your budgie wont star breeding until it is about 1 year of age. if your budgies aren't breeding, don't worry, they might not be ready or mature. when they are kissing and preening each other, then they are ready.
Mice reach sexual maturity as early as 5-6 weeks old but I do not recommend breeding them until they are 10-12 weeks old because breeding them at an early age can cause serious problems such as...