BIRD LIFE
Species Diversity and Endemism
Rennell has 43 breeding land and water bird species, of which four are species endemic to Rennell, nine are subspecies endemic to Rennell and seven are subspecies endemic to Rennell and Bellona. The proportion of endemic taxa (47%) that is found on Rennell (including the seven subspecies also found on Bellona) is extremely high. The East Rennell area is important because it includes all the habitats found on Rennell and it contains a viable representation in natural conditions of most of the endemic bird species. The endemic species are actually endemic allospecies i.e. members of superspecies whose other allospecies occur on other Pacific islands. Bellona has 15 breeding bird species of which seven are the subspecies endemic to Rennell and Bellona.
Why does Bellona have so few species and why does Rennell have so few species compared to similar-sized islands located centrally in the Solomons (e.g.65 breeding species on the nearly equal-sized Vella Lavella and Kolombangara)? Why does Rennell have such a high degree of endemism, the feature for which it is famous?
These questions of species diversity and endemism are not unique to Rennell and Bellona but arise with any island. The number of breeding bird species on Solomon islands increases with island area and decreases with island isolation. Rennell and Bellona have close to the number of species expected from their isolation 160 kilometres from the main chain of the Solomons and from Rennell’s moderate area of 684 square kilometres and Bellona’s small are of 19.7 square kilometres. Larger islands have more species because they have more habitats and also larger populations are less at risk of extinction. Remote islands have fewer species because they received immigrants at a lower rate.
The percentage of endemic bird taxa on Pacific islands increases with island area and isolation because development of an endemic taxon requires that a colonists population survive long enough to differentiate. On small islands near colonization sources, colonists arrive too often and disappear too quickly to differentiate. Rennell has evolved its famous “endemic status” because it is by far the largest out-lying island in the Solomons. Bellona is poor in endemic species because it is too small for populations to survive for long in isolation.
BIRDS ENDEMIC TO RENNELL AND BELLONA
The Australian Dabchick (Tachybaptushas novaehollandaie rennellianus, local name = Manusigi) a subspecies endemic to Rennell. It is found around the lake shore where it is fairly common. It occurs singly or in pairs and in calm weather can be found at the centre of the lake.
The Little Pied Cormorant is also a subspecies endemic to Rennell. It is common at Lake Tegano, swimming in many islands including Tautiage, Sangingagito, Gigiogo and Halogu.
The White Ibis is a subspecies endemic to Rennell and Bellona. It is fairly common in groups of up to 30 birds. It feeds on the ground on earthworms and grubs and can be seen in villages with the chickens, along roads, on sandy or rocky beaches and even in the forest. When breeding, it nests in small colonies in trees in the forest or on the lake islands. Grey Teal (Anas gibberifrons remissa, local name = Ghamanaghi mai Hatuhoa) is a subspecies endemic to Rennell. It is possibly extinct. It had been collected in 1928 from Lake Tegano by the Whitney Expedition but has not been observed since. It could have been overhunted or it is possible that the introduction of the fish Tilapia mossambica to the lake affected its’ food supply.
The Pink-spotted Fruit Dove (Ptilinopus richardsii cyanopterus, local name = Higi) is a subspecies endemic to Rennell and Bellona. It is one of the commonest and most ubiquitous species of Rennell both in forest and second-growth. It is found mainly in the canopy but comes lower, to about 4 metres from the ground, in second-growth. It occurs usually singly or in pairs but occasionally forms groups of up to 30 when feeding on fruits such as figs. It flies at canopy level and its diet is of fruit (at least 38 different species taken) from 0.1 to 3 cm in size. It sometimes hangs upside down from a branch to pick fruit. It nests in trees and has a single egg.
The Song Parrot (Geoffroyus heteroclitus hyacinthus, local name = Ghisua) is a subspecies endemic to Rennell. It is fairly common, particularly at West Rennell, and occurs in groups of up to four in the canopy or in the crowns of trees near the forest. It is not found on the lake islands. It eats large fruits that require biting and nests in holes in dead trees. It has two young.
The Shining Cuckoo (Chrysococcys Lucidus harteri, local name = Tangionge) is a subspecies endemic to Rennell and Bellona. It is common singly in the forest and is heard more frequently than seen. It is also found on the large islands of the lake. It feeds on caterpillars from leaves and it parasitises that nest of the Fantail Warbler.
The Glossy Swiftlet (Collocalia esculenta desiderata, local name = Pekapeka) is a subspecies endemic to Rennell and Bellona. It is common and flies slowly with a fluttering wing beat. It does not fly high in the open but forages low over the ground in gardens, on the beach, over fores-hung roads, close to cliffs or close to the crown of trees. It has been seen on three lake islands. It roosts in limestone caves and nests made of moss and feathers have been found in large crevices in almost vertical cliffs along the coast.
The White-collared Kingfisher is a subspecies endemic to Rennell and Bellona. It is fairly common and middle storey and is occasionally seen on the ground. It is solitary but is sometimes seen in pairs. It has been recorded from the islands on the lake and it feeds on lizards and large insects. It nests inside termite mounds.
The Island Thrush is a subspecies endemic to Rennell. It is fairly common and is found in the forest and dense second growth, always within or close to cover. It is not found on the islands in the lake. It is strictly solitary and usually seen on the ground where it forages for invertebrates, especially earthworms and snails. Its nest consists of a moss cup outside, lined with fine vines. It nests in trees and there are usually one or two young.
The Fantail Warbler (Gerygone flavolateralis citrina, local name = Lokeloke) is a subspecies endemic to Rennell. It is a very common bird in forest and second-growth and it is found in the understorey to lower crown. It is mostly seen in pairs and threes and rarely singly. It was found on most islands in the lake. It makes a basket nest at a height of about 3 – 6 metres, suspended from a vine or limb and with a side entrance, and lays two to three eggs. This species is the main victim of the parasitic Shining Cuckoo.
The Rennell Fantail (Rhipidura rennelliana, local anme = Magighape) is a species endemic to Rennell. It is fairly common in the forest and second-growth, usually near cover but it is not found on the lake islands. It is seen singly or in pairs and joins mixed – species flocks. It is usually seen at lower levels in the forest and often on the ground. The wings are held drooped.
It often perches on vertical trunks or vines and catches insects by hover-gleaning off leaves, plucking off bark and in flight while doing acrobatic spins and twists. It even plucks spiders from their webs. The nest is in the understorey and has one young.
Other allospecies in the same superspecies are:
Rhipidura drownei Bougainville and Guadalcanal, Rhipidura tenebrosa San Cristobal, Rhipidura spilodera Vanuatu, New Caledonia and Fiji, Rhipidura nebulosa Samoa
The Rennell Shirkebill is a species endemic to Rennell. It is a common bird throughout the forest but is mainly seen below 10 metres. Only one was seen on an island in the lake. It is usually seen singly or in pairs and infrequently in mixed species flocks. It moves by short hops and feeds by gleaning and hover-gleaning, occasionally by sallying. Prey includes locusts, grasshoppers, stick insects, snails and lizards and are very often large. The nests are made of moss and they have one or two young.
Another allospecies in the same species is Clytorhynchus nigrogularis Santa Cruz and Fiji
The Broad-billed Flycatcher (Myiagra caledonica occidentalis, local name = Tangitangibiilage) is a subspecies endemic to Rennell. It is uncommon and is more often heard than seen. It is usually in the crown and middle storey of tall forest vegetation and generally not in the very exposed places. It is solitary or in pairs and feeds by sallying to hover-glean. It tail-quivers like other members of the Flycatcher family. It nests in the middle storey of tall forest trees and the nest is a small woven cup.
The Golden Whistler (Pachycephala pectoralis feminina, local name = Taataga) is a subspecies endemic to Rennell. It is moderately common with regularly spaced territories in tall forest and dense second-growth. It is more often heard than seen and is never seen in the open and rarely at the forest edge. Unusually the Rennell race often feeds on the ground. When foraging, it perches for 5 – 50 seconds, peering intently, then hops a short distance to a new perch. It perches on the trunks of vertical saplings, hops on the ground, on fallen logs and hops up vines. The diet consists of invertebrates. It is one of the smaller races of Golden Whistler. The nest has only one young.
The Rennell White-eye is a species endemic to Rennell. It is an uncommon forest bird and is found mainly in the understorey and middle storey of forest and second-growth. It is absent from the islands on the lake. It is seen in pairs, sometimes singly or in groups of three, but it never forms large flocks although it will join mixed-species flocks. Its’ diet consists mainly of insects and some fruits but these are limited to those smaller than 0.8cm. The Rennell White-eye feeds from bark, on trunks, hops up vines, hover-gleans, hangs upside-down and gleans at dead leaves and twigs. The nests are woven cups 3-5cm in diameter with live green moss on the outside and dry fibres inside.
Other allospecies in the same species group are:
Zosterops rendovae New Georgia Group
Zosterops luteirostris Gizo
Zosterops splendida Ranonga
Zosterops vellalavella Vella Lavella
Zosterops griseotincta Southeast Papuan islands, Nissan and several Bismarck islands.
The little Pied Cormorant, Local name = Manukitai is common at Lake Tegano and nests in the forest at the lake edge and on the islands. (Patrick Pikacha)
The White Ibis (Threskiornis molluccus pygmaeus, local name = Tagoa) is a subspecies endemic to Rennell and Bellona and is commonly seen near villages. (P. Ryan)
The White-collared Kingfisher (Halcyon chloris, local name = Ligho) is a subspecies endemic to Rennell and Bellona. It is fairly common. (Mary LeCroy)
The Island Thrush (Turdus poliocephalus rennellianus, local name = Gagango) is a subspecies endemic to Rennell. It is fairly common and is found in the forest or in dense second growth. (M. LeCroy)
The Rennell Shrikebill (Clytorynchus hamlinii, local name = Ghoghoviu) is endemic to Rennell and is common in the forest. (P. Ryan)
The Rennell White-eye (Zosterops rennelliana, local name = Suusuubagu) is endemic and is an uncommon forest bird. (M.LeCroy)
Woodford’s White-eye (Woodfordia superciliosa, local name = Ghagha) is a species endemic to Rennell and is commonly seen in the forest and gardens. (M. LeCroy)
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Woodford’s White-eye is a species endemic to Rennell. It is a very common bird both in the forest and near gardens and occurs on the islands in the lake. It is mainly seen in the middle and understorey of the forest and usually in small groups of three and, sometimes, up to six. It joins mixed-species flocks. The foraging technique and diet are varied. It gleans insects, especially caterpillars from leaves, hops up vines, hangs upside-down to glean, captures spiders and eats land snails. The diet also includes many fruits; small fruits are swallowed whole while large fruits are pecked at. Nests are woven cups of twigs, fine fibres and vines with a few bits of green moss on the outside. The clutch size is generally two, sometimes one.
There is one other allospecies:
Woodfordia lacetosa Santa Cruz
The Cardinal Honey-eater (Myzomela cardinalis sanfordi, local name – Baghigho) is a subspecies endemic to Rennell. It is a very common bird near coconut palms and moderately common in the forest. It is found on all the lake islands where it is the most abundant species. It is seen singly or in pairs and occasionally in mixed-species flocks. It feeds mainly by gleaning insects from leaves and occasionally hovers to take spiders from webs. It also probes flowers. Nests are cups of dry fibres and the clutch is two, occasionally one.
The Rennell Starling (Aplonis insularis, local name = Ghaapilu – mouku) is a species endemic to Rennell and Bellona. It is a moderately common forest bird usually seen impairs but occasionally singly or in threes. It is found on the lake islands and it can easily be recognised in flight from the Singing Starling by its short tail. It is widely distributed over Rennell while the Singing Starling is confined to the vicinity of the lake. The diet is diverse with fruit of many species, such as figs and pawpaw. Insects and land snails are also eaten. Land snails are taken to a particular stone which is used as an anvil and where broken shells accumulate. The nest is a hole in a dead tree that provides a soft cavity such as a pandanus or pawpaw trunk. The clutch size is two or three.
Source; Nomination of EAST RENNELL, SOLOMON ISLANDS by the Government of the Solomon Islands for Inclusion in the World Heritage List Natural Sites.
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