Micronesian myzomela

The Micronesian myzomela was first formally described by René Lesson in 1827 as Cinnyris rubrater.^[3] In 1835 it was designated Certhia cardinalis^[4] and moved a year later to Cinnyris cardinalis by Heinrich von Kittlitz.^[5] In 1850, Charles Lucien Bonaparte became the first to place it in its current genus, Myzomela, assigning it the specific epithet sanguinolenta^[6] (from Latin sanguis, meaning "blood".)^[7] It was then renamed by Gustav Hartlaub, first in 1852 as M. rubrater,^[8] then in 1854 as M. rubratra,^[9] which it has kept since.^[10] In 1932, Ernst Mayr deemed it conspecific with the cardinal myzomela,^[11] however it is now recognized by most major authorities as its own species.^[10] Its specific epithet, rubratra, is a compound of Latin rubra and atra, meaning "red" and "black" respectively.^[12] 7 subspecies of the Micronesian myzomela are recognized.^[10]

• M. r. rubratra (Lesson, 1827)—The nominate subspecies. Found on Kosrae of the Caroline Islands. The adult male's body is almost entirely scarlet or scarlet-red, excluding the thighs and the lores (the area between the eye and nostrils), which are black. The adult female's plumage is similar, although she is smaller in size, and her coloring is duller. The juvenile of both sexes is reminiscent of the adult, although it is of a lighter tone in comparision, and its coloring is not as vivid.^[13]
• M. r. dichromata Wetmore, 1919—Found on Pohnpei of the Caroline Islands. The adult male strongly resembles that of the nominate subspecies, except that the black markings on his lores and below the eye are more substantial. and the tips of his colored feathers are brighter. The adult female is similar to the nominate, though the extent of her red plumage is greatly reduced. Her chin, throat, and the underside of her tail are reddish. The rest of her body is colored varying shades of brownish-gray, occasionally with reddish patches. The juvenile male resembles the adult, except that his scarlet coloring is less vivid and is thinner on his rump, forehead, underparts, and the base of his tail. The red coloring is usually absent from his neck and the top of his head. The juvenile female is also like the adult, but her scarlet coloring is thinner and only visible on her back, rump, underpartds, and the base of her tail.^[14] Its name comes from Latin dichromata, meaning two-colored.^[15]
• M. r. major Bonaparte, 1854—Found on Chuuk Lagoon of the Caroline Islands. Both sexes look similar to nominate. The adult male's feathers are lighter on the tips. The adult female's underparts are colored a brighter scarlet-red. The juvenile male looks similar to the adult female, except the feathers on his head and neck have less scarlet coloring on the tips. The juvenile female resembles the juvenile female nominate subspecies, except that her upperparts are grayer and her underparts are darker.^[16] Its name comes from Latin major, meaning greater or larger.^[15]
• M. r. kurodai Momiyama, 1922—Found on Yap of the Caroline Islands. The adult male resembles the adult male M. r. saffordi, although his leg is shorter, and his plumage is less orange-hued. The adult female's upperparts are a dark green-brown. Her underparts are paler but otherwise similar, though her breast and abdomen may be yellow-gray. Her head, rump, and lower back, along with her entire frontside, are all tinged scarlet-red.^[17] It is named after Nagamichi Kuroda, a Japanese ornithologist.^[15]
• M. r. kobayashii Momiyama, 1922—Found on the islands of Palau.^[15] The adult male resembles nominate; however he is smaller and the scarlet coloring on his body is darker, more so than that of any other subspecies. The adult female resembles the female M. r. dichromata, although her abdomen, the underside of her tail feathers, and her "armpits" (axillary feathers) are rust-gray. Unlike all other subspecies, the top of her head is only partly colored red. The juvenile male resembles the adult except for his lighter and scantier scarlet-red coloring. His wings and tail are green-brown, and the underside of his tail is off-gray. The juvenile female is like the adult, just that her scarlet-red coloring is paler and her underparts are tinted red.^[18] It is named after Keisuke Kobayashi, Sr, a Japanese ornithologist and oologist.^[15]
• M. r. asuncionis Salomonsen, 1966—Found from Anatahan to Asuncion of the Northern Mariana Islands. All ages and genders are visually identical to M. r. saffordi.^[15]
• M. r. saffordi Wetmore, 1917—Found on the southern islands of the Northern Mariana Islands, namely Rota, Aguiguan, Tinian, and Saipan. Formerly found on Guam, before its extinction there.^[15] Both sexes resemble nominate, with minor differences. The adult male is slightly smaller and his scarlet-red coloring is more orange. Unlike the other subspecies, the wings and tail of male M. r. saffordi are tinted olive. The adult female is also smaller and paler in color. Her upperparts are dark green-gray occasionally mottled with scarlet, and the underside of her tail and her abdomen are red-gray. She can be differentiated from other subspecies by her scarlet-tipped feathers on the top of her head, and the dark olive coloring on the edges of her tail feathers.^[19] It is named after William Edwin Safford, a botanist.^[15]

The Micronesian myzomela is a small honeyeater measuring 13 cm in length.^[20] The sexes differ in size and appearance: The adult male weighs 15 g (range 12.7–18 g)^[21] and has a 72 mm wing chord, a 13 mm bill, a 55 mm tail, and a 21 mm tarsus,^[22] and the adult female is smaller, weighing 12.7 g (range 10.4–15 g)^[21] and with a wing chord measuring 66 mm, a 11 mm bill, a 55 mm tail, and a 20 mm tarsus.^[22] In both sexes and at all ages, the bill is distinctly curved downwards. It is colored brown with a yellow base in juveniles, darkening with age, becoming completely black in adults. Similarly, the gape also darkens with age, starting bright yellow and becoming black in adults. The tongue and interior of the mouth are bright yellow. Its iris is dark brown, and its toes and tarsi are scaly and dark brown, with the undersides of the feet being dull yellow.^[23]

The female has dusky brown tail and wing feathers fringed with olive, and a predominantly black or brown body with scarlet-red patches. The male is similar, though his patches are more vermilion and he lacks any brown coloring. The extent and placement of the patches vary between subspecies in both sexes.^[24] Juveniles of both genders are much browner compared to adults and have little to none red patches.^[25]

The Micronesian myzomela is a permanent resident of the Caroline and Mariana islands.^[29] It has not been observed moving between islands, but the short distances between some in a chain may still permit dispersal.^[30] It can be found in and on the edges of forests, including secondary, Clinostigma, mangrove, and agroforest types. It also inhabits coconut plantations, coastal strand, savanna brush, villages, towns, and gardens.^[31]

On Kosrae, it inhabits every land habitat up to 589 m, including tall trees along lagoons, mangroves, canals,^[32] coconut groves,^[33] coconut palms near houses and gardens, and riverbanks.^[32] It is especially common in the lowlands.^[33] On Pohnpei, it can be found in most habitats,^[33] with more found in undisturbed vegetation, mangroves, and agroforest, and less in secondary vegetation, although the species is detected more often in disturbed habitats. On Yap, it can be found in all suitable habitats on all islands, being most abundant in low brush.^[32] Across these island chains, densities are generally greatest in mangroves (particularly those composed of Sonneratia alba), and appear related in part to tree maturity.^[32]

In Palau, it can be found in open woodlands, secondary vegetation, forest edges and openings, broken forest, and agroforest near villages.^[32] It also inhabits coconut groves, flower gardens, and other areas around human habitation,^[34] but is uncommon to rare in unbroken mature native forest and was not recorded in dense jungle. On Guam, it could be found in scrub, second growth, and mixed woodland, as well as grassland, riparian habitats, low shrubs along streams, mangrove swamps, and coastal strand near wetlands, and by 1981 reached its highest densities in the relatively undisturbed forests of the north. It also inhabited gardens, yards, and coconut groves, including palms around the resort hotels of Tumon Bay, and visited the flowers of coconut palms, banana trees, and day-blooming jasmines.^[32]

In the Northern Mariana Islands, it is especially common where nectar-producing flowers are present, and is most abundant in mixed second growth near village gardens; within native forest it primarily occupies the upper canopy. It is typically absent from open, grassy savanna, but sometimes forages where flowering herbaceous vegetation is present. On Rota, it can be found in open forest and in Pemphis scrub near the beach, and occasionally in fields on the high-elevation Mt. Sabana. On Sarigan, it occupies native forest and coconut palm agroforest. On Aguiguan, it occupies native forest on steep limestone escarpments, where browsing by feral goats leaves the understory open, as well as thickets of the introduced Lantana camara on level ground formerly cultivated for sugarcane.^[32] On Saipan and Tinian, it can be found in native limestone forest, upland forest, and secondary forest of coconut palm, Delonix regia, and various large fruit trees. It is more abundant in native forest and second growth than in Leucaena leucocephala thickets, where less nectar is available. It also inhabits littoral Casuarina stands, beach strand, mangroves, cultivated areas, suburban areas, and vegetation around habitations, and is particularly common near coconut groves, but is largely absent from swordgrass savanna. On Mt. Tapotchau, where near-cloud-forest conditions occur at the summit, it frequents native and secondary forest, appearing regularly from about 1.3 km below the summit downward.^[32]

With few exceptions, all honeyeaters are monogamous.^[35] The Micronesian myzomela is a weak flyer, usually only travelling at most 5 meters by flight. It primarily locomotes while foraging by flying or hopping.^[36]

Breeding

The Micronesian myzomela nests year-round, and likely breeds year-round as well.^[37] On Pohnpei, eggs were recorded in nests from July to September. On Chuuk, eggs have been found year-round, with most nests dated to May–July and one to March. On Kosrae, a nest with nestlings was found in April. During 1983–1984, newly fledged birds were recorded on Chuuk in March, on Yap in May, and on Kosrae in July.^[38] On Saipan, nest-building has been observed in February in each year from 1988 to 1993, and seven nests were found there in 2003–2004; two contained eggs, two contained nestlings, two were empty, and the seventh was occupied by a female, which prevented the nest's contents from being checked.^[39] Courtship was observed on Aguiguan in May 1992, and newly fledged birds on Rota in March 1982.^[38] Courtship on Aguiguian consisted of the pair walking in tandem along a sturdy branch with elevated heads, periodically switching directions so that the follower became the leader.^[40] On Guam, courtship interactions was observed to take place throughout the year, at any time of day; they usually consisted of flights lasting for 20–30 seconds, where the male pursued the female along circular, vertical, or zig-zag paths, often touching wingtips. The male may utter quiet staccato notes during such flights.^[41]

On Chuuk, nests are most often found near houses that had flowering plants nearby. The nests are usually built less than 4.6 meters from the ground. They are typically in small trees with thick foliage, often on the edges of wooded areas or open areas. Nests are usually composed of weed stems, bits of leaves, grasses, and coir, and lined with fine grasses. On the outside, they are on average 20 mm deep, and 50 mm wide.^[42] On Guam, nests were usually placed 1.2–2.4 meters off the ground, in shrubs or trees, and more rarely 2.5–4.6 meters off the ground, on the outer branches of trees.^[43] There, nests had deep cups made of grasses and rootlets, withl the outside composed of leaves, wool, cobwebs, and the like. They were 50–70 mm deep and 60–80 mm wide.^[44] On Pohnpei, nests are cup-shaped, and are made up of two layers; the inner layer is composed of one material, such as dead grass, fine roots, or coir, however the exact material varies by nest. The outer layer is composed of a mix of stems, ferns, fine roots and the like. The inner and outer diameters of the nest are 65–85 mm and 43–58 mm respectively. Nests are around 20 mm deep, and measure 35–45 mm in height.^[45]

These eggs are usually white and gray with dark yellow-brown speckles concentrated at the narrower tip.^[46] On Chuuk, eggs are on average 18.5 by 13.6 mm. They are glossy white or light cream with reddish-brown speckling concentrated torwards the larger end.^[42] On Pohnpei, eggs are white to pale creamy, with brown (sometimes with hues of yellow or red) spots on the surfaces. The subsurfaces of the eggs are pale purplish. Clutches are usually two eggs; in a sample of 13 nests, 10 had two eggs, and three had one egg.^[45] On Saipan, eggs are creamy white, with two distinct rings of brown spots on either end.^[47]

On Saipan, egg incubation lasts for 15–16 days, and is probably done exclusively by the female.^[48] The incubation behavior resembles that of other honeyeaters.^[49] At birth, nestlings are altricial, and, until their red pin feathers erupt, resemble nestling bridled white-eyes. In one nest, nestlings were around 2 cm in length, with dark pink skin and had down on their wings and backs. By days 6–7, their eyes started to open, and the pin feathers on their backs began to erupt. Both nestlings prematurely fledged on days 13–14; one of them was returned to the nest, and fully fledged on day 15-16.^[50] On Pohnpei, the female exclusively feeds the young.^[51]

Foraging and diet

The Micronesian myzomela forages with its mate, following the same route every time. The male leads, and the female follows.^[54] On Pohnpei, it can be found foraging throughout the forest, though it is more common near nectar sources. On Yap and Kosrae, it forages in shrubs, in savannas and small ravines, respectively.^[55] On Guam, an adult (followed by a juvenile) was observed probing a morning glory, and another adult was observed probing a white flower on a shrub.^[56] It was commonly found foraging around the day-blooming jasmine, feeding on nectar and insects. It was also common near coconut palms, especially when their reproductive parts were developing.^[19]

On Saipan in 1988–1989, it was observed foraging in trees 20–47 (avg. 34) m high. Most (82.5%) of these trees were canopy trees (trees that occupy the uppermost layer of foliage). Trees used during foraging included Indian coral trees, coconut palms, hibiscus trees, white leadtrees, Delonix regia, Premna serratifolia, and Aidia cochinchinensis. Bitter melon vines were also used. About 92.5% of foraging time was spent in the upper strata, and the remainder in mid-strata. Around 90% of foraging perches were flowers, 7.5% live leaves, and 2.5% flower buds. Around 36% of perches were less than 0.5 cm thick, and 64% were larger.^[55] Gleaning accounted for 10% of foraging behavior, with probing accounting for the remaining 90%.^[57]

On Saipan in 1990–1991, it was observed foraging in trees 27–43 (avg. 35) m high.^[58] 85% of foraging time was spent in the upper strata, the remainder being spent in mid-lower strata. Native forests were usually occupied during the dry season, when Indian coral trees were in bloom.^[59] Additional trees used during foraging included forest wild coffee, Aidia cochinchinensis, and Cynometra ramiflora.^[60] Vines on trees were also used. Tree and strata preference was noted to be similar to that of the bridled white-eye; however, unlike it, the Micronesian myzomela primarily foraged in Indian coral trees.^[55] 81% of foraging perches were flowers, 14.3% live leaves, and 4.8% without a perch.^[59] 35% of perches were less than 0.5 cm in size, and 65% were larger.^[60] Gleaning accounted for 16.7% of foraging behavior, the remaining 83.3% being probing.^[60]

On Aguiguan in May 1992, 73.7% of foraging time was spent in the upper strata, the remainder being spent in mid-lower strata. Trees used during foraging included forest wild coffee, lebbek, Bikkia mariannensis, and Delonix regia. It was also found using Lantana camara. Of foraging perches, 68.4% were flowers, 15.8% live leaves, and 15.8% branches; 72.2% of perches were less than 0.5 cm thick, and 27.8% were larger. Gleaning accounted for 30% of foraging behavior, the remaining 70% being probing.^[55]

The Micronesian myzomela is omnivorous, feeding on nectar and small invertebrates, mainly insects.^[20] It feeds on flowers from tall-stilt mangrove, coconut palm, noni, cassava, Lantana camara, Morinda citrifolia Sonneratia alba, as well as species from the genera Clinostigma, Parinari, Musa, Hibiscus, Schefflera, Elaeocarpus, and Cyrtandra.^[61] Ernst Mayr estimated that on Guam, 60% of their diet was nectar, 40% insects.^[62] In Palau, both specimens acquired had vegetable matter, seeds, and small insects in their stomaches.^[34]

The Micronesian myzomela is a least-concern species on the IUCN Red List,^[1] with an estimated total population of 850,000–900,000 individuals^[71] spread across an estimated range of 2,520,000 km².^[72] It was known as "egigi" or "hibiscus bird" on Guam,^[73] "chuhurica" on the Mariana Islands, "likeitepar" on Chuuk, "srusr" on Kosrae, "chesisebangiau" on Palau, "pwiliet" on Pohnpei, and "umel" on Yap.^[74]

On Kosrae, there were 1,433 individuals per square kilometer in July of 1983, with a total estimated population of 136,358.^[27] As Kosrae has relatively low population and development, there are no serious threats to survival there.^[75] Children have been observed using homemade slingshots to shoot the Micronesian myzomela.^[27]

On Pohnpei, there were 423.4 individuals per km² in 1977;^[c][77] in 1983–1984, there were 1,071 individuals per km² (range 995–1,118), with a total estimated population of 358,065.^[76] On Chuuk, there were 688.3 individuals per km² in 1977,^[c][77] and in 1983–1984, there were 2,067 individuals per km² (range 1,564–4,803), with a total estimated population of 165,440.^[76] On Yap, there were 169.0 individuals per km² in 1977,^[c][77] and in 1983–1984, there were 1,098 individuals per km² (range 836–1,792), with a total estimated population of 109,363.^[76] On Palau, there were 36.6 individuals per km² in 1977,^[c][77] and in 1991, there were 138 individuals per km², with a total estimated population of 35,362, and notably, it was not recorded on Angaur.^[76] On Agrihan, there were 2,239 individuals per km² in 2000.^[c][77]

On Asuncion, there were 713 individuals per km² in 2008.^[c] On Alamagan, there were 390.5 individuals per km² in 2017, with a total island population of 1526±166. On Guguan, there were 197.5 individuals per km² in 2016, with a total forest population estimated at 327 and a total island population of 876; this was higher than the 2000 estimate of roughly 450. On Sarigan, island-wide density estimates were 1,679/km² in 1990, 1,677/km² in 1997, 945/km² in 1999, 859/km² in 2000, and 1,240/km² in 2006, with breeding pairs estimated at 4,130 in 2006; despite these population estimates, detections per station grew from 1990 to 2006.^[76] On Guam, the species was found on 37.6% of 125 roadside counts in 1945;^[76] there were 231.3 individuals per km² in 1977;^[77] and in 1981, density was computed at 62/km² (range 3–160/km² at sites where present), with a total estimated population of 2,682 (range 2,300–3,140); in 1983, populations declined by 73% in only two months, and the last individual recorded on a survey was in 1984.^[76] On Saipan, there were 101.3 individuals per km² in 1977;^[c][77] island-wide density estimates using updated analytic techniques were 360.1±57.6/km² in 1982, 386.7±63.8/km² in 1997, and 482.3±76.7/km² in 2007, with a total 2007 population estimated at 64,351 (range 47,192–86,556) and a significant 25-year population increase; a reanalysis of these surveys added a 2018 estimate of 254±230/km² and yielded reassessed total populations of 49831±3851 in 1982, 35157±3680 in 1997, 51058±5179 in 2007, and 30207±2775 in 2018.^[76]

• List of birds of Guam
• List of birds of the Northern Mariana Islands