You can use Blender for bird cartoon animation! Blender is a powerful, free, and open-source 3D creation software, and it supports both 2D and 3D animations.
It is definitely possible to work alone on Blender, and many creators do so. However, the complexity of the work determines the feasibility of working solo. For smaller or simpler projects, a single person can manage every aspect, but for large-scale projects (like full-length animated movies, complex game assets, or intricate visual effects), collaboration with a team might be more efficient.