Usually they are quite bitter, probably will not hurt you but not very palatable. The C. pepo varieties. Lagenaria varieties are more palatable. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/18208/136Gourds.pdf?sequence=4 http://www.specialtyproduce.com/produce/Ornamental_Gourds_992.php

I sliced up a young Lagenaria ( birdhouse gourd) and ate it raw , and it was pretty mild-tasting, not bitter as I expected. And I am still alive! ;)

I've read that yellow crookneck squash when allowed to mature, becomes like an ornamental gourd. If yours are C. Pepo I would not doubt you can cook them like any summer squash.

The bird house gourd is a bottle gourd. Many varieties are very popular in India and southeast Asia, http://www.nutrition-and-you.com/bottle-gourd.html