to koloa,” according to the poster.

The bigger threat comes from feral mallards, descendants of birds deliberately introduced to the islands. The first wave arrived in the 1800s, brought here to stock ornamental ponds and to raise as poultry. In the 1950s and 1960s, the territorial, and then the state, government imported mallards by the hundreds and released them as game birds.

Closely related to the feral mallards are domestic duck breeds, including common barnyard ducks. When contained on farms, such birds are unlikely to breed with wild koloa, but, the poster notes, scientists are concerned about “the numbers of abandoned domestic ducks found on public water bodies and the possibilities that these ducks harbor bird and human diseases.”

One of the thorniest problems raised by the interbreeding is simply identifying the hybrids. “Until recently, scientists believed that more than 2,000 ‘true’ koloa remained, primarily on the islands of Hawai`i, Kaua`i, and Ni`ihau,” the poster states. “However, recent evidence shows that even these populations contain mallard x koloa hybrids.”

Saving the koloa as a distinct species may depend on removing the feral mallards. To save its mottled duck population, Florida has outlawed possession of mallards (with certain narrow exceptions), requires proper caging of permitted ducks, and prohibits sales of mallards to anyone not having a permit. Such an approach could be a model for Hawai`i, Uyehara and her colleagues suggest.

Scientists know little about the koloa; it is smaller and more secretive than the gregarious mallard. Its range extends from wetlands at sea level to ponds at 10,000 feet elevation. It “skillfully maneuvers winding river corridors and forest canopy,” the authors say. “However, little else is known about the breeding ecology, home range, movements, or population dynamics of this endangered duck.”

Apart from controlling the introduction and release of feral mallards, the poster lists several tasks for scientists and the public as part of an overall strategy to save the koloa. Among them are to find a way to more easily distinguish between koloa and koloa-mallard hybrids; to educate the public about the threat mallards pose to koloa; and to “humanely remove existing feral mallards and hybrids from the wild.”

***
West Nile Virus Devastating to `Amakihi

It took just seven years for the West Nile virus to spread from the Eastern seaboard of the United States to its western coast. As it swept across the continent, it ravaged populations of what were thought to be some of the hardiest birds, hitting crows and jays especially hard, as well as causing some local populations of raptors to die off.

According to Dennis LaPointe, an expert on mosquito-borne bird diseases who works with the U.S.G.S. Pacific Island Ecosystems Research Center in Volcano, of 20 continental bird species, seven are in decline, including several endangered or threatened species. The virus has “a high-risk pathway to the Hawaiian Islands,” LaPointe said. Airline cabins and cargo holds could easily carry infected mosquitoes. If it does arrive, it would probably end any chance that the `alala (Hawaiian crow) could be restored to the wild.

In an effort to understand how Hawai`i’s birds would respond to the virus, LaPointe and several associates conducted a series of tests on healthy `amakihi (Hemignathus virens). (They did not import the virus to Hawai`i, but rather exported the birds to a Wisconsin laboratory, where the tests were conducted.) The birds were exposed either by injecting the virus directly or by bites from one of the species of mosquito found in the islands (Culex quinquefasciatus). About a third of the birds exposed through injection died; more than two-thirds of those infected via mosquitos died. Birds that did survive generally recovered within a week to 10 days.

All of the birds became anorexic and lethargic after exposure to the virus, LaPointe said. For the tests, all birds had access to food, but in the wild, the birds probably would be unable to forage. “We predict increased mortality in the wild as a result of predation, starvation, thermal stress, and concomitant infections,” LaPointe and his colleagues concluded.

Hawai`i’s culex mosquitoes proved to be a “competent vector” for the disease, LaPointe noted. Not only could mosquitoes pass the virus from one bird through another, they could transmit it “vertically” as well, from one generation of mosquitoes to the next. Considering that the health of many of Hawai`i’s forest birds is already compromised through exposure to diseases such as avian pox and malaria, infection with West Nile virus could result in even higher mortality rates than those observed in the tests, LaPointe said.

All told, he concluded, the virus “could readily become another limiting factor of native Hawaiian bird populations.”

— Patricia Tummons

Volume 18, Number 3 September 2007