Northern Saw-whet Owl (Aegolius acadicus)

Adult Northern Saw-whet Owl banded at Turtle River State Park in 2015.

​With its big, bright eyes and large head, this tiny owl is often adored by those who have encountered it.  Northern Saw-whet Owls (NSWO) are forest dwelling birds who prey on small rodents, bats and occasionally small birds and insects.  While quite common, these little owls are rarely seen as they are nocturnal and nest in tree cavities.  As an adult, they are mottled brown in color with white facial disks and a spotted head.  As a juvenile, they don a caramel colored chest and rich chocolate colored head with white markings. Typical adults weigh between 65-120 grams (a stick of butter weighs about 100 grams) and can weigh more during breeding season.  
​
During the banding process, we measure wing length (chord and flat), weight, tail length, amount of fat present, age, sex, and eye color.  Sex is determined by their wing length and weight.  Age is determined by examining the feathers to determine which feathers are old and new.

Juveniles banded near Valley City, ND in 2017.

Determining age by the molt pattern under a black light. The pink color is caused by the porphyrin in the feathers, which fades over time with UV exposure. The older the feather, the less pink is seen. This is a NSWO in its second year (SY).

Measuring wing length (chord and flat).

Adults banded at Turtle River State Park in 2016.