A Black-throated Blue Warbler hovering to bite bits out of a kousa dogwood fruit. This particular tree was hosting half a dozen species in its branches and on the ground, where a lot of the fruit had already fallen and was perfuming the air with rot.
A siren-song to fruit flies.
The Spot-winged Fruitflies, evidently, Drosophila suzukii.
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This work by Matthew Wills is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Backyard and Beyond 
Did you see this season’s “magic” tree yesterday at Sylvan Water that had a huge number of Kinglets and warblers gobbling down very small insects? At one point there were somewhere around twenty-five birds in the same small tree. I was able to get as close as 6″ and the Kinglets didn’t pay any attention.
I’ve had similar experiences around Sylvan recently. Cherry, wych elm, and dogwood (for the fruit in this case) just dripping with birds. The tiny flies (gnats?– I was unsuccessful in catching any) hardly seem like a meal, but then numbers matter.