Biology
Facts About Cardinals
A male Cardinalis cardinalis at a February feeder looks finished. Brilliant, sealed, complete. He is not. He is mid-audition.
The female on the branch above him is evaluating the same carotenoid pigments she has been eating all autumn - dogwood berries, mulberry, wild grape. She absorbs them too. She knows what good diet looks like because she has lived on it. When she studies the red male, she is not admiring him. She is reading him. Cornell’s NestWatch programme confirms that feather brightness reliably signals territory quality and condition. The male cannot fake it. He cannot manufacture carotenoids. He borrows them from the food chain and routes them into his feathers during the annual late-summer moult, and by February the record is set.
The bird most people stop to photograph is, in the biological sense, the one being evaluated.
Quick reference
| Feature | Detail |
|---|---|
| Scientific name | Cardinalis cardinalis |
| Family | Cardinalidae |
| Length | 21-23 cm |
| Weight | 42-48 g |
| Wingspan | 25-31 cm |
| Wild lifespan | Typical three years; oldest banded female 15 years, 9 months (Pennsylvania) |
| Range | Eastern US, Midwest, desert Southwest, southeast Canada, Mexico, Central America |
| Migration | None - resident year-round |
| Conservation status | Least Concern (IUCN); estimated 130 million birds (Partners in Flight) |
| State bird of | Illinois, Indiana, Kentucky, North Carolina, Ohio, Virginia, West Virginia |
The female is the more interesting bird
Most cardinal accounts are profiles of the male. The female earns more attention than she receives.
Only a small number of female songbirds in North America sing at all. The female cardinal sings. She sings from the nest during incubation - not as a territorial display but as a signal to the male, telling him when to bring food and when to stay away so his conspicuous plumage does not draw predators to the nest. Cornell’s All About Birds notes that a mated pair shares song phrases but the female may sing a longer and slightly more complex song than the male. Research published in The Condor found that females sing roughly 0.5% as often as males and rarely sing alone. The song is functional and mostly private. She uses it to coordinate the whole operation.
During courtship, the male feeds her - bill to bill, with her wings quivering in the posture of a young bird begging for food. Audubon’s field guide records this behaviour, noting that the female may assume a begging posture to solicit feeding from the male throughout nest-building and incubation. The behaviour is a pair-bond test dressed as tenderness. A male with surplus territory can afford to feed his mate without shortfalling himself.
The nest is entirely her construction. She builds an open cup, typically 3-10 feet above ground in dense shrubs or vines - holly, hawthorn, privet - from twigs, grass, and strips of bark. The Audubon Society records the finished structure at roughly four inches across with an inner cup about three inches wide. She incubates alone for 12-13 days. Two or three broods follow, from March through September.
The female cardinal sings from inside her nest to direct her mate. She is one of the very few female North American songbirds that sings at all - and her song may be more complex than his.
Why the male is red
The colour is not arbitrary and not purely decorative. Cornell’s All About Birds states that male cardinals cannot synthesise carotenoid pigments themselves - they absorb them through diet, particularly from seeds, insects, and native fruit. The pigments are deposited into feather barbs during the prebasic moult each late summer. A male holding territory rich in native fruit - dogwood, sumac, wild grape - grows brighter feathers than a male on a depleted patch.
This is why yellow cardinals exist. Audubon reports a rare genetic mutation that disrupts the enzyme converting yellow dietary pigment to red, producing a yellow-orange bird structurally identical to his red neighbours. He is not albino. He has the same pigments, unprocessed.
The female is brown with warm reddish tints in the wings, crest, and tail. She has the same massive orange-pink bill, the same pronounced crest. She is built for the same food and the same cover. She is simply not the one being evaluated.
Range and the feeder effect
The Northern Cardinal began its northward spread in the early twentieth century. Audubon traces the expansion to warming winters, suburban development, and - the factor that most visibly accelerated it - bird feeders stocked with sunflower seeds through cold months. Cardinals are non-migratory, which makes them dependent on winter food supply. As feeders spread across New England and the upper Midwest, the range followed.
The species now reaches southeastern Canada. Partners in Flight estimates the global breeding population at 130 million. The North American Breeding Bird Survey records an increase of roughly 0.32% per year since 1966. The IUCN lists the species as Least Concern. This is a bird that expanded its range on the back of a human behaviour - filling a tube feeder in January - which is not the usual conservation story, and is worth knowing.
The American Ornithological Society recognises 19 subspecies, 14 of them distributed through Mexico and Central America. Research published by scientists at the American Museum of Natural History found that Sonoran Desert and Chihuahuan Desert populations - separated by only 120 miles - diverged approximately one million years ago and show enough vocal and physical differences that their status as separate species was formally proposed, though not yet adopted.
The breeding season in numbers
| Stage | Detail |
|---|---|
| Eggs per clutch | 2-5, whitish to pale bluish-green with brown and purple marks |
| Incubation | 12-13 days, by the female |
| Fledging | 9-11 days after hatching |
| Broods per year | Two to three |
| Breeding season | March through September |
The oldest recorded wild Northern Cardinal was a banded female found in Pennsylvania at 15 years and 9 months - well above the three-year average. That gap between typical lifespan and maximum lifespan is wide enough to suggest that most cardinals die young, not old. The pair bond, for most pairs, lasts as long as it does because three years is a long career for a small bird.
What the name actually means
The “Northern” was added by the American Ornithological Society in 1983, to distinguish this species from southern relatives. For most of its documented history in English, the bird was called simply the cardinal - named for the crimson robes and caps of Roman Catholic cardinals, as Audubon’s field guide records. The group noun for cardinals is a ‘college’ or ‘conclave,’ both borrowed from the same ecclesiastical Latin. A group of cardinals at a winter feeder is a college - which is not a bad name for birds whose plumage quality depends on what they studied all autumn.
The male who attacks his own reflection in a window for weeks during breeding season is not confused. He is responding correctly to the stimulus in front of him: a red-crested male who will not retreat. A sheet of paper taped to the outside of the glass removes the reflection and stops the behaviour. For more on the species as a whole and conservation status, follow the links below.
What the facts describe, taken together, is a bird where the visible partner is the least powerful one. The female reads his colour, builds the nest, incubates the eggs, and directs the season from inside a cup of twigs with her voice. He is brilliant, conspicuous, and being assessed. She chose the territory. She is running it.
