What changes the finch canary dove questions answer
Do not mix birds just because both are small. Canaries are often kept singly or in careful same-species plans, while many finches need compatible finch company. A mixed cage has to be sized and managed like a group home, not decoration.
Start with separate quarantine
New birds should not go straight into a shared cage. Quarantine, health checks, and observation protect the birds you already have.
Use real flight space
A small cage is not fair for a mixed group. You need width, multiple perches, more than one feeding area, and enough distance for a bird to leave another bird alone.
Watch for quiet bullying
Feeder guarding, chasing, blocking sleep spots, feather damage, stress calling, or a bird sitting apart are signs the setup is not working.
Default safer choice
If you are new to finches and canaries, keep species setups separate until you understand normal behavior.