Bird Term: Sexual Dimorphism

Supurb Fairy Wrens

Sexual dimorphism refers to observable differences between males and females of the same species. In basic terms, it means that a male of a species is easily distinguished from a female. In birds this usually means differences in size or in plumage. It can also be noted in behavior differences and other traits.

Earlier on this blog we talked about the extreme sexual dimorphism in Eclectus Parrots, where males and females show extreme differences in their plumage: males are bright green while females are shades of red and blue.

Sexual dimorphism exists in most species of raptor. In birds of prey, males are often smaller than the females of the species. However, this is often difficult to discern in wild birds, especially if seen at a distance or when only one bird is present.

Many common birds also exhibit sexual dimorphism. Male ducks are often colorful, while females tend to be drab. You can see this in the common Mallard.

Mallard ducks
Mallard ducks by Connor Mah (CC BY-SA 2.0)

In songbirds, males may be brightly colored while females have a similar plumage with more muted tones, as seen in Baltimore Orioles, American Robins, Eastern Towhees, and Black-throated Blue Warblers.

Eastern Towhee, female and male
Eastern Towhees: female (left) by Brian Henderson (CC BY-NC 2.0), male (right) by Dendroica cerulea (CC BY-NC-SA 2.0)

In other birds, like the Eclectus Parrot mentioned above, the plumage differences are extreme. Examples of this can also be seen in the Superb Fairywren of Australia, and the Sage Grouse.

Can you think of other bird species where the male is easily told apart from the female? Do you have birds like this where you live? What about birds that aren't sexually dimorphic? Can you think of species where male and females are impossible to tell apart by looking at them?

Birdorable Designs Featuring Sexual Dimorphism


Spurwing Plover on November 13, 2015 at 7:43 PM wrote:
With almost all birds the male is more colorful then the female most likely so they can easly idenifie each other during the mating season
Jay on December 28, 2015 at 8:40 PM wrote:
I had experienced from watching cardinals, the male being by far the brightest of gender, also came to observe the feeder grounds first before the female and young. They , at first seems to make sure it was a safe place for their family. They would hang around with the mate, bringing attraction to themselves first because of their spectacular bright red plummage, thus using this attraction to themselves other than their mate. It is quite possible they have greater attractive qualities than their female to keep predators away from the female, and towards themselves. "The males in my observation certainly act protective over their mates.
Heather Richards on November 13, 2016 at 4:02 PM wrote:
Oink oink oink. Shelbiloop. (I was writing with my eyes closed.)
Louise Warner on February 12, 2017 at 10:01 AM wrote:
i had a experienced american redstarts,the male would puff-up and show off his red breast.the female would hop around him.this side looks good.then he would show his wings off.its a great male too! then the female would let him preen her.then left to find a nest.first he took a little look around before the the female laid her eggs.the nest was good.but rock pigeons came but...payed no attention.but that was because they might eat the eggs! so the pigeons are gone but the male is too? he was hunting for food.IT WAS A PERFECT PAIR! cool right?

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