I've got a wall of a text below so I do apologise in advance.
So a bit of a weird one: one of our budgies has recently (last couple of weeks) developed a strange behavioral problem with refusing to leave the cage and I'm trying to work out what it is.
Bit of a background: because one of our birds was overweight, we decided to only have food on the outside of the cage when we were around, forcing him to fly up to get the food. This has worked well, and both budgies were fine with it.
However, one of our budgies now seems to be incredibly scared of coming out of the cage at all. I can bring him out myself by having him stand on a food bowl etc., but when he's out, he will immediately try to go back in 90% of the time. The other 10% seems to be a unique event where he will eat for a bit then fly back in. He never used to do this and always enjoyed running around the top of the cage and dive bombing everyone.
When I've been around, he's been completely normal inside the cage: talking to bells; playing with toys, and even flying around at the bottom of the cage. He naps at normal times, and relaxes quite a bit but always on one foot. BUT, he absolutely refuses to come out by himself. He has the occasional wet poo but his diet is very wet (mashed pellets and vegetables), and dries up nicely when we give him seed.
Today, my misses was in all day and has been keeping an eye on him. She said that he's hardly been doing anything (not in a sleepy way, but in a scared way), and even hasn't been out for food the entire day. She tried giving him food earlier but he refused to take it from her (the other bird happily did). She said that if he refused food from me she would be taking him to the vet ASAP (rightly so).
When I got in, he immediately saw me with the food bowl and ran toward me and started eating like a piggy. He's also talking to the bells and squawking, which he hadn't done for most of the day.
She's really concerned that she's done something wrong. She thought for a moment that she's 16 weeks pregnant, and wondered if there's anything about that which could be putting him off.
Other than that, he recently started moulting. He's definitely less active when this happens, although this cage hogging is new.
Has anything changed in the house?
New furniture, rearrangement of items, etc?
If he's scared, then he's only going to feel safe in his home which is his safe place. If both budgies are now at a normal weight, it would be best that you start feeding them in the cage so the one that is afraid (name would be helpful) will be able to eat when you aren't around.
Molting definitely will contribute to budgies being more lethargic.
Keep an eye on him to ensure he is eating, drinking and pooping normally. Is he sitting all fluffed up when he's quiet?
When you are particularly concerned about one of your budgie's behaviors, it is a good time to take it in to your Avian Vet for a well-birdie checkup to ensure there is nothing amiss.