Hummingbirds are a unique and fascinating group of birds found exclusively in the Americas. With their ability to hover mid-air and fly backwards, their tiny size, and their beautiful iridescent plumage, hummingbirds capture the imagination of people around the world. But where did these incredible creatures come from? What was the ancestral lineage that gave rise to modern hummingbirds? In this article, we will explore the evolution of hummingbirds and trace their lineage back to their closest living relatives.
The Origin of Hummingbirds
Hummingbirds belong to the avian order Apodiformes, along with swifts. Together, hummingbirds and swifts make up the clade Apodiformes. Phylogenetic studies based on morphological and genetic data suggest that hummingbirds and swifts share a common ancestor that lived about 50 million years ago in the Eocene epoch.
The earliest hummingbird fossils date to around 30 million years ago in the Oligocene epoch and were found in Europe. However, hummingbirds likely originated in South America and later spread to North America and the Old World. The European hummingbird fossils represent an early dispersal event.
By the Miocene epoch about 20 million years ago, modern hummingbird groups started to appear in the fossil record in South America. From there, hummingbirds radiated into the diverse species we see today, adapted to specialized niches across the Americas.
Closest Living Relatives
Since hummingbirds and swifts share a relatively recent common ancestor, swifts are considered to be hummingbirds’ closest living relatives.
Like hummingbirds, swifts are highly aerial birds with long, curved wings adapted for continuous flight. Both groups share anatomical similarities like short legs that are not well suited for walking or hopping, and very short bills. These similarities reflect their shared evolutionary history as aerial insectivores.
However, there are also some key differences between swifts and hummingbirds. Swifts have drab coloration compared to the brilliant iridescent plumage of hummingbirds. Swifts are also unable to hover or fly backwards like hummingbirds can. And unlike the small body size of hummingbirds, swifts are medium-sized birds.
Other Apodiformes
Hummingbirds and swifts belong to the larger group Apodiformes, which also includes three small families of ‘proto-swifts’ found only in Africa and Asia:
– Hemiprocnidae (tree swifts)
– Cypseloididae (crested swifts)
– Apodidae (true swifts)
These proto-swift families represent more ancestral lineages that diverged earlier than the split between swifts and hummingbirds. While they are a bit more distantly related, tree swifts and crested swifts still share some similarities with hummingbirds, like aerial lifestyles and small body sizes.
Divergence from Swifts
The ancestral hummingbird lineage diverged from swifts sometime between 50-40 million years ago in the Eocene epoch, based on molecular clock analyses.
Some researchers have specifically proposed that the Malagasy or Madagascar spine-tailed swift (Zoonavena thomensis) may represent the closest living relative to hummingbirds. This is because Malagasy swifts share some anatomical characteristics with hummingbirds that are not seen in other swifts, like enhanced hovering flight muscles.
However, not all data supports Malagasy swifts being the living sister group to hummingbirds. More research is needed to clarify the relationships between different swift lineages and pinpoint exactly when hummingbirds diverged evolutionarily.
In any case, the common ancestor of hummingbirds and swifts was likely an agile, aerial insectivore that could flap its wings in a figure 8 pattern to facilitate hovering and maneuverability in flight. This ancestral form later gave rise to both hummingbird and swift lineages.
Traits of the Common Ancestor
While the common ancestor of hummingbirds and swifts lived around 50 million years ago, scientists can use the features of early fossil hummingbirds and swifts, as well as comparative anatomy, to infer what this ancestor was likely like.
Some key traits of the hummingbird-swift common ancestor may have included:
- Small to medium body size
- Long, curved wings for sustained flight
- Short legs and feet adapted for perching rather than walking/hopping
- Short, thin bill
- Long tongue for nectar-feeding
- Highly efficient respiratory and circulatory systems for energy demanding flight
- Enhanced wing musculature and shoulder joints allowing hummingbird-like hovering and maneuverability
- Insectivorous – feeding on flying insects captured aerially
These ancestral traits gave rise to an evolutionary lineage well-equipped for the aerobatics and hover-feeding that hummingbirds still exhibit today. By tracing hummingbirds back to their swiftlets, we gain insight into the evolutionary origin of hummingbirds’ unique and captivating traits.
Key Events in Hummingbird Evolution
| Time Period | Evolutionary Events |
|---|---|
| 50 million years ago (Eocene Epoch) | Divergence of ancestral hummingbird and swift lineages from a common ancestor |
| 40 million years ago (Eocene Epoch) | Further divergence of hummingbird lineage into unique family (Trochilidae) |
| 30 million years ago (Oligocene Epoch) | Earliest hummingbird fossils found in Europe represent early dispersal from South America |
| 22 million years ago (Miocene Epoch) | Modern hummingbird groups emerge in South America |
| 5 million years ago (Pliocene Epoch) | Hummingbirds expand northward into North America |
This table summarizes key branching events and dispersals that led to the evolution of modern hummingbird diversity we see today. Tracing the lineage back 50 million years, we can follow the divergence from their sister group the swifts and the origin of unique hummingbird characteristics.
Conclusion
In summary, hummingbirds and swifts share a common ancestor that lived about 50 million years ago and exhibited aerodynamic features for aerial maneuvering and feeding. Of the swifts, Malagasy swifts seem to be the closest living relatives to hummingbirds based on anatomical similarities. However, the exact divergence point of the hummingbird lineage remains unclear. What we do know is that from this common ancestor, hummingbirds evolved their own suite of distinctive traits related to hovering flight, nectar-feeding, iridescent plumage, and tiny body size. Tracing the evolutionary history and relationships among swifts and hummingbirds provides insight into how these captivating creatures came to acquire their remarkable abilities.
