I've heard the phrase bird vocalization before but I really don't know exactly what it means.
Its not a common theme but it refers to bird calls and bird songs
Made by the birds themselves correct"
Made by the bird themselves but I guess if a human could mimic it then it should count also. Its a bird sound that is melodious to human ears.
Ah okay, that's interesting. Especially how different birds have different calls and for different things too.
Bird vocalization
Bird vocalization includes both bird calls and bird songs. In non-technical use, bird songs are the bird sounds that are melodious to the human ear. In ornithology and birding, songs (relatively complex vocalizations) are distinguished by function from calls (relatively simple vocalizations).
Definition.
The distinction between songs and calls is based upon complexity, length, and context. Songs are longer and more complex and are associated with courtship and mating, while calls tend to serve such functions as alarms or
refusal, he later varies it in comic ways. For example, he renders the phrase in colloquial terms in chapter 12 of "Joy in the Morning", when explaining to Nobby that he could not stand up to Florence:
"And if you think I've got the force of character to come back with a "nolle prosequi"—""A what?""One of Jeeves's gags. It means roughly 'Nuts to you!' If, I say, you think I'm capable of asserting myself and giving her the bird, you