Henderson reed-warbler (Acrocephalus taiti)
|Also known as:||Henderson sparrow, Henderson warbler|
|Synonyms:||Acrocephalus vaughani taiti|
|Size||Length: 17 cm (2)|
Male weight: 22.5 – 30.5 g (2)
Female weight: 21 – 25 g (2)
Classified as Vulnerable (VU) on the IUCN Red List 2007 (1).
The Henderson reed-warbler is one of four land birds that are endemic to the virtually ecologically pristine island of Henderson in the eastern South Pacific (3). It is a large warbler with olive-brown plumage on its upperparts, with a variable amount of scattered white feathers, so that some individuals appear nearly all white. The underparts are white with a yellowish tinge. The top part of the head is olive-brown, with a paler lower half, and a dark stripe extends through the eye. The bill is relatively short, the irises are dark and the legs are grey (2). Henderson reed-warblers do not sing, but call with a harsh, short note (4).
Endemic to Henderson Island, an uninhabited island in the Pitcairn Islands, southern Polynesia (2).
The Henderson reed-warbler inhabits forest. Henderson Island is covered in mostly undisturbed forest, which in the interior of the island is tangled and almost impenetrable (2).
The forest-dwelling Henderson reed-warbler feeds primarily on a wide variety of insects, including moths, caterpillars, ants, large wasps, flies, beetles, cockroaches and land snails, but seeds and fruit may also be eaten (2). It forages for this food at all levels of the forest, plucking its prey from foliage, twigs, branches, bark crevices and from the ground, often moving about in family groups (2).
The breeding season of the Henderson reed-warbler extends from late August to early January. The majority of nesting groups comprise one male and one female, but around one-third of nesting groups are made up of three adults. These trios, of two males and one female, or one male and two females, are unrelated, but co-operate to incubate and feed the young, whether or not they are the parents of the chicks. This remarkable teamwork may be due to young birds being more likely to secure a sought-after nesting territory when belonging to a trio rather than a pair (5). The pair or trio construct a bulky deep cup nest of dry leaves, coconut, rootlets and other plant fibres, into which they lay a clutch of two to three eggs. The eggs are incubated for 15 days and the chicks continue to receive some of their food from the adults for at least six weeks after fledging (2) (5).
At present, this reed-warbler is relatively abundant on Henderson Island and the island remains practically untouched by human presence (2) (3). However, like other species restricted to one location, the Henderson reed-warbler is very vulnerable to any threatening events that may rapidly impact every individual in the population. The primary risk to this species is the accidental introduction of alien species, especially predatory mammals such as the black rat (Rattus rattus), which may be unintentionally brought to the island by passing ships that visit (2) (4). The Pacific rat (Rattus exulans) has already been introduced to the island, but apparently is not having any significant impact on the Henderson reed-warbler (4).
In 1998, Henderson Island was designated a World Heritage Site due to its outstanding universal value in being the only raised and forested coral atoll with its ecology virtually intact. This has had a number of beneficial outcomes, including raised awareness of the island’s importance and the completion of a management plan for the site (3), but further measures are necessary to protect the fauna and flora of this unique island. A monitoring strategy is required that can spot threats, such as alien species, early enough to enable appropriate action to be taken and, more specifically for the Henderson reed-warbler, surveys to monitor numbers and population trends in this species has been recommended (4).
For further information on the Henderson reed-warbler see:
Authenticated (08/05/08) by Dr Michael Brooke, Department of Zoology, University of Cambridge.
- Atoll: an island formed from a coral reef that nearly or entirely encloses a relatively shallow lagoon.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Incubate: to keep eggs warm so that development is possible.
IUCN Red List (September, 2007)
- del Hoyo, J., Elliott, A. and Sargatal, J. (2006) Handbook of the Birds of the World. Vol.11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.
UNESCO World Heritage List: Henderson Island (March, 2008)
BirdLife International (March, 2008)
- Brooke, M. de L. and Hartley, I.R. (1995) Nesting Henderson reed-warblers (Acrocephalus vaughani taiti) studied by DNA fingerprinting: Unrelated coalitions in a stable habitat? Auk, 112(1): 77-86.