I felt at ease while drawing from the picture because I knew that all the details were already captured and always there for reference.
I'm not sure that any of it came easily; I had to think about every part. The part that was especially challenging was creating the varied texture on the branch. Oh, and capturing the bird's expression was tough.
Had I not drawn it, I wouldn't have noticed the extra detail around the bird's eye or its nostril. Not having those details would not have a dramatic difference while journaling but having them makes it more special.