Something is Peeling the Lemons on My Tree?

We have a lemon tree and have not had any problems with pests in the 20 or so years we have had he tree, here in southern CA. It produces a bountiful harvest every year, and has a lot of ripe fruit on it now. This last week we have discovered over 26 ripe fruit on the tree destroyed partially or completely by some sort of pest.

Most of the fruit is partially peeled with no apparent damage to the fruit, a few others have been peeled and eaten. It doesn't appear to have any tell-tale signs that it was rodents, as I do not see any gnawing signs. I'm thinking it might be birds, do you have any ideas what it could be? Thanks.

Hardiness Zone: 11

By Mark from LA, CA