On a collection of birds from the Anamba Islands, South China Sea
F.N. Chasen and C. Boden Kloss published this systematic ornithological account in 1928, describing a bird collection made for the Raffles Museum on the Anamba Islands (South China Sea) during September and October 1925. The paper assesses the islands’ avifauna in light of the earlier, more extensive work of Harry Oberholser (1917) and argues that, after twenty-five years of collecting, the resident bird population of the Anambas is now fairly well known, adding only four non-migratory land species to the known list.
Summary
The Anamba Islands, situated roughly twice as far from Borneo as from the Malay Peninsula on the shallow Sunda shelf, had previously been studied only through the 1899–1900 collections of Abbott and Kloss, which Oberholser reported on in 1917. Chasen and Kloss’s 1925 expedition, conducted with three native collectors across Siantan, Ringi, Telok Pau, and Jimaja, was designed to fill gaps in that earlier record. The collection proved remarkably conservative: excluding migrants, only four resident land birds were new to the islands’ avifauna—Geopelia striata (likely introduced as a cage bird), Columba argentina, Spilornis cheela, and Eurystomus orientalis—leading the authors to conclude that the islands’ ornithology was essentially exhausted (p. 44).
The paper’s more substantial contribution lies in its taxonomic revision of the subspecies described by Oberholser. Chasen and Kloss accept 19 of the 22 Anamba races Oberholser had proposed, rejecting five that they consider unsupported, and describe two new subspecies of their own: Orthotomus atricularis major and Malacopteron magnirostris flavum (pp. 44, 58–60). A recurring theme is that the Anamba races are characteristically larger than their mainland counterparts, with nine of the 19 accepted subspecies separable on size alone and a further nine combining size with faint colour differences. The authors also offer a critical discussion of the Redshank (Totanus totanus) racial complex, questioning the validity of the recently proposed terrignotae and arguing for the continued use of Oberholser’s eurhinus (pp. 50–51).
Faunal comparisons place the Anambas most closely with the Malay Peninsula, less closely with Sumatra, and only slightly with Borneo—a conclusion the authors reach independently of Oberholser’s but with a stronger emphasis on the Peninsular–Sumatran affinity (p. 44). The paper also records detailed field observations on frigate-bird behaviour, noting that thousands congregate nightly on Pulau Ringi and that the Malays associate their presence with the fish Thynnus (pp. 53–54).
Key Findings
- Only four non-migratory land bird species were added to the Anamba avifauna: Geopelia striata, Columba argentina, Spilornis cheela, and Eurystomus orientalis (p. 44).
- Two new subspecies were described: Orthotomus atricularis major (type: adult male, Siantan, 5 Sept. 1925; wing 48 mm, bill from gape 19 mm) and Malacopteron magnirostris flavum (type: adult male, Siantan, 21 Sept. 1925; wing 85 mm, bill from gape 24 mm) (pp. 58–60).
- Of Oberholser’s 22 described Anamba subspecies, the authors accept 19 and reject 5; of the 19 accepted, nine are separable from their nearest allies on size alone (p. 44).
- Fregata andrewsi was recorded from Pulau Ringi with a series of 13 females (total length 919–1020 mm; wing 630–660 mm) and one male (wing 605 mm), extending the known range to include Christmas Island, Cocos-Keeling, Sarawak, Java, and Celebes (p. 52).
- The Pycnonotus plumosus chiroplethis series from Siantan (14 males, wing range 85–92 mm, average 89.1) is maintained over plumosus (average 85.9) on size alone, with no colour difference detectable (p. 57).
- Orthotomus atricularis major males average 47.3 mm in wing length compared with 44.4 mm for southern Peninsular atricularis and 44.5 mm for nitidus from Siam, a difference the authors consider sufficient for recognition given the large series examined (p. 60).
Conclusion
Chasen and Kloss conclude that the Anamba Islands, ornithologically speaking, are now fairly well known after twenty-five years of collecting, with the resident avifauna closely allied to that of the Malay Peninsula and Sumatra rather than Borneo. The dominant pattern across the island’s endemic and near-endemic races is one of insular size enlargement, a fact they regard as a consistent and interesting biogeographical feature of the group (pp. 44, 57).
Context
- The primary archival material consists of the Raffles Museum (Singapore) collection, with direct comparison against reference series from the Selangor Museum and the British Museum (Natural History).
- The paper represents a continuation of the Straits Settlements museum tradition of systematic faunal documentation, building directly on Oberholser’s 1917 monograph and the earlier Abbott–Kloss 1899–1900 cruise collections.