Like any avid birder, spotting brightly coloured wildlife is high on my list of goals when venturing into the wilderness. One species that offers particularly colourful plumage is the Red Northern Cardinal – but why are they so brightly colored? 

The males are among the most recognizable birds in North America, with their brilliant scarlet feathers standing out against green trees, brown branches, and even winter snow.

The remarkable red plumage of a male Northern Cardinal is closely connected to what it eats, how its feathers develop, and how cardinals choose mates.

So, if you’ve ever wondered why the Red Cardinal looks the way it does – or you’re looking to attract them to your garden – then you’ve come to the right place. 

Image Credit: Jay Brand

A cardinal’s red feathers start with its food

The secret behind that unmistakable red color is found in a group of natural pigments called carotenoids.

Carotenoids are pigments found in many plants, fruits, and other foods. Birds can obtain these pigments through their diet and, in some species, use them to produce the bright colors seen in their feathers.

Northern Cardinals are particularly dependent on carotenoid-rich foods for their red plumage.

According to the Cornell Lab of Ornithology, the species’ diet includes seeds, grains, fruits, and insects, with berries and other plant foods providing important sources of carotenoids.

But it’s more than just eating certain foods that makes the Red Cardinal so bright – it’s how the species processes carotenoids. 

The bird processes the pigments it consumes and deposits carotenoid-derived pigments into growing feathers. This is one of the reasons the quality and availability of food can influence how intensely colored a male cardinal appears.

In other words, that brilliant red coat is partly a reflection of what the bird has been able to eat.

Why are male cardinals so much brighter than females?

This is where things get particularly interesting – male Northern Cardinals are famous for their bright red plumage, while females are mostly warm brown with reddish highlights.

That dramatic difference is known as sexual dimorphism – when males and females of the same species have noticeably different physical characteristics. And as you probably guessed, the reason has a lot to do with attracting a mate.

Image Credit: Nicki Dick

Bright plumage can act as a signal of a male’s condition, and research has found that carotenoid-based coloration in male Northern Cardinals is associated with social and reproductive behavior.

The basic idea is surprisingly simple: producing and maintaining vivid coloration can require access to the right foods and the ability to process those pigments.

That means a particularly vibrant male may be advertising more than just his appearance. 

Cardinals don’t all look exactly the same

Look closely at a group of male cardinals and you may notice something interesting. Not every male is exactly the same shade of red.

Some appear intensely scarlet, while others can look slightly duller or more orange-red. There are several reasons for this variation, including age, feather wear, diet, and the way pigments are deposited during feather growth. Take young males, for example; they don’t immediately develop the spectacular red appearance associated with adult birds, as they haven’t fully developed yet. Instead, they gradually acquire adult plumage as they mature.

This is another reason that the color of a cardinal isn’t simply a fixed genetic “paint job.” The bird’s appearance is influenced by a combination of genetics, physiology, and environment.

So why did cardinals evolve such bright feathers?

The answer isn’t completely straightforward, but like many other bird species, it comes down to sexual selection through thousands of years of evolution. 

For many bird species, females can be selective about mates, and males have evolved elaborate colors, songs, displays, and other characteristics that help attract them.

The male’s vivid red plumage is part of his overall courtship display, alongside his distinctive song and other behaviors. I’m sure you all remember the amazing Birds of Paradise videos, which show similar characteristics.

There’s also an interesting twist, though: cardinals are highly territorial.

A male’s bright coloration isn’t only seen by potential mates. It is also highly visible to other males, meaning that his plumage can play a role in social interactions and territorial competition. That makes the cardinal’s red feathers something of an all-purpose signal.

Why we Recognize Red Cardinals so Well

There’s another reason cardinals are such a favorite among backyard birdwatchers: their coloration is particularly conspicuous. A bright red male against a snowy winter landscape is almost impossible to miss – and one that certainly improves your morning cup of coffee. 

And because Northern Cardinals don’t migrate long distances in the way many other North American songbirds do, they can remain in the same general area throughout the year.

That means the cardinal visiting your feeder in January could be the same individual you saw in your backyard months earlier.

Their year-round presence, distinctive crest, bright red plumage, and familiar song have made them one of the most recognizable backyard birds in North America.

Overall, the Red Cardinal is a stunning bird that is welcome in millions of homes across North America. Keep in mind the notes above, and you may be able to spot intricate differences between Red Cardinals next time you’re out and about.