While working on a book project I needed a photo that showed the zygodactyl feet of woodpeckers. If you knew what you were looking for, several of my photos showed the four toes of woodpeckers but this photo of the Downy showed the four toes most clearly.
Nikon D4 camera, 500mm f/4 lens + 2x teleconverter
1/3200 sec at f/11, ISO 2500
Most songbirds have three forward-facing toes, and one backward-facing. Woodpeckers have two toes pointed forward, and two toes pointed backward. This toe arrangement helps support the woodpecker as it climbs up and down the bark of a tree. Exceptions to the rule: Black-backed woodpeckers and the American and Eurasian three-toed woodpeckers have only three toes on each foot.