ECOLOGY AND BREEDING BIOLOGY OF THE HAWAII ELEPAIO (CHASIEMPIS-SANDWICHENSIS-BRYANI)

Elepaio (Chasiempis sandwichensis bryani) were studied on the island o f Hawaii from 1970 through 1981. The species had a protracted breeding season from February through August, with most intensive breeding fro m April to June. Annual breeding season length varied among years (ran ge 3-7 months). Elepaio retained mates for more than one season and re mained in their territory throughout the year. An Elepaio territory en compassed the nest site, all food resources, and had similar boundarie s in succeeding years. Nests were statant, open-cupped, with mamane (S ophora chrysophylla) trees the preferred nesting substrate. Clutch siz e of 23 nests was two eggs and did not vary among years. Both parents incubated, brooded, and fed the young. Incubation periods averaged 18 (range 17-19) days; hatching success of eggs incubated to term in 22 n ests was 75%. Nestling periods averaged 15.6 days; fledging success wa s 89.3% and young fledged synchronously. Total reproductive success, b ased on 19 nests with complete records, was 65.8%. The most important factor that influenced annual Elepaio productivity on Mauna Kea was le ngth of the breeding season, followed by the number of nesting birds a nd eggs laid that failed to hatch (25%). Inter-island subspecies compa risons revealed many similar behaviors (e.g., courtship chasing, terri tory type, clutch and egg sizes, nest placement, adult roles in nest b uilding, incubation, brooding and feeding). Differences among subspeci es appeared to revolve mainly around the influences of forest-type in which birds bred. In mesic habitats on Oahu and Hawaii, predation of e ggs and young by introduced mammals played a major role in decreasing annual productivity, whereas in the dry forest of Mauna Kea predation on C. s, bryani nests was much lower.