In Japanese they are called Kurosagi, which means a black heron, so some people call the white morph ones Shiro-Kurosagi (White Black Heron)! Confusing!
That reminded us of Red Kites, Buzzards, Rooks, Jackdaws and Gulls in Wales:)
At the high tide, lots of waders gathered near the beach/on the rock.
When we were with Mr Kobayashi, he showed us a Cinnamon Bittern (Ryukyu Yoshigoiリュウキュウヨシゴイ), Slaty-legged Crake (Ookuinaオオクイナ), Osprey (Misagoミサゴ), Brown Booby (Katsuodoriカツオドリ), Eurasian Scops Owl (Ryukyu Konohazukuリュウキュウコノハズク), Spotted Redshank (Tsurushigiツルシギ), Ruff (Erimakishigiエリマキシギ), Greater Sand Plover (Oomedaichidoriオオメダイチドリ), Marsh Sandpiper (Koaoashishigiコアオアシシギ), Wood Sandpiper (Takabushigiタカブシギ), Sharp-tailed Sandpiper (Uzurashigiウズラシギ), Red-necked Stints (Tounenトウネン), Long-toed Stints (Hibarisigiヒバリシギ), Curlew Sandpipers (Saruhamashigiサルハマシギ), Scaly-breasted Munias (Shimakinparaシマキンパラ), White-breasted Waterhens (Shiroharakuinaシロハラクイナ) and quite a few Snipes (either Pin-tailed Snipe (Harioshigiハリオシギ), Swinhoe's Snipe (Chujishigiチュウジシギ) or Latham's Snipe (Oojishigiオオジシギ)).
The day-out and night-tour with Mr Kobayashi were both just incredible and we really recommend his tours to anyone who plans to go to the island for bird-watching and who would like to know/see the birds and wildlife there.
Here is Kobayashi-san's site again.
Thank you very much, Kobayashi-san!