Why Do Male and Female Animals Sometimes Look Different?

by Trudyann Buckley

Good morning, nature lovers, and Happy Almost-Valentine’s Day! While you’re outside this weekend, make sure to look for our favorite Valentine-colored bird: the Cardinal!

The Male looks like this:

A Male Cardinal

Photograph by Joe Sebastiani.

 

And the Female looks like this:

A female Northern Cardinal. Photograph by Joe Sebastiani.

Photograph by Joe Sebastiani.

 

When a male and female of the same species look different, that species is called dimorphic (Pronounced dye-morf-ik). You may have known this was true of Cardinals, but do you know why?

There are lots of reasons for dimorphism, but it all comes down to attracting that special someone to build a nest together. Scientists think that a male cardinal’s redness has to do with how much nutrition he gets. So, he is advertising to the female that he is healthy, and knows where good food is to provide for babies.

Mallard ducks are also dimorphic. The more of a certain type of vitamin the male duck eats, the more orange their beak becomes! Female mallards are attracted to males with nice orange beaks.

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A male Mallard Duck. Photograph by Joe Sebastiani.

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A female Mallard Duck. Photograph by Joe Sebastiani.

 

Of course sometimes color has nothing to do with health and a female just chooses the male she thinks is the prettiest.

When a species is dimorphic, it really all depends on which gender is competing for the attention of the other. Lots of males often compete for the attention of one female, and the female chooses the male she’s most impressed by. If female cardinals are always choosing the reddest male cardinals, then their male babies will inherit that redness. Thus, very bright red males are born in a few generations!

Meanwhile the female cardinal doesn’t get anything out of being red. She’s not competing for a male’s attention; she’s choosing. Her coloration helps her camouflage with her surroundings instead. This is especially useful when they have to tend to a nest without predators finding them.

But why aren’t the females colorful too?

Sometimes the females are more colorful, like the Belted Kingfisher. Sometimes females and males are colored identically, like Blue Jays and Tufted Titmice. It all depends on the birds’ evolution, and how they interact with each other and their environment.

Blue Jay Bucktoe Creek Preserve

A Blue Jay. Photograph by Joe Sebastiani.

Tufted Titmouse 2 2.11.2010

A Tufted Titmouse. Photograph by Joe Sebastiani.

Is dimorphism only about color differences? Nope! Males and females might be the same color, but different sizes or shapes! Remember Blue Jays? Females of that species tend to be smaller than males.

At Coverdale Farm preserve, our roosters are bigger than females. Compared to hens, roosters generally have bigger combs on their heads and wattles under their chins. That’s another way to attract females, but it also helps keep the bird cool in the heat of summer: that’s two purposes in one!

Do you want a chance this weekend to see some of these birds in real life? On February 13th, 2016 from 10am to 11:30pm, Ashland Nature Center invites families of all ages to Feed The Birds! Come hike to our bird feeders and birdwatch, as well as peak through our new bird blind. You’ll even make a bird feeder of your own so you can see these birds outside your own window. Try to spy some species you’ve never seen before, too! Register HERE, or call (302) 239-2334 to register over the phone.

If your family would like to see our chickens, cows and other farm animals, Coverdale Farm Preserve will show you around in Farm Valentines, where you’ll deliver a Valentine’s gift to fuzzy and feathered friends, and then make a valentines treat for someone you care about! This program will run on Valentine’s Day: February 14th, 2016, 1pm to 3pm. Register HERE, or call (302) 239-2334 to register over the phone.

And don’t forget, this weekend is the nationwide citizen science program: the Great Backyard Bird Count! Find out how to participate HERE.

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