Kiribati Reed-Warbler (Acrocephalus aequinoctialis)
The 16 cm long Kiribati Reed-Warbler is the only (recent) resident passerine bird in Kiribati, all other passerines possibly seen there are winter visitors.
The species can be split into two subspecies (in fact they may even represent three – but this need further investigation), both show a grey and white plumage and differ only slightly from each other.
The Kiribati Reed-Warbler was first described in 1790 from the giant atoll of Kiritimati, where its total population today is estimated at only 300 to 400 birds.
Another form was discovered in 1881 on the small atoll of Tabuaeran, 224 km northwest of Kiritimati, it was described as a distinct subspecies (Acrocephalus aequinoctialis ssp. pistor Tristram) in 1883, but was last seen in the year 1924, and is now considered extinct.
Again, another form was discovered in 1921 on the island of Teraina, 120 km northwest of Tabuaeran, and this was subsequently assigned to the ssp. pistor (but may indeed by a distinct third subspecies).
In Kiribati this bird is called bokikokiko resp. kokikokiko.
Tabuaeran Reed-Warbler (Acrocephalus aequinoctialis ssp. pistor)
Depiction from: ‘H. B. Tristram: On the Position of the Acrocephaline Genus Tatare, with the Descriptions of two new species of the Genus Acrocephalus. The Ibis 5(1): 38-46. 1883′