In Adobe Illustrator we were introduced to custom shapes with curves by using the tools: pen tool, add anchor point tool, delete anchor point tool and convert anchor tool. These tool can be used to form any shape you want. You can start by making a shape from scratch or by a supporting image. We had a supporting reference picture of a duck which is Photoshop testing picture.
We traced around the duck point to point with straight lines around the duck until we made one complete circuit for the duck. Next we made the curves by adjusting the points by using the convert anchor tool. This tool allows use to make points curve by clicking on points using the tool which should make appear two handle bar. These bars will allows use to make each line between two points curve at different angles. Now we just need to look at the duck and copy all of the curves. When we have done the main yellow body shape we can now do the other shapes like the beak, eyes and feathers shaping by making new shape.
Next I do something similar to this I might experiment with shading by making shapes with gradients to make it a bit more realistic from the shading of the duck/object.