“Hummingbirds are all about extremes. They flap their wings faster than any other bird, have a faster metabolism than almost any other animal, and have some species that are among the smallest living vertebrates. The hummingbird has adapted to such extremes because they are probably the oldest nectivorous birds, meaning they have had over 40 million years to perfect the ability of living almost entirely off of nectar.”

“This pathway,” Moth Light Media explains, “has made them gain abilities that make them truly unique among birds.”

Why nectar? Why are hummingbirds so small? And what examples do we have in the fossil record to help biologists better understand the evolution of these jewels of the sky?

Take a look at a few of the key characteristics that more than 300 modern species of North and South American hummingbirds share, and peek into a world tens of millions of years ago where an unexpected European hummingbird provides more clues and mysteries: The Evolution of Hummingbirds. More from Audubon.org:

“The similarity between these fossils and New World hummingbirds could be an example of convergent evolution—when two species are not closely related yet develop similar traits over time by adapting to similar environments—but [UC Berkeley biologist Jim] McGuire and [Senckenberg Research Institute paleontologist Gerald] Mayr both believe the family probably originated in Eurasia and somehow migrated to the Eastern Hemisphere. ‘It is still theoretically possible that those fossil hummingbirds are not really hummingbirds but another bird group,’ McGuire says. But after closely comparing the morphology of the fossils to modern hummingbirds, he thinks convergent evolution is “unlikely” in this case. “

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