Backyard
Do cardinals use birdhouses?
No. And the way most people learn this is by buying a cardinal-themed nest box at a garden centre, hanging it on a tree, waiting an entire spring, and finding it as empty in August as it was in March.
The cardinal who occupies your garden has different ideas about what a nest is. He wants tangled cover. She wants thorns. They build a cup of bark and grass and lined with hair and that is the nest, sited where a chipmunk cannot reach it and a hawk cannot see it. A wooden box with a hole drilled through it does not enter the conversation.
The two kinds of bird nest
Cavity nesters use enclosed spaces - tree holes, woodpecker excavations, nest boxes. They evolved on the assumption that a defendable hole with one entrance is better than an exposed cup. About fifteen per cent of North American breeding birds nest this way. Bluebirds, chickadees, titmice, swallows, wood ducks, kestrels.
Open-cup nesters build a cup of woven plant material on a horizontal branch or in a fork. The cup is camouflaged by the surrounding vegetation. The bird relies on concealment, not enclosure. About eighty-five per cent of North American breeding birds nest this way, the cardinal among them. Robins, mockingbirds, finches, jays, orioles.
The difference is hardwired. A cavity nester will use any cavity of roughly the right dimensions, whether natural or human-made. An open-cup nester will not enter a cavity at all. It is not a preference. It is wiring.
Where a cardinal nest actually goes
| Feature | Detail |
|---|---|
| Height | 1 to 4 m, almost always under 3 m |
| Substrate | Dense shrub or vine tangle |
| Preferred plants | Holly, hawthorn, multiflora rose, blackberry, dogwood, honeysuckle, boxwood |
| Construction | 3 to 9 days, built almost entirely by the female |
| Materials | Twigs, bark strips, leaves, grass, lined with finer grass and animal hair |
| Reuse | Almost never. A new nest is built for each brood. |
The female does the building. The male brings materials. He may sing from a nearby perch but he does not place a single twig himself. The structure she produces is loose and slightly untidy - cardinal nests are notably less neatly woven than, say, an oriole’s pendant - but it is enormously well-camouflaged. The first cardinal nest most birders find is usually located by watching a female disappear repeatedly into the same patch of holly.
What you can offer instead
Two things, in order of usefulness.
1. Plant a hedge. This is the single highest-impact thing a homeowner can do for nesting cardinals. A run of dense shrubs along a property line gives you nesting habitat for cardinals, plus probably catbirds, mockingbirds and song sparrows. Choose for thorns and density:
- Holly (any of Ilex opaca, I. glabra, I. verticillata).
- Hawthorn (Crataegus species).
- Native viburnums.
- Dogwood.
- Multiflora rose if your county does not list it as invasive.
- Climbing honeysuckle on a trellis or fence.
- Boxwood for evergreen density.
The hedge does not have to be perfect. A four-metre stretch of mixed dense shrub against a fence will support a breeding pair.
2. Mount a nesting shelf. Not a box. A platform with a roof and an open front, mounted against a wall, fence or tree trunk, 1 to 3 metres up, placed where it is partially screened by vegetation. Cardinals will occasionally use these, especially in a yard with insufficient natural shrub cover. The shelf is a poor substitute for a real hedge but it is the best supplemental structure you can offer.
What does not work, regardless of how it is marketed at the garden centre:
- An enclosed box with a 5 cm entry hole. The cardinal will not enter.
- A box with a removable front. Still a cavity.
- A “cardinal house” with a wide opening but enclosed sides. The bird still reads it as a trap.
- A roosting pocket. These are for winter cover, not nesting.
A note on the cavity-nesting birds that will use your box
If you buy a nest box and the cardinal does not use it, you have not wasted your money. The box may attract Eastern Bluebirds (3.8 cm hole), House Wrens (2.8 cm hole), Tree Swallows (3.8 cm hole), or Carolina Chickadees (2.9 cm hole). The hole size matters - it is what excludes invasive House Sparrows from sites you have made for native species.
The cardinal will not be among them. He will be in the holly.
