Is the Kurkevan: stomach? gizzard? or crop? you seem to translate it "crop", although the food is ground in the bird's gizzard, as far as I know.
I'm asking in ref. to an article that I'm posting online on our site
The digestive tract of a bird has three receptacle organs. They are -- in order of the progression of food through the tract -- the Zefek, Keivas ha'Belutos, and the Kurkevan.
The Zefek, which in English is the crop or craw, receives the food from the Veshet (esophagous) and stores it, but does not digest it.
The Keivas ha'Belutos is a small glandular stomach (small, relative to the Zefek and the Kurkevan). It begins the digestive process.
The Kurkevan, or gizzard in English, recieves the food from the Keivas ha'Belutos and continues the digestive process. (Many birds swallow small stones which end up in the Kurkevan and aid in the digestion process by grinding the food, as the Beraisa says in Berachos (61b): "the Kurkevan grinds.")
Hence, the Kurkevan is the gizzard.