Northern Saw-whet Owl nestled in a tree.

The Northern Saw-whet Owl

When the cooler weather sets in, our friends at Bird Lab begin their owl banding season.

One of North America’s most enigmatic and least understood birds is the owl, which may not be totally surprising given the nocturnal habits of these birds. But the Northern Saw-whet Owl (Aegolius acadicus), unlike most other owl species, migrates across the continent. They favor habitat with thick vegetation, and their journey starts in the Boreal Forest where they breed. 

Similar to other raptor species, female Saw-whets are larger than males, allowing us to determine their sex through various measurements. A combination of wing length and mass often aids in distinguishing between the sexes, although intermediate individuals are not uncommon. Bird Lab’s research reveals a pattern: females tend to migrate further south compared to males, leading to a predominant capture of female birds in the southwestern region of Pennsylvania. Banding a male in our area is noteworthy. 

Populations of Northern Saw-whet Owls in this area experience fluctuations. Some years, we band dozens, while in other years, only a handful. These population trends and patterns are influenced by various factors on their breeding grounds in the Boreal Forest. Monitoring the number of individuals we band and determining the number of individuals as Hatch Year birds, signifying their first migration after hatching this summer, helps us assess the success of the breeding season.


All bird banding is conducted under State and Federal permits by highly trained individuals for research purposes. Data is collected efficiently and birds are released unharmed.