Darters and Rooks should be dropping certain gems from what I can remember.
Jades, Pearls, Topaz, Flame Agate, and Ivory. Have seen a few drop from Darters, but nothing off of a Rook.
Have never seen an Ivory, Jade, or Pearl. Could just be bad luck though.
They should also been dropping 1 or 2pp occasionally. I have only looted gold.
Also looked a Peridot off of a Rook, and I believe these should only drop off of Harriers, and Avocets.
Rook
http://everquest.allakhazam.com/db/npc.html?id=3312
Darter
http://everquest.allakhazam.com/db/npc.html?id=3308