Plumages, Molts, and Structure

‘Ö‘ö are characterized by bill equal to or longer than head, and nostrils long and bare of feathers, partly covered from above by large operculum. Mandibular tomia are serrated near distal end; serration is more pronounced on upper mandible. Tongue is highly protractile; tubular and bifid, it terminates in a brush-like tip to form a sucking organ. Plumage very soft and long, except short and scaly on head. Wings have 10 primaries and 9 secondaries. Tail is graduated, but shape of tips of rectrices and color vary among species. Plumage generally brownish or black, with patches of yellow feathers, often forming tufts. Sexes are similar in coloration but differ in size: Males are larger. Tarsus and toes are large and strong. Large scales in front of tarsus are more or less fused. Prominent ridge on rear of tarsus is connected with lateral sheath by soft skin (Rothschild 1893a Rothschild, L. W. (1893a). Avifauna of Laysan and the neighboring islands with a complete history to date of the birds of the Hawaiian possessions, Pt. III. London, U.K: R. H. Porter. Close , PWS).

Kioea shares most structural characteristics with ‘ö‘ö, but its measurements are larger; its plumage is brownish rather than black, much streaked, and lacking feather-tufts or yellow patches; feathering of its head and body is very soft, as result of open structure of barbs and barbules; and it has very pronounced, outward-curving, black bristlelike feathers on head and throat.

Molt sequence unknown.

Hatchlings

See Breeding: young birds, above.

Juvenile Plumage

No information.

Basic I Plumage

Fledgling female labeled “Juv,” collected 2 Jul 1893 (AMNH 693927), showed no molt; male labeled “young,” collected on same date and at same locality (AMNH 693928), had feathers fully emerged but sheaths at base of primaries and rectrices. Recently fledged male, collected May 1895 (BPBM 321), was undergoing some body and tail molt; sheaths were present on R1 pair. This bird had no streaking on back or underparts, except for faint white arrowhead markings on throat and chin. No streaking or scaly appearance on crown. Patch on front edge of wing pale gray. Belly with russet wash. Margins of inner primary webs pale; remainder of feathers brownish black. Feathered part of leg black, washed with russet (PWS). Basic I plumage resembles adult Definitive Basic plumage; overall duller, with lighter underparts, glossy-black wings and tail, no white on front edge of wing, and no yellow on feathered part of leg (Munro 1944a Munro, G. C. (1944a). Birds of Hawai'i. Honolulu: Tong Publ. Co. Close , J. L. Sincock unpubl.).

Definitive Basic Plumage

Male. Limited specimen material tends to show worn plumage from midspring through early summer, and unworn plumage from early fall through early spring; probably a complete molt immediately following breeding (see Figure 4). General appearance: mostly black, with brownish wash and bright-yellow thigh-feathers. Head black; entire crown darker black than remainder of plumage, with a few faint longitudinal streaks of white formed by light-colored shafts; in live bird, faint, light-colored markings radiated like an open fan in auricular region (PWS); light-grayish or white malar line; and indistinct white crescent above eye in living bird, but difficult to see in most specimens (PWS). Upperparts slaty brown, becoming russet on rump; chin, throat, and upper breast black, each feather subterminally barred white in shape of arrowhead, giving scaly streaked appearance; sides and flanks russet; crissum rufous brown; remainder of underparts slaty brown, with feather shafts gray, forming fine indistinct streaks; wings and tail black. Vestigial axillary tufts pale grayish buff; anterior edge of wing at wrist and underwing coverts white; crural feathers chrome yellow.

Female. Timing of molt probably similar to that of male. Plumage like that of male, but feathers of chin, throat, and upper breast much more extensively barred white, giving appearance of well-defined whitish patch.

Bill And Gape

Nestling. See Breeding: young birds, above.

Fledgling. Bill (male, BPBM 321): upper mandible black, lower mandible horn-colored; gape color unknown.

Adult. Bill glossy black; gape color unknown.

Iris

Bluish gray in nestlings and fledglings (Munro 1944a Munro, G. C. (1944a). Birds of Hawai'i. Honolulu: Tong Publ. Co. Close ); pale yellow in adults.

Legs And Feet

Nestlings. See Breeding: young birds, above.

Fledgling. Paler than in adult (Munro 1944a Munro, G. C. (1944a). Birds of Hawai'i. Honolulu: Tong Publ. Co. Close ); yellow-brown in specimens.

Adult. Glossy black; digital pads yellow; claws glossy black.

Linear Measurements

In all 5 species, males larger than females. See Appendix 3, and Table 2 in Lepson 1998 Lepson, J. K. (1998). Notes on appearance and speculated behavior of the O'ahu 'O'o (Meliphagidae). Pacific Science 52:210-219. Close , for size ratio of sexes.

Mass

No measurements of mass reported for Hawaiian honeyeaters. A crude estimate of mean mass for both sexes of the 5 Hawaiian species was derived from calculations using linear regression for each sex separately plotting mean mass and cube of mean wing chord of species from New Guinea, Australia, and New Zealand (n = 9 species) in which means of both variables were available (Diamond 1972b Diamond, J. M. (1972b). Avifauna of the Eastern Highlands of New Guinea. Bulletin of the Nuttall Ornithological Club 12. Close , Robertson et al. 1983a Robertson, H. A., A. H. Whitaker and B. M. Fitzgerald. (1983a). Morphometrics of forest birds in the Orongorongo Valley, Wellington, New Zealand. New Zealand Journal of Zoology 10:87-98. Close , Dunning 1993b Dunning, J. B., Jr. (1993). CRC Handbook of Avian Body Masses. CRC Press, Boca Raton, FL, USA. Close , J. M. Diamond, J. B. Dunning, Jr., and T. Ivison pers. comm.). Estimated mean masses are given here.

Kaua'i 'Ö'ö. Male, 39 g; female, 38 g.

O'ahu 'Ö'ö. Male, 56 g; female, 43 g.

Bishop's 'Ö'ö. Male, 59 g; female, 42 g.

Hawai'i 'Ö'ö. Male, 67 g; female, 43 g.

Kioea. Unknown sex, 97 g.