Refers to the male of a species (see 脽), generally bipedal, in a courtship display flaunting his best point. PLUMAGE fully displayed, or a two-legged animal with no tail such as a male human being but still able sent a single PLUME arching from time to time. Used when referring to a bird as a characteristic while not in flight, that is, while on the ground and in a COURTSHIP DISPLAY, expressing a DESIRE TO MATE, COPULATE.「Bird」in this case depicts the male groin, as in 'flip someone the bird,' a pecker, or hard poking head on an elongated, twisting neck scavenging for meat as might a condor, the largest remaining bird species.
　As in TO FLAUNT ONE'S BIRD, attempting to ATTRACT A MATE as do bonobos:
　「Sometimes females would rather GG-rub [genital-to-genital rubbing] with each other than copulate with a male. Parish filmed a 15-minute scene at a bonobo colony at the San Diego Wild Animal Park in which a male, Vernon, repeatedly solicited two females, Lisa and Loretta. Again and again he arched his back and displayed his erect penis—the bonobo request for sex. The females moved away from him, tactfully turning him down until they crept behind a tree and GG-rubbed with each other.」
　　[　https://www.discovermagazine.com/mind/casual-sex-play-common-among-bonobos 2023-05-14, emphasis ours　]　
　In dynastic China, female groins with soft pelts were termed 'pussycat' 'bunnies' and 'chicks' or referred to as other large rodents besides coney [pronounced 'cunny' and rhymes with both 'money,' 'honey']: muskrats and beavers, both species with hairless tails, dangerous teeth that gnaw wood, partially-webbed hind feet, and make slapping noises by the way.
　Birds and humans are (so far) the only animals that regularly walk upright on two legs, and, along with cattle, animals that can contract gonorrhea…an interesting set of animal species, that is: birds, humans, and meat chattel in herds.
　However, birds cannot yet walk backwards due to physiological limitations of anatomy, so a male in a courtship display will continue approaching and not back off, not unlike a male human after grasping his own erection due to the psychological limitations of his anatomy.
　Scholars explain this glyph refers to a 'bird with a short tail,' but more likely is a bipedal animal with a 'short tail' dangling between the legs, a human male with a bird as a tail, but one that is not in the normal tail position behind a non-human animal: instead, raised erect and spread in FULL PLUMAGE, courtship behavior such as that of a male peacock, for example:「Courtship displays are performed by animals seeking to advertise their willingness to mate, attract a partner and sometimes to warn off rivals. Famous examples include the dazzling display of a peacock's tail, and the elaborate dancing and acrobatics performed by birds of paradise. In monogamous animals, such as swans and albatrosses, the male and female often do a mutual courtship display, to reaffirm and reinforce the bond between them.」
　　[　https://www.bbc.co.uk/nature/adaptations/Courtship_display 2012-12-27　]　

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)
Chinese: short-tailed bird
Japanese: kanji "old bird" radical
Unihan extended: bird
EDRDG: bird; old bird radical (no. 172)