A small white egg in Michigan is most often from a cavity-nesting bird like a woodpecker, swallow, owl, or hummingbird, because white eggs are common in dark nest cavities. One specific Michigan possibility from the search results is a Cedar Waxwing , and another forum answer mentioned bobwhite as having nearly all-white eggs, though that bird is less likely in many everyday backyard finds.

Most likely candidates

  • Mourning Dove : plain white eggs, often in simple nests, and commonly seen around homes.
  • Hummingbird : very tiny white eggs; the smallest U.S. bird eggs are from hummingbirds.
  • Swallow or bluebird : can lay pale or white eggs, especially in nest boxes or cavities.
  • Woodpecker or owl : white eggs are typical for cavity nesters.

What matters most

Egg color alone is not enough for a reliable ID, because many species can lay similar-looking eggs. Nest location, egg size, number of eggs, and whether the nest was in a cavity or out in the open matter a lot more.

Practical read

If the egg was very tiny , hummingbird is a strong guess. If it was small but not tiny and found in a nest box, tree cavity, or sheltered spot, swallow, bluebird, or woodpecker become more likely. If it was a single clean white egg in a flimsy nest on a ledge or porch, mourning dove is a common possibility.

Safer next step

Try to note:

  1. Egg size compared with a coin.
  2. Nest type and location.
  3. Whether there were one, two, or several eggs.
  4. Any adult bird seen nearby.

If you want, I can narrow it down by the egg’s size and where you found it.