What Is a Hummingbird Genus and Why Does It Matter?

Hummingbird 101

Aug 10

If you have ever looked up a hummingbird and noticed it has two names, a common one like Rufous Hummingbird and a scientific one like Selasphorus rufus, you have already encountered the concept of a genus. That first word in the scientific name is the genus, and it tells you more about the bird than most people realize.

Understanding what a genus is, why it changes over time, and what it means for the hummingbirds you watch and photograph makes field guides easier to read and gives you a much clearer sense of how the roughly 365 hummingbird species on Earth relate to one another.

What Is a Genus?

A genus (plural: genera) is a level of scientific classification that sits between family and species. It groups together species that are more closely related to each other than to any other species outside the group. Think of it as an immediate family within the larger hummingbird clan.

Every bird species has a two-part scientific name. The first part is the genus, always capitalized. The second part is the species, always lowercase. Together they form a unique name used consistently across every language and checklist in the world. Archilochus colubris is the Ruby-throated Hummingbird. Archilochus alexandri is the Black-chinned Hummingbird. Both share the genus Archilochus, which tells you they are close relatives within the larger hummingbird family.

Genus names are written in italics because they follow the conventions of the International Code of Zoological Nomenclature, the global system that governs how animals are scientifically named.

How Are Genera Organized Within Trochilidae?

As of 2025, Trochilidae contains approximately 113 genera. Those genera are not scattered randomly across the family. They are organized within the six subfamilies and nine clades we covered in earlier articles. Each genus belongs to one clade and one subfamily, giving it a precise address within the hummingbird family tree.

Some genera contain many species. Phaethornis, the hermit genus, contains roughly 37 species of long-billed forest hummingbirds across Central and South America. Selasphorus contains 9 species of small, fast-moving hummingbirds familiar to North American birdwatchers. Chlorostilbon holds 10 emerald species spread across the Caribbean and South America.

Other genera contain just one species. When a species is so distinct from all others that it stands entirely alone in its genus, it is called monotypic at the genus level. The Giant Hummingbird (Patagona gigas) is one example, occupying its own genus as well as its own subfamily.

Why Do Genus Names Change?

This is one of the most common sources of confusion for birdwatchers and collectors of field guides. A species you have known under one scientific name for years suddenly appears under a different one. The common name may stay the same but the genus shifts, and every checklist and app seems to be on a different page.

The reason this happens comes down to new research. For most of ornithology's history, genera were defined based on physical traits: bill shape, plumage pattern, body size, foot structure. Scientists grouped species that looked alike or behaved similarly into the same genus. The problem is that looking alike does not always mean being closely related. Two species can evolve similar features independently in response to similar environments, a process called convergent evolution, while being only distantly related on the family tree.

Since the early 2000s, molecular phylogenetic studies have used DNA analysis to map the actual evolutionary relationships between species. When the genetic data reveals that a traditional genus contains species that are not each other's closest relatives, taxonomists have to act. Some genera get split into several smaller ones. Others get merged. Species get moved from one genus to another to better reflect true ancestry.

For hummingbirds, the emerald clade (Trochilini) has seen the most revision. The old genus Amazilia once held roughly 29 species spread across a wide range of Central and South American habitats. Genetic studies revealed that those 29 species were not all closely related, meaning the genus was not a true natural group. As a result, many species were reassigned to other genera including Saucerottia, Uranomitra, Chionomesa, and others, while a smaller core Amazilia was retained for the remaining species.

This is not a sign that taxonomy is broken. It is a sign that the science is working as intended, getting closer to an accurate picture of how these birds are actually related.

What This Means for Birdwatchers

Genus changes can feel frustrating when a bird you have known for years suddenly has a new name on every app and checklist. A few things can help make sense of the shifts.

First, the common name almost never changes when a genus is revised. The Rufous-tailed Hummingbird is still the Rufous-tailed Hummingbird whether it is listed under Amazilia tzacatl or a revised genus name. Common names are stable anchors even when scientific names move.

Second, when a genus name changes it usually means the species has been placed more accurately on the family tree. The new name is a more honest reflection of where that bird actually belongs among its relatives.

Third, different checklists adopt changes at different times. The IOC World Bird List, the Clements Checklist, and Birds of the World do not always update simultaneously, which is why you may see the same species listed under different genus names depending on which source you consult. This is normal and expected.

Finally, knowing which genus a hummingbird belongs to can enrich what you notice in the field. Species within the same genus often share behavioral traits, habitat preferences, or display patterns. When you see a Selasphorus hummingbird, you can expect a small, fiery, aggressive bird. When you see a Phaethornis, you can expect a long-billed forest specialist moving quietly along a predictable route rather than defending a bright patch of flowers.

Frequently Asked Questions

If you still have questions about what a genus is and how it works in the hummingbird world, the answers below cover the most common ones.

As of 2025, Trochilidae contains approximately 113 genera. That number shifts gradually as new research prompts genera to be split, merged, or revised.
A monotypic genus contains only one species. The Giant Hummingbird (Patagona gigas) is a well-known example. It is so genetically and physically distinct from all other hummingbirds that no other species is placed in its genus.
The old Amazilia genus was large and convenient but not genetically coherent, meaning the species inside it were not all each other's closest relatives. Molecular research showed the group needed to be reorganized, and many species were reassigned to more accurately reflect their true evolutionary relationships.
Rarely. Common names like Ruby-throated Hummingbird or Rufous Hummingbird are assigned by regional committees and updated on a separate schedule from scientific names. A genus revision will not typically trigger a common name change.
There is no single universal answer. The IOC World Bird List, the Clements Checklist, and Birds of the World are all widely used and each updates on its own schedule. For your region, check which checklist your local birding organizations and eBird use, as that tends to be the most practical standard for field use. I personally use Clements/eBird.