How big should a breeder box hole be for entry for the birds.

what type of bird

How big should a breeder box hole be for entry for the birds.

 

 

How big is the bird?

 

Mine are 50mm diameter.

4.5cm budgie

that should be k

unless you got huge birds

my teails can get in out my breeding boxes if they like and mine same size i think

so i doubt a budgie going to be larger than a teail