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Three different bird species found in NYC and at least three physical characteristics that can be used to identify them.
What are: Red-tailed hawk, Peregrine falcon, Ruby-throated hummingbird, Barred owl, American kestrel, Northern flicker, Rock Dove/Pigeon, House sparrow, European starling, American robin.
Wing span/size, color, beak shape, silhouette, bird call, etc.