What are exceptions to bird characteristics?

While most birds share common characteristics such as feathers, beaks, and the ability to fly, there are notable exceptions. Flightless Birds like ostriches, emus, and penguins have evolved to live without flight due to their specific environments and lifestyles. Additionally, some birds, such as the kiwi, have reduced wing structures and unique adaptations for ground living. Furthermore, certain species exhibit variations in feather structure, coloration, and reproductive behaviors that diverge from typical bird traits.