If it's smaller than a hummer, it's probably a hummingbird moth.
From the post-gazette.com
The hummingbird moth is often confused with the hummingbird as it feeds in the same areas and manner as the hummingbird.
From the post-gazette.com
Summer evenings will often bring the hummingbird moth, also called the Sphinx or hawk moth, to this favorite food plant.
From the chron.com
Like the hummingbird, the moth has to be stable in the air to get a drink.
From the npr.org
Recent sightings include the hummingbird hawk moth, little-ringed plovers, sandwich terns, and a spoonbill.
From the independent.co.uk
It is also one of the best places in Britain to see the hummingbird hawk-moth, looking, as it feeds, exactly like the tropical nectar-gatherer for which it is named.
From the independent.co.uk
A large, day-flying moth, the hummingbird hawkmoth hovers over flowers such as buddleia and valerian, hence its name.