Research: Banding Season Recap
The 2020 saw-whet owl banding season officially drew to a close last week. Compared to the last two years, it was a great success! I ended up with 15 new saw-whets in the nets, plus one “local recapture”, and one Eastern Screech-Owl. The 15th and final owl of the season was a male. He was the smallest male I’ve captured, weighing 70 g! For those of you who don’t speak metric, that’s about the weight of 12 quarters and slightly less than a deck of standard playing cards.
Here’s the season breakdown for saw-whet owls:
Female: 7 hatch year, 3 second year
Male: 3 hatch year
Unknown: 2 hatch year
For those of you who have followed along with the project for several years, you may recall the last irruption year was 2016. This resulted in the capture of 36 saw-whet owls here in Arkansas. According to many researchers to our north, 2020 was an irruption year set to beat 2016. It did in several places, particularly in the Great Lakes region, but those numbers never trickled down into Arkansas…at least not during the banding season. Given the species’ nomadic tendencies, I suspect there may be more to come this winter. Despite lower numbers than predicted, the birds captured in Arkansas collectively exhibited an age ratio expected during irruption years—a whopping 80% of owls captured were hatch year birds! In the chart above, you can see only 3 adults were captured and “young adults” at that.
The most prominent reason for observing lower numbers than expected this year is weather. During the banding period, there was never a long window of dry cold fronts. Dry cold fronts came in spurts, surrounded by either warm, windy fronts, or wet cold fronts; neither of the latter two options are great for capturing owls. A colleague from up north also cited the idea that there isn’t yet as much snowpack in the saw-whet’s boreal range as there might typically be by now. This may keep the tiny owls closer to their summer homes, hunting uninhibited by snow. Saw-whets aren’t large enough to take a deep dive for prey in fluffy white drifts like their larger cousins.
While great numbers of saw-whets may not have arrived in Arkansas during migration, I still had some of my best nights in a long time! I had a four-owl night, which was also a two-male night; a never before accomplished feat here in Arkansas. Males are relatively rare to find in the nets.
On top of that, add a local recapture! A local recapture is the term banders use for a bird that has already been captured once during a banding season. This one was a hatch-year female captured exactly 15 days after originally being banded on 11/15/20. Local recaptures don’t happen often, but can provide interesting information on migration/overwintering stopover period. She was clearly enjoying the area and will hopefully continue to do so.
With this owl, I was bestowed one of the most serene experiences I’ve had in nature. After her release the second time, she immediately flew to a shortleaf pine and settled down to roost against a rising full moon. I and others were able to quietly enjoy this scene for the rest of the night. I was even able to capture some slow shutter speed shots of her perched silently among the pine boughs; silhouetted against the moon. This is the kind of moment in nature that gives me chills—the good kind—that come from knowing some things aren’t coincidence, but planned exactly for us when we need it most.
Unusual that she settled down to roost at night, huh? Maybe not. When thinking about owls, classic denizens of the night, most don’t consider the effect things like temperature and moon phase have on our feathered friends. Everything has trouble making a living in the cold and, if the owl had eaten recently, may better bide benefits from metabolism by roosting rather than expending more energy. Too, a small owl like a saw-whet is always in danger of being predated by larger owls, but that danger is exacerbated during full moons when they could be spotted more easily
Not much could beat the aforementioned experience, but another multi-owl night tried when an Eastern Screech-Owl zoomed into the nets. Screech-owls are often present at the banding site, but have never seemed interested in the saw-whet owl’s audio lure, so are captured very infrequently. I suspect they only get captured accidentally while hunting in the net lanes. This particular screech-owl was a hatch year female, strikingly larger than the saw-whets captured just an hour earlier. She was also a red morph; fiery in both plumage and demeanor. After lashing talons, snapping bill, and shooting poop, she was released with a shiny new band. The screech-owl perched on its release branch for a long time, getting reacquainted with the night.
Screech-owls are a bit of an anomaly in the owl world, existing in 5 subspecies and even more color morphs—along the spectrum of red to gray—throughout their range. Northwest Arkansas is at the heart of an intergrade zone, where multiple subspecies likely hybridize. Red morphs are most common, but what subspecies this individual was is anybody’s guess.
Now that the season has closed, it’s time for lab work! Blood samples will be analyzed, both for parasitic infection and molecular sexing. Stay tuned for more updates to come.
Acoustic Monitoring Season
The banding season may be over, but I am smack in the middle of my acoustic monitoring project. I have small recording units spread out across the western Ozark Highlands listening for saw-whet owls in upland pine forest. So far, I have data from 2 of 5 deployment periods: 44 sites across 28 days. No, I haven’t observed a saw-whet owl yet, but I have also only analyzed sound files from two days at one site :-D That’s a very small fraction of the data I have so far. I’m finding that sound file analysis isn’t a walk in the park. Most of my time has thus far been spent refining code for a computer program that will search for sounds of interest in my files from the field. While I have yet to find a saw-whet owl in the data I’ve gone through, I have captured the sound of a Barn Owl at one of my sites. This was a shock, as the species is quite rare in northwest Arkansas!
I don’t have much to speak about here yet, but stay tuned for more!