The secret world of owl migration

Outside, beyond the frosted windows, things are swathed in darkness. Within the warmth of the research station, all is silent but for the heater purring at your feet, and the rasp of pages being turned idly—your crew member, reading a book that details the patterns in which bird feathers grow. You check your watch. 1:30 AM.

“It’s time,” you say, and you both get to your feet. A quick zip of the jacket and you head wordlessly into the night, hooked wooden pole in hand and satchel slung over the shoulder.

Instantly, as if waiting impatiently just beyond the barrier of the door, a new sound punctures the air—an insistent too-too-too call, each note fast, even, and shrill. The sound of owls.

As you head for the noise, you leave a trail of breath in your wake, illuminated by the silver moonlight shining weakly through venous treetops. Beneath your feet is the crunch of unseen leaves that have long since forsaken their lonely branches. As one, the two of you switch on your headlamps. The call is louder now, as you wend through the paths that tunnel between towering oak trees. At a split in this trail, you and your partner peel off, and foray deeper into the woods alone.

You are very close to your destination now. You slow down, picking your way carefully, attempting consummate silence. The tip of a wide mesh suddenly materializes into view: a mist net, stretching long and tall between two poles, almost too fine to see. Though it’s out of sight, you know that a speaker lies just beyond the net playing owl calls on loop; it is this that you’ve been hearing. This is your setup as an ornithologist, rigorously trained to study and capture wild birds. With the speaker playing a male owl’s mating call, you can lure in curious females and pugnacious rivals alike. The net, constructed of tiers of baggy pockets, will catch the owls within. It’s important to check the net at frequent intervals, to ensure that all birds are promptly extracted.

With the focused beam of the headlamp you scan the net . . . there! A thrill of excitement shivers through you. Up high is a small shape, suspended in midair via the net. An owl! A Northern Saw-Whet, to be precise.

You lower the pockets of the net to a height that you can reach using your hooked staff, and hastily shift your headlamp to red light. Though owls have incredible night vision—this is thanks in part to light receptors known as “rods” in their eyes, of which owls have a million per square millimeter—they lack almost all color-sensitive “cones”, thus allowing you to approach the owl without dazzling it. The large yellow eyes spear you now, peering up from a mottled brown and white head. Its eyes are not “eyeballs” in the true sense of the word, for they are stationary and the owl can only adjust its vision by moving its head—which it now demonstrates, tracking your movement warily. If it chose to, this owl could rotate its head 270° left-to-right, or 90° up-and-down.

With deft fingers, you begin to work the saw-whet free from the net. You’re careful to take hold of the feathered legs first—though saw-whets are small, maybe 20 cm in size, they are still fierce little owls, and their claws are their most dangerous asset. With the claws freed, you can then tug the net gently over what approximates as the owl’s shoulder, the crook between the humerus and coracoid bones. The saw-whet clacks its beak menacingly at you, a classic intimidation tactic, but you are undeterred. You procure a cloth bag from your satchel and tuck the owl within, knotting the drawstring tight and looping it around your wrist. With this, you will carry the owl back to your banding station, where you and your partner will quickly determine its age and sex, and fit its leg with a numbered bracelet, or “bird band”, which will help you re-identify birds and keep track of those you may have already caught. This is especially important now, during the fall migration season, when owls move in huge and stealthy swaths at night.

Many, though not all, saw-whets migrate. On a fairly good night, the birds come thick and fast, and a banding station can catch hundreds of owls. But numbers are often at the mercy of the weather—wind direction, temperature, cloud cover, and precipitation can all sway the totals—and there are deeper ecological gears at work too. Saw-whet populations fluctuate in response to those of small rodents, their prey, which in turn spike in years when boreal trees have especially abundant cone crops. As such, saw-whet migrations are cyclical, and every few years, a veritable torrent of owls will sweep through North America like a feathery flood.

By dint of banding birds, you therefore can gauge population trends much more easily. Without a way to identify one bird from another, you would have no way of knowing whether that sixth owl of the night was the same owl caught six times, or six different owls! It is also especially helpful to keep track of how many young birds you capture, to get an idea of how well the species is faring. Low numbers of juveniles could spell trouble for the future of those birds—that likely means very few owlets fledged or survived to migrate, which may in turn lead to fewer owlets in the following seasons. Comparing the numbers each year can give you a stronger sense of what is typical—or worrisome.

In this sense, bird banding stations are an essential line of defense in conservation efforts. After cross-examining banding data across many stations, scientists determined that, in the last 50 years, North American bird populations have declined by roughly 30 percent. That equates to over 3 billion birds lost, or over one out of every four. These numbers are incredibly saddening, and very alarming. Without monitoring programs, our understanding of how perilous the world has become for birds—and indeed, all animals—would be hearsay at best. But now we know better.

With awareness comes the responsibility to act. There are many simple actions that can help birds immediately—turning off your lights at night, which otherwise disorient migrating birds; adding window decals to alert birds of glass surfaces and circumvent collisions; keeping domestic cats indoors; planting native species and avoiding pesticide use in your yard, if you have one; recycling your plastics; and simply watching birds, and reporting what you see! Just as bird banding is a critical piece in the conservation puzzle, so are citizen science initiatives, such as globally-renowned eBird.

Birds are beautiful, alluring animals, ones that we must strive to keep safe. Among these, sawwhets still remain somewhat enigmatic, but our knowledge of their movement and behavior is growing.

With the saw-whet in hand, having completed a swift examination and banding, you step once more into the frigid air. You gently place her, standing, on a flat surface nearby and retreat to watch her. For a moment, she’s entirely still, letting her eyes adjust. Then she unfolds her graceful wings, and, without a sound, she flies away into the night, off to continue her mysterious journey.

Further Reading

All About Birds. 2019. Northern Saw-Whet Owl.
lifehistory. Accessed on September 18, 2020.

National Geographic. 2020. Bird’s Eye View.
Accessed on September 18, 2020.

The Cornell Lab of Ornithology. 2020. Nearly 3 Billion Birds Gone.
back/. Accessed on September 18, 2020.

This article is from issue


2020 Dec