Why is my budgie biting aggressively and acting stressed all the time?

It's possible he could be hot or stressed. Moving Smelborp to a cooler location, or providing a shallow dish to bathe in may help. You can also use a water bottle filled with cool water on a "mist" setting to help give him a shower (and a chance for both of you to bond). Offering a favorite treat every time you interact with him may also help him feel better and make him less likely to bite- if the weather is hot, a nice chilled piece of fruit may be enjoyable! A stressed or tired budgie may bite if they wanted to be left alone. If you suspect this is the case, giving him some time to himself to relax and rest before attempting to interact again is best.

If you've been working with him a lot on taming it could just be that he is finally getting used to you (this is good!) However, if you are concerned by his sudden behavioral change, or you are seeing any signs of illness, scheduling a vet checkup to rule out any health issues is always good.

If Tootoo was otherwise happy and calm around family, but recently began to bite there are a few possibilities. One can be pain or underlying illness, which may cause behavioral changes such as sudden aggression as a way to hide illness. A vet checkup to rule out any health issues is always best. Being startled or scared by something may also cause a bird to lash out or become more aggressive, such as if a new family member or pet was introduced, new items, or even loud or strange noises. Giving Tootoo some time to relax and settle down, and then gradually regaining trust with treats and toys may help decrease aggressive behavior. Birds that want to mate may become aggressive toward family they see as "competition" to a mate (or someone they consider a mate, such as a family member). Discouraging this behavior by stopping contact when he becomes aggressive, not giving attention to perceived mating behaviors, or using toys and treats to discourage and distract from bad behaviors may help.

I'm sorry to hear Minty isn't doing well. It is possible that there is an underlying issue such as pain or injury causing the aggression, especially if it came on rapidly or is a complete reversal of their usual behavior. Other issues such as sexual maturity, being startled by something, etc may also cause a bird to become fearful or aggressive. Removing any nesting material, providing some fun toys to interact with and spending time bonding/offering treats when Minty is calm and relaxed, rather than nervous or aggressive may help. If the behavior continues or worsens, or you see signs of illness, seeking a vet exam is always best to rule out any potential issues that could be causing the change.

A sudden behavioral change can sometimes indicate a health issue that is underlying, so a good first step is always to schedule a vet checkup and rule out any health issues. If Banana checks out healthy, looking to things that could have changed (new neighbor with a loud car? New pet? People in the house visiting) may help you clue into why he is having a behavioral change. Adding in some toys that can distract him or that he can snuggle with may help, as well as offering a treat every time you interact to help him relax. In some cases, sexual maturity may cause behavioral changes (though this usually involves lashing out rather than hiding/being fearful.) Lowering the amount of protein in his diet and decreasing daylight hours may however help if the change is hormonal related.

Thanks for reaching out about your birds. Well birds are fairly adaptive but are stressed by changed in routine. Monitor water and food intake. If concerned, a veterinary visit is recommended. Good luck.

Thanks for reaching out and including photos. Training birds can be difficult, especially as they reach sexual maturity. Continue with the training process and establish a dominance hierarchy with you primary. A book titled "A Guide to a Well Behaved Parrot" is a good start. Good luck.