White-eyes

(Zosteropidae)

Class Aves

Order Passeriformes

Suborder Passeri (Oscines)

Family Zosteropidae

Thumbnail description
A fairly uniform group of small perching birds, mostly with a white eye-ring and a brush-tipped tongue, distributed widely in the Old World except in Europe and in arctic and arid regions

Size
4–6 in (10–15 cm); 0.3–1.1 oz (8–31 g)

Number of genera, species
13 genera; 86 species

Habitat
Woodlands, forest edges, and gardens

Conservation status
Recently Extinct: 2 species; Critically Endangered: 6 species; Endangered: 1 species; Vulnerable: 14 species

Distribution
Sub-Saharan Africa, Asia, New Guinea, Australia, and Oceania, introduced to Hawaii and Tahiti

Evolution and systematics

In 1766, Linnaeus named two species of white-eye, but in early years they were variously placed within wagtails (Motacilla), northern treecreepers (Certhia), flycatchers (Muscicapa), warblers (Sylvia), and flowerpeckers (Dicaeum). In 1826 Vigors and Horsfield created a new genus, Zosterops, for those species with a white eye-ring; and Gadow, who figured the tongue of an Australian species (Z. lateralis), placed the genus in Meliphagidae (honeyeaters) because of the brush-tipped tongue. In 1891 Sharpe elevated it to Zosteropidae, on the mistaken grounds that the tongue of Zosterops resembled that of a tit (Parus) and that it had no similarity to the brush tongue of Meliphagidae. In 1888 Newton also separated them as a single family. Recent molecular work places Zosteropidae under a passerine superfamily Sylvioidea and includes in this family the Endangered golden white-eye, Cleptornis marchel, of Mariana Islands and the Bonin white-eye, Apalopteron familiare, of Ogasawara Islands, which had been placed under Meliphagidae (honeyeaters) previously.

Those with a white eye-ring, from which the English name white-eye, the German name Brillenvogel (spectacle-bird), and the genus name Zosterops are derived, consist of four African continental, two Gulf of Guinea island, seven Indian Ocean island, and 49 Asia-Pacific species. This forms an extraordinarily uniform genus. For example, the Madagascar white-eye, Zosterops maderaspatanus, is almost indistinguishable from the New Guinea white-eye, Z. novaeguineae; the Annobon white-eye of Gulf of Guinea, Z. griseovirescens, is very similar to the Christmas Island white-eye from south of Java, Z. natalis; and the Australian yellow white-eye, Z. luteus, has the same plumage color as the East African subspecies of the white-breasted white-eye, Z. abyssinicus flavilateralis. Indeed, the relationships between the African and Asian species of Zosterops are yet to be clarified.

Physical characteristics

White-eyes have somewhat rounded wings with only nine functional primaries (the outermost primary is much reduced), and a brush-tipped tongue, quadrifid and fimbriated both at the sides and at the tip, showing a high degree of specialization for nectar feeding. In nearly all species, a white eye-ring appears soon after fledging, formed of minute silky white feathers. The ring is interrupted usually by the blackish lore. Iris color ranges from gray to brown and does not relate to age, sex, or race. The apposition of melanins and yellow carotenoids produces various shades of yellow-green, depending on the amount and distribution of these pigments and the structure of the feathers. The upperparts are green to greenish yellow, with gray upperback in some species, and the underparts are yellowish from throat to undertail coverts in some species or grayish to white in others. Flank color varies from light gray to dark brown. There are no seasonal changes in plumage color and the sexes are similar, though males tend to be larger and more brightly colored or darker than females in colder parts of Australia and New Zealand (Z. lateralis). Their short, thin bill is blackish, slightly decurved, and sharply pointed. The legs are grayish to brownish, the

first-year birds having darker colors and young fledglings and old birds having a pinkish color. Older birds (older than 5 years) molt into longer wing and tail feathers.

Continental species typically have short wings (2.2–2.6 in [55–65 mm]) and weigh 0.3–0.5 oz (9–15 g), with a cline following Bergmann's rule (larger in higher latitudes), but the derived island species and races tend to increase bill, leg, and body sizes. For example, in the eastern races of silvereyes (Z. lateralis) in Australia and New Zealand, a comparison between local populations indicates that the South Island population of New Zealand is the largest and the northern Australian population the smallest. At northern sites the winter populations are diluted by large southern migrants, except on wooded islands of southern Great Barrier Reef, where the Capricorn race (Z. lateralis chlorocephalus) is resident and much larger (body weight 0.49–0.53 oz [14–15 g]) than the mainland races (0.3 oz [10 g]) that migrate. Another genus of this family, Lophozosterops, with six species, mostly mountain birds of Indonesian and Philippine islands (Java, Bali, Sumbawa, Flores, Sulawesi, Seram, and Mindanao), contains not only very large species (wing greater than 2.8 in [70 mm]) but also atypical forms. They have a gray or brown crown, which is often striped or has small white spots. One species, Lophozosterops dohertyi, has a crest. In the giant white-eye, Megazosterops palauensis, of Palau island, the wing length reaches 3.3 in (85 mm) and weighs up to 1.1 oz (31 g). In the mountain blackeye, Chlorocharis emiliae, of northern Borneo and Bonin white-eye, the feathers around the eye are black.

Distribution

White-eyes are distributed widely in sub-Saharan Africa and the Asia-Pacific region. In Africa four polytypic species occur on the continent, with one species extending its range to Yemen. The Gulf of Guinea islands support an endemic genus and several species. In the Indian Ocean white-eyes are found in Mauritius, Réunion, Comoros, Aldabra, Madagascar, and Seychelles. On the Asian continent they occur from Pakistan and Afghanistan in the west to the Amur River in the north. In the Pacific they occur on Japanese islands in the north to New Zealand in the south. Practically all wooded islands of the Asia-Pacific region support white-eye populations, which extend eastward to Samoa. They have been introduced to Hawaii (Zosterops japonica), Tahiti (Z. lateralis), and Pulo Luar in the Cocos-Keeling Group (Z. natalis).

Habitat

White-eyes live in forest edges and canopy, and they frequent bushes in gardens. They occur from sea level (Z. luteus is associated with mangroves and coastal vegetation) up to 9,800 ft (3,000 m) of high mountains in Java (Lophozosterops javanicus). Z. citrinellus and Z. lateralis chlorocephalus live on many wooded coral cays that are too small to support a breeding population of other passerine birds. Other offshore islands are also colonized by white-eyes. In New Zealand, explorers and settlers noticed silvereyes (Z. lateralis) in the South Island in 1832 (Milford Sound) and 1851 (Otago), and eventually large numbers appeared in the North Island in the winter of 1856, when the species, not previously known to the Maori, was given the name tauhou (meaning stranger). This was indeed the Tasmanian race (Z. lateralis lateralis). Half a century later, Dr. Metcalfe of Norfolk Island, who regularly corresponded with the Australian Museum, wrote in 1904 that a new bird had just arrived on Norfolk Island and that he was sending the first two specimens to the museum. It turned out to be the brown-sided Tasmanian race, considered to have colonized there from New Zealand at that time. Today, we know that the Tasmanian race contains both migrants and residents and that migrants do not migrate every year. Occasionally they must also attempt dispersal across the ocean.

Behavior

White-eyes are highly social birds, often seen huddling together. Foraging, bathing (including bathing in dew on leaves), resting, and roosting activities are governed by social factors. Sunning is done individually. Allopreening (mutual preening) occurs between sexual pairs, parent-offspring, young siblings, and prospective partners in pair formation, which starts as early as one month of age. Silvereyes in Australia normally mate for life and remain in pairs in winter flocks. On Heron Island in the Great Barrier Reef, older birds tend to stay near their summer territories while younger birds range widely in flocks. They continue to improve their foraging skills until their third year. They exhibit ritualized forms of aggression, such as wing fluttering and bill clattering, leading to dominance hierarchies within flocks. Dominance contributes significantly to differential survival and reproduction among individuals. Courtship involves horizontal wing quivering and sometimes motions of nest building without nest material. Males sing for up to 20 minutes at dawn throughout the breeding season. Some also sing for a shorter period at dusk and sporadically through the day. Their melodious and rich warbles are similar across the different species. Males also have a soft courtship warble and both sexes have a long-drawn plaintive call and short calls. Incessant exchanges of high-pitched short calls that characterize migratory flocking and take-off may also be heard in the predawn sky during the migration. In addition, they have a distinctive alarm call, a roosting call, a soft huddling call, a begging call, variable aggressive calls, and a distress call.

Continental species in the temperate region migrate to warmer areas in winter. Zosterops erythropleura, a chestnut-flanked species, breeds along the lower Amur and Ussuriland in the high latitudes that no other species of the family has reached. It migrates a distance of 2,200 mi (3,500 km) to winter in mountain forests of Myanmar, Thailand, and southern China. In Australia, for a long time Sydney ornithologists were familiar with yellow-throated and fawn-flanked silvereyes in summer and gray-throated and chestnut-sided silvereyes in winter, and thought that silvereyes had different plumage in summer and winter, which was accepted as fact since this species had two molts a year, spring and autumn. Allen Keast found that only some members of the Sydney population had brown flanks in winter and that in the aviary individual birds did not change plumage color over an entire year. He also noted that the brown-flanked birds did not appear until late April, long after the molt of the local birds, and thus concluded that the gray-throated, brown-sided birds were migrants from Tasmania and did not breed locally in the Sydney area. Large-scale banding of silvereyes started in 1958, and soon one bird banded in Sydney became the first of many to be recovered across Bass Strait to prove the migration theory. Silvereyes are easy to trap and have become the most popular species among the Australian bird banders. Between 1953 and 1997, 285,345 silvereyes were banded, yielding long-distance recoveries of up to 1,000 mi (1,600 km) and longevity of up to 11 years.

Feeding ecology and diet

Silvereyes in Australia are highly flexible foragers. Foliage gleaning is the most common mode of foraging, but they also hawk, snap prey from a substrate (even small insects caught in spiders' webs), probe small clefts in clumps of leaves, bark, buds, flowers, and nests of other birds by forcefully opening the bill to widen the clefts in search of arthropod prey, and scavenge on the ground in tourist resort areas. They are the most common bird at bird tables (bird feeders) in New Zealand. Flocking in winter helps to locate sources of food in woodlands as well as to detect predators. They collect nectar with a brush-tipped tongue, peck succulent fruit, and swallow berries. They are known to disperse figs and other seeds of trees and shrubs.

Reproductive biology

In Africa and Australia white-eyes have a long breeding season, normally starting in September or October (triggered by summer rain) and lasting up to six months. The territory density of monogamous silvereyes varies from 3.4–8.7 per 25 acres (10 ha) in Canberra suburbs to 75 per 25 acres (10 ha) at the height of season on Heron Island. Nests and eggs are known from only about half the species. The nest is cupshaped

and mostly made of plant fibers. It is usually slung in a slender fork under cover of vegetation at any height. Eggs are pale blue to bluish green and somewhat glossy (with spots in four species), measuring 0.55 by 0.43 in (14 by 11 mm) to 0.79 by 0.59 in (20 by 15 mm). Incubation starts when two eggs are laid out of a normal clutch of three (varies 1–5) and normally lasts 10 to 12 days. The nestling period is 11 to 15 days depending on food supply. Both parents take part in nest building, incubation, and feeding of young. Young are nidicolous (reared for a time in the nest) and weigh about 0.07 oz (2 g) when born. They are fed with insects when small, but fruit usually becomes a significant portion of their diet by fledging. Fledglings are fed for three weeks or more, and the second clutch usually starts while the first clutch fledglings are still fed. A new nest is constructed for each clutch and older pairs may produce up to five successful clutches in a season while some first-year birds may not breed at all.

Conservation status

Small isolated populations, particularly on islands, are under threat of extinction from the disappearance of habitats. Two recently Extinct species are both insular species: the robust white-eye, Zosterops strenuus, of Lord Howe Island became extinct between 1919 and 1938 as a result of predation by ship rats, which became abundant on the island and caused extinction of 14 endemic forms of birds on the island, and the white-chested white-eye, Z. albogularis, of Norfolk Island, which has not been seen since 1980 and is now considered extinct as a result of habitat destruction. Of six other species, which are Critically Endangered, four are on the islands of Comoro, Mauritius, Seychelles, and Mariana, and two are known from the mountains of Kenya. One species Endangered is an island species (Truk Islands), and 14 considered Vulnerable are also mostly island birds. Population viability analysis of island birds shows that they are at risk of extinction in one hundred years even without destruction of habitats, if mortality increases greatly as a result of introduction of new predators or frequent severe storms. For example, the golden white-eye, Cleptornis marchei, of Northern Mariana Islands was very common until the brown tree snake, Boiga irregularis, was introduced to Saipan in early 1990s. This white-eye species is now nearly extinct.

Significance to humans

White-eyes are valued as cage birds for their songs in some Asian countries. Because they are difficult to breed in aviaries they are trapped legally or illegally in the wild each winter. The trappers and dealers must know how to tell the sex of the birds, as only the males sing. They are also considered pests in vineyards and orchards in Southern Africa and Australia, though they consume large quantities of aphids and other pest insects as well as soft fruit.

Species accounts

List of Species

Cape white-eye

Zosterops pallidus

taxonomy

Zosterops pallidus Swainson, 1838, Rustenburg, Transvaal, South Africa. Seven subspecies.

other common names

English: African pale white-eye, pale white-eye; French: Zostérops du Cap; German: Kapbrillenvogel; Spanish: Ojiblanco Pálido.

physical characteristics

Length, 3.9–5.1 in (10–13 cm); weight, 0.28–0.53 oz (8–15 g); wing, 2.0–2.7 in (52–68 mm); tail, 1.6–2.2 in (40–56 mm); tarsus, 0.6–0.8 in (15–20 mm); culmen, 0.4–0.6 in (9–15 mm). Underparts gray, upperparts pale green.

distribution

Southern Africa to Ethiopia.

habitat

Forests, woodlands, savanna, exotic plantations, and suburban gardens.

behavior

Some migrate while others remain sedentary. Readily come to bird feeders.

feeding ecology and diet

Feed on insects, spiders, soft fruit, berries, nectar.

reproductive biology

Nests at the start and end of the monsoon season, with a peak between September and December. Two to three eggs per clutch, incubated for 11–12 days, and nestlings fed for 12–13 days.

conservation status

Not threatened. Abundant in woods and suburban areas.

significance to humans

A popular species among the bird banders of southern Africa. Band recoveries have begun to demonstrate the complex nature of movements, molt patterns, and longevity.

Seychelles gray white-eye

Zosterops modestus

taxonomy

Zosterops modestus Newton, 1867, Mahé, Seychelles. Monotypic.

other common names

English: Seychelles white-eye, Seychelles brown white-eye; French: Zostérops des Seychelles, German: Mahébrillenvogel; Spanish: Ojiblanco de Seychelles.

physical characteristics

Length 3.9 in (10 cm). A dull olive-gray bird with obscure eye-ring.

distribution

Mahé and Conception Islands of Seychelles.

habitat

Mixed secondary forest between 1,000 and 2,000 ft (300–600m), confined to about 2 mi² (5 km²) on Mahé.

behavior

Very active in small flocks, giving contact calls frequently.

feeding ecology and diet

Feed on small insects and berries among shrubs, and search bark crevices of trees for arthropod prey.

reproductive biology

Nests in Oct–Nov and Feb–Mar at start and end of monsoon season. Clutch size is two.

conservation status

Critically Endangered. Fewer than 100 left on Mahé but common on the small island of Conception.

significance to humans

Has the conservation value of being the only species of white-eye left on Seychelles, as the Seychelles yellow white-eye, the Seychelles race of the chestnut-sided white-eye, Z. mayottensis semiflavus, on Marianne is extinct since about 1890.

Japanese white-eye

Zosterops japonicus

taxonomy

Zosterops japonicus Temminck & Schlegel, 1847, Nagasaki, Japan. 11 subspecies on different islands.

other common names

French: Zosterops des Japon; German: Japanbrillenvogel; Spanish: Ojiblanco Japonés.

physical characteristics

Length, 4.7 in (12 cm); weight, 0.4 oz (11 g); wing, 20.5–25.6 in (52–65 cm); tail, 13.4–18.1 in (34–46 cm); tarsus, 5.5–7.5 in (14–19 cm); culmen, 3.5–5.1 in (9–13 cm). Olive-green back and pale gray under, with lemon-yellow throat and undertail coverts.

distribution

Japanese islands, China, Taiwan, Hainan Island, and the Philippines. Introduced into Hawaii and Bonin Island.

habitat

Broadleaf evergreen forests and deciduous forests on lowlands and foothills of mountains.

behavior

Form small flocks after breeding, sometimes move in mixed flocks, to hunt arthropod prey, and soft fruit and berries. Partial migrant, appearing in villages and suburban gardens in winter.

feeding ecology and diet

Apart from arthropod prey, they feed on fruit and nectar. Famous examples include nectar from camellia on warm temperate islands and fruit of ripe persimmon on main islands of Japan.

reproductive biology

Breeds in spring, each pair holding a small nesting territory. The cup-shaped nest is hung from a fork in shrubs and 3–4 eggs are incubated for 11 days.

conservation status

Not threatened. Common in most parts, but some isolated populations on islands are vulnerable.

significance to humans

Males were kept in cages for songs. One of the familiar birds of the countryside in Japan, often featured in various forms of art and literature.

Resources

Books

Collar, N. J., M. J. Crosby, and A. J. Stattersfield. Birds to Watch 2, The World List of Threatened Birds. Cambridge, United Kingdom: BirdLife International, 1994.

Kikkawa, J. "Social Relations and Fitness in Silvereyes." In Animal Societies: Theories and Facts, edited by Y. Ito, J. L. Brown, and J. Kikkawa, 253–266. Tokyo: Japan Scientific Societies Press, 1987.

Periodicals

Brook, B. W., and J. Kikkawa. "Examining Threats Faced by Island Birds: A Population Viability Analysis on the Capricorn Silvereye using Long-Term Data." Journal of Applied Ecology 35 (1998): 491–503.

Mees, G. F. "A Systematic Review of the Indo-Australian Zosteropidae Parts I–III." Zoologische Verhandelingen 35 (1957): 1–204; 50 (1961): 1–168; 102 (1969): 1–390.

Moreau, R. E. "Variation in the Western Zosteropidae." Bulletin of the British Museum (Natural History), Zoology 4, no. 7 (1957): 311–433.

Prys-Jones, R. P. "Movements, Mortality and The Annual Cycle of White-eyes in Southern Africa." Safring News 14 (1985): 25–35.

Robertson, B. C., S. M. Degnan, J. Kikkawa, and C. C. Moritz. "Genetic Monogamy in the Absence of Paternity Guards: The Capricorn Silvereye, Zosterops lateralis chlorocephalus, on Heron Island." Behavioral Ecology 12 (2001): 666–673.

Jiro Kikkawa, DSc