I discovered that the challenge is about using the pen tool, so I gave it a try, normally I use sktchy tool with on fall off on max, if I want to do just lines.
The wonderful ref is from sktchy, I struggled with the beak.
I am tempted to add forever more detail but I know that will ruin it.
For the ardent observer, I did not do an exact copy. Like with the feet, in the photo you cannot see both feet, I made them more visible, and I changed the composition a bit. I live that you can so easily select and transfer in sketchclub, it my way of working, not having a plan up front but adjusting all the time.
I added some random little random lines around the bird to show the energy.