When wildlife managers try to rescue a bird whose numbers are critically low, the risks are high and choices are few. Dealing with endangered species that are more abundant, even if still rare, takes off much of the pressure.
Consider the Palila (Loxiodes bailleui). It was a member of the first group of birds placed on the federal list of endangered species soon after the Endangered Species Act was passed by Congress some 30 years ago. (Twenty of the 36 birds in that club were endemic to Hawai`i.)
The Palila was also the plaintiff in a landmark lawsuit that forced the state, much against its will, to protect Palila habitat (upper elevation mamane forests of Mauna Kea) by removing ungulates, especially feral goats and Mouflon sheep.
According to Paul Banko of the Biological Resources Division of the U.S. Geological Survey, the habitat is coming back nicely, but the bird population, while not crashing, is not rebounding, either. The most recent estimates place its numbers at about 4,200, Banko said.
“The Palila is not a bird that easily recovers itself,” Banko told Environment Hawai`i. “There’s been a great improvement in the habitat, but the birds don’t seem to be responding.”
Banko goes on to note, though, that what may look like terrific habitat to the human eye may look pretty trashed to the Palila. The mamane trees that are growing back “are still very small,” he said. “We have ten years of habitat recovery; it may be ten or twenty years more before the really big trees make a comeback.”
“People have to be very, very patient,” Banko notes. At the same time, he gives credit to the territorial foresters who, starting in the 1920s, “recognized the watershed value of the forest and got the feral cattle off the mountain. By the 1950s, sport hunting took over.” Mouflon sheep were introduced in 1954; efforts to remove ungulates (other than by hunting) ceased, and the stage was set for the decline of the mamane forest.
“That 25-year effort of the early foresters is probably what saved the Palila,” Banko says. And while it may take another quarter century or longer to see Palila numbers begin a steady upward trend, he credits the fact that they have any chance of doing so at all to the vision of those early foresters.
Faithful Birds
Almost all of the wild Palila inhabit a small area on the western slope of Mauna Kea. In recent years, as the mamane trees have been making a comeback following the removal of sheep and goats, scientists have attempted to establish Palila in other areas.
The Palila have not cooperated. Starting in 1993, scientists with the Fish and Wildlife Service captured Palila from the western slope and translocated them to “good looking habitat” in the eastern side of the mountain, where a dwindling population of Palila held forth. “They moved 36 birds, most of them adults. About four birds died within a day of their release, but the rest survived short-term,” Banko relates.
“The birds had radios and seemed to be doing well until the radios’ batteries started to go out — about two months after the release. At that time, the birds started to move. About half of them moved back home.
“The highlight of the move was that at least two birds paired and nested,” Banko says — back on the western slope. The small population on the eastern side of the mountain has since gone extinct.
In later years, scientists tried the experiment again, this time using younger birds, between 6 and 10 months old. This time, there was no massive shipment of birds; rather, they were relocated to the north side of Mauna Kea as they were caught — one or two at a time. “But we got the same result we did in 1993,” Banko says: “Almost all of them came back.”
Last year, starting in October 1997 and continuing through March 1998, the experiment was repeated, using still younger birds (between 3 and 6 months old). “Everything went well,” Banko says, “but then, the birds started getting hung up in trees.” In an effort to hold down expenses, he explains, the BRD had placed cheaper radio transmitters on the birds, but the longer antennas were a problem. “We had to catch the birds, remove the transmitters, and replace them,” he says.
“But we continued to have problems: the birds were getting clobbered by predators,” Banko says — something that had not occurred in previous years. Cats and rats, as well as Pueo (the Hawaiian owl) and `Io (the Hawaiian hawk) were the chief suspects.
Nor are the Palila helped by their own site-faithful roosting behavior. “The Palila are very traditional about their night roost,” Banko says. “They seldom change it. Often there’s fecal accumulation, and a cat or rat, if cued by scent, would be drawn to these places.”
As in previous years, most of the birds translocated have returned back to the western slope. However, about three birds hang out in the north slope area, including a female that Banko suspects of commuting between the western and northern sites.
This year, another effort to translocate birds is planned. Banko hopes an expanded predator control program at the north site might help: “A year ago, I didn’t think the Palila were too vulnerable to predators. Now, I’ve changed my tune. It isn’t the No. 1 priority even now, but it has risen in stature.”
Captive Propagation
Eggs from wild Palila nests have been successfully hatched in the Big Island captive breeding facility at Keauhou, operated by The Peregrine Fund with funds from the Fish and Wildlife Service. Banko is pretty confident that captive-reared birds would not display the same site-fidelity of the wild-reared ones, and thus could form the core of a second wild population.
Plans to release captive-reared Palila have been put on hold, however, following concerns that they might be infected with a type of mycoplasma bacteria.
There are strongly divergent views on the nature of the threat that this bacteria poses. Alan Lieberman, head of The Peregrine Fund’s Hawai`i operations, told the Board of Land and Natural Resources last year that this the mycoplasma was “a brand new limiting factor” that could prevent introduction into the wild of the captive-reared Palila.
The Keauhou facility did experience high mortality rates in 1996 among Palila chicks. Of 32 eggs removed from the wild, 22 eggs were viable and 21 hatched. Of those 21, 10 died from six to 10 days after hatching.
The cause of mortality has not been pinned down with any certainty. There are several strains of mycoplasma, not all of them killers. In fact, some samples of blood from wild Palila tested positive for a strain of mycoplasma, as did a sample taken from an `Amakihi.
Banko is less concerned than Lieberman about the presence of mycoplasma in the Palila population: “The disease just isn’t wiping the whole darn population out. It may be affecting the birds in ways not yet known, but as far as a wholesale wipe-out goes, it isn’t happening.”
In 1997, three captive Palila died — one in an Aspergillosis outbreak at The Peregrine Fund’s Keauhou facility, two others from unknown causes (possibly shock or stress).
As of August 31, 1998, seven Palila were reported living at the Keauhou facility. According to a report to the state prepared by The Peregrine Fund, the captive Palila showed no sign of breeding activity in 1998.
To be sure, 1998 was not a terrific year for breeding among the wild Palila, either, thanks to El Nino. Banko has seen two El Nino periods since he has been studying Palila. “The first, in 1992, was unbelievable,” he says. “We found five nests, instead of the usual 90 or so.”
The 1997-98 breeding season was delayed for about two months. After El Nino broke in the early part of the year, “the birds bred in pretty good numbers. We had a mediocre year — only mediocre, but that’s great. We found more than 40 nests.”
Wasps
Scientists continue to learn more about the Palila, and about possible impediments to its recovery. One area of inquiry focuses on changes in the food sources available to the birds.
“My father, Winston Banko, thought that changes in the birds’ diet might explain their failure to thrive. The Palila’s morphology” — especially its beak — “reflects a specialized diet. My father suggested we also need to look at changes in food resources,” including insects that might not be part of the adult bird’s diet, but food for nestlings.
“Green mamane seeds are the primary food for adults and young,” Banko says, “but the young also eat caterpillars. We’re trying to find out how important the caterpillars are.
“There are three introduced small, black wasps, called parasitoid, because they are parasitic on the juvenile stage of their hosts,” Banko continues. The wasps, introduced years ago as a means of biocontrol for agricultural pests, inject their eggs into the larvae of moths that are deposited on the mamane seed pod. The wasp larvae then eat the caterpillar from the inside out before emerging as adults.
To get an idea of the parasitism rates, scientists place seed pods into tightly sealed containers. “After a time, either a moth emerges, or a parasitoid wasp comes out,” Banko says. Parasitism rates are estimated on this basis. What scientists are seeing is like nothing reported before, he says. “We’re getting 100 percent in some areas — a free-for-all for the wasps.”
Whether this is a problem for the Palila is not known. “At this stage, we think it isn’t a major limiting factor, but certainly something to consider in reintroduction.”
— Patricia Tummons
Volume 9, Number 5 November 1998
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