None of these are true ferns but are forms of asparagus, except potentially the lace fern. But I'm assuming the ASPCA is referring to something like
Asparagus setaceus as opposed to
Microlepia strigosa when they mention lace fern. I'll look around the ASPCA website sometime and see if maybe they have something listing the scientific names.
Asparagus, emerald, emerald feather and plumosa ferns are definitely asparagus. I wonder about true ferns...
I'm a big fan of ferns an was wondering this myself. Did your ferns ever end up proving harmful to your chicks?
Wikipedia has an interesting article listing a few species of ferns used for human consumption, "fiddlehead greens".
http://en.wikipedia.org/wiki/Fiddlehead_fern