The Northern Saw-whet Owl (Aegolius acadicus) is one of the smallest owl species in North America. Despite its tiny size, the Northern Saw-whet Owl has a fierce reputation and distinctive features that make it stand out among other owls.
In the following sections, we will explore the average size of these petite raptors, looking at their total length, wingspan, weight ranges, and how their size compares to other owls. Understanding the diminutive dimensions of the Northern Saw-whet Owl provides key insights into their hunting strategies, habitat preferences, and ability to thrive across much of North America.
Total Length
The total length of a Northern Saw-whet Owl from the tip of its bill to the tip of its tail is approximately 20-24 cm (about 8-9.5 inches).
To put that into perspective, that’s about the length of a dollar bill or a typical computer mouse. From head to tail, these owls measure only slightly longer than the span of an adult’s hand.
Their small stature allows them to maneuver nimbly through dense underbrush and thickets as they hunt. It also enables them to roost in cavities and nest boxes that are too cramped for larger owl species.
Wingspan
While Northern Saw-whet Owls have a remarkably compact body, their wingspan is disproportionately broad compared to their overall size.
These owls typically have a wingspan measuring approximately 50 cm (around 20 inches). Fully extended, their wingtips nearly reach the width of a standard 21-inch computer monitor.
This generous wingspan allows the tiny owl to generate enough lift to carry its small body through the air while hunting at night. The broad wings also enable the owl to perform agile aerial maneuvers as it navigates through dense forest habitats.
Weight
To match its petite frame, the Northern Saw-whet Owl is also one of North America’s lightest owl species.
Adults weigh a mere 75-150 grams on average. That’s about 2.5 to 5 ounces, or about the weight of a baseball or a hockey puck.
Some key weight comparisons:
- 75 grams = 2.5 ounces
- 100 grams = 3.5 ounces
- 150 grams = 5 ounces
Females tend to be heavier than males on average. The owls’ light weight enables them to hunt small rodents and birds their own size, and also allows them to perch on flimsy branches that could not support heavier raptors.
Size Relative to Other Owl Species
The Northern Saw-whet Owl is one of the smallest owl species found in North America. Here’s how its diminutive size compares to some other common owl species of the region:
Barn Owl
- Length: 34-43 cm
- Wingspan: 80-95 cm
- Weight: 330-600 grams
Barn Owls are more than twice as long, with triple the wingspan and up to six times the weight of Northern Saw-whet Owls.
Barred Owl
- Length: 35-46 cm
- Wingspan: 85-110 cm
- Weight: 500-1,050 grams
Barred Owls are about twice the length with double the wingspan and up to seven times the weight of Northern Saw-whet Owls.
Great Horned Owl
- Length: 43-64 cm
- Wingspan: 110-152 cm
- Weight: 1,100-3,000 grams
Great Horned Owls are over twice the length with a wingspan over triple that of Northern Saw-whet Owls. They outweigh them by a factor of 10 to 20 times.
Snowy Owl
- Length: 50-65 cm
- Wingspan: 125-150 cm
- Weight: 1,600-3,000 grams
Snowy Owls are 2-3 times longer with a wingspan of 2.5 times greater than Northern Saw-whet Owls. They are a whopping 15 to 20 times heavier on average.
Eastern Screech Owl
- Length: 19-24 cm
- Wingspan: 50-61 cm
- Weight: 110-170 grams
Eastern Screech Owls are the most similar in size, being only slightly smaller than Northern Saw-whet Owls in length, wingspan, and weight.
Size Differences Between Males and Females
There are some minor size differences between male and female Northern Saw-whet Owls:
- Males average 74 grams while females average 104 grams
- Females are approximately 10% heavier on average
- Females may have a slightly longer total length
- Wingspans are similar between the sexes
The size dimorphism is relatively small between males and females. However, the female’s slightly larger size may provide some advantage for incubating eggs and protecting hatchlings.
Do They Grow Much After Hatching?
Northern Saw-whet Owls grow quickly from vulnerable hatchlings to independent fledglings. Here are some key growth benchmarks:
- Hatchlings weigh about 10 grams and are 5-6 cm long
- By 2-3 weeks they reach about 70 grams
- Fledglings at 4-5 weeks weigh around 100 grams
- They reach adult size by about 10 weeks old
So Saw-whet Owls achieve most of their adult size within 2-3 months after hatching. Their rapid growth helps them leave the nest and start hunting on their own fairly quickly.
Why Are Northern Saw-whet Owls so Small?
There are several theories as to why Northern Saw-whet Owls evolved to be so petite compared to other owl species:
Forest Habitat
Their small size enables them to easily maneuver through dense trees, shrubs, and thickets of their forest habitat when hunting. Larger owls would have more difficulty navigating these cramped spaces.
Prey Size
They primarily hunt small mice, voles and songbirds, so they don’t need the power of larger owls that tackle rabbits or ducks. Their compact size allows them to efficiently hunt prey close to their own diminutive proportions.
Cavity Nesting
Their tiny bodies allow them to nest in natural tree cavities, old woodpecker holes and artificial next boxes that are too small for bigger owls. More nesting options improve breeding opportunities.
Thermoregulation
A pint-sized body with a proportionally ample wingspan provides a higher surface area relative to volume. This improves heat dissipation and cooling in hot weather.
Agility and Speed
With quick, nimble movements, Northern Saw-whet Owls can surprise prey and escape predators. Their petite build enables maneuvers unavailable to heftier owls in the cramped forest understory.
Interesting Facts about Northern Saw-whet Owl Size
Beyond the basic size statistics, here are some fascinating tidbits about the tiny Northern Saw-whet Owl:
- Nicknamed “Forest Owl,” “Swamp Owl,” or “Teeny Owl” due to its small size
- Often mistaken for an Eastern Screech Owl, which is nearly identical in size
- Talons are only about 1 cm long but have an extremely powerful grip
- Their boots (covered feet) are among the smallest of any raptor, about 3 cm long
- The Saw-whet Owl’s minute legs are feathered all the way to the toes
- Average human thumb is larger than a Saw-whet Owl’s head and body put together
- Light enough to perch on thin twigs and wires that cannot support heavier birds
- Roosts in dense foliage that provides safety for this petite owl from larger predators
Conclusion
The Northern Saw-whet Owl punches far above its weight class. Despite being one of the tiniest owls in North America, with a total length of just 20-24 cm and weighing a mere 2.5 to 5 ounces, it leads a remarkably successful life in the dense northern forests where it makes its home.
The Saw-whet Owl’s compact size allows it to hunt tiny prey, move through cramped spaces, and nest in small cavities. Its broad wings provide outstanding aerobatic abilities. While charming and even cute in appearance, this diminutive raptor remains a fierce predator perfectly adapted to its environment. So never underestimate the power packed into the Northern Saw-whet Owl’s petite frame!
