The Northern Cardinal (Cardinalis cardinalis) exhibits sexual dimorphism, meaning there is a clear difference in appearance between males and females. This distinct variation in physical traits makes telling the sexes apart relatively straightforward. Identification relies heavily on visual cues like body color, subtle physical markings, and behavioral patterns.
The Striking Difference in Plumage Color
The most immediate method for sexing adult cardinals is observing their plumage color, which presents a dramatic contrast between the male and female. The adult male is covered almost entirely in a brilliant, unmistakable scarlet red or crimson color. This striking coloration is consistent across his body, from the prominent crest on his head to the tail feathers, ensuring he stands out clearly against any background. The intensity of this red is derived from carotenoid pigments obtained through the bird’s diet, and the vibrancy is thought to be a factor in mate selection.
The female cardinal, in sharp contrast, employs a much more subdued palette, which is beneficial for camouflage during nesting. Her overall body plumage is primarily a reddish-olive or fawn color, featuring grayish-brown tones. Instead of solid red, she displays warm reddish accents specifically on her wings, tail feathers, and the distinctive crest.
Distinguishing Physical Features Beyond Color
Beyond the overall body color, secondary physical traits offer further confirmation of a cardinal’s sex. Both males and females possess a thick, cone-shaped bill designed for cracking seeds, and both bills are a noticeable bright orange-red or coral color. The subtle difference is that the female’s beak can sometimes appear a slightly more muted orange compared to the male’s brighter hue, though this is not a reliable standalone identifier.
The most telling feature after plumage is the black facial mask surrounding the bill. On the adult male, this mask is intense, solidly black, and extends further down the throat and around the eyes. The female’s mask is often smaller, less defined, and may appear more gray or blackish, covering a smaller area of the face.
Behavioral Clues for Identification
Behavioral patterns can serve as reliable clues, especially when the bird is partially obscured by foliage. Vocalization provides one such indicator, as the male is primarily responsible for singing loudly to mark and defend his territory. While both sexes are among the few songbird species where the female also sings, her vocalizations are softer, less frequent, and often used as a contact call near the nest.
During the breeding season, a particularly telling behavior is the courtship feeding ritual. The male will collect a seed and present it to the female, feeding her directly from his beak to hers. Observing one actively feeding another in this manner is a definitive sign that the feeding bird is the male and the receiving bird is the female. The male also takes on the role of supplying food to the incubating female while she is on the nest.
How Juvenile Cardinals Differ
Identifying juvenile cardinals requires noting characteristics that differ from the adult rules. Young cardinals, both male and female, have predominantly brownish-gray plumage. They lack the vibrant red of the adult male and the distinct reddish-olive tones of the adult female.
The most helpful marker for a juvenile bird is the color of its bill, which is dark gray or black upon hatching. This dark bill contrasts sharply with the bright orange-red bill of all adult cardinals. Juveniles molt into their adult plumage and acquire the signature orange-red bill color by the time they reach their first fall.