Female Ruby going for nectar. She does not have the flaming ruby throat of the male. That white patch behind her eye is very attractive. This hummingbird was common at the REGUA feeders and it says (online) that they are common in their area, but it is also mentioned that the bird is on the IUCN (International Union for the Conservation of Nature) Red List.
Hummingbirds can hover in air and also fly backwards. When we watch special effects in the movies of let's say, space alien attack ships, they too can hover and fly backwards. Interesting that that is what we did with the Hummingbirds' natural abilities. Sorry, should not be so negative.
*"The white-throated hummingbird is a species of hummingbird in the Trochilidae family. It is the only member of the genus Leucochloris. It is found in north-eastern Argentina, south-eastern Brazil, Paraguay, and Uruguay." Happily for this species it is common and found in open spaces, gardens and the like and not considered endangered. *Quoted from Wikipedia