The Northern Pygmy-Owl (Glaucidium gnoma) is a small owl native to western North America. This petite raptor has several distinctive features, including long ear tufts, yellow eyes, and brown and white plumage. One of the defining physical characteristics of the Northern Pygmy-Owl is its relatively small wingspan compared to other owl species.
Wingspan Measurement
Wingspan is measured as the distance from the tip of one wing to the tip of the other wing when the bird’s wings are fully outstretched. For most bird species, wingspan is a reliable indicator of the bird’s overall size and proportions.
The average wingspan of a mature adult Northern Pygmy-Owl is approximately 14-17 inches (35-43 cm). This makes it one of the smallest owl species in North America. In comparison, large owls like the Great Horned Owl have wingspans exceeding 4 feet.
There can be moderate variations in pygmy-owl wingspans based on the sex, age, and regional population of the individual bird. On average, female Northern Pygmy-Owls are slightly larger than males. Therefore, females may fall at the upper end of the average wingspan range while males occupy the lower end. Juvenile owls not fully grown may have shorter wingspans than mature adults.
Wingspan Differences Between Sexes
As with most raptor species, female Northern Pygmy-Owls are typically larger and heavier than males on average. This trend of females being larger than males is known as reverse sexual dimorphism.
Consequently, female pygmy-owls often have marginally longer wingspans than males. Published research indicates the average wingspan for female Northern Pygmy-Owls is about 15.7 inches (40 cm). Male average wingspans are closer to 15 inches (38 cm).
However, there is considerable overlap between the sexes. It is not always possible to determine the sex of an individual pygmy-owl based on wingspan alone. But as a general rule, longer wingspans in excess of 16 inches suggest the owl is likely female.
Example Wingspan Measurements by Sex
| Sex | Wingspan Range |
|---|---|
| Female | 15 – 17 inches |
| Male | 14 – 16 inches |
Geographic Variation
Research has identified slight variations in average Northern Pygmy-Owl wingspans correlated to geographic location. Populations in the northern and eastern extents of the species’ range appear to have marginally shorter wingspans.
For instance, pygmy-owls in British Columbia average 15.2 inches in wingspan. Going further south along the Pacific Coast, the average is closer to 16 inches in California and the Southwestern United States. This trend may reflect subtle localized adaptations in body size due to factors like climate and habitat.
Average Wingspan by Region
| Region | Average Wingspan |
|---|---|
| Pacific Northwest – British Columbia | 15 inches |
| Western U.S. – California to Rockies | 16 inches |
| Southwestern U.S. – Arizona, New Mexico | 16 inches |
Wingspan Comparisons
The Northern Pygmy-Owl has one of the smallest wingspans of any North American owl species. For perspective, here are some wingspan comparisons between the pygmy-owl and other owls it overlaps with in range:
- Barn Owl – 39 to 43 inches
- Barred Owl – 39 to 43 inches
- Great Horned Owl – 48 to 60 inches
- Long-eared Owl – 35 to 39 inches
- Short-eared Owl – 33 to 40 inches
The only owls with similarly small wingspans are other pygmy-owls like the Elf Owl and the Ferruginous Pygmy-Owl. But these species occupy different regions without overlap or contact with Northern pygmy-owls.
The exceptionally small wingspan allows Northern Pygmy-Owls to maneuver nimbly in dense forests and woods. But it likely comes with trade-offs, like reduced long-distance flight capabilities compared to larger-winged relatives.
Functions of Pygmy-Owl Wings
Despite their small size, a pygmy-owl’s wings serve the same functions as wings in other bird species. The key roles of the wings include:
Flight
The pygmy-owl’s broad, rounded wings provide the lift and thrust required for flying. The wings must support the bird’s weight in the air and propel it forward.
In flapping flight, the wings flap up and down repeatedly. Primary flight feathers at the wingtips help generate forward thrust on each downstroke. The owl angles and twists its wings to maneuver through dense vegetation.
Balance and Stability
Pygmy-owl wings act as airfoils to provide stability and help balance the bird in flight. Minor adjustments and positioning of the wings keeps the owl level in air and enables precise landings on perches.
Braking
By spreading the wings outward, pygmy-owls can increase wind resistance and drag to slow down their flight for controlled landings. This air braking mechanism reduces speed and prevents injuries.
Thermoregulation
The vascular wings help regulate body heat and temperature. Opening wings allows heat dissipation, while folding them in traps body heat.
Signaling
Pygmy-owls may fan out and flutter their wings during territorial or courtship displays. Prominent wing patches may also serve as visual signals.
Protecting Young
While perched over nests, female pygmy-owls will cover and conceal juveniles beneath their wings for warmth and safety.
Feather Maintenance
The owl runs its beak over wing feathers to clean, straighten, and redistribute waterproofing oils on the feathers’ surface.
Hunting and Foraging
Northern Pygmy-Owls put their small wings to work while hunting for the mice, voles, birds, and insects that make up their diet. Here’s how they utilize wings when foraging:
Short Swift Flights
Pygmy-owls will flap in short bursts to swiftly fly between perches. Their fast, agile flight allows chasing down small birds.
Zigzagging Through Forests
The owl flies in an erratic zigzag pattern, weaving through dense trees and foliage while homing in on auditory cues to pinpoint prey scurrying under leaves.
Pouncing From Perches
After observing potential prey from an elevated perch, pygmy-owls swoop down with wings folded back to snatch targets from the ground with their talons.
Wing Buffeting
Flapping wings directly at roosting songbirds may startle them into flight, making them easier to catch mid-air in the owl’s talons.
Defense and Camouflage
In addition to hunting utility, a pygmy-owl’s wings serve defensive functions and concealment:
Distraction Displays
When threatened, pygmy-owls may perform distraction displays by flapping and dragging their wings on the ground to lure predators away from a nest.
Mobbing Deterrent
Pygmy-owls being mobbed by small songbirds may face the source and spread their wings to appear larger and more intimidating.
Camouflage Against Trees
Perched with wings folded back and ear tufts raised, pygmy-owls blend into the bark and lichen of trees to avoid detection.
Injury Protection
Wings wrapped around the body conceal the owl and shield it from attacks.
Conclusion
With an average wingspan of just 15 inches, the Northern Pygmy-Owl has adapted its diminutive wings for life and hunting in dense, old-growth forests. Maneuverability and concealment are prioritized over speed and strength in pygmy-owl wing design. By flapping in brief, nimble bursts between perches, these tiny raptors are able to sustain stable flight and catch their prey through woodland habitats across much of western North America.
