Healthy bees poop on the wing, which is a good reason not to dry your washing near a bee hive.
Bee poo is generally bright yellow and high in pollen remnants. However, if the droppings are browner and near or in the hive, a beekeepers thoughts will go in the direction of two fungal infections, Nosema Apis and Nosema Ceranae. A serious incidence of either of these pathogens will impact overall hive health and survivability.
The presence of Nosema can be readily confirmed by the beekeeper with a microscope (at x400). If Nosema spores are present, the beekeeper will undertake hygienic measures, such as comb replacement to help the colony fight off the fungus.