Are Cardinals Territorial? Aggression, Windows and Mirrors

If a cardinal is attacking your window or car mirror right now, skip to "How to stop a cardinal attacking your window or car mirror" below. For the species as a whole, see the Northern Cardinal guide.

Yes. In the breeding season a pair defends a territory of about 0.5 to 6.4 acres (0.21 to 2.6 ha), with average territories of 0.93 to 1.5 ha in different studies. Active defense of the boundaries stops in late summer or early fall and starts again between January and March. Some pairs, for example in Mississippi, defend their territory all year.¹

The boundaries stay much the same from year to year, even when new birds take over some of the territories.

Mostly with song. Males sing back and forth with their neighbors, matching each other's songs, and switch songs faster as they get closer. A cardinal threatening a rival lowers its crest and gives harsh chuck calls; at higher intensity it crouches forward with its bill open and wings quivering before it lunges. Chases between rivals can go on for 10 to 30 minutes, but real fights, grappling with the feet and pecking, are rare and last only a few seconds.

Yes. Females chase other females off the territory, sometimes singing as they do it, and guard the nest against other cardinals. In one Ohio population, females with larger, darker masks were the more aggressive. More: female cardinals.

It sees its reflection as a rival cardinal on its territory and tries to drive it away. Both males and females do it, most often in spring and early summer, and a bird may keep at it for hours. It does not learn that the rival is not real.²

Most cases stop after a few weeks as the birds' hormone levels fall, though one female kept it up every day or so for six months.³ It is usually harmless to the bird, though a few deaths after attacking reflections have been reported.¹

Get rid of the reflection, from the outside of the glass. Audubon suggests:

• cover the outside of the window with a sheet, a blanket or cardboard;
• an exterior screen;
• soap rubbed on the glass;
• bird-collision decals;
• a Mylar balloon tethered outside;
• for a car, folding the mirrors in or covering them with paper bags (not plastic).

Fighting a reflection is different from flying into a window, which can kill.

In winter males push females and young birds aside at feeders, and adults dominate juveniles. Males become more tolerant of their mates as spring approaches. Cardinals also drive House Sparrows and other sparrows away from feeders.

Cardinals also watch who is already at a feeder. In one study, males avoided feeders with another male on them but approached those with a female, while females avoided both, whatever seed the feeder held.⁴

Attacks on people are rare, if they happen at all: Birds of the World describes none. Near the nest they give sharp chip calls and fly at predators such as snakes and jays, and in towns they let people come closer than country cardinals do.

Fights between cardinals are rare and last a few seconds; most disputes are settled by song, displays and chases.

1. Halkin, S. L., Shustack, D. P., DeVries, M. S., Jawor, J. M., Linville, S. U. (2021). Northern Cardinal (Cardinalis cardinalis), version 2.0. Birds of the World (P. G. Rodewald and B. K. Keeney, editors). Cornell Lab of Ornithology. doi:10.2173/bow.norcar.02
2. McGlashen, A. (2026). Why Birds Attack Windows and Mirrors, and How You Can Stop Them. Audubon magazine. Accessed 6 October 2026. Source
3. Cornell Lab of Ornithology. Northern Cardinal: Overview and Identification. All About Birds. Accessed 6 October 2026. Source
4. Millican, D. M., McGovern, P. G., Stanback, M. T. (2012). Effects of conspecifics on feeder choice by Northern Cardinals. The Wilson Journal of Ornithology 124(4): 808-811. doi:10.1676/1559-4491-124.4.808
5. Kaufman, K.. Northern Cardinal. Audubon Guide to North American Birds (text adapted from Lives of North American Birds, 1996). Accessed 6 October 2026. Source