Simplify the following text for a Grade 7 native English-speaking person.
Original: Not only were shell fish available from the sea , but the many swamps and creeks in the district would have yielded birds , fish , eels , eggs and snakes . Early white settlers in the region noted plenty of kangaroos and possums , which would also have been a source of food .
Simplified: They ate shell fish , birds , fish , eels , eggs , snakes , kangaroos and possums which were found across their lands .