In late May and early June of 2005, a pair of eastern screech-owls (Otus asio) with their four recently-fledged young took up residence in our front yard—an excellent opportunity for photography and study.
↓ Owlet in treetop.
↓ Adult female with a mouse. Screech-owl diets vary with season and location. A Michigan population studied by John and Frank Craighead preyed heavily on mice, at least in the winter, but Baylor University researcher Frederick Gehlbach (The Eastern Screech Owl: Life History, Ecology, and Behavior in the Suburbs and Countryside) indicates that owls in his Texas study area relied primarily on birds.
↓ The adult female (center) feeds one of the fledglings (upper left) while another (lower right) waits its turn. The adult male does the majority of the hunting, but his mate always feeds the young. According to Gehlbach, these roles are so stereotyped that if the female is lost before the nestlings are capable of tearing their own food, they may starve in the midst of abundant but whole prey delivered by the male.
To my innocent eyes the only thing that falcons, owls, and parrots have in common is their oddly anthropomorphic habit of holding their food up to their mouths in one foot as they nibble.
—Stephen Bodio, A Rage for Falcons
↓ A study in camouflage: the grey color and tree-bark pattern of adult screech-owls help them remain hidden from predators and prey alike. Eastern screech-owls come in two basic color forms, rufous (red) and grey. Red is dominant to grey in terms of Mendelian genetics, but red screech-owls outnumber grey ones only in humid eastern forests. Grey makes for better camouflage in drier habitats, and for some reason red screech-owls are apparently less hardy in cold weather. Unsurprisingly, then, almost all screech-owls in Nebraska are grey.
↓ Screech-owls do well in suburban environments, partly because suburban owls have fewer predators and competitors to contend with than their rural counterparts. To survive to adulthood, though, these young screech-owls will have to avoid housecats, dogs, and cars—many screech-owls are struck and killed while catching worms on city streets during periods of rainy weather. Secondary poisoning is another threat.
↓ Once acclimated to human activity, screech-owls can become very confiding. The adults would take mice mere feet in front of us, in broad daylight. (The pressure of extra mouths to feed was undoubtedly a factor—outside of the breeding season, screech-owls are more strictly nocturnal.) They were frequently mobbed by robins but paid little attention. Gehlbach reports, incidentally, that the species most likely to mob screech-owls are those which figure most prominently on their menu. [Paper here.]