Tropical birds come in various shapes and colors and have extraordinary talents. Peacocks look dressy; shoebills look scary; hummingbirds can fly upside down and backward; and cassowaries are champion runners.
Explanation: I changed "boast" to "have" to make it simpler and clearer for a young child. I changed "colours" to "colors" (American English spelling) but you can keep "colours" if British English is preferred. I used semicolons to separate the different birds for better clarity. I also changed "backwards" to "backward," which is more common with 'fly' in this context.