I was out at the Bosque checking our bee traps for the pollinator study we are working on when about 50 yards away under a cottonwood tree I spied a huge owl looking at me. My car was about a 1/4 mile away, it was hot and the terrain uneven and difficult, but this was a great opportunity to capture a shot of a Great Horned owl, so I slowly backed off without disturbing it and sprinted to my car (1/4 mile) to get my camera with the long lens.Returning stealthily to the scene, I could see it hadn’t moved so I slowly raised my lens and...WARNING-CHANGE BATTERIES flashed at me. Since he hadn’t moved I retraced my steps, (1/4 mile), and grabbed my spare set. Back to the scene (1/4 mile) I started taking photos as I moved ever so slowly closer. The big bird watched, frozen in it’s shady shelter.After about 10 shots without change I had enough and gave him a quiet thank you . Back at the car (1/4 mile) I couldn’t wait to see my images. I blew them up on the camera screen and....see the attached, look closely- I wish I had!