Adult Ruby-throated Hummingbirds, Archilochus colubris, are sexually dimorphic; i.e., the adult male and adult female are different in external appearance. However, young males "masquerade" as females until their first winter, at which time they attain adult male plumage. This can make ageing and sexing difficult during summer and fall after young of the year have fledged. From May through October, do not assume all white-throated hummers at your feeders are females; some undoubtedly will be young males.

Click below for more details about RTHU external characteristics and hints on how to differentiate between age and sex classes.

When perched, a Ruby-throated Hummingbird measures about 3" (7.5cm) from tip of beak to tip of tail; the bill itself makes up about one-fifth of the length. Unlike most animal species, in RTHUs adult females are typically about 15-25% LARGER than adult males. (There are still "big" males and "small" females, however, so ruby-throats should not be sexed by size.)

All hummingbirds are fully grown and capable of flight when they leave the nest; there are no "baby hummingbirds" at feeders. In other words, baby hummingbirds can't fly. Any tiny hummingbird that is hovering at a flower or feeder is undoubtedly a Hummingbird Moth.

The bird in the photo above right is a juvenile male RTHU with an incomplete red gorget. (See next section for plumage characteristics.)

ALL normal Ruby-throated Hummingbirds have metallic green backs, but some appear dingier or brighter. In general, adult males appear darker than females and young males. Remember that hummingbird colors are structural in nature and vary with light intensity and angle. In poor light, a Ruby-throated Hummingbird can look almost black rather than green or red.

Adult Male: Throat metallic ruby-red (rarely has a golden or bronze cast); back metallic green or bronze-green; wings near-black; tail feathers pointed and all dark (no white tips); tail forked; breast and belly usually brownish-gray; flanks metallic bronze-green; crown metallic dark green. White area below gorget may appear to create a light ring around the bird's neck. Because of the adult male's gray breast, dark tail, and red gorget, he often looks much darker than a female or juvenile male--especially in poor light.

Female: Throat white, or with occasional faint buffy streaking (very, very rarely a black or red throat feather may occur in an old female); back metallic green or bronze-green; wings near-black; tail feathers rounded; outer three feathers white-tipped; tail fan-shaped; belly and vent white, flanks light brown; crown metallic dark green.

All text & photos © Operation RubyThroat & Bill Hilton Jr.

Young: Similar to female, except young males USUALLY with more or less dark streaking (green or black, sometimes buffy) on the throat; later in summer young males often show one or more red throat feathers. (Nearly all birds with noticeably streaked throats are young males; see photos below.) Young birds of either sex may have brownish edges on otherwise green body feathers--especially on the crown and back (above). Because females AND young males can have white throats, the ONLY time you can positively age white-throated Ruby-throated Hummingbirds at a feeder is in SPRING before young birds of the year have left the nest.

Only the ADULT male Ruby-throated Hummingbirds has the full red gorget (top photo above) that gives this species its name, although the red may not be apparent if the bird is viewed from the side (bottom photo above).

Female Ruby-throated Hummingbirds of any age have a white throat that is sometimes marked with faint gray or buffy streaking (two photos above). Older females occasionally have one or two black throat feathers (below); very, very rarely they may have a single red feather on the throat. Note that young males (see next section) resemble females.

A young male Ruby-throated Hummingbird also may have a white throat like a female, but more often it is streaked to a greater or lesser degree with black or green; this gives the appearance of a "five o'clock shadow." The bird just above is the most heavily streaked we have seen; the one above it is more typical.

Near summer's end, young males MAY show one to several red throat feathers but do not get a full red gorget until their first winter. When a young male returns the following spring, some researchers believe his gorget may have an irregular bottom edge (below), and one or more of the throat feathers may be brownish instead of red; this may be a useful ageing characteristic but needs further study.

All text & photos © Operation RubyThroat & Bill Hilton Jr.

Adult male Ruby-throated Hummingbirds (above left) have pointed rectrices (tail feathers) that are all dark with no white tips; the tail is forked. However, young males (above right)--like females of any age--have white tips on the outer three rectrices on each side; each feather is rounded and the tail is fan-shaped. This similarity between females and young males complicates trying to determine the sex of free-flying hummingbirds at feeders in early summer after young begin to fledge. In spring, however, any bird with white tail tips is an adult female.

The bill of the Ruby-throated Hummingbird is dull-to shiny-black; it sometimes appears whitish or yellowish because of pollen deposits. The bill of young birds is lightly etched with tiny lines called "corrugations" (above) that either fill in and/or wear down starting at the tip. This creates a smooth appearance after about 6-8 months; even adult birds, however, can show corrugations near the base of the bill. Corrugations (which most people require a magnifier to see) are usually only visible on birds-in-the-hand. In the second photo above, the tip of the bill already shows some smoothing, so this bird would be scored as having about 80% corrugations--a young bird late in its first summer. As in many bird species, the gape (corner of the mouth) is yellow in young birds (see both photos below), and ivory, white, or pinkish-white in adults.

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All text & photos © Operation RubyThroat & Bill Hilton Jr.

EYE

All text & photos © Operation RubyThroat & Bill Hilton Jr.

The eye of the Ruby-throated Hummingbird appears all dark; viewed in the hand, the iris is actually a dark brown and the pupil is black. In both sexes there is a small spot of white feathers behind each eye. In some birds, juveniles have an iris that is "muddy"; i.e., it lacks the clarity of the adult eye. This does not seem to be the case in hummingbirds and, thus, cannot be used as an ageing technique. The bird in the photo at left is an immature female that has been color-marked with a swath of green dye on her upper breast/lower throat. See Color-marking.

The wing of a Ruby-throated Hummingbird appears curved and pointed when held at rest against the bird's side. The tip of the wing extends well past the junction of the body and tail and usually past the tip of the tail itself. In flight, the wing has the shape of a tall right triangle. The relative length of the wing against the body is one field mark that sometimes can be used to identify North American hummingbirds.

In the hand, a close look at the tip of the #6 primary feather can be used to confiorm the sex of even a young RTHU. Males always have tapered and sharply pointed #6 primaries (below left and bottom), while in females this feather is more or less rounded (below right).

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FOOT

All text & photos © Operation RubyThroat & Bill Hilton Jr.

The Ruby-throated Hummingbird's leg is very short (left); the band is nearly as tall as the length of the "tarsus"-- more correctly called the "tibiotarsus"--and the toes of the foot seem quite long by comparison. There are three toes in front and one (the hallux) in back; each toe has a long, curved nail. Males usually have thinner legs than females--especially during nesting season when the legs of females often swell. Hummingbird feet, which are grayish-black, are well-adapted for perching but not for walking; a flightless hummingbird is essentially helpless on the ground.

NOTE: Ruby-throated Hummingbirds with aberrational plumage sometimes occur. These include albinos and leucistic birds with varying degrees of pale or white feathers. Please report sightingss of these birds to Operation RubyThroat at Hilton Pond Center. For details about these unusual plumages, click on the photo below.