Northern cardinals, often called redbirds, are among our best known and loved resident birds and are usually the first species European friends want to see when they visit, for there is no really red bird in Europe. The bright red males and their more somber brown mates make themselves well known by singing loudly and fighting windows or anything else that reflects their image. Moreover, cardinals come readily to bird feeders and are invariably the first and last birds to do so, especially at dark in winter when the demand for food is high and daylight is limited.
Can that be why eastern screech owls catch them so often? Cardinals are third among birds on the owl's local shopping list. More males than females are caught, although I find both sexes feeding equally early and late. I think it's because of the boldness and dominance of male cardinals, who displace shyer females at feeders. I can readily retrap banded males but not females, who seem to learn caution more quickly. Regardless of species or sex, however, it is the inexperienced fledglings that screech owls catch most often in the nesting season, and afterward they catch more of the domineering males.
The male cardinal's red plumage is no factor, because red is the weakest wavelength of visible light and is rapidly filtered out, especially at night when the eyes of diurnal animals become more sensitive to blue. Furthermore, red isn't seen by nocturnal, mostly color-blind predators. In trying to figure out why rufous screech owls predominate at mid-latitudes in North America, I discovered that those areas have the most humidity and cloudy weather. Water vapor in the air readily scatters weak red light and, together with overcast conditions, tends to hide reddish organisms.
Of course, male cardinals don't suffer excessive predation, or we wouldn't have cardinals. I banded one that lived eleven years, another one lived eight. Those that survive their first winter average three more, although I did find a small difference in longevity favoring females. Despite their predilection to catch permanent-resident birds in cold weather when cold-blooded prey are unavailable, eastern screech owls have made no dent in any of the ravine's breeding bird populations. Actually, as suburbia sprawled, cardinals and most other permanent residents increased in numbers. None declined!
Today, northern cardinals are building nests about head high in dense young cedars. Brown-headed cowbirds are least abundant now, so these first nests are scarcely parasitized. First fledglings will appear in late April. Second nests are started within a few days at the peak of cowbird parasitism and screech-owl predation on young cardinals in behalf of young owls. But any hard-hit cardinal pair will raise one or two more broods. Cowbirds are finished egg-laying and screech owls are through nesting when the last cardinal nest is started in late July, and the redbird's success increases accordingly.