Ruby-throated hummingbirds are one of the most common hummingbird species found in North America. While the adult male Ruby-throated hummingbirds have their trademark bright red throat, females and juveniles can be harder to identify. Knowing the key differences between female and juvenile Ruby-throated hummingbirds can help you better recognize these birds when you see them.
Identifying Adult Female Ruby-throated Hummingbirds
Adult female Ruby-throated hummingbirds lack the bright red throat patch that gives the males their name. However, there are still some key features that can help you confirm an adult female Ruby-throated hummingbird:
- Green back – Females have a metallic green back, similar in color to the males.
- White throat – Their throat is white.
- Gray underparts – Their underparts and flanks appear gray rather than the deep rusty color of the males.
- Forked tail – They have the same forked tail shape as males.
- Bill shape – Their bill is long, straight, and very slender like the male’s bill.
Adult females are very active at feeders, aggressively chasing away other hummingbirds. They are feisty and do not like other birds crowding in on their food source. Watch for hummingbirds that lack red throats and exhibit aggressive “guarding” behaviors around feeders as these are likely adult female Ruby-throats.
Distinguishing Juvenile Ruby-throated Hummingbirds
Young, juvenile Ruby-throats have only recently fledged and left the nest. They can be identified by some key features:
- Small size – Juveniles will be much smaller than adult females. Their overall body size is tiny at only 2.5-3.5 inches long.
- Shorter bill – Their bill will be noticeably shorter than an adult’s.
- Grayish-brown plumage – Juvenile plumage is dull gray-brown on the back and chest before they molt into adult feathers.
- Speckled throat – Their throats have dark speckling rather than a clear white or red patch.
- Lacks color – You’ll notice an overall lack of bright definitive colors throughout their plumage.
Juveniles tend to be quite skittish compared to aggressively territorial adult females. They will avoid human-occupied areas and feeders with lots of activity. You can recognize them by their small size, lack of coloration, and avoidance of busy feeders.
Behaviors to Differentiate Ages & Sexes
While plumage is a key identifier, behavior can also help clue you into whether you are observing an adult female or juvenile Ruby-throat:
Adult Females:
- Territorial at feeders
- Aggressive chases and diving
- Fearless around humans
- Constantly vocalizing
- Routine favorite feeding areas
Juveniles:
- Wary and easily startled
- Only quick feeding visits
- Frequent short rests between feedings
- Erratic unpredictable movement
- Quiet, rarely vocalize
An adult female will aggressively defend a feeder as her territory, while a young bird will dart in for a brief visit then disappear. Vocalizations also differ, with juveniles rarely vocalizing while adult females frequently emit calls.
When Do Juveniles Reach Adult Appearance?
Young hummingbirds molt into adult plumage when they are between 1-2 years old. At the one year point, males will begin to acquire red throat feathers. The full vibrant red throat may take an additional year to fill in completely. Females replace their juvenile gray-brown body feathers with shiny green and white adult feathers over this same time span.
So while that drab little hummingbird at your feeder could still be a juvenile, at some point in its second year you will notice it take on definitive adult male or female Ruby-throated characteristics.
Comparison Table of Characteristics
| Characteristic | Adult Female | Juvenile |
|---|---|---|
| Size | 3.5-4 inches long | 2.5-3 inches long |
| Bill length | Long, straight | Shorter |
| Throat | White | Speckled gray |
| Plumage | Green back, gray underparts | Dull gray-brown |
| Behavior at feeders | Aggressive, territorial | Wary, skittish |
| Vocalizations | Frequent calls | Rarely vocalize |
Conclusion
Telling apart female and juvenile Ruby-throated hummingbirds comes down to a few key differences. While adult females lack the flashier red throat of males, their larger size, aggressive behavior, white throat, and green back help identify them. Juveniles exhibit small size, speckled throat, dull plumage, skittish behavior and lack of vocalizations until they acquire their adult features over the first 1-2 years of life.
Understanding these subtle but distinguishing characteristics will help you identify the female and juvenile Ruby-throats that visit your feeders alongside the brighter adult males. Paying attention to the variations in size, appearance, behavior, and sounds that these birds exhibit is the best way to determine if you are observing an adult or juvenile of either sex.
With a little practice, you’ll be able to confidently tell juveniles and females apart. Getting to enjoy views of Ruby-throats at all stages of development is one of the joys of attracting these spectacular hummingbirds to your own backyard.
