Birds

Yesterday during my yoga practice I was looking out my second floor window at a stunning bright red cardinal who was eating the seeds off the topmost branches of the tree in front of our house. He didn't seem to mind me watching him, but the second I pulled out my camera he flew away. This has happened almost every time I have tried to take a picture of the birds in my neighborhood (ducks not withstanding). I wonder why birds don't like to have their pictures taken?