Eastern screech owls are small, secretive owls found throughout eastern North America. Their cryptic plumage allows them to blend into their surroundings, making them a challenge to observe in the wild. These intriguing raptors have a number of interesting behaviors and adaptations that suit their nocturnal lifestyle. But are eastern screech owls strictly nocturnal like most other owls? Or do they deviate from the typical owl activity pattern? Let’s take a closer look at the daily rhythms of these mysterious birds of prey.
The Nocturnal Lifestyle of Owls
Most owls, including eastern screech owls, are considered nocturnal. This means they are most active at night and sleep during the day. Nocturnality provides owls with a number of advantages.
Avoiding Overheating
Daytime temperatures can reach uncomfortably hot levels for owls with their thick plumage insulation. Hunting at night allows owls to avoid overheating.
Increased Prey Availability
Many of the small mammals and insects owls prey on are also nocturnal. More prey is available under the cover of darkness.
Lower Risk of Predation
Owls face fewer dangers from daytime predators like hawks and falcons when they are active at night. Their camouflage also helps them blend into the darkness.
Enhanced Hearing Sensitivities
Owls have specialized auditory adaptations like asymmetrical ear placement that enhance their hearing for locating prey in darkness. Hunting at night optimizes their unique hearing abilities.
Nocturnal Behaviors of Eastern Screech Owls
Eastern screech owls exhibit many typical nocturnal owl behaviors.
Hunting and Foraging
Like most owls, eastern screech owls do the majority of their hunting under the cloak of night. Using their exceptional low-light vision and keen hearing, they forage for small mammals like mice, voles, squirrels, and rabbits. They also prey on insects, reptiles, amphibians, fish, and even other birds. Peak hunting occurs in the first few hours after dusk and before dawn.
Vocalizations
Eastern screech owls become quite vocal at night as they establish territories and attract mates. Their eerie, whinnying songs carry through the darkness. They also make a variety of calls including barks, hoots, and screeches to communicate.
Roosting and Sleeping
During the day, screech owls return to roost in tree cavities or nest boxes where they sleep. Their plumage helps them blend into the bark of trees for camouflage.
Nesting
Eastern screech owls nest in natural tree cavities or old woodpecker holes. Females lay eggs and incubate them during the night. They also brood and feed chicks after hatching under the protection of darkness.
All of these behaviors follow the typical nocturnal schedule of most owl species. But eastern screech owls have some flexibility that allows for occasional daylight activity as well.
Evidence of Diurnal Behaviors
While eastern screech owls are primarily nocturnal, they sometimes exhibit diurnal, or daytime, activity patterns. Here are a few examples:
Vocalizations
While peak vocal activity is at night, eastern screech owls may call and duet during daylight hours, especially during the breeding season and in winter.
Roosting and Basking
Screech owls may emerge from their roosts during the day to bask or loaf near the cavity entrance, especially on sunny winter days. Their dark plumage absorbs heat from the sun.
Nest Defense
If their nest is approached by a predator or curious humans during daylight, screech owls may swoop out to defend it despite the brightness. Their protective parental instinct overcomes their preference for nocturnality.
Mobbing Potential Predators
Screech owls may join other birds like songbirds and jays in mobbing and harassing potential daytime predators that encroach on their territory, such as hawks, crows, squirrels, and cats. This helps advertise their presence and drive threats away.
Hunting and Foraging
While uncommon, screech owls sometimes opportunistically hunt during the day, especially on overcast or rainy days. Their pursuit of prey overcomes their typical nocturnal tendencies.
So while they are certainly at their most active after dark, eastern screech owls do occasionally override their nocturnal programming to take advantage of diurnal opportunities.
Crepuscular Behaviors
Eastern screech owls are also active at dawn and dusk, the times of day known as crepuscular hours. Their crepuscular behaviors include:
Foraging
Screech owls often hunt intensively at dawn and dusk which coincide with peak activity of their prey. The low light conditions match their visual capabilities.
Vocal Activity
Screech owls ramp up their vocalizations at dawn and dusk, using calls, duets, and songs to communicate and defend territories.
Roosting
Before dawn, screech owls will return to their cavity roosts after a long night of activity. They emerge again in the evenings at dusk to start the nightly routine.
Transitions
The crepuscular hours allow eastern screech owls to transition smoothly between day and night. Their activity reflects the changing light levels.
The crepuscular nature of eastern screech owls demonstrates their flexibility between the opposing cycles of night and day.
Benefits of Diurnal Flexibility
The ability of eastern screech owls to override their nocturnal instincts when needed likely provides them with some key benefits:
Increased Foraging Opportunities
Hunting during daylight expands their feeding opportunities, increasing the likelihood of getting enough calories.
Enhanced Territorial Protection
Mobbing predators and vocalizing during the day allows eastern screech owls to better advertise territory ownership and drive away intruders over a 24-hour cycle.
Added Nest Protection
Daytime nest defense enables screech owls to protect eggs and young around the clock from predators and nest competitors.
More Efficient Use of Resources
Basking and roosting near the cavity entrance during cooler daylight hours allows screech owls to balance thermoregulation with energy conservation.
The ability to override strong nocturnal instincts when conditions warrant allows eastern screech owls to survive and reproduce more successfully in their environments.
Differences Between Subspecies
There are two recognized subspecies of the eastern screech owl that may differ slightly in their nocturnality:
Eastern Screech-Owl (Megascops asio)
This is the nominate subspecies that occurs in eastern North America. It is very strongly nocturnal but displays some flexibility to hunt, roost, or vocalize during daylight hours when conditions are favorable.
Western Screech-Owl (Megascops kennicottii)
As its name suggests, this subspecies inhabits western North America. While also primarily nocturnal, it appears to be even more willing to overcome its nocturnal instincts to vocalize and hunt during daylight hours. However, more research is needed to determine if this is a true subspecies difference.
The increased diurnal flexibility of the western screech-owl may be an adaptation to its more western exposed environments where shade and nighttime forests cover are reduced compared to eastern forests inhabited by the nominate race.
Influence of Prey Availability and Predation Risk
Two major factors likely influence the willingness of eastern screech owls to overcome their nocturnal instincts and hunt during daylight:
Prey Availability
In times of abundant diurnal prey like songbirds, nestlings, and reptiles, screech owls may opportunistically hunt during daylight. Food drives their flexible behavior.
Predation Risk
If predators like hawks and falcons are scarce, screech owls may hunt during daylight because the threat of predation is reduced. But they likely stick to nocturnal activity when larger diurnal raptors are more common. Predation risk drives their flexible behavior.
Balancing energy gains from extra prey capture against danger from diurnal predators probably shapes the frequency of diurnal activity in screech owl populations.
Influence of Light Pollution on Behavior
There is some evidence that artificial night lighting impacts nocturnal behaviors of eastern screech owls near human infrastructure:
Disrupted Foraging
Excessive light pollution may impair eastern screech owls’ ability to locate and capture nocturnal prey like rodents. It also disturbs natural activity rhythms of prey.
Altered Singing and Territorial Behaviors
Unnatural night lighting appears to alter hormonal cycles controlling breeding behaviors. Screech owls near lights may sing at abnormal times or abandon territory defense.
Increased Risk of Predation
Bright night lighting reduces screech owls’ concealment in darkness from predators. It may force them to roost and hunt in riskier or suboptimal areas.
More research is still needed, but minimizing artificial light pollution likely promotes healthier nocturnal behaviors in eastern screech owl populations near human infrastructure.
Conclusion
Eastern screech owls are well-adapted to be successful nocturnal hunters and survivalists. However, their ability to flexibly override their nocturnal instincts when conditions warrant allows them to balance energy gains against risk and thrive over 24-hour cycles. Diurnality provides screech owls added opportunities to feed, communicate, thermoregulate, protect territories and offspring, and avoid predators. Their adaptive flexibility demonstrates how owls and other wildlife skillfully adjust behaviors to match dynamic environments. With continued research, we can better understand and support the fascinating circadian rhythms of eastern screech owls.