Wordwind told me recently that the "spiked golfballs" that threaten to roll under my feet on my daily walks are the equivalent of nuts from black gum trees. I had seen many crows and pigeons eating something in the street, but on inspection of the area could not tell what it was. The only thing I could think of was the black gum nuts, after being run over by automobiles. A lady raking them up said squirrels do eat them. I have since several times seen a squirrel on the green strip between sidewalk and curb. And I have seen crows foraging there. I suppose squirrels eating them spill seeds that the birds find. So I searched for"Squirrels black gum nuts" and found a site that confirms my impression:
http://www.dlia.org/atbi/species/animals/vertebrates/mammals/sciuridae/Sciurus_carolinensis.html

Sorry the screen went wide.