Seedfork said:sfrangu,
Try the trees and shrubs forum, I have never been to it, but it sounds like the right place. If you don't get any response maybe the all things gardening forum.
Seedfork said:For me it's oak seedlings, I pulled up over sixty in one small bed just yesterday.
I wondered the same thing, but I had no knowledge of bird parts.
Definition:" A bird's crop is a compartment of muscle tissue that birds use to store and soften their food before it moves on to be processed by the gizzard."