SPECIES

Akekee Loxops caeruleirostris Scientific name definitions

Jaan Kaimanu Lepson and H. Douglas Pratt
Version: 1.0 — Published March 4, 2020
Text last updated January 1, 1997

Plumages, Molts, and Structure

Molts

Descriptions based on museum specimens examined by JKL, supplemented by observations in the field. Capitalized, numbered colors were matched to Smithe (Smithe 1975).

Molt sequence not reported for ‘Akeke‘e, but probably resembles that documented for ‘Akepa (see Lepson and Freed 1997) and other Hawaiian honeycreepers (Amadon 1950, Baldwin 1953). In these species, shortly after leaving nest, Juvenile plumage is replaced by Basic I plumage in Prebasic I molt, which may extend through autumn. Although body plumage is replaced, Juvenile flight-feathers are not, or at least not completely. Similar appearance of the sexes and variability in appearance within the sexes require long-term studies of banded individuals to determine whether a subadult plumage exists in ‘Akeke‘e, as occurs in the closely related ‘Akepa (Lepson and Freed 1995; see also Lepson and Freed 1997). Adult Hawaiian honeycreepers undergo a single annual (Prebasic) molt, typically in summer and fall after their offspring fledge (JKL). Body-feathers begin to molt slightly before flight-feathers, and body molt continues after all flight-feathers are replaced. Primaries are replaced in order from P1 to P9; secondaries nearly concurrently in the following order: S8, S9, S7, S1–S6 (Baldwin 1953). All rectrices may molt nearly simultaneously, resulting in tail-less appearance, frequently seen in other honeycreepers (JKL).

Hatchlings

No information.

Juvenile Plumage

No information on Prejuvenile molt, but probably resembles that of ‘Akepa (see Lepson and Freed 1997).

Juvenile plumage mostly dull grayish pale Olive-Green (47) to Grayish Olive (43) on upperparts, with thin dark gray feather edges. Underparts pale Buff-Yellow (53) to Cream (54), with broad, dark Smoke Gray (45) to Grayish Olive (43) feather edges creating faint mottled effect, heaviest on upper breast. Flanks intermediate between Spectrum Yellow (55) and Olive-Yellow (52). Pale gray face with dark lores, but no mask. Remiges, wing coverts, and rectrices dark brown, edged green or Yellowish Olive-Green (50). Tertials usually edged with broad white margins on inner web. Sexes similar.

Basic I Plumage

No information on Prebasic I molt. If this molt occurs, it probably resembles that of ‘Akepa (see Lepson and Freed 1997).

No information on Basic I plumage. If this plumage occurs, it probably resembles Definitive Basic plumage; no significant differences in plumage color that may be related to age are obvious in museum specimens. Duller adult specimens (see below) may be in Basic I plumage, but studies of marked birds in the wild are needed to determine this.

Definitive Basic Plumage

No information on Definitive Prebasic molt. Probably resembles that of ‘Akepa (see Lepson and Freed 1997).

Male. Spectrum Yellow (55) to Sulphur Yellow (57) on underparts, face, forehead, and crown, sometimes tending toward Olive-Yellow (52) on breast and throat; rarely shows tinge of pale Spectrum Orange (17) on crown and sides of breast. Vent white, often obscured. Prominent blackish triangular mask, intermediate between Dusky Brown (19) and Jet Black (89), encircles base of bill, and ends in point behind eye. Mask extends 1–2 mm above and below eye and ends 3–5 mm behind eye. Back and nape vary from a color intermediate between Greenish Olive (49) and Citrine (51) to Yellowish Olive-Green (50). A few feathers on upper back may have yellow edges. Rump and uppertail-coverts close to Olive-Yellow (52), contrasting with greener back. Remiges, wing coverts, and rectrices dark brown, edged Olive-Yellow (52) to Spectrum Yellow (55), brightest near base of tail and on P5–P9.

Female. Similar to but duller than male. Underparts Sulphur Yellow (57) to Olive-Yellow (52). Face mask smaller, Blackish Neutral Gray (82); does not completely encircle bill below. Some females also have darker flanks tinged with olive. Forehead usually yellow green, close to Olive-Yellow (52) or Sulphur Yellow (57), with pale cap smaller and less contrastingly yellow than that of adult male. Back close to Greenish Olive (49). Rump and uppertail-coverts slightly yellower than back, close to Citrine (51), but not as bright as in male. Remiges, wing coverts, and rectrices dark brown, edged Olive-Yellow (52), tending to Sulphur Yellow (57) on P5–P9.

Bare Parts

Bill And Gape

Bill notable for lateral asymmetry: lower mandible curves to left or right, resulting in slightly skewed bill-tips (see also Figure 3A and B in Lepson and Freed 1997). Lower mandible curved to right in 20 of 34 males (59%) and in 12 of 22 females (55%) among museum specimens examined, but this tendency to curve to the right not statistically significant (Hatch 1985a). ‘Akeke‘e bill not studied in detail, but is very similar in appearance to that of closely related ‘Akepa, in which asymmetry is due primarily to differences in the horny ramphothecae, although it is reflected in bones and muscles of jaw and skull as well (Richards and Bock 1973, Knox 1983). See Lepson and Freed (Lepson and Freed 1997) for more details.

Bill blue gray, close to Light Sky Blue (168D) in males (Pratt 1989b), sometimes with a dark tip; grayer in females. Originally described as “light Prussian Blue, darker on maxilla” (Wilson 1889a). Becomes brown or gray as specimens age (JKL). Juveniles have mostly brownish bills, shorter and blunter (thus appearing noticeably “stubbier”) than those of adults. Gape not described.

Iris And Orbital Ring

Iris dark brown (notes on specimens at Bernice Pauahi Bishop Museum) or dark hazel (Wilson and Evans 1890), appearing black in field. Orbital ring black.

Legs And Feet

Black or dark blue gray in adults, close to Blackish Neutral Gray (82) in specimens. Brown to pale brown in juvenile specimens.

Measurements

See Appendix 1 . No mass data available for internal organs. In 'Akepa, Knox (Knox 1983) noted a minor asymmetry of legs, which probably also exists in 'Akeke'e (see Lepson and Freed 1997).

Akekee 'Akeke'e; Alakai Wilderness, Kauai, HI; 3 March 2005.
Enlarge
'Akeke'e; Alakai Wilderness, Kauai, HI; 3 March 2005.

; photographer George Armistead

Recommended Citation

Lepson, J. K. and H. D. Pratt (2020). Akekee (Loxops caeruleirostris), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.akekee.01