Robins feasting on Mountain Ash berries, getting intoxicated? 

The mountain ash tree in our yard has had bright red berries all summer and in fall birds will all of a sudden come and strip the whole tree of its berries in just a few hours. I was around to see and photograph this event this year.
Apparently the berries ferment & birds can actually get drunk on them, there was sure a lot of squawking and birds fighting over the harvest.
Mostly these were robins with a few flickers involved as well.