Chaunoproctus ferreirostris


 
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Bonin Grosbeak
(Chaunoproctus ferreirostris)

 
syn. Coccothraustes ferreirostris

 
distribution:

Japan: Chichi-jima / Ogasawara Islands

 
local name:

Ogasawara Mashiko (Japanese)

 
size: 20 - 22 cm (length)

extinction date: last seen in 1828

 
All that we know today about this bird species' behaviour sourced from the accounting records of H. J. von Kittlitz, who stayed on the Ogasawara Islands (Bonin Islands) in the year 1828. According to his notes the Bonin Grosbeak was a very leisurely bird, completely tame faced with people, and stayed singly or in pairs at the ground, or at least near the ground, while searching for its food (von Kittlitz examined the crops of killed birds and recorded fruits and buds).

The sexes differed in their colouration, the females in contrast to the males were olive brown, patterned with somewhat darker spots.

The accounting records of H. J. von Kittlitz also represent the last record of this bird species at all.

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Already in the year 1828 the Ogasawara Islands harboured introduced feral pigs which multiplied freely on some of the islands. Pigs are well known to be omnivorous animals and they do of course not stop at the nests of groud-breeding birds.

Then in the year 1830, when Chichi-jima, which was known as Peel Island at that time, was permanently settled, people also introduced rats, sheep and goats, as well as dogs and cats to the island. Altogether these were no good prospects for the island's native fauna and flora.

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The museum specimens of the Bonin Grosbeak which still exist today show very striking differences in colouration and sizes, what may result from different stages of plumage dependent on the age of the bird or the season in which the bird was taken, so it may well be possible that for example juvenile birds were less colourful than adult birds.

But because some of these specimens lack complete information of their exact origin ('Boninissima' - without naming a certain island; or actually 'Laysan' - which is in the Hawai'i Islands) it is also possible that the Ogasawara Islands once harboured several distinct subspecies, if not at all distinct species, which were restricted in their distribution each on a single island of the archipelago.

But hitherto this seems not to have been analyzed.

 
left:

Bonin Grosbeak (Chaunoproctus ferreirostris), male


Depiction from aus 'The zoology of Captain Beechey's voyage; comp. from the collections and notes made by Captain Beechey, the officers and naturalist of the expedition, during a voyage to the Pacific and Behring's Straits performed in His Majesty's ship Blossom. London, H. G. Bohn, 1839'

http://www.biodiversitylibrary.org

 
References:

- Dieter Luther: Die ausgestorbenen Vögel der Welt. Westarp Wissenschaften 1986
- Errol Fuller: Extinct Birds. Penguin Books (England) 1987
- Nanyan Guo: Ogasawara Islands: An Evolutionary Laboratory of Nature and Culture. New Zealand Journal of Asian Studies 9, 1 (June 2007): 80-95