Birding in the National Parks: Northern Saw-Whet Owls At Assateague Island National Seashore

The Northern saw-whet owl is hard to spot, but well worth the effort. Photo by Tammy Otto.

“I’ll need some time off in November to go to Assateague to band owls.”

That remains one of the best excuses for some time off I’ve ever heard, and of course it was legitimate. Who would be creative enough to make up that? My co-worker at the time was Tammy Otto, a graduate student in the Department of Fisheries and Wildlife at Michigan State University. She spent six years banding Northern Saw-Whet Owls at Assateague Island National Seashore as a volunteer with Project Owlnet.

We’ll get back to the park and the project in a moment, but first let’s talk about the owls.

Northern saw-whet owls (Aegolius acadicus) are tiny denizens of coniferous forests and, less often, mixed or deciduous forests. They tend to inhabit tree cavities, such as those created by woodpeckers, or the abandoned nests of other raptors.

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This Northern saw-whet owl stuck around after being released. Tammy Otto photo.

An adult saw-whet is only 7-9 inches in length, not even as big as the common American Robin. Unlike the worm-eating robins, saw-whet owls are opportunistic predators, taking small rodents, songbirds, large insects, or small reptiles and amphibians.

Many birders put the Northern saw-whet owl among their high priority targets. With their small size and shy, nocturnal habits, finding one isn’t easy. Most searchers will hear, rather than see, their first saw-whet owl. Their call is a whistle of rapidly repeated notes that some think is reminiscent of the back-up alarm on a construction truck.

In the old days, the call was likened to the noise made when a saw is sharpened on a whetstone, hence the odd common name for this bird. These owls are most easy to find during the late fall and early winter, which brings us back to Assateague Island, where an intrepid troupe of owl-banders are currently capturing, “processing”, and releasing owls for scientific research.

The banding station at the national seashore is part of the Project Owlnet network of more than 100 sites in North America. The project was conceived and founded in 1994 by Dave Brinker, an ecologist with the Maryland Department of Natural Resources. Today it is managed by Brinker, Steve Huy, and Scott Weidensaul with more than 300 researchers involved in the collection of data primarily on Northern Saw-whet Owl migration.

The photos here show some of the fascinating tasks and critters Ms. Otto was involved with at the Assateague Island station. When you want to put a leg band on a bird, the first thing you need to do is safely capture the bird without injuring the bird or the handler. Bird banders are trained in the handling of wild birds like owls, and take pride in their ability to capture an owl without harming the animal, though they’ll readily admit they sometimes pay with their own blood.

The owls are trapped in strategically placed mist nets, fine nets stretched between poles that are essentially invisible to the bird. The soft fabric doesn’t harm the bird, but quickly ensnares it. A bander will respond rapidly to a trapped owl and carefully remove it for processing.

Removing a bird from a mist net can be a tricky operation. Having assisted in extracting a few small songbirds myself, I can attest to the skill and practice required. Ms. Otto looks at it as a puzzle. She needs to figure out which part of the bird impacted the net last and work backwards from there, extracting one bird part at a time. If she gets the order not-quite-right, she can easily end up entangling the bird more than it was in the first place – a very stressful situation for both bird and researcher.

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Untangling an owl from a mist net can be tricky. Tammy Otto photo.

Luckily, northern saw whet owls have a reputation for being among the most laid back birds when caught in a net. The vast majority of them relax and give no resistance during the extraction.

The banders are thankful for this, all being well aware of what owl beaks and talons are capable of doing, even on such a tiny owl. Ms. Otto says her worst problems have occurred when things like downy woodpeckers end up in the owl nets, recalling a particular encounter that left her with a woodpecker-inflicted hole in her hand.

Once the owl is in hand, the “processing” begins where the bird is marked, and measured, with everything being studiously recorded.

Ms. Otto describes the process for each owl: “Marking consists only of banding a leg. Measurements include weight, wing cord (measure from "wrist" to tip of primaries without changing the natural airfoil shape of wing), wing flat (exact measure from "wrist" to tip of primaries), culmen length, eye color, fat score (based on visual estimate of the amount of fat under an owl's very thin and translucent skin in the "armpit"), and tail length. We also estimate sex (using weight and wing cord) and age (the condition of the flight feathers reveals fairly predictable patterns of molt - the molt pattern is used to estimate age). We also record time of capture, location, which net the owl was trapped in, which deck (or tier) of the net the owl was trapped in, and the direction in which the owl was traveling when it was netted."

All of this data is ultimately shared with other migration researchers and continues to contribute to our understanding of the natural history of birds in general, with some especially useful information about Northern Saw-whet Owls in particular.

Banded owls are often recaptured, and each time they stumble into a mist net, a clearer picture of their habits and migration emerges. Assateague Island and its unique inhabitants present some extra fun for the owl researchers on the island every fall. Sika deer do a lot of bugling during their rut in November and the rookie banders aren’t always fully let in on the fact that the eerie noise is from a harmless miniature elk until after they squirm for a while.

The island’s famous wild horses provide some exciting moments as well.

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Leg bands help researchers keep track of individual owls. Photo by Tammy Otto.

Asked for a horse story, Ms. Otto was quick to recall a notable encounter:

“I think it was my second year banding at Assateague. I got up for the 0300 net check. It was a particularly dark night, a couple weeks before the lunar cycle would reveal a bright full moon. I was walking out to the nets rather sleepily, LED headlamp aglow atop my head. As I turned the corner a pair of dull, blue eyes just taller than me met my gaze not 3 feet away. It was a horse! We both were startled by the other. The horse threw its head up, turned and trotted away. I, on the other hand, was now wide awake and trying to put my heart back into my chest.”

All in a day’s (or night’s) work for an owl-bander on Assateague Island.

Comments

I should add that setting up a mist net to catch migratory birds isn't something you can just go somewhere and do. It's not legal! There is a permitting process that reviews the research being done and the methods used. In this case there was also additional permission required from Assateague Island National Seashore, for which they should be applauded.

Hi there. Just reading your great posting regarding the Northern Saw-Whet Owl. I was very interested in learning about your efforts to study the migration patterns of these beautiful little birds. I live in Toronto, Ontario, Canada, and this past Friday, my wife and I came upon an adult Saw-Whet Owl out in the bush. This was the first time as birders that we had ever seen a Saw-Whet Owl. Fortunately, we had our camera with us and got some good pictures and video. We have posted them for anyone interested at: http://frametoframe.ca/photo-essay-northern-saw-whet-owl-sighting