Under the wings is where they start with their regular molt but if this seems way more than normal then you may want to see an avian vet with him just to check him out.
If you do not have an avian vet you may be able to find one through this site
www.aav.org/vet-lookup
If he is pulling feathers then irritation of some sort may be the issue. Boredom, nutritional issues, mites or skin infection can all cause this.
If you recently gave him new perches or toys or food you might want to stop and swap back to the old type to see if he is itchy from the change.
But see the vet with him to make sure all is well.
Hope this helps you!
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