I have read that in northern hemispheres, most female songbirds can't sing (Example: Blackbird). Things are more different in Tropical regions, but birdsong is male for some species; it is utilized to defend territories and/or attrack other females. While it seems impossible that female songbirds can't do any complex song, can it be possible for captive birds?
In the case of testosterone injection, I have read some Reports, females can start to sing. But the interesting Question is: Can birdsong be trained at females without testosterone injections or some absolutely invasive Actions on them? A Reply would be appreciated.