Some friends of mine who live on a narrow-boat on the inland waterways, have a number of plant boxes on the roof of the boat in which they grow flowers and vegetables. For years they've used Canada Geese droppings - probably more as fertiliser than compost. It's easily found in large volumes nearly everywhere they moor, and some helpful fowls even deposit it onboard for them ! When it's dry, it's very crumbly and easy to handle, when it's wet, it's green and gooey and with a bit more water makes an excellent liquid feed.

They get incredible results.