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 bird 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
Some bird species are dimorphic, which means there are visible differences in appearance between male and female birds’ plumage. In most cases, male birds will sport brighter, bolder colors as a way to attract mates during the breeding season. Female birds are usually duller, with less distinctive markings that make it easier for them to blend in to the surroundings while they mind a nest or protect young birds.
The appearance differences between male and female birds are most apparent during the spring and summer breeding season, when brighter colors can 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.
Another 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. The larger birds of prey, such as the golden eagle, have larger, more prominent size differences between males and females.
Gender Differences by Behavior
Unfortunately for meticulous birders, many bird species are monomorphic, which means there are no easily visible differences between male and female birds. 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 a mate as well as to advertise their presence and mark their territory. During courtship in many bird species, the males will feed females with behavior similar to how they will offer food while the female tends recently laid eggs.
Watching which birds tend the nest and feed fledglings can be another clue to a bird’s gender. In many species, however, both parents will tend the nest and care for the young birds, so this may not always be a reliable way to judge a bird’s sex.
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, gender differentiation is easy. If both male and female birds look alike, careful, long term observation may be necessary before a positive gender conclusion can be reached.
Photo – Northern Cardinal Pair © Nathan Siemers