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Male and female cardinals get their gorgeous red feathers from the berries, nuts and seeds they eat. A female might assume that a redder male makes a better partner.

Don Severson • Special to the Star Tribune,

Northern cardinals are at their noisiest in spring

  • Article by: VAL CUNNINGHAM
  • Contributing Writer
  • May 14, 2013 - 3:26 PM

They’d be hard to miss, those brilliant red birds on the tops of the trees, singing a song that sounds like spring. Northern cardinals are a treat to see any time of the year, standing out against the snow in winter, but so welcome in early spring, when few other birds are making music.

As breeding season rolls around, male and female cardinals are singing to each other to build their pair bond and prepare themselves to mate and raise their brood. Most female songbirds don’t sing, so this countersinging between the sexes sets cardinals apart. When males sing alone, they’re announcing they’ve staked out a territory and warning other cardinals to stay away.

If songs aren’t enough, males will even fight to drive off a competitor. Two or three males will whip through the back yard, almost beak to tail. They fly heedlessly, weaving between tree branches and through traffic, at times grappling in the air. Males may battle so fiercely that they lock feet and peck and bite at each other as they tumble to the ground.

Cardinals fight to hold a good nesting territory, determined by the quality of the habitat — how much cover it offers in terms of trees and shrubs, and how much promise it holds for providing insects for nestlings. Where food is abundant, a cardinal family can survive in a smaller territory, but if it’s scarce, a larger territory is needed to sustain a brood. For this reason, a cardinal territory may vary in size from two to 10 acres (a football field covers about one acre).

No Perry Comos

Cardinals are a much-studied bird and there are some fascinating new findings. You might think that older, more mature birds would sing the most complex songs, but that doesn’t hold true. Cardinals with less complex and shorter songs turn out to hold better-quality territories and their nests turn out more young cardinals than those who put more into singing. Researchers found that as cardinals mature they put less time and effort into singing and more into caring for and defending their young.

Why are male cardinals so standout red? If we can see a red bird, predators can, too (last winter I saw a Cooper’s hawk easily snatch a male cardinal out of a shrub tangle). The usual explanation is that there is a cost to being so obvious (predation) but also a benefit: Female cardinals may choose the brightest males as mates, interpreting color as a sign of how successful a bird is at finding food. So the inference is that benefits outweigh costs.

(But then, another study found no preference among females for bright males and concluded that they might be more impressed by the quality of the territory a bird holds.)

Fooling females

Since a cardinal’s feather color comes from the foods it eats, brighter birds probably are in better shape for breeding. Females seem to favor the reddest birds, but are they being fooled? Alien plant species might be throwing a wrench into the works.

Urban gardens are becoming full of exotic honeysuckle, which spreads when birds expel the seeds. Cardinals snap up honeysuckle berries, which are rich in feather-dying pigments. But this fruit isn’t very nutritious, so city cardinals can be bright but not in peak shape. A further complication: Cardinals that eat seeds at bird feeders are getting a better diet but less pigment. These males’ feathers may be duller, but the birds are healthier.

So a female might pick a mate who’s bright but not a standout forager. We’re complicating cardinals’ breeding season, but it’s too soon to tell what the impact might be.

Still, with windows open and the clamor of spring rushing in, it’s hard to miss the commotion caused by one of our most beloved back-yard birds, as males and females settle down for nesting season.

St. Paul resident Val Cunningham, who leads bird hikes for the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at val​writes@comcast.net.

Double trouble

If a cardinal discovers its image reflected in a window, car mirror or even a shiny bumper, it might think it’s seeing a rival for its territory. The bird may spend hours trying to drive off this “intruder,” banging into the reflective surface over and over again. If it keeps it up it could damage its beak. Please cover the window area a bird is bashing with a piece of cardboard (on the outside of the window) and place a towel over the car mirror when the car is not in use.

Favorite foods

Cardinals are big fans of seeds and fruits, and insects, especially in nesting season. They enjoy the fruits of serviceberry, dogwood, arrowwood virburnum and red cedar. At platform and hopper feeders they’ll snap up sunflower and safflower seeds and cracked corn. They’re naturally ground feeders so you might find them under feeders as often as on top.

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