I used to always make:
Broccoli
Spinach
Bell Pepper
Carrot
Lettuce(any Lettuce, except iceberg, it's not toxic but low in nutrients and can cause watery droppings due to high water content)
I also made onfe:
Okra(I do NOT reccomend it, unless you want your chop to look and feel slimy)
Broccoli
Bak Choi(I think I spelled it right?)
Carrot
Bell Pepper
Another recipe I made once:
Carrot
Spinach
Broccoli
Cauliflower
Beetroot
(I think that's it, it's many months ago)
Recent chop:
Beet greens
Spinach
Chilli
Sweet Pepper(two colours)
Plus chia for the moisture
I will try remember some more! And I'll look in my birb book.
(Oh, you just gave me inspiration to continue my bird care scrapbook! Thanks!)