Advanced birders often want to go beyond simply identifying each bird species they observe. Knowing how to tell the difference between male and female birds takes keen observation and a dedication to detailed birding. While not all species have easily visible gender differences, it is often possible to determine which birds are male or female by either appearance or behavior.
Gender Differences by Appearance
Many bird species are dimorphic, or they show visible differences between male birds and female birds. In most cases, male birds sport brighter, bolder colors as a way to attract mates. Female birds are usually duller, with less distinctive markings that make it easier for them to blend into the surroundings while they mind a nest or protect young birds.
The physical differences between male and female birds are most apparent during the spring and summer breeding season, when brighter colors attract mates more effectively. Bold colors are also less dangerous in the summer months, when colorful birds can still blend into bright flowers and foliage. For some species, males molt into a less brilliant, more camouflaged plumage each fall but will refresh their brighter colors each spring. Examples of distinctively dimorphic species include:
- Northern cardinals, with brilliant red males and much differently colored reddish-tan females
- Many different duck species with outrageous male plumages but camouflaged females
- Painted buntings, with rainbow-colored males and monochrome greenish females
- Many grouse, quail, and pheasants where males have plumes or other unique feathers and colors but females are much more camouflaged
For some birds, such as northern flickers, plumage differences between sexes is much more subtle. For these woodpeckers, both males and females have barred backs, spotted underparts, and bold black bibs. Males, however, have colorful malar stripes, while females have plain faces. Other examples of similar, subtle plumage differences include:
- Other woodpeckers that have only minor differences between males and females, such as the extent of color on the head or face
- Some hummingbirds where males have colorful gorgets while females have plain throats, though the rest of the plumage may be similar
- Parrot species that have identical plumage though the size and color of the cere can be used for sex determination
Another common appearance difference between bird genders is size. In many cases, female birds are larger than males, though in most songbirds the size differences may not be noticeable unless two birds are side by side. Larger birds of prey, such as the golden eagle, typically have much more prominent size differences between males and females. Even if the birds' overall sizes may not be too different, there may be gender size differences in bill length or in specialized feathers, such as taller crests or longer tail streamers.
Gender Differences by Behavior
Unfortunately for meticulous birders, many bird species show no easily visible differences between male and female birds. This is true for species such as gulls, titmice, chickadees and many sparrows. Careful observation of birds’ behavior, however, can still offer clues about which individuals are which gender.
Male birds may migrate sooner than female birds so they can stake out and defend territories. Those same male birds are often vocal and talented singers, using their songs to attract mates as well as to advertise their presence and mark their territory to potential competitors. Females may join in duets, but are often much more silent, particularly while nesting.
During courtship in many species, males feed females similar to how they will offer food while the female tends recently laid eggs. Males may also have more elaborate dances, posturing or other actions to try and entice females that watch their displays. Males are often more aggressive than females, chasing away intruders or actively engaging in fights against other birds or even non-bird predators.
Watching which birds tend the nest and feed fledglings can be another clue to a bird’s gender. In many species, however, both parents tend the nest and care for young birds, so this may not always be a reliable way to judge a bird’s sex unless one bird is doing the majority of the nest care. Even then, that dominant parent might be either male or female.
Tips for Determining Bird Gender
To accurately identify a bird’s gender, the first step is to make a positive identification of the species. If the species is dimorphic, sex determination is easy. If male and female birds look alike, careful, long-term observation may be necessary before a positive gender conclusion can be reached. In some cases, it may be nearly impossible to be absolutely certain which bird is male and which is female. Even if the genders cannot be confirmed, however, the careful observation of partner interactions will help birders sharpen all their identification skills and better appreciate every bird they see.