Robin bird using one eye to get a better view

redbreast robin erithacus rubecula winter birdwatching snow bird rubecula bird watching wildlife migrate orange ornithology avian binocular branch migratory erithacus lone stereo vision alone outdoors distinguish eyesight european optic see depth robinet ruddock sensory stereo perceive eye observe tree stereopsis perception navigation vision compass notice visual field watch magnetic europe orientation magnetic field magnetoreception