I don't think these are hummingbirds, Toto...
With their diet of liquid nectar, yellow pollen, and red cactus fruit, the watery, bright yellow or magenta guano that these nectarivorous bats produce is quite unlike that of other bats, and it can be used as a distinctive sign of their presence, either in caves, mines, or under hummingbird feeders (move feeders off of patios during bat season if they are making a mess).
Yes, you did read that. Hummingbird feeder bats:
Two species of nectivorous bats occur here in Arizona, the threatened Mexican Long-tongued Bat (Choeronycteris mexicana) and the endangered Lesser Long-nosed Bat (Leptonycteris curasoae), and both of these bat species visit hummingbird feeders.
These nectivorous bats normally fatten up on the sugary nectar of agave flowers in preparation for their fall migrations south to Mexico and Central America, but they have learned that hummingbird feeders are also good sources for sugary nectar. Bats of both species will rapidly lap up the feeder's sugar water with their unusually long tongues, like the Mexican Long-tongued Bat (Choeronycteris mexicana) shown below.