In the caption for this image:
there was a statement that Eastern Tiger Swallowtail, Papilio glaucus
, was not normally observed feeding at dung, whereas the Canadian Tiger Swallowtail, Papilio canadensis
, feeds frequently at dung. I've not really researched the matter, but here is a photo of Eastern Tigers feeding at the dung of the Canada Goose at a local park. Canadian Tigers do not occur in my area, I believe--low elevation in the North Carolina Piedmont.