Robin with a deformed beak

I saw this robin with a distorted beak yesterday. If you look closely you can see that the upper and lower parts are out of alignment and cross at the tip, like a crossbill. The upper part is hooked. The bird has survived since last summer with this deformity, so it must have adapted its feeding technique, but I imagine that preening might be difficult - especially removing small parasites from feathers.

I have seen similar beak deformities in starlings, but the most spectacular example was the herring gull in this post.