Ink pens are a smart choice because there’s no need to constantly dip the pen in ink, making it easy to avoid stains. However, depending on the type of pen you use, it might be hard to tell the difference between solid, thick lines and hairlines.
Start by redrawing the contours and give your bird a few feather details.
After erasing the original construction lines, use hatching to create some shadows. Be careful to leave a few light areas to maintain the bird’s dimensions.
Adding feathers will give more volume to the wings.
You can continue to add more line details, but make sure not to overdo it.