why are cardinals so red? — continued

The proximate (immediate) answer to the question of why cardinals are red is that they have a diet rich in carotenoid pigments (e.g., the pigment that makes carrots orange), and will incorporate those pigments into their feathers as they develop each year during feather molt.  To read more about this process, click here to read an article from Bird Watching Daily that explains where feather colors come from.

northern cardinal

Resident Cardinal male posing on a garden stake in the backyard.  He’s bright and he’s loud, and he makes sure his mate and all the other would-be holders of his territory know it.

But I’m interested in the evolutionary basis for why cardinals stand out among other species residing year-round in northern climates in retaining their bright red coloration instead of molting to more muted shades during the non-breeding season, like, for example American Goldfinches do.   Cardinals undergo a post-breeding feather molt, just like other species, so why risk attracting predators with bright red, when you might escape notice with a dull brown plumage instead?

summer vs winter American Goldfinch plumage

Summer (top) vs winter (bottom) American Goldfinch plumage

Does sexual selection (that is, female choice for the most beautiful male, as Richard Prum argues) play a role?  Please see the yesterday’s Back Yard Biology post for more information about the importance of beauty in female choice.)

Some additional facts regarding male-female relationships in Cardinals and their close relatives, the Pyrrhuloxias of the southwestern U.S., might help to answer the question.

Cardinal vs Pyrrhuloxia--DFW Urban Wildlife

A comparison of two closely related Cardinal species, the Pyrrhuloxia, Cardinalis sinuatus (1 and 2) and the Northern Cardinal, Cardinalis cardinalis (3 and 4). Illustration in Chris Jackson’s DFW Urban Wildlife blog.

The first thing you notice from the illustration above is that the Pyrrhuloxia male and female look more alike than Northern Cardinal male and his mate do.  Why might that difference have arisen in such closely related species? And does it have anything to do with female choice for brightly colored, beautiful males?

The second and interesting difference between the two species is that Pyrrhuloxia share a pair bond only during the breeding season, breaking up in the non-breeding season into loose, often mixed-species flocks of seed-eating birds that move around to find food in their dry, desert habitat.  Each year, males vie for available females by staking out and advertising their territories, often very aggressively.  In contrast, Northern Cardinals may maintain their pair bond year-round, often for multiple years, unless one of the pair dies, and the pair stays in the same general area in which they nested, year-round.

cardinal courtship feeding-rudiger merz

A year-round pair bond exists in Northern Cardinal mates, which renews its strength in the spring with courtship feeding.  (Photo by Rudiger Merz)

Female Cardinals are making a choice of more than just a breeding partner; they may be choosing a life partner and his residence (territory).  Richard Prum might argue: what’s a male to do, but be the most beautiful thing she has ever seen?  And if he is better looking than his neighbors, she stays with him through that year and the next.  They raise multiple broods of young Cardinals together, and he passes on his good looks to the next generations.

This is an amazing high definition video of male and female Cardinals feeding their chicks (by FrontYardVideo).

In other words, it’s possible that their long-term pair bond and high fidelity to a territory year-round makes it possible for choosy female Cardinals to drive the accentuation of  beauty (in this case, “redness”) in their male partners, to the extreme that male Cardinals never lose their red color during the year.

how to eat a juniper berry

The fall harvest season is on:  it’s time to pick pumpkins and apples, the last of the field corn and soybeans; and if you’re a bird and you like fruit, it’s time to feast on the berries of the eastern red cedar, commonly known as juniper.  Actually to be entirely correct, these “berries” are actually just fleshy cones that surround a few seeds within.  They are covered with a waxy coating, which is also digestible if a bird has the right pancreatic enzymes to break it down.

Yellow-rumped Warbler eating juniper berries

Yellow-rumped Warblers love these juicy “berries”, gobbling them up whole.

Yellow-rumped Warbler eating juniper berries-3

Sometimes this large round nugget is a little hard to choke down, though, and the bird continually adjust the berry’s position in its mouth before swallowing.

Yellow-rumped Warbler eating juniper berries-5

Dark blue ones are the ripest, green ones the least ripe, and the birds seem to be quite choosy about which ones they take.  There are so many berries within reach, but this bird needs to stretch upside down to get the perfect one.

Robins eating juniper berries-4

Robins joined the feast, with three or four birds all foraging within a few feet of each other.

Robins eating juniper berries-2

Being a much larger bird than the warbler, the robins had no trouble downing the berries, one after the other.

Robins eating juniper berries-6

Robins toss their heads back as they swallow, and occasionally lose the berry in the process.

Catbird and juniper berries

A couple of catbirds got into the action as well, but they preferred to consume their berries in private, away from the camera lens.

Juniper berries are the only fruit/spice from conifers we use in cooking, and of course they give gin its characteristic flavor.  Beneath the waxy coating, green pulpy flesh surrounds a few seeds.  Fruit-eating birds normally quickly separate the pulp from the seeds in their gut, digesting the sugary pulp and converting it to fat stores rather quickly.  They then excrete the seeds as they fly off to other foraging areas, thus helping the plant spread into new locations.

But seed-eating birds might have a different strategy…

Female cardinal eating juniper berries-3

This female cardinal was systematically picking off berries and crushing them between her mandibles, squeezing the pulp and then discarding it.

Female cardinal eating juniper berries-5

It’s hard to tell whether she discards the pulp to get at the seeds, or discards the whole mass after squishing out berry juices.  

Seed-eating specialists probably have stronger gizzard muscles  that can crush the seeds to extract their nutrients, and seeds typically have higher fat and protein content than the sugary, pulpy mass that surrounds them.

Whatever the strategy, juniper berries provide a useful resource for migratory as well as non-migratory birds in the fall.

Cardinals mixing it up

In many cases close (geographic) encounters between two different, but closely related, species results in accentuation of their differences — in song, or behavior, or even their distinctive markings.  It’s possible that a female’s choice of mates plays an important part in driving what can often be subtle changes between the two species.  However, in southeastern Arizona, Northern Cardinals (Cardinalis cardinalis) and Pyrrhyloxia, or desert cardinals (Cardinalis sinuatus), are playing a little fast and loose, and it looks like they might be sharing more than habitat.

Before I get to the evidence, let’s review the players in this story.

(1) Northern Cardinals have been expanding their range from eastern North America northward toward Canada as well as southward into the deserts of the southwestern U.S. and Mexico.  Although they tend to stick to the wetter habitats in riparian areas, they often forage and even nest in drier desert habitat, especially where people have been feeding birds, providing lots of seed and bird baths.

male Northern Cardinal-

Most everyone easily recognizes this emblematic, cheery red bird, with its black mask, bright red feathers, and wide, straight, orangey-red bill.  Newly molted male Cardinals have grayer feathers on their back, but the tips of those feathers wear off during the winter, making spring Cardinals bright red all over.

(2) Pyrrhuloxia are less well known, occurring only in the extreme southern parts of Arizona, New Mexico and parts of Texas, as well as most of Mexico.  They prefer the desert scrub and mesquite habitat, foraging for seeds and insects on the desert floor, but will also visit the lusher gardens with bird feeders and bird baths where they no doubt meet up with their close relative, the Northern Cardinal.

male Pyrrhuloxia-

At first glance they look completely different from their cousins, with mostly gray plumage, mottled with red in the face and breast in the male only, a much bigger crest of head feathers which they keep erect unlike the Cardinals, and a yellow-orange beak with a distinctive bend in it.

Cardinal and Pyrrhuloxia -angelamccain.smugmug.com

Pyrrhuloxia and Northern Cardinal males looks distinctly different (photo by Angela McCain, smugmug.com, from Edinburgh, Texas)

female cardinal vs pyrrhuloxia-birdswesee.com

Female Cardinals are a bit browner and the Pyrrhuloxia are grayer overall, but there are distinct differences in beak shape and coloration between the two species.

At the Sonoran Desert Museum in Tucson, a captive adult Cardinal mated with a captive adult Pyrrhuloxia, and hybrid offspring of this original pair now populate the aviary and freely interbreed with one another.  The hybrids share characteristics of both species, with intermediate plumage (grayer than Cardinals, redder than Pyrrhuloxia) and slightly curved beaks.

Cardinal-Pyrrhuloxia hybrid-Sonoran Desert Museum

A Cardinal-Pyrrhuloxia hybrid at the Sonoran Desert Museum has grayer plumage on its back and a slightly decurved upper beak.

The ability to produce viable, reproductively capable offspring means that these two supposedly distinct species, really aren’t different at all!  Differences in their habitat preferences and their former separate geographical distributions probably kept the two “species” isolated from one another.

But an aviary is an unnatural situation, in which partnering mistakes might be inevitable. More important is whether interbreeding in these two closely species has actually been observed in the wild?  Perhaps. Hybrid “Cardhuloxia” have been reported from Baja California, Mexico, and I’m wondering whether there has been some gene sharing going on in southeastern Arizona as well.

Male Northern Cardinal -Portal AZ

This male possible Cardhuloxia hybrid seen in Portal, Arizona, has an unusually long red crest, a much grayer than usual plumage on its back, and a distinctly un-Cardinal-ish song.

How to land (gracefully) on a stump

Taking a rapid series (10 frames per second) of high-shutter speed (1/5000 sec) images of flying birds allows one to see just how birds manage some of their aerial dynamics, like how to land gracefully on a small spot.  The test for the birds was to flap-glide-brake from bushes about 25 feet away to land precisely on the edge of a stump feeder filled with delicious suet.


Wings and legs fully outstretched, the Green Jay makes a perfect landing.

What amazed me was that all five species we observed used the same technique:  flap, fold wings in horizontal posture, making them look like a speeding bullet, then brake by spreading wings wide with huge gaps between the flared primary feathers and switching to a vertical posture with outstretched feet.  This is the type of flight used by many small to medium-sized songbirds, often viewed as roller coaster, or bounding flight.

Flap-glide pattern of bounding flight in small birds

Flap-glide pattern of bounding flight in small birds (Cornell Lab).

Bounding flight like this accomplishes at least two important things:  first, it saves energy, 15-20% over the cost of continuous flapping because of the reduced drag during the glide (closed wing) phase; second, it lowers the cost of flying more slowly between closely spaced perches.

Orange-crowned Warbler bounding flight

Orange-crowned Warbler bounding flight with wings closed prior to full braking mode of outstretched wings and feet.

Female Hooded Oriole bounding flight

Female Hooded Oriole bounding flight. The bird might have changed its mind a little too late to make a totally graceful landing — it was still in bullet shape quite close to the stump.

Green Jay bounding flight

The Green Jays were masters of this technique, transforming from bullet shape to full braking mode in milliseconds.

Male Cardinal bounding flight

Streamlined like a torpedo, then suddenly, full flare of the wings, tail, and feet for stopping short.

Golden-fronted Woodpecker flight

I didn’t catch the glide phase of the Golden-fronted Woodpecker as it made its approach. A full flap, then glide, then landing was this male’s approach like all the other species.

Not every approach to the stump was completely graceful, but birds are such adroit athletes, even being slightly off-balance on approach can be immediately corrected.


Can you just imagine the alarms going off in the bird’s brain as it makes sudden changes in its approach for landing?


Birds in flight

I’m currently in Alamo, Texas attending a bird photography workshop run by Alan Murphy, and learning how to set up for taking photos of small birds in flight. Today’s challenge — learn how to pre-focus the camera in the place you expect the birds to be. Sometimes it worked, but most of the time, I captured an empty perch.

Great Kiskadee vs Red-winged Blackbird

Great Kiskadee vs Red-winged Blackbird

Green Jays

Green Jays

Golden-fronted Woodpecker vs Cardinal

Golden-fronted Woodpecker vs Cardinal

Golden-fronted Woodpecker

Golden-fronted Woodpecker vs Blackbird

A pair of cardinals

Not a mated pair of Northern Cardinals, as the title might imply, but a pair of closely related cardinal cousins — the Northern Cardinal and the Pyrrhuloxia or Silver Cardinal.

Northern Cardinal

I really didn’t expect to see cardinals in the Sonoran desert, but Ventana Canyon outside of Tucson has a rushing stream that runs all year (as well as an 80 foot waterfall), so there is an amply supply of lush vegetation and insects to keep any bird happy.


Hidden in a thorny mesquite bush, this male Pyrrhuloxia sports a long, red crest, and has a red face and breast stripe in contrast to his metallic gray body.

Pyrrhuloxia look like their closely related (same genus) cousins, but have a much bigger, parrot-like beak.  They are truly well-adapted desert birds, able to eat a wide variety of seeds and fruits, as well as insects, and tolerate the extreme heat of the Sonoran desert summers well.  Their summer diet of insects even enables them to remain somewhat independent of water, as they rarely visit waterholes then.

Pyrrhuloxia may mate for life, and though territorial and asocial during the breeding season, they join up in huge flocks of 1000 birds during the winter.  What a sight that must be!!

the good provider

It’s springtime, and romance is in the air — males showing off their physical prowess and gaudy colors, females watchful and discerning.  One of the rituals of springtime courtship among some bird species involves the male bringing some delectable, nutritious food to his female.

courtship feeding-lilac-breasted roller

The male Lilac-breasted Roller (on the right) presents his female with a small insect. (Photo shot in Botswana in October 2015)

northern shrike-courtship food

Northern Shrikes impale their prey on a sharp object like thorns or barbed-wire fences. This male shrike is leaving his gift of a fresh vole for his intended mate.  (Photo by Marek Szczepanek)

Why do some male birds do this?  Is it to show what good providers they will be for their offspring?  Is it to further cement the bond between male and female, like human males might gift their sweeties with jewelry, roses, or candy?  Or is it really an important part of their pre-nesting behavior, to increase the food/energy intake of females that will shortly undertake big expenditures of energy laying eggs and incubating them for long periods of time.  Courtship feeding might be important for all of these reasons, but most likely it has evolved in those species for which the energy demands of reproduction are particularly high in the female.

northern cardinal-

Northern Cardinal males keep a close eye on their females, and offer them tidbits of sunflower seeds, even though the female is sitting right there next to or on the feeder.

northern cardinal female-

He’s looking at her (above), and she’s looking at him, wondering what he will bring her next.

I missed the actual feeding because the pair darted behind the leaves, but it looks like this.


Photo by Rudiger Merz

northern cardinal-

Females have the luxury of choice, so this male has to not only be good-looking but savvy at providing food.

Blending in… or not

In the winter, everything seems to take on shades of gray and brown, even the several day’s old crusty snow.  When I looked out in the backyard early one morning recently, I saw a few members of the local deer herd wandering down the hill toward the pond, but didn’t think there was much of photographic interest there.  So I just snapped a quick couple of images.  When I finally got around to looking at those photos, I found the deer match their gray-brown background so well, I didn’t even see the large buck having a morning rest in the snow.

white-tailed buck resting

It’s easy to miss even large-bodied animals, like the buck in the left background, when they aren’t moving around.  When the light is dim in the early morning, and the world is gray-brown, whte-tailed deer blend in nicely with their surroundings.

white-tailed buck resting

A little photo “massage” makes the buck stand out a little better.

Most of the gaudy male birds wear their less conspicuous plumage in the winter — to better blend in and avoid being someone’s lunch.  But there’s always an exception to that general rule:

male Northern cardinal - wnter-

Mr. Cardinal doesn’t stay in one place long, and he is obviously the brightest thing visible in this monochromatic (almost) background.  He visits the feeder right at dawn and again at dusk, and stays tucked into dense vegetation during the rest of the day.

female cardinal - wnter

Mrs. Cardinal is less colorful, but she too only visits the feeders at dawn and dusk, when there is barely enough light for me to see which birds are there.

Dinner for two

The temperature in the backyard yesterday rose to a balmy 20 F, and suddenly birds were zooming around the feeders, making up for lost time feasting on peanuts and sunflower seeds.  Birds I hadn’t seen all winter showed up (subject of another post — sorry), but the light was absolutely terrible and capturing any decent photographs was tough.

a pair of northern cardinals

And this pretty awful image is what I wound up with after trying to lighten and enhance the color in Photoshop!  Previously the birds were just black blobs.

But I liked the composition of the photo with the pair of cardinals dining together and posed so symmetrically on the feeder.  So what do you do when the skies are a gloomy gray, the subject is backlit on a white snowy background, and even Photoshop can’t improve the color and contrast?  Play with the Photoshop enhancement tools, and have some fun with the lousy lighting.

northern cardinals at the feeder-arty

And this is one of the ways to do it — I might use it for a greeting card, for example.

Not hiding in plain sight

Brightly colored animals seem to flaunt the potential danger of being someone else’s dinner.  Calling attention to themselves with bright colors and flashy appendages seems counter-intuitive to survival.  So why do it?

It’s all about the advertising.  Bright color can be a warning to other animals.  Don’t eat me:  I’ll make you sick, my bite is lethal, I have a wicked sting.  You’ve undoubtedly seen these types of warnings in your garden.

monarchs on blazing star-k_eckman

Monarch butterfly orange and black warning coloration stands out on any background, but especially well on the purple blazing star. Photo by Karen Eckman

Some animals copy these bold aposomatic patterns, hoping to mimic the warning signal closely enough to avoid predation themselves.  Many insects copy the yellow and black warning coloration of bumblebees, hoping to fool a potential predator.

things that sting

The things that sting have bright yellow and black coloration; some have fuzzy hair and some don’t — even that pattern is copied.

things that don't sting

The mimics might even try to act like their models — hovering in front of flowers (hoverflies) or between perch sites (robberfly)

Some brightly colored fish purposely flaunt their colors to signal that they have a service to offer to others.


A brightly colored bluestreak cleaner wrasse hovers near the much larger and cryptically colored puffer fish to pick off parasites and extraneous food bits as a cleaning service.  Bright colors advertise the service at this “cleaning station”.  Photo from Wikipedia.

Bright colors in birds, especially the brightly colored plumes or other adornments projecting from their bodies, are a different kind of advertising.  By calling attention to themselves, colorful male birds are advertising their potential as a parent, or even just a sperm donor.  It’s as if they are saying to females, “I can survive in spite of attracting the attention of predators, or in spite of all these silly plumes that compromise by ability to escape, so choose me”.

Peacock_Flying-Wikipedia copy

A male peacock’s size may deter some predators, but all a predator has to do is grab hold of that long tail, and the advertisement becomes a liability.  Typically, the peahen raises the chicks, so all this male is advertising is his vigor (and sperm) as a potential mate.


Male Cardinals advertise more than just their vigor and ability to escape predation.

Bright colors mean the bird is in good health, and are an indication that these birds know where to find the food that makes them healthy, as well as brightly colored.  A female cardinal might choose one male over another for his ability to feed their chicks the right kind of food which, in turn, enhances their survival.  The female’s choosiness thus drives the male color pattern and feather adornments — sometimes to ridiculous or risky levels.  But if a flashy male survives the risks, then he’s the one.