Welcome to the board!! in my experience the lines for quilting are hard to wash away. I would recommend a good soak. I used to use all-fabric bleach (sodium perborate) but I can't find it anymore. There are special quilt washes, someone will mention the names. You do need to soak it (Not a washing machine!!) and it may take a while.
Even if the lines do fade, you can always use your own quilting pattern or do simple quilting around the birds. I would want to know how clean it is going to get before I spent any more time on it.