Bonin greenfinch

The Bonin greenfinch (Chloris kittlitzi), also known as the Ogasawara greenfinch, is a small passerine bird in the finch family Fringillidae that is endemic to the Ogasawara Islands of Japan, where it is found on the Bonin Islands and Volcano Islands. It was formerly considered a subspecies of the grey-capped greenfinch (C. sinica) and some authorities consider it as such, but a 2020 analysis found it likely to represent a distinct species that diverged from C. sinica about 1.06 million years ago, and the International Ornithological Congress now recognizes it as such, making it the eleventh endemic species in Japan (alongside the Copper pheasant (Syrmaticus soemmerringii), Okinawa rail (Hypotaenidia okinawae), Amami woodcock (Scolopax mira), Japanese green woodpecker (Picus awokera), Okinawa woodpecker (Dendrocopos noguchii), Lidth's jay (Garrulus lidthi), Bonin white-eye (Apalopteron familiare), Izu thrush (Turdus celaenops), Ryukyu robin (Larvivora komadori), and Japanese accentor (Prunella rubida)).^[2] There are fewer than 400 individuals in the population and it is considered critically endangered by the Japanese government, necessitating protection.^[3][4][5] According to the Yamashina Institute for Ornithology, as of December 2021, the Ogaswara greenfinch is Japan's most endangered bird.^[6][7]

Bonin greenfinch
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Fringillidae
Subfamily:	Carduelinae
Genus:	Chloris
Species:	C. kittlitzi
Binomial name
Chloris kittlitzi (Seebohm, 1890)^[1]
Synonyms
Carduelis sinica kittlitzi Chloris sinica kittlitzi Fringilla kittlitzi (protonym)^[1]

Taxonomy

 

Nakōdo Island in the Muko-jima Islands, the type locality^[1][8]

The presence of the greenfinch on the Bonin Islands was first noted by Kittlitz at the beginning of May 1828 and reported to the Imperial Academy of Sciences in Saint Petersburg in a paper read on 28 April 1830, but he did not distinguish it from the European greenfinch, recording it under the binomial Fringilla chloris.^[1][9] The Bonin Island greenfinch was first described by Henry Seebohm in 1890, as Fringilla kittlitzi.^[1][10] Subsequently treated as a subspecies of the Oriental (or grey-capped) greenfinch, under the trinominal Carduelis sinica kittlitzi or Chloris sinica kittlitzi, a paper of 2020 recommended it again be raised to species rank, as Chloris kittlitzi, and styled the Ogasawara greenfinch.^[5] The split was implemented in the IOC World Bird List update of January 2021, in recognition of the "deep genetic divergence" and "morphological differences".^[3] There are three syntypes (BNHM 1898.11.1.60) collected on "Nakondo-Shima" [ja], one of the Muko-jima Islands (formerly known as the Parry Islands), on 14 June 1889 in the collection of the Natural History Museum.^[5][8] In its native Japan, the greenfinch goes by the vernacular name Ogasawara-kawarahiwa (オガサワラカワラヒワ), or Oga-hiwa (オガヒワ) for short.^[11] Among the Bonin islanders, it as also sometimes known as the kuzaimon (クザイモン).^[12][13]

Description

The Ogasawara greenfinch has a total length of around 13–14 centimetres (5.1–5.5 in) and weighs some 17.5–19.5 grams (0.62–0.69 oz).^[7][14][15] Compared with the Oriental greenfinch, from which the species has been recently split, the wings are shorter and overall body size smaller, but the beak is longer.^[5][14][15] In particular, compared with the Japanese greenfinch (Chloris sinica minor), the beak is "longer, deeper, and thicker".^[5][15] In males, the average wing, tail, tarsus, and culmen lengths are a little longer than in females.^[15] Like the Oriental greenfinch, the Ogasawara greenfinch is an olive-green, with patches of yellow on the secondaries and tail-feathers, and a pink beak.^[1][16] Seebohm observed that, compared with the Oriental greenfinch, the Ogasawara greenfinch has less yellow, while its crown and nape are olive rather than grey or brown.^[1] The males have more vibrant colours.^[17]

Ecology

 

Wikstroemia pseudoretusa seeds are a preferred food source^[5][15]

The main breeding season is from April to June.^[6][14] Clutch sizes, of 3–4 eggs, are smaller than those of the Japanese greenfinch (3–6 eggs), though the eggs themselves are somewhat larger, weighing on average 1.99 grams (0.070 oz) as opposed to 1.8 grams (0.063 oz).^[6][15] Its diet largely comprises seeds, for which it forages both on the ground and in shrubs and trees.^[14] Among preferred species are Casuarina equisetifolia (as an alien tree, this has recently been eradicated^[5]) and in particular Wikstroemia pseudoretusa; since the seeds of the latter are considerably larger than the grass seeds that comprise the majority of the diet of the Japanese greenfinch, it is thought that the larger beak of the Ogasawara greenfinch has evolved in response.^[5][15]

Distribution

The Ogasawara greenfinch is a non-migratory or resident bird endemic to the Bonin and Iwo Islands.^[14] Its preferred habitat for breeding is the dry lowland forest, in particular arid evergreen shrubs with a height of less than 2 metres (6 ft 7 in),^[15] and it now breeds only on the small satellite islands around Haha-jima (Mukō-jima [ja], Ane-jima [ja], and Imōto-jima [ja]^[18]) and South Iwo Jima.^[5][14] Previously it bred also on Muko-jima, Chichi-jima, and Haha-jima.^[15][19] Outside the breeding season, it may be found on islands beyond its breeding grounds, and it forages also in more open spaces, including agricultural land and among the grasses in the settlements of Ogasawara.^[14]

Conservation status

Reduced numbers of the then subspecies were already reported at the end of the 1920s.^[15][19] The Ogasawara greenfinch is now extinct in the Muko-jima Islands, Chichi-jima Islands, and North Iwo Jima and Iwo Jima in the Volcano Islands.^[14] In response, a Population and Habitat Viability Assessment (PHVA) has been conducted (Japan's fourth after those for the Tsushima leopard cat (Prionailurus bengalensis euptilura), Okinawa rail (Hypotaenidia okinawae), and Japanese wood pigeon (Columba janthina)).^[12] As a restricted-range species, it is particularly vulnerable to extreme weather events such as typhoons and localized droughts, while the small population size threatens genetic diversity.^[12][17] The Ogasawara greenfinch only breeds on islands where there are no black rats (Rattus rattus), and the rat's presence is thought to be linked to the local extinctions.^[14] Invasive brown rats (Rattus norvegicus) and feral cats (Felis catus) are also linked to predation during periods of foraging on the ground, and management of these mammal species has been recommended, alongside ex situ conservation via a captive breeding programme, to reduce the risk of extinction.^[12][14] It is estimated that the species comprises 200–400 individuals in total, with a breeding population of approximately a hundred birds around Haha-jima and a further hundred birds on South Iwo Jima.^[5][7] In 2020, the breeding population in the Haha-jima Islands was 1/10 of that twenty-five years before.^[7] As a subspecies, the Ogasawara greenfinch is classed as Critically Endangered on the Ministry of the Environment Red List,^[20] and has been designated a National Endangered Species under the 1992 Act on Conservation of Endangered Species of Wild Fauna and Flora.^[21][22] Extinctions amongst other local restricted-range endemics following human settlement in the nineteenth century include those of the Bonin grosbeak (Carpodacus ferreorostris ),^[23] Bonin wood pigeon (Columba versicolor),^[24] and Bonin nankeen night heron (Nycticorax caledonicus crassirostris).^[7][21]

See also

• List of birds of Japan
• Ogasawara National Park

References

1. Seebohm, Henry (1890). "On the Birds of the Bonin Islands". The Ibis. 6. 2 (V): 95–108 [101]. ISSN 0019-1019.
2. 日本固有の鳥が1種増える！？ ―海洋島で独自に進化を遂げた希少種オガサワラカワラヒワ― [Japan's Endemic Birds to Increase by a Species!? — An Endangered Species that has Evolved Independently on Ocean Islands, the Ogasawara Greenfinch] (in Japanese). Forestry and Forest Products Research Institute [ja]. 27 May 2020. Retrieved 6 May 2022.
3. "Species Updates – IOC World Bird List". Retrieved 2021-01-23.
4. "Chloris sinica kittlitzi (Ogasawara Greenfinch) - Avibase". avibase.bsc-eoc.org. Retrieved 2021-01-23.
5. Saitoh, Takema; Kawakami, Kazuto; Red'kin, Yaroslav A.; Nishiumi, Isao; Kim, Chang-Hoe; Kryukov, Alexey P. (May 2020). "Cryptic Speciation of the Oriental Greenfinch Chloris sinica on Oceanic Islands". Zoological Science. 37 (3): 280–294. doi:10.2108/zs190111. ISSN 0289-0003. PMID 32549542.
6. 「オガサワラカワラヒワ」のパンフレットができました [Pamphlet on the Ogasawara Greeninch] (in Japanese). Yamashina Institute for Ornithology. 2 December 2021. Retrieved 6 May 2021.
7. 絶滅寸前！日本の固有種オガサワラカワラヒワ [On the Verge of Extinction! Japan's Endemic Species, the Ogaswara Greenfinch] (in Japanese). Yamashina Institute for Ornithology. 2 December 2021. Retrieved 6 May 2021.
8. "Bird type specimens: Passerines>Fringilla>kittlitzi". Natural History Museum. Retrieved 6 May 2022.
9. Kittlitz, F.H. von (1831). "Uber die Vogel der Inselgruppe von Boninsima beobachtet zu Anfang May 1828". Mémoires présentés à l'Académie impériale des Sciences de St.-Pétersbourg par divers Savans et lus dans ses assemblées. 1: 231–248 [241]. ISSN 1560-0106.
10. Seebohm, Henry (1890). The Birds of the Japanese Empire. London: R. H. Porter. p. 128.
11. 「オガサワラカワラヒワ」のパンフレットができました [A Pamphlet on the Ogasawara Greenfinch] (in Japanese). Yamashina Institute for Ornithology. 2 December 2021. Retrieved 6 May 2022.
12. オガサワラカワラヒワを知っていますか？ [Do you know the Ogasawara Greenfinch?] (in Japanese). Tokyo Zoological Park Society. 18 June 2021. Retrieved 6 May 2022.
13. オガサワラカワラヒワを絶滅させない！ [Don't let the Ogasawara Greenfinch go Extinct!] (in Japanese). WWF Japan. 15 December 2020. Retrieved 6 May 2022.
14. オガサワラカワラヒワ [Red Data Book Tokyo: Chloris sinica kittlitzi] (in Japanese). Tokyo Metropolitan Government. Retrieved 6 May 2022.
15. Nakamura Hiroshi [in Japanese] (1997). "Ecological Adaptations of the Oriental Greenfinch Carduelis sinica on the Ogasawara Islands" 小笠原諸島におけるカワラヒワの生態適応 [Ecological Adaptations of the Oriental Greenfinch Carduelis sinica on the Ogasawara Islands]. Japanese Journal of Ornithology 日本鳥学会誌 (in English and Japanese). 46 (2): 95–110, 136. doi:10.3838/jjo.46.95.
16. 小笠原諸島のオガサワラカワラヒワを独立種とすることを提唱する研究成果を論文発表しました [Paper Published Recommending Independent Species Status for the Ogasawara Greenfinch] (in Japanese). Yamashina Institute for Ornithology. May 2020. Retrieved 6 May 2022.
17. オガサワラカワラヒワ [Ogasawara Greenfinch] (in Japanese). Ministry of the Environment. Retrieved 6 May 2022.
18. Ministry of the Environment, ed. (2014). レッドデータブック2014 —日本の絶滅のおそれのある野生生物— 2 鳥類 [Red Data Book 2014 — Threatened Wildlife of Japan — Volume 2, Birds] (in Japanese). Gyōsei Corporation. pp. 72 f. ISBN 978-4-324-09896-7.
19. Momiyama Tokutarō 籾山徳太郎 (1930). 小笠原諸島並びに硫黄列島産の鳥類について [On the birds of the Ogasawara Islands and Iwo Islands]. Bulletin of the Biogeographical Society of Japan (in Japanese). 1: 89–186.
20. 鳥類 [Birds] (in Japanese). Ministry of the Environment. 27 March 2020. Retrieved 6 May 2022.
21. 国内希少野生動植物種一覧 [List of National Endangered Species] (in Japanese). Ministry of the Environment. 24 January 2022. Retrieved 6 May 2022.
22. オガサワラカワラヒワ [Ogasawara Greenfinch] (in Japanese). Ogasawara Village. Retrieved 6 May 2022.
23. "Bonin Grosbeak". International Union for Conservation of Nature. Retrieved 6 May 2022.
24. "Bonin Woodpigeon". International Union for Conservation of Nature. Retrieved 6 May 2022.