Photo: Northern Saw-whet Owl, Gary Zeng/Audubon Photography Awards
Deidra Bryant
There’s something truly delightful about autumn nights. The crispness of the air, the sound of the trees rustling in the wind, and catching a glimpse of fluttering owls from deep within the woods. Northern Saw-whet Owl migration kicks off in late October which means another season of observing these elusive raptors!
The Northern Saw-whet Owl (Aegolius acadicus) is tiny, with adults averaging 8 inches long and weighing 2.8 ounces. That’s lighter than most smartphones! They can be found in the coniferous and sometimes mixed or deciduous forests of North America. However, they are very difficult to find due to their diminutive size and ability to camouflage into their environment. During my first year of graduate school I had the opportunity to observe these tiny hunters on clear nights atop South Mountain at Kings Gap Education Center in Carlisle, Pennsylvania.
Each autumn, these owls migrate southward from Canada, while licensed banders and dedicated volunteers capture, band, and safely release them back into the wild. This large-scale project in PA dates back to 1997 and is coordinated by natural historian Scott Weidensaul. Project Owlnet tries to learn when saw-whet owls migrate, map their movements, and contribute to an informal data network consisting of information from at least 120 stations across the continent.
Saw-whet owls are lured into mist nets with recordings of the males’ breeding call while scientists await their arrival nearby, taking turns checking the nets every 40 minutes. Once caught, a volunteer or two will carefully remove the owl from the net and put it into a cotton drawstring bag to calm and protect it en route to a room with a licensed bander. Upon arrival, birds are weighed and everything is measured to age and sex them. This includes their wingspan (females tend to weigh more and have a longer wingspan than males), the size of their beaks, and the amount of fat they have on their bodies.
A black light is another valuable tool which is used to observe color patterns in the feathers and estimate the age of each individual. On most owls, the undersides of the remiges (flight feathers) will glow a brilliant neon magenta in the presence of ultraviolet light. This is due to porphyrins – a type of pigment that many orders of bird species use to pigment their egg shells as well as their plumage. Sunlight exposure causes porphyrins to break down. As a result, older feathers will fluoresce less brightly, showing new growth.
After measurements are documented, the birds are then banded with unique numbers on their legs and released back into the wild. Each owl differs in temperament, which adds to the whole experience. Some will puff out their feathers and clack their beaks in a menacing manner, while others will show a curiosity towards the scientists. I highly recommend anyone who’s interested in bird banding to volunteer!