Add feet and eyes. Simple lines and dots can work well for these details.
Draw a beak triangular shape in the middle of your oval or circle.
Add wings. These wings can be flying, closed in tight, or just at their sides. Simple lines and shapes work really well.
Add additional details such as tail feathers, patterns, feathers on top of the head, or even simple glasses can be added to your bird cartoon.
Notes
Modify this sketch to make a bird cartoon you will love.
Remember to sketch lightly with your pencil.
If using a pen afterward, erase the pencil lines.
Encourage children to add their own unique characteristics and details to their simple cartoons. You can show them different ideas & details by demonstrating how to change the egg shape, but they don't need to follow you exactly step-by-step.