Breeding

The below pertains to the Hawai'i 'Akepa, unless otherwise noted. Presumably, the Maui 'Akepa is similar.

Pair Formation

Pairs form as early as Jul–Aug during postbreeding flocking period. New pairs often seen together by Sep.

Nest-Building

Early Mar–late May.

First Brood Per Season

Figure 6 . Nest construction observed early Mar to mid-May. Egg-laying occurs mid-Mar to late May, hatching occurs late Mar to early Jun. Departure from nest observed 20 Apr to 30 Jun.

Second Brood Per Season

Generally only 1 nesting attempt/yr. Pairs can renest if nest fails early in season or cycle; not seen to renest if nest fails after eggs hatch. One male seen to renest once with what appeared to be the same female as in the first brood; first attempt succeeded, but second attempt apparently failed (JKL). In a previous year, that pair renested after their first attempt failed because of a severe storm during incubation; no other pair had begun nesting by that time. No other instance known of renesting after loss of first clutch, but some pairs have renested after abandoning nest during construction (JKL).

Selection Process

Nest site selected after pair bond forms. Male and female explore potential nest cavities both before and after pairing, but pair up before choosing nest site (JKL, LAF). Cavity exploration observed beginning in early Sep, 6 mo before onset of nesting (JKL, T. K. Pratt pers. comm.); frequency of exploration peaks Jan–Mar, just before start of nesting (JKL). Some cavities appear to be preferred, and have been chosen by several pairs over a 7-yr period (but not used every year) at Hakalau Forest NWR, where cavities appear numerous (LAF, JKL) and do not seem to be limiting. These “attractive” cavities vary widely in height above ground, internal depth, canopy cover, surrounding ground cover, and exposure (LAF, JKL).

Microhabitat

See Site characteristics, below.

Site Characteristics

Hawai‘i 'Akepa is an obligate cavity nester in large old-growth ‘o¯hi‘a and koa trees; no nests yet found in other plant species. Most nests are within openings in wood, but a few are located in bark crevices or between bark and wood (Freed et al. 1987 ). Cavity typically in knothole or rotted base of broken branch. Dependent on naturally formed cavities; no Hawaiian birds known to excavate cavities. Only large trees develop cavities, and of these, the larger trees are preferred (LAF). Most nests are in trees >1 m in diameter at breast height (dbh); the largest trees, particularly ‘o¯hi‘a, are centuries old or older. Mean cavity height 10.2 m ± 4.1 SD (range 1.5–19.4, n = 54). Mean nest-tree height of koa 22.1 m ± 6.5 SD (7.9–37.4, n = 33), and mean dbh 1.2 m ± 0.4 SD (0.7–2.4, n = 33); mean height and dbh of ‘o¯hi‘a 21.9 m ± 4.9 SD (14.2–31.4, n = 21) and 0.9 m ± 0.2 SD (0.6–1.4, n = 21), respectively.

Maui 'Akepa observed constructing a nest “high up in a tall ohia, toward the end of a branch” (Perkins 1895 ; no description given of nest, but wording implies it was an open cup).

Construction Process

Female does all nest construction, unlike many insectivorous and nectarivorous Hawaiian honeycreepers (Eddinger 1970 , 1972 ), but typical of the large, finch-billed species (Morin 1992 , T. K. Pratt pers. comm.). Male generally not seen close to female during nest construction. Construction takes about 1 wk, but rate of accumulation of nesting material unknown because of inaccessibility of nest cavities. Female takes material to nest every 1–2 min during active construction bouts (JKL).

Structure And Composition Matter

Builds cuplike nests in cavities; nests may fill smaller cavities (JKL, LAF). Nests composed of fine ‘o¯hi‘a rootlets, small twigs, lichens (primarily Usnea spp.), bark strips, ferns, bryophytes, mosses, introduced pine needles, and grass and sedge leaves (Sincock and Scott 1980 , Collins 1984 , JKL). Females observed peeling strips of bark from ‘o¯hi‘a and ‘o¯lapa (Cheirodendron trigynum ) to take to nest (JKL). Detailed lists of nest materials given in Sincock and Scott (1980 ) and Collins (1984 ). Maui 'Akepa observed collecting fine woolly hairs of tree ferns (probably Cibotium sp.; Perkins 1895 ).

Microclimate

No information.

Dimensions

Inner diameter of 4 nests averaged 5.3 cm (range 4–8), outer diameter of 3 nests averaged 8.4 cm (range 6–10), depth of 2 nests both 3 cm, rim of 1 nest 1.8–2.2 cm thick (Sincock and Scott 1980 , Collins 1984 , Freed et al. 1987 , JKL). One of these nests, located in a large horizontal cavity, was constructed primarily of grasses and other fine fibers on a platform of ‘o¯hi‘a rootlets and coarse lichens measuring 20 cm in diameter (JKL).

Maintenance Or Reuse Of Nests

Only 1 brood/season (n = 74), with the possible exception of 1 pair in one year in a different tree after the original nest-tree fell (Lepson and Freed 1995 ). Pairs frequently reuse the same cavity from year to year, even when nesting attempt fails, but there is individual variation. One pair used same cavity at least 5 yr in a row; other pairs have changed nest sites, even after successful breeding attempts. Males and females usually change nest sites after pairing with new mate; but in 1 instance, female joined male at his previous nest cavity, and in 1 instance, male joined female at her previous nest cavity (JKL).

Shape, Size, And Mass

Few records. Short oval to short subelliptical. Dimensions (length x breadth, in mm) of 2 eggs from same clutch at Hakalau Forest NWR were 19.4 x 14.4 and 18.8 x 14.1; both weighed 1.8 g when 4–6 d old (JKL). Female averaged 10.1 g (range 9.8–10.5) in 6 captures over 5 yr; thus egg represents nearly 20% of adult female mass. Other reported egg measurements from Hawai‘i I. are 16.3 x 12.5 mm from Ka‘u (Sincock and Scott 1980 ), and 17.8 x 13.3 mm and 17.6 x 12.9 mm from a clutch at Keauhou (weights of these unknown age eggs 1.4 and 1.3 g, respectively; Collins 1984 ). These 5 eggs had average shape index (a measure of breadth versus length) of 75.1 ± 1.50 SD (range 73.3–76.7) and average volume of 1.66 cm³ ± 0.30 SD (range 1.29–2.04), as calculated from formulas cited in Banko and Williams (1993 ). No data from Maui or O‘ahu Is.

Color

Background color dull white, with brown and blackish blotches heavily concentrated around blunt end; ≤10% of surface area pigmented (JKL).

Surface Texture

No data.

Eggshell Thickness

No data.

Clutch Size

One to 2, rarely 3. In 26 nests where nestlings were visible at entrance before departure, 9 had 1 nestling and 17 had 2 nestlings. One nest reported having 3 eggs, only 2 of which hatched (Sincock and Scott 1980 ).

Egg-Laying

Lays eggs mid-Mar–early Jun. Exact dates unknown because of inaccessible nature of most nests and because most nests are discovered during incubation. Timing unknown; presumably 1 egg laid/d. Egg-laying appears to begin within 1 wk after completion of nest construction, but in one case commenced after a pause of 4 wk.

Incidence Of Intraspecific Egg-Dumping

Intraspecific egg-dumping unknown, but no genetic studies of parentage have been carried out. One banded female briefly entered nest of unbanded female shortly before incubation began. No other instances known of conspecific nonparents entering a nest, but other species (‘I‘iwi and ‘Apapane) have been seen rarely to enter nests (see also Behavior: social and interspecific behavior, above).

Onset Of Broodiness And Incubation In Relation To Laying

No data.

Incubation Patch

Only female develops incubation patch, which is probably acquired by the time clutch is completed.

Incubation Period

Imperfectly known because of inaccessibility of nests. Eggs hatch after about 14–16 d of incubation (JKL).

Parental Behavior

All incubation by female. Male regularly feeds female off nest during incubation, but female also forages for herself. Time between feedings averaged 32.42 min ± 16.51 SD (range 2–99, n = 116 feeding observations at 30 nests); no differences between third-year subadult and adult males (Lepson and Freed 1995 ).

Female generally sits quietly on nest when not foraging or soliciting male. She turns eggs, and also appears to sleep briefly (data from 2 nests where female visible from outside; JKL). Approaching male often calls to incubating female, who responds from nest with distinctive double calls (keewee-keewee ). Vocal exchange between the 2 may continue for >1 min before female emerges and is fed by male nearby. Female then either forages or returns immediately to nest. Female may also emerge on her own to search for and persistently solicit from male with same double call. Female spent average of 5.4 min off nest (range 10 s–23 min, n = 146 observations of 23 nests) during each feeding session at Hakalau Forest NWR (JKL).

Hardiness Of Eggs To Temperature Stress

No data.

Preliminary Events And Vocalizations

No information.

Shell-Breaking And Emergence

Little known. At 1 nest, 2 eggs were present at 18:00, and both had hatched by 12:00 the next day. Degree of synchrony not known, but 1 chick had half of the eggshell attached, suggesting it had hatched somewhat later (JKL). The male had shown behavior consistent with the presence of chicks by 07:30 that morning.

Parental Assistance And Disposal Of Eggshells

Not known if parents assist with emergence. Eggshells not found by nest; female is presumed to carry them off, but this behavior not yet observed. Male comes to nest to feed female within a few hours of egg-hatching (Figure 7 ); this is the best indication of hatching at inaccessible nests (JKL).

Condition At Hatching

Naked except for sparse, dark gray down along spinal and capital feather tracts (JKL). Chicks orangish, probably because of red blood cells showing through transparent skin, as in cardueline finches such as the House Finch (Carpodacus mexicanus ; Hill 1993 ). Eyes closed; no ear passage visible. Flanges yellow, inside of mouth reddish pink, bill dark orange. Nestlings able to squirm at hatching

Growth And Development

Mostly unknown. Tarsus measurements (mm) of 2 chicks at 1 nest on days 1, 2 and 4 after hatching were 6.5, 7.0, 10.0, and 6.0, 6.7, 9.9, respectively (JKL). Masses (g) on days 2 and 4 were 2.1, 4.1, and 1.8, 3.8, respectively. Eyes still closed on day 4, but open on day 6. Down still present only on capital and spinal tracts on day 4.

Responses poorly known, since few nests are accessible. Nestlings at 1 nest raised head and gaped at human observer on day 6 after hatching (JKL). Continued to gape at observer on day 9. Did not gape and did not show fear of observer before handling on day 12, but showed fear thereafter. Begging chicks audible about a week after hatching; appear in entrance to nest cavity (see Figures 8A and 8B ) up to a week before fledging, around days 16–20 (JKL).

Acquisition of Juvenile plumage mostly unknown. On day 4, blood vessels visible in wing where secondaries later develop, but no other evidence of Juvenile plumage at that point (JKL). Nestlings appear fully feathered by day 12. Some downy feathers remain on crown and nape, also sometimes after leaving nest.

No data on nestling physiology.

Brooding

Female largely remains on nest and broods young steadily for first few days after hatching; male feeds female on nest. After several days, female leaves nest frequently to forage and broods much less, but observed still to brood 8 d after hatching (JKL).

Feeding

Both male and female feed young. Male also feeds soliciting female on nest, who then passes food to chicks (JKL), but usually male feeds chicks directly. In observations at 24 nests, time between feedings averaged 26.2 min ± 16.4 SD (range 1–89, n = 156) for females and 39.1 min ± 23.0 SD (range 2–132, n = 72) for males. No differences in feeding rates between adult and subadult males (Lepson and Freed 1995 ). All feeding by regurgitation of crop contents directly to chick; chick inserts bill into parent's mouth. Feeding accompanied by loud begging calls of chick. Composition of food given to young unknown, but presumed to be primarily arthropods, on basis of adult diets. Parents feeding young in nest forage in same manner as adults not feeding offspring (JKL).

Nest Sanitation

Both sexes carry away fecal sacs of young, and have been observed to eat the sacs (JKL). Chicks void fecal sacs while being fed, and fecal sacs are immediately removed by parents. After about 5 d, young will void fecal sacs onto edge of nest, and parents take them from there. Some fecal sacs are not removed, and begin to accumulate on rim of nest by the time of fledging. This accumulation, typical of related cardueline finches, is unusual among Hawaiian honeycreepers, and known otherwise only in Laysan Finch (Telespiza cantans ; Morin 1992 ), the finch-billed Palila (Loxioides bailleui ; T. K. Pratt pers. comm.), and Maui Parrotbill (Pseudonestor xanthophrys ; T. K. Pratt pers. comm.).

None reported.

No brood parasitic species known from passerines in Hawaiian Archipelago.

Fledging peaks in May and Jun. Earliest known date to leave nest 20 Apr; latest 30 Jun (JKL).

Departure From Nest

Young leave nest approximately 16–20 d after hatching. Young frequently come to cavity entrance up to 1 wk before fledging and occasionally exercise their wings. Departing young still retain some down, especially on head, and have short tails and noticeably stubby bills. Departure observed 07:00–15:00. Three of 4 fledglings maintained level flight when they left nest; the other lost altitude but landed in a shrub (JKL). Hawaiian honeycreepers frequently leave nest before they can fly if they are disturbed (and are popularly called “jumplings”). This is presumed to happen with ‘Akepa, but has not been observed, possibly because cavity nests are less susceptible to disturbance. One fledgling found on ground was unable to fly, possibly because of premature departure; this bird was being fed by its parents (JKL).

Association With Parents Or Other Young

Parents not present when young observed to leave nest. Fledglings sit quietly until parents appear, then give distinctive, soft nasal calls (see Sounds: vocalizations, above), which last only a few days after departure from nest. Fledgling gives loud begging calls when parent approaches and feeds it. Young appear to be led away from vicinity of nest soon after departure, then are sedentary. After several days they begin to follow parents, and at this point begin to give the louder, distinctive mewing call (see Sounds: vocalizations, above) for as long as they receive parental care. As greater numbers of nests fledge, family groups begin to form large mixed-species flocks with Hawai‘i Creeper and smaller numbers of Hawai‘i ‘Amakihi and ‘Akiapo¯la¯‘au (see Behavior: social and interspecific behavior, above). Both parents have been seen feeding same juvenile, but in some cases they have joined separate flocks, each parent tending to 1 juvenile (JKL). Parental care of juveniles observed up to 10 wk after young leave nest (JKL). Juveniles may be more vulnerable to predation than adults because of inexperience and continuous calling. Both instances of predation on ‘Akepa by ‘Io (Hawaiian Hawk: Buteo solitarius ) were on dependent juveniles (JKL), who never form the majority of the population, unlike many temperate species that have much larger clutch sizes (see Demography and populations: causes of mortality, below).

After parental care ceases, postbreeding flocks begin to dissipate, and by Oct immatures are mostly solitary. Immatures behave similarly to adults, appearing to forage in same manner and giving calls that sound identical to human ears. Young males not reported to sing before spring of their second year.