White Eyes and Their Allies

White Eyes and Their Allies

White Eyes are small greenish birds with white eye-rings—forage in gardens and forest edges and flock around bird tables in parts of Africa, Asia, New Guinea, Australia, and South Pacific islands. They have short, pointed bills and brush-tipped tongues, with which to collect nectar. They also hunt insects and spiders by gleaning foliage, probing into small crevices, and hawking. They appear in orchards and eat fruits as well as aphids. With versatile feed-in habits, they exploit a variety of resources to survive and breed even on small wooded islands where most other passerines fail to establish themselves.

Some white-eyes on continents migrate regularly in winter to lower latitudes, though part of the population remains resident in the cold region. They also disperse in flocks to remote islands. In thei8 50s white eyes from Tasmania colonized New Zealand across 2,000km of sea. Successive generations on oceanic islands and isolated mountains differentiated into new forms by becoming large (either Black-capped superiors) and/or losing certain pigments from plumage (egg the Cinnamon white-eye) or even the white eye-ring (egg Olive black-eye).

As such differentiations take place in a relatively short geological time; successive invasions of original stock have led to the present coexistence of two or three species on some islands. Yet the similarities between some distant species, resulting from convergence, are so remarkable that it is often difficult to establish true affinities among them.

Most white-eyes pair for life and breed in small territories. Members of a pair often perch together and preen each other. On Heron Island, Great Barrier Reef, where the Gray-breasted white-eye maintains a very high density with more than 400 adults in 6 ha (40 acres), they attempt to nest two or three (occasionally four) times between September and March (southern summer).

From a clutch of three eggs, two young usually fledge after I days of incubation and 1 2 days of feeding in the nest by both parents. Birds nesting in their first year produce fewer young than older birds (they have fewer clutches); when an adult loses its mate it tends to pair with another bird of similar age rather than a first-year bird. Very few change partners. Juveniles suffer higher mortality than adults, but for those that survive the first year the mortality rate remains constant thereafter and the oldest birds die in the Tooth or z the year.

In cyclone years the population is reduced considerably, but it recovers in the following year after an extended breeding season. The same ritualized form of aggression used in territorial defense is used in winter when fighting over food. Aggressive birds flutter their wings at their opponent. Equally matched birds may take to the air to fight. After a period of mutual display. Sometimes they supplant a feeding bird or attack and chase an approaching bird with beak clatterer challenge calls.

Some specialized species on islands are endangering extinction as their population sizes are small and their available habitats are being destroyed through local development. The Norfolk white-throated white-eye of Norfolk Island, the largest member of the genus Zosterops, is one such species. White eyes are kept as cage birds in some Asian countries because of their attractive songs. However, they do not breed in aviaries.

Sunbirds are small. Brightly colored, nectar-feeding birds of the Old World tropics. As the ecological counterparts of hummingbirds of the New World, sunbirds are closely associated with flowers that depend on them for pollination and offer large quantities of neck tar as a tempting reward.

Africa and its islands are the home of most sunbirds (76 of 116 species), but other species inhabit the Middle East, India, Ceylon, the Himalayas, Burma through Malaysia, the East Indies, New Guinea, and Australia. The Palestine sunbird alone is found in Israel and Palestine. Many colorful, long-tailed species of the genus Zletliopyga occurring India and the Himalayas, while spider-hunters are restricted to Malaysia.

The largest sunbird is the Giant sunbird, which is restricted to the island of Sao Tomean the Gulf of Guinea. Other large, spectacular species. The Golden-winged sunbird, Scarlet-tufted malachite sunbird, and Tacazze sunbird live in the mountains of East Africa. Three medium-sized species of West Africa, the superb sunbird, Splendidsunhird and Johanna’s sunbird, and several Himalayan species are renowned for their spectacular colors. Most highly colored species in Africa are found in open habitats while plain-colored species inhabit shady forests.

Spider-hunters lack the bright plumage colors of other sunbirds and their bills are larger, stronger, and down-curved. They feed primarily on spiders as their name implies. Their nests are cup-shaped like those of many passerine birds, not hanging, bag-like structures. Both sexes incubate, unlike other sunbirds where this is the job of the female. Sunbirds are small to very small birds with long, thin, curved bills. Fine serration on the edges of the delicate bill helps to cap-true and hold insects.

The nostrils are covered by flaps (opercula) which keep out flower pollen. The tongue is mostly tubular except for its split tips. Sunbirds have strong feet with short toes and sharp claws that aid difficult perching while feeding on flowers.

The variable tail shapes include long central feathers in males of some species. Although many sunbirds aggregate enlarges numbers at suitable flowers, they rarely form cohesive flocks. Some species, especially insect-eating species of Anthreptes, participate in parties of mixed species. Many species are highly
nomadic and are known to wander great distances in search of nectar. Sunbirds feed on insects and nectar. Even subtle differences in sunbird bill size affectabilities to feed different kinds of flowers. Small, short-billed sunbirds find insects in the foliage and extract minute volumes of nectar from small insect-pollinated flowers. Large, long-billed species depend more on nectar in large, conspicuous red or orange flowers.

Long corollas should exclude short-billed species. Short-billed sunbirds, however, often pierce the bases of these flowers to obtain the nectar. Sunbirds normally perch while feeding on flowers they rarely hover like hummingbirds. Typical sunbird flowers in Africa include species of the following: Erythrina„Spathodia and Symphonic. Many mistletoe flowers depend on sunbirds for pollination.

They explode when a sunbird visits them. A new mistletoe flower houses spring-like filaments and anthers hearing pollen. When a sunbird pokes its long bill into one of the slits on the side of the flower, the trap is sprung and the flower bursts open to spray a cloud of fresh pollen onto the forehead of the sunbird for transport to another flower.

Studies in Kenya of sunbirds feeding at one mistletoe (Loran thus dshallensis)
revealed that whereas young sunbirds exploded flower after flower in their faces and became covered with pollen, adults often ducked quickly after they tripped the trigger.

Nesting by sunbirds is related to rainfall and in turn to peaks in the availability of flowers and insects. Some species may breed at almost any time of the year, and pairs may resent up to five times in succession. In contrast to hummingbirds, which are promiscuous, sunbirds are monogamous. Male sunbirds feed their young but do not help with nest-building or incubation. Instead, they often defend flowers which are their mate’s energy supply. Breeding male sunbirds have a reputation for being extremely pugnacious.

Subordinate species in East Africa may breed successfully only when large dominant species do not usurp their nectar supplies.

See more: Honey Eaters