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.
There is a difference between songs and calls as its based on its length and context and complexity.
So what are songs used for by birds?
Obviously the songs are longer and are primarily used for courtship or mating.
Ohh okay, yeah that would make the most sense.
The birds song is a best developed in order Passeriformes.