Burroughs Backyard

Backyard biology from a field ecologist's perspective

The loveliest time of day; or, in search of short-eared owls

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Yesterday evening was perfect. With the Wallkill River a hundred feet to my back and the black-dirt farms in front of me, I watched twilight time descend on the grasslands. There was no spectacular sunset, but the peace of a late-winter evening was overpowering. Tinges of oranges and yellows and pinks highlighted the hills to the north and to my back, made moody and calm with the blue and gray tones that permeated the view.

During the winter, we conduct surveys for short-eared owls (Asio flammeus) in grasslands where they roost during the day and forage at night. Not a year-round resident of New York, the owls migrate south to our region for the winter before heading back to Canada to breed in the warmer months. Short-eared owls, though their range spans much of the globe, are declining in some areas and are listed as endangered in New York. We conduct surveys in grassland areas they might utilize, trying to determine which fields they use for roosting and for hunting, and the ranges over which they move and forage during the season.

Last night, about 40 minutes before sunset, my coworker dropped me off at one of the Wallkill River Wildlife Refuge parking areas. Her survey was to be conducted at the refuge’s main viewing platform; I was hiking in along the river a little way to see whether a different vantage point would yield more information on where the owls are active. I found my station looking out over an expanse of fields, covered in crusted snow, with a few solitary trees along an edge and forested hills in the background. I could just make out the platform’s parking area through my binoculars, and the road rising above the fields that acted as a point of reference in my panoramic view. The portion of the Wallkill that I paralleled during my walk in had been frozen over, but just behind me it made a sharp bend, with a few rocks and riffles that kept the water open.

As twilight progressed, it was the best thing in the world to be stationed there, watching it. In the early evening, the view was calm. Several red-tailed hawks were perched in trees at the edge of my field of view, and there was little motion. A rough-legged hawk flew across and landed in a tree. A red fox appeared in the distance and sniffed the air one way and another before disappearing over a rise. A small flock of Canada geese flew overhead, close enough for me to hear not only their honking and the softer whistling sound they make, but also the buzzing sound of the wind snapping against their wing feathers (you can just hear it if you listen carefully to the “flight calls” recording on the Cornell Lab of Ornithology’s page). As sunset neared, increasing numbers of geese in flocks of 2 to 30 started congregating in the air behind me, banking sharply to land just out of sight where the river bends and the water was open. Hundreds of them must have landed there within the twenty minutes preceding sunset. In the distance a few owls started calling: the “hoo-hoo…hoo…hoo” of a great horned owl and the “who-cooks-for-you” of a barred owl.

Then, 8 minutes after sunset, the short-eared owls appeared. I did not see them rise from their roost, but suddenly there were several high in the air, difficult to see against the background hills, and two more flying low over the fields. Two minutes later, three were circling high before flying elsewhere to forage. They disappeared as quickly as they appeared; I felt like if I’d blinked, I would have missed it. What a treat to see them!

Short-eared owls, when they fly, look a bit like moths to me – something about the way they flap their wings and the proportion of their large rounded wings to their smaller heads – I’m not sure what it is, but I mean it in a good way. Some nights I’ve seen 6 or 8 at a time flying low over a grassland or swooping down and back up again, banking sharply downward or towards one another, making their scratchy calls as they fly (listen to “bark calls in flight” but imagine lots of them talking to each other at the same time). It’s special and fun to be able to observe them, especially since they seem to playful in their antics.

Other nights, not only do we observe them, but we attempt to trap them. The objective is to attach a radio transmitter: a small, lightweight device with an antenna that we glue to a tail feather, which emits a very specific radio frequency. Once an owl has a transmitter, we can go out on subsequent days with an antennae attached to a radio receiver and search for that specific frequency. Taking the direction in which the frequency is strongest from several different points lets us triangulate the owl’s location to learn which areas it is using for roosting or foraging. It gives us information on the movements of an individual owl – for instance, whether it returns to the same roosting and hunting areas each day or moves around – that we can’t get by doing our evening count surveys. (More information on this project is described in this story, though we now use a different type of transmitter.)

A month or so ago, I got to participate in a successful owl trapping effort! Just as it was getting too dark to accurately monitor the trap through binoculars, an owl landed on the starling bait, we pulled the release cord, and caught the first owl of the season! And – experience of experiences – I got to hold the owl as we took measurements and attached a transmitter! Two things surprised me: first, the owl was much smaller than I’d imagined. Seeing short-eared owls flying, swooping and turning, I’d thought they would be, well, larger than the football-sized bird in my hands. Second, the owl was calm through the entire experience. Once out of the net, it didn’t struggle in my hands. My coworkers tell me this is normal for short-eared owls (though every once in a while you might get a “sassy” one), but I had expected a bit more restlessness, or a swipe or two at my hands with a beak or talon.
SEOW hold2
We weren’t able to track that owl for long – she lost (or pulled out) the tail feather that the transmitter was on after a few days, but we captured another owl not long after that. We tracked it to a number of roosting locations until the recent two-foot snowstorm, after which we haven’t found it. One hypothesis is that it moved closer to the coast, where the weather is milder and there’s less snow over the grounds. But we don’t really know. We’ll just need to keep conducting surveys and see where the owls come and go over the season!

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