Male and Female

It’s common knowledge that there are male and female birds. Birders are keenly aware of this fact, because some of their greatest identification challenges come with female birds. In fact, some female birds are so drab or different that successful identification is worthy of bonus points!

The scientific term is sexual dimorphism. Males have one appearance, and females have a different appearance. This is most commonly noted in color patterns, but it can also be a size difference or even a difference in shape or adornment feature.

Not all birds exhibit sexual dimorphism, (or at least nothing humans can easily distinguish). Bald eagles, turkey vultures, Canada geese, barn owls, mourning doves, blue jays, European starlings, black-capped chickadees, and field sparrows are just a few of the species in which the males and females look alike. Gulls, terns, and sandpipers are likewise basically homogenous.

For some species the dimorphism is minor. Female American robins, white-breasted nuthatches, and American black ducks are somewhat paler than the males. Female Cooper’s hawks are a little larger than males and may have some subtle differences in coloring. Male downy and hairy woodpeckers are distinguished by a small red patch on their heads, and the red stripe on the head of the male red-bellied woodpecker is complete, rather than broken on the female.

Sometimes the females have beautiful color, but they are still less flashy than the males. Northern cardinals are a well-known example; the males are vibrant red, while the females are buffy or orangish with dull red highlights. Female eastern towhees are chocolate-brown and rusty, compared to the males’ vibrant black and rusty colors. The bright yellow summer coat of the male American goldfinch can be seen even in overhead flight; the female’s yellow is dull in comparison and lacks the bold black highlights. There isn’t much like the bold black and orange of a male Baltimore oriole; the female is mostly yellow with just hints of orange. The male scarlet tanager, bright red with black wings and tail, is one of our most eye-catching birds, but his wife is plain yellow. Female eastern bluebirds still have beautiful blue and orange, but significantly reduced compared to the male.

For many species, male and female birds display vast differences in appearance. A notoriously difficult bird for new birders is the female red-winged blackbird, which looks brown and streaky like a large sparrow, while the males are shiny black with bright red shoulder patches. Male purple finches and house finches are brightly colored, while females are brown and streaky. Male house sparrows are richly brown, with a gray cap and a black bib, but the females are plainer buffy brown and unadorned. The very dull brown female indigo bunting takes the name of her bright blue husband. The female black-throated blue warbler is so different that it was long thought to be different species from the male.

Many duck species are strikingly different (wood ducks, mallards, hooded mergansers, American wigeons, green-winged teals, northern shovelers, northern pintails, buffleheads); the males get wildly patterned faces, flamboyant green heads, white crowns, orange heads, warm chestnut patches, and other striking patterns, while the females are generally brown and unmarked. Male game birds like ring-necked pheasants, California quail, and wild turkeys get an extra feature – a horn, a tall head plume, or a beard – in addition to their larger size, brighter coloring, and extra feather features.

When there are differences, the males are almost always more colorful. There are a few rare occasions where the female gets the extra color. In North America, the best example is the belted kingfisher. The male is beautiful blue with a white collar and blue bib. The female gets all of this, plus a special orange band on her chest and sides. Phalaropes (Wilson’s and red-necked) are less familiar and less common birds, but the females of these species also get brighter colors and more vibrant markings than their male counterparts. Globally, the Moluccan eclectus (parrot in Indonesia) is another example.

What is the purpose behind the dimorphism? God created the birds as male and female, and He did so for the purpose of reproduction, for continuation of the species. “Also of the birds of the sky, by sevens, male and female, to keep offspring alive on the face of all the earth” (Genesis 7:3). It is interesting that the color variation between sexes is basically tied to reproduction.

The fact that the females are duller, plain and drab, often brown, gives them protection for nesting. Imagine a duck sitting on a nest of eggs for 28 days. If the female wood duck were as brightly colored as the male, she would be an easy mark for predators – a sitting duck! Most female ducks are brown and gray, so they are camouflaged and able to blend into their surroundings.

The males of many species have their bright colors just for the breeding season, so even their bright colors are tied to reproduction. The males with the best outfits can most easily attract a mate. (Healthy birds with a good diet have the brightest color.) In some cases, the mating displays highlight the male’s special colors, or displaying those colors can be used to intimidate the competition.

Most birds (about 90%) are monogamous. One male and one female pair up together to raise a brood of chicks, and they remain together for the season. The next season, if both birds are still alive and both return to the same breeding area and they have previously been successful in raising chicks, they might pair up again. Given all those factors, it is also true that many birds will choose new mates in a new season. There are birds that are lifetime monogamous, however. This is especially true of larger birds with longer life expectancies and that are more heavily invested in the prolonged raising of fewer offspring. Some examples are swans, eagles, cranes, and storks.

In most cases, both the father and mother bird share in raising the young, though the division of labor varies between species and even within species. Typically, the mother (or both) build the nest; the mother most often sits on the eggs and tends to the chicks in the nest, while the father (or both) are responsible for bringing food.

While it may seem that the only reason for sexual dimorphism is to make life more challenging for birders, God has His good reasons. Through them He provides us with beauty and diversity, and He provides birds with the necessary traits to survive and prosper.

Scripture taken from the NEW AMERICAN STANDARD BIBLE ®, Copyright © 1960, 1962, 1963, 1968, 1971, 1972, 1973, 1975, 1977, 1995 by The Lockman Foundation. Used by permission.