Kids are intrigued by examining how each kind of animal is adapted (it body is constructed in a way) such that it carries on life in a particular way. Most basic are adaptations for herbivorous (plant eating) versus carnivorous (meat eating) behaviors. (In the following, please post questions that arise.)
Mammals: Have kids contrast the body structure of herbivores and carnivores and discuss how each is adapted to feeding and living in the manner it does. Type into your browser: herbivores versus carnivores images
Birds: Most insightful is focusing on a bird’s beak, how that beak adapts the bird to feed in a particular way.