The Chinese bird names section of the Sibagu site features the following languages (aside from the Latin names): Chinese, English, Japanese, Korean, Vietnamese, and Mongolian. In the case of Chinese, due the country's vast, almost imperial extent, there are many languages which could be included. Since there is limited space on the page, deciding the languages was a difficult choice.
Chinese: Given that Chinese is the official national language of the country, it goes without saying that it should be listed.
Chinese names as used in Taiwan are listed separately. In the interest of clarity, it has been considered preferable to keep the Taiwanese terminology in a separate column. That is because the Taiwanese names form a separate system and cover a separate (albeit much smaller) area. Taiwanese usage tends to be more conservative and thus shows more clearly the Japanese influence on Chinese names.
English: English names appear to have become universal among ornithologists and birders, perhaps even more so than the Latin names. English is also the native language of the creator of this site. English names are thus given to the right of the scientific names.
Japanese: Japan was long a student of China, being heavily influenced by Chinese language, thought, and culture. However, in the 19th century, Japan took the lead in adopting Western science (including ornithology), and in so doing had a profound influence on Chinese bird naming. Japan is also one of only two Asian nations -- the other being China -- to have a worldwide list of bird names.
Korean: Korea is a major nation in East Asia and shares many birds with eastern China. There is also a large Korean ethnic minority living in the northeastern part of China.
Vietnamese: Vietnam is the only Southeast Asian nation contiguous to China with an (accessible) official bird list. Vietnamese has many birds in common with the southern part of China. There is a very small Vietnamese ethnic minority in the south of China.
Mongolian: Mongolia is an important birding country to the north of China with an official bird list. There is also a large Mongolian minority in China, in the Inner Mongolian Autonomous Region. At the moment only the Cyrillic script of Mongolia is shown, but I'm in the process of adding the traditional Mongolian script, which is still in full use in China.
Left out: The languages that didn't make it into the list are Thai (which does not border on China), Kazakh (Kazakhstan has more in common with Xinjiang than the central part of China), and Malay (further away even than Thailand).
The result of including this range of languages is hopefully a more borderless view of the natural environment of China than is available from using just the official names of the national language.