They are called Bananaquits. They are about the size of Chickadees, but just a little bit less plump.
Nectar eaters in the wild, these chappies seem to have adapted to the cruising lifestyle. They will investigate and try anything.
Finding their way in didn't seem a problem. It was a different story when it was time to leave. After a few days, the novelty wore off, the droppings on our furnishings could not be ignored, and it was time for drastic measures. Flapping arms competed with flapping wings. Giggles became noisey "Out, out, out!"
I guess this comes under the heading of Interspecies Communications.
What wild life would you invite into your home? What other species would you like to communicate with?