A drawing does not start with the details. It begins with observing and capturing the basic shape. This initial framework is non-committal and plastic. Lines, especially ones that are bold and deliberate have a sort of gravitational pull. Once the line is on the paper, your brain tends to tell you “yes, this is right”. Changing it takes work and our brain would rather take the lazy route. For this reason you must fight locking onto your initial lines. One way to avoid line lock is to make your initial lines fast, light, loose, and sketchy. instead of drawing one line, make several. Your brain will be able to select which ones it likes the best out of those drawn on the paper, give it a little choice. Above all, wait on adding detail to your drawing. Once it is there, you are not going to want to erase anything and will contort proportions and negative spaces to fit what you already put on the paper.
To draw a hawk such as the Osprey in this demonstration, I make a light framework, often using an erasable non-photo blue pencil such as the Prismacolor Col-erase. I double check this frame before adding detail. While it is still in the blue pencil stage, it is easy to change any aspect of the shape without erasing, I just draw over the lines already there, refining the shape as I do.
Click on the first image in this series to watch a step by step slide show.
The “two circles” approach helps you capture the proportions or the relative size of the head to the body. However, it is easy to end up with a drawing that looks like you drew your bird by putting two circles together- because you did. The result is a Frosty the Snowman (bird). The circles easily overwhelm the drawing. It is as if our brains have a “snap to grid” function. We end up doing what is easy, following the lines already on the paper, instead of following the angles and planes of the real bird in front of us. The circles are not the contours of the bird. They are only there to help with getting the size of the head and body to be proportional. That is why it is critical to follow the circles with the step of carving in the angles. In this stage I overemphasize the angularity of the bird to combat the gravitational pull of the circles.