When observing birds, a common source of fascination is their diverse and striking coloration. Many species exhibit visual differences between males and females, a phenomenon known as sexual dimorphism. This leads to curiosity about the appearance of female birds, particularly those associated with vibrant hues, as their plumage can be quite different from their male counterparts. Understanding these distinctions helps in identifying various bird species and appreciating the subtle beauty in the avian world.
The Female Northern Cardinal
The female Northern Cardinal, known for the male’s brilliant red, has a more subdued appearance. Her plumage is primarily a pale brown or grayish-brown, providing a less conspicuous profile. Her base color is accented with reddish tints, noticeable on her wings, tail, and crest.
Like the male, she has an orange-red beak, contrasting with her facial feathers. Her face also features a gray to black mask around the bill, though less defined than the male’s darker mask. The crest, a notable feature, is similar in shape to the male’s but shares her muted reddish tones.
Other Reddish-Feathered Birds
Beyond the Northern Cardinal, several other bird species have males with reddish coloration and females with distinct appearances. The House Finch, for instance, has males with rosy red feathers on their face and upper breast. Female House Finches, however, are plain grayish-brown with thick, blurry streaks across their underparts and an indistinctly marked face, lacking any red coloration.
The Purple Finch male is characterized by a delicate pink-red wash on its head and breast, blending into brown on its back. In contrast, female Purple Finches lack any red. They are brown with crisp, coarse streaking on their underside and distinct facial markings, including a whitish eyebrow stripe and a dark line running down the side of their throat.
Summer Tanager males are entirely bright red. Female Summer Tanagers are orangish-yellow, with slightly greener backs and wings. Their pale, thick bill is distinguishing. Similarly, male Scarlet Tanagers are crimson with black wings and tails. Their female counterparts are olive-yellow with darker olive wings and tails.
Why Color Differences Exist
The differences in coloration between male and female birds, known as sexual dichromatism, are a result of various evolutionary pressures. A primary reason for duller female plumage relates to camouflage, particularly during nesting. Females perform most incubation duties, and a less conspicuous appearance helps them blend into their surroundings, reducing the risk of predator detection while on the nest.
Male coloration, conversely, evolves due to sexual selection, where vibrant feathers serve to attract mates and signal health and genetic fitness. Brighter, more elaborate plumage can indicate a male’s ability to forage successfully for carotenoid-rich foods, which are important for producing red, orange, and yellow pigments. While males benefit from attracting females with their displays, females gain an advantage by remaining camouflaged to protect their offspring, reflecting a balance between reproductive success and survival.