The nictitating membrane protects and lubricates the eye, while still allowing light to pass. In this rare photo, the membrane is halfway across the eye. This bird is singing in the valley oak (Quercus lobata), covered in mistletoe, that I call the "Phainopepla Tree". The next images tell more about its ID. You can see a little mistletoe here. On Road F. Full images of this tree are in the ajacent gallery with the same date.