Note the oval tan areas on the branch. Those are scale insects; they feed off sap of the plant and in large numbers can cause localized death of plants, as well as transmit diseases harmful to the vitality of the plant.
What we have here is a Yellow-Rumped Warbler picking off the insects. Currently, I am seeing flocks of 10-20 individuals moving through at fairly frequent intervals...Just a guess but I would say about 300 warblers are passing through per daily surge, just imagine how many damaging scale insects are consumed.