第 I 類﹕ 在香港有明確野生紀錄。
第 IIA 類﹕ 中國東南部地區繁殖的鳥種，現時在香港的繁殖群落被認為是由逃逸的籠鳥所繁衍的，但亦可能在棲息地出現變化前已在香港出沒。
第 IIB 類﹕ 非原居鳥種；經人為引入香港，現無需靠額外幫助已能繼續繁衍。
第 IIC 類﹕ 曾經在香港有野生群落的鳥種。
第 III 類﹕ 根據已發表所有香港紀錄顯示，此鳥種可能在飼養時逃逸或人為放生。
*第 III 類鳥種並非香港鳥類名錄正式確認的鳥種，香港鳥類名錄只包括第 I 類及第 II 類。
The species category definition is as follows:
Category I: species that have been recorded in an apparently wild state in HK.
Category IIA: southeast China breeding species, the currently established HK breeding population of which is considered to derive from captive stock, but which probably occurred in HK prior to habitat changes.
Category IIB: extralimital species that, although originally introduced to HK by man, maintain a regular feral breeding stock without necessary recourse to further introduction.
Category IIC: previously established feral species.
Category III: species for which all published HK records are considered likely to relate to birds that have escaped or have been released from captivity.
*Category III species do not form part of the official HK List which is only Category I and II species.