A mango bird is a species of green-breasted hummingbird, although indigenous to the Americas and was not likely the inspiration for these elements. Parrots squawk a lot, parakeets twitter, both are responses when someone is sitting upon one's abdomen or chest, or spurting jism into one's face neck lips eyes and hair, respectively. The Chinese oriole does not seem to have an especially large chest or breast, and was/is a euphemism in China for a wandering prostitute, a very pretty bright yellow-breasted songbird that represents a Chinese singing girl, perhaps with a very finely shaped breast set that helps earn her daily bread. Note that all species of actual birds do not produce breast milk, which is a characteristic of mammals and not of birds.
　Green being the color of gonorrhea gleet, generally, and yellow being the color of pus. Both colors describe a client with whom a service provider may not want in contact with any mucous membranes but she is still interested due to not wishing to lose the fee, hence an offer to tit-fuck that results in the colorful breasts…it goes without saying that such an offer could not be refused without some thought:
　「Since mammary intercourse is a non-penetrative sex act, the risk of passing a sexually transmitted infection (STI) that requires direct contact between the mucous membranes and pre-ejaculate or semen is greatly reduced. Notably, HIV is among the diseases that require such direct contact and is therefore very unlikely to be transmitted via mammary intercourse. A study of the condom usage habits of New Zealand's sex workers said that they offered various safe sex alternatives to vaginal sex to clients who refused to wear a condom. A sex worker said that mammary intercourse was one alternative used. Mammary intercourse performed by a woman with large breasts felt to the client like penetrative vaginal sex」
　　[　https://en.wikipedia.org/wiki/Mammary_intercourse 2013-09-11　]…and it likely did for clients in China, too…or anywhere else for that matter.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Unihan extended: the mango-bird; the Chinese oriole
EDRDG: the mango-bird; the Chinese oriole