Young Scientist Studies Winter Ecology of Saw-whet Owls

Walking through snow-dusted meadows and tangled woods, Tyler Christensen is researching the wintering habitat of the rarely seen Northern Saw-whet owl on the 950-acre Watershed Reserve.

On a recent outing to explore the winter ecology of the owls, Tyler and his sister, Dana, have been tracking several of these owls using tiny radio transmitters that emit a signal indicating their whereabouts. Spotting these small birds is tricky. As the smallest owl in eastern North America, a typical Saw-whet weighs about three ounces — roughly equal to a deck of playing cards — and is about the size of a soda can.

“Very little is known about the overwintering and migration habits of our local saw-whets,” said Tyler, weaving through the central New Jersey woods as the radio signals become louder, indicating that the bird was close by. “Because they are small, secretive, and remain silent during the winter, they were until recently thought be rare.  But they are here – right over our heads – we just don’t see them.”

He said growing up near the Watershed gave him the freedom to roam and explore.  As a child, he came to a variety of the Watershed’s children and family programs.

“I was lucky to grow up right around the corner from the Watershed Center, and I came here a lot as a kid to come on nature programs or just to explore the woods.  One of my first birding experiences was as a teenager when I participated in the Christmas Bird Count here at the Reserve.  The fact that the Watershed was one of my stomping grounds makes it extra fun to be here doing research,” said Tyler, 27, who is completing his undergraduate degree in ecology at Rutgers University-New Brunswick.

The Christmas Bird Count, one of the largest and longest-running citizen science programs in the world, helped stoke Tyler’s passion for birds. “I am grateful that I had the Watershed Center when I was growing up to provide access to the outdoors and great ways to learn about science and nature.”

He said his passion for science evolved from insects to birds, and he discovered kindred spirits with Education Director Jeff Hoagland and others here.

Snow crunching underfoot, the radio transmitter began chirping more frequently. Each owl’s  transmitter is on a different frequency, helping Tyler determine that one owl he first tracked at a Pennington park a month ago has migrated over to the Watershed Reserve.

In the two locations Tyler is researching, he said there is a range of habitats for the owls to select, including young and mature forests. The Saw-whet owls have a life span of about three-to- five years.

“If we want to keep these birds coming back every winter, we’d better have a good understanding of what it is they like,” he said. “Using vegetation data from these owls’ roosts, we can get a clearer picture of their habitat preferences.”

The trackers looked for whitewash, or scat, spat out owl pellets and other signs to narrow down an owl’s whereabouts to a specific tree. Peering high into the branches, sometimes with the help of binoculars, he spots the bird.

Once found, Tyler examined the nearby vegetation to see what the owls have eaten and recorded their habitat preferences, noting the types of trees where the owls roost. He also uses a forestry tape measuring tool to measure the height of the owl’s perch.

The scientists are looking for patterns on the three owls they’ve tracked so far. Do these owls prefer eastern Red cedar trees, as conventional wisdom has shown? If so, why did one recently roost in a Pin oak tree?

He intends on tracking the birds from early December until late February or early March.

“These birds are very vulnerable, just about every other owl species can eat Saw-whets, as do larger hawks,” Tyler said. “The results of this project are expected give us more information on what kinds of habitats we should promote to  ensure a healthy Saw-whet population.”

This project is one of several that Christensen has done with the new nonprofit organization, the Wild Bird Research Group, Inc.  The year-old nonprofit was formed to tie together several small, independent bird research projects, including a Saw-whet Owl migration study that takes place on the Watershed Reserve each fall.  The organization also studies neotropical migratory songbirds, including warblers, tanagers, buntings, and thrushes, that migrate to Costa Rica in the winter.

“We expect to track the owls at the Watershed during the winter for at least two years.  Hopefully this project will teach us a lot about our local Saw-whet populations, and tell us how they’re utilizing the habitats available to them at the Watershed Reserve and elsewhere in the region.”