cedar waxwings and robins
I know much of this is anecdotal and subject to imperfect memory but here are some observations from ~25 years of having one or two berry-laden Hawthorne trees in winter in central GJ.
Our family recollection is that for the first ten years or so we had large (20+) flocks of cedar waxwings stripping the trees by about January 1. We always said, "the cedar waxwings always eat all the berries." Then, it became ~every other year until the past five or so years, waxwings were few—if seen at all. At least twice, we had a robin commandeer the tree and methodically chase every waxwing—even from nearby yards if any happened to appear. The robin stayed in the tree all winter seemingly living only on Hawthorne berries. This year, we have been visited on at least three occasions—today being one—by a flock(?) of approximately 20 robins and ten (or less) waxwings—all feeding together in the tree. I do not see any correlation in the preceding 25 years of CBC data with my observations of cedar waxwings. Nonetheless, the varying behavior of waxwings vs robins is curious. (Note, another flock of CEWAs just flew in--now there are ~25.)