When the Williamson's Sapsucker male arrived to feed the chicks a mouthful of ants, he perched sideways on the aspen trunk. It was impressive agility, balance and strength. Also, humorous! Canon 5Dmk3, Canon EF f/5.6L 400mm USM, 7/6/14 12:52pm, Upper Beaver Meadows, f/5.6, 1/500s, ISO 640, lens focal length 400mm.