Mountain Blackeye

The mountain blackeye is a small passerine, ranging in length from 11 to 14 cm (4.3 to 5.5 in). Compared to most other white-eyes, it is larger and longer-tailed. The only known measured individual (sex unknown) weighed 13.9 g (0.49 oz). Male and female are similarly plumaged. The adult of the nominate race, emiliae, is dark olive-green on the head and upperparts with a blackish tinge to the green, particularly on the crown. Its underparts are somewhat paler, with a yellowish tint, particularly towards the center of the belly. It has a black eye-ring and black lores, which connect to form a small dark mask, edged by a yellow border. It has a bright yellow-green supraloral and throat. Its iris is brown, and its long, slender, pointed, decurved bill is brown on the upper mandible and bright yellow-orange on the lower. Its legs and feet are dark yellowish-brown to black, with yellow soles. The immature bird is like the adult, though with a duller-colored bill; this is typically dull orange to blackish. The subspecies trinitae is similar to emiliae, but brighter and more yellowish overall. Its belly is almost completely yellow, and it shows more yellow on the face. The subspecies fusciceps is smaller and relatively shorter-tailed than emiliae, with a sepia tint to its crown and forehead. Its underparts are yellow. The subspecies moultoni is similar to fusciceps. …

The mountain blackeye is endemic to the high mountains of Borneo, where it is the most common bird on the summit slopes of the island's highest mountains: Kinabalu, Tambuyukon and Trus Madi. It is also found on several isolated lower mountains. It occurs in both Malaysian states (Sabah and Sarawak) and four of the five Indonesian provinces (North Kalimantan, East Kalimantan, Central Kalimantan, and West Kalimantan) on the island, but has never been recorded in Brunei. Its habitats include primary upper montane forest, summit scrub, and gully vegetation. While it generally occurs at elevations above 1,800 m (5,900 ft), it may move to lower elevations during periods of drought.

Much of the life history and ecology of the mountain blackeye is not well-known. The species is resident, with no migratory movements. Its generation length is estimated at 4.4 years.

Feeding. The mountain blackeye feeds on nectar, pollen, insects (particularly caterpillars, grasshoppers and beetles), and small berries, including raspberries. It has a modified tongue—tubular with a brush-like tip—which allows it to easily sip nectar. It feeds at all heights, from the ground to the canopy, often foraging in small groups. It visits the flowers of Eugenia, Schima, Elaeocarpus and several Rhododendron species. Studies indicate that it may be an important pollinator of Rhododendron buxifolium; it also regularly visits Rhododendron ericoides and Rhododendron acuminatum. It is an occasional partner in a symbiotic relationship with Nepenthes lowii, a pitcher-plant which is also endemic to Borneo. The plant produces waxy secretions on the lid of its pitcher. Although treeshrews are the primary consumers of these secretions, mountain blackeyes also partake, sometimes defecating into the pitchers as they do so. Treeshrew and bird feces provide nutrients for the plant; studies have shown that some plants get 57–100% of their nitrogen from animal feces. …