Incorporating a camera into my birding adventures has, among other things, allowed me to observe and appreciate the pretty and peculiar feet of birds. Binoculars do not have an image saving or zoom function in the same way, and often I am too preoccupied with the colors and behaviors of the bird to really study the feet. It is after the fact, when reviewing photos, that I get to focus on the large and small variations in bird feet and guess at their development, design, and function.
Most bird feet are anisodactyl, meaning they have three toes facing forward with one strong toe (hallux)/thumb connected to the achilles tendon (equivalent) in the back.

Here we have the foot of a green heron. The knuckles are sticky and beady to help grip on slippery rocks.

I was really surprised at how off-center the thumbs/hallux were on the bird. I haven't been able to have this view of song bird feet so I can't compare, but I assume theirs line up more so with the middle toe.

The zygodydactyl feet of the roadrunner, with two toes to the front and two to the back, like many woodpeckers. Presumably this allows for a better grip when running, whereas on woodpeckers it allows for a vertical/parallel/upright ascent and circumvention of trees--not a hobby of the Greater Roadrunner's.

Here is such a Woodpecker foot Here is another Greater Roadrunner foot. This one also has the same gnarled back-right toe. The upper scaling, for lack of a better word, is noticeably thick and overlapping. This protects the Roadrunner's feet as it rushes through thorny desert vegetations and grapples with similarly armored lizards.

The backs of a Cactus Wren's feet. Their halluces (rear toe, equivalent of the big toe on a human foot) are almost as long as the frontal toes, with heavier scaling above and a rough, grippy skin below.

These European Starling feet are kinda creepy. They seem much more alien than other bird feet. The Starling is an invasive species after all...perhaps from another world?

Guess who's lovely leg this is!?

The lobed feet of the American Coot compromise swimming with terrestrial dexterity. They're not very dexterous on land though, so swimming seems to have won out. They do like to nest in marshy reeds and the like, and I imagine the lobed toes are preferable in those conditions to the fully palmated feet of ducks and other waterbirds.

Raptor claws! Although this Elf Owl isn't tackling big game, his bristly talons will still help him seize lizards, insects, and maybe even a small mouse (for Thanksgiving)!