Palila

Loxioides bailleui

Description

The palila, Loxioides bailleui, is one of the Hawaiian finches, which are the largest birds among the honeycreepers. It is between 6 and 6.5 in (15 and 16.5 cm) long and weighs about 2 oz (56 g). This thick-billed bird has a golden-yellow head, gray back, and whitish abdomen. The bill itself is dark, and a black mask (lore patch) runs from the bill to the eyes. Females and juveniles have more subdued coloring than males. This species was formerly classified as Psittirostra bailleui.

Behavior

The nesting season of the palila begins in late spring and lasts five or six months. These monogamous birds defend a small territory around the nesting tree and forage over a larger area. Females construct nests on horizontal branches of the larger mamane (Sophora chrysophylla ) and naio (Myoporum sandwicense ) trees from grasses and large dead twigs, and line the nests with lichens and rootlets. The female usually lays two brown-splotched white eggs, which are incubated for 18 days. The palila will often renest if a first effort in the early part of the season is unsuccessful. Parents care for the young and feed them mamane seeds and insects for about a month until they fledge. The young move with the parents in a family group for an extended period of time.

Habitat

Palila depend on the mamane-naio forest ecosystem for all their feeding and nesting needs, as such they concentrate in areas where large mamane trees carry fully developed green pods.

Distribution

Palila were formerly found throughout the higher regions of the island of Hawaii in the north and south Kona districts, the Hamakua district on the eastern slope of Mauna Kea, and the mamane and naio forests on the southern and western slopes of Mauna Kea. The palila is now confined to the ma-mane-naio forests of Mauna Kea above 6,000 ft (1,825 m), inhabiting a small portion of what appears to be suitable forest habitat. In 1988 biologists from the Patuxent Wildlife Research Center's Hawaii Research Station and state personnel conducted a comprehensive survey of the palila on the slopes of Mauna Kea. The population, riding an upward trend, was estimated to be 4,300. A follow-up census the next year revealed that the population had decreased by almost 20%, to about 3,500 birds. Fewer palilas nested on the island of Hawaii in the 1992 season than in any season since 1988, possibly as the result of a severe drought. Only five active nests were found, compared to 85, 84, 52, and 71 during the respective previous four years. Two of the 1992 nests successfully fledged young, and one of the pairs renested unsuccessfully. Apparently, the low breeding effort resulted from a drought brought on by an El Nino event. Counts of mamane pods, the bird's main food, were also below average before the drought began and became progressively lower throughout the year. Insects, another food of the palila, especially chicks, were captured at low rates during the drought.

Threats

Until now, little research has been done to discover the reasons for palila decline. Although forest habitat seems adequate to support a healthy population, the mix of forest plants has changed over the years and may be affecting the palila in ways that are not understood. Weather may account for palila decline in some years. Rains, infrequent but usually heavy, may kill young birds if adults are away from the nest when a storm occurs. As the 1992 drop in nesting exhibits, a severe shortage of rain can be nearly as damaging to the palila population as an excess—drought seems to cause a reduction in the food supply of mamane pods and insects. Another threat comes from other creatures. Tree-climbing roof rats, cats, mongooses, and other potential predators have increased in number. Because palila nests are usually placed on horizontal branches, both cats and rats have easy access to them.

Conservation and Recovery

A full-scale radio telemetry study was begun in 1988 to determine this bird's habitat selection and use, daily movement patterns, and home range. Findings from this research are filling in many of the blank spaces in our knowledge of the palila. A mamane forest on the east slope of Mauna Kea was selected in 1992 as the site for a proposed experimental translocation of palilas. Factors considered during the selection process included available food supply, elevation of the site, relative abundance of predators, and logistics.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

References

Scott, J. M., et al. 1984. "Annual Variation in the Distribution, Abundance, and Habitat Response of the Palila." Auk 101: 647-664.

U. S. Fish and Wildlife Service. 1978. "Palila Recovery Plan." U. S. Fish and Wildlife Service, Portland.

Van Riper, C., III. 1980. "Observations on the Breeding of the Palila Psittirostra bailleui of Hawaii." Ibis 122: 462-475.