Yep, that's from mating
Saddles do offer some protection from the nails and spurs, but the feathers underneath will still get worn and broken. Inspect under the saddle at least once a week for any abrasions/weakened or broken skin. Even with a saddle, he will mate her A LOT since she is a favorite.
She has what looks like intact feather shafts in the skin, so she won't most likely will not regrow feathers there until she molts at 16-18months of age (or when she goes through her adult molt).
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