Monday, November 19, 2012

Northern Saw-whet Owl

Lisa holds a Northern Saw-whet Owl, Aegolius acadicus, shortly after it was captured in a mist net near Chillicothe, Ohio. I was down for my annual visit to this banding operation lasat Friday night, and this was one of two birds caught that evening.

Until the mid-2000's, no one had any clue as to just how common Northern Saw-whet Owls were in Ohio. If one were to go only by the relatively few reports made by birders who lucked into roosting birds, you'd have had to assess their status as rare, or uncommon at best. Of course, it stands to reason that such a secretive animal would largely go undetected. In my guide, Birds of Ohio, which came out in 2004, I made the statement: "...the vast majority of Northern Saw-whet Owls no doubt go undetected in Ohio".

Such opinions are speculative, however - concrete research is needed to prove or disprove such things. Well, 2004 was the year that the Chillicothe banding station whose work is featured here got fired up. Since that time, they have captured well over 300 owls, in a habitat and a locale that no one would have predicted as being optimal for saw-whets. Their efforts are not solo - a few others also focus on saw-whets in Ohio or nearby, and they too have captured a great many birds. Thesee banding stations are part of a systematic nationwide survey of Northern Saw-whet Owls known as Project Owlnet, and this research collaborative has revealed reams of information about the migratory habits of what was not long ago one of our most poorly understood North American birds.

Having an accurate  knowledge of an animal is key to successfully conserving its populations, and in the case of the Northern Saw-whet Owl, it is the efforts of banders who have revealed the mysteries of what could be our most charismatic owl.

The team works on an owl back at the research station a short walk from the nets. Dan and Ryan, in the foreground, and Lisa and Kelly Williams-Sieg in the back. Kelly is the driving force behind this banding station, with much help from this crew, and Bill Bosstic and Bob Scott Placier.

Owls caught and banded in Chillicothe have been recaptured numerous times at far-flung places across eastern North America, and the Chillicothians have captured a number of owls that were banded in other areas. All of this work via Project Owlnet has revealed a scope of migration that no one was previously aware of. October through mid-December is the tiime of the big southward push, and it appears that such irruptions are cyclical, and probably related to populations of voles and other small animals which are the owls' primary prey.

Dan checks the keel, or breastbone, of this owl, feeling for muscle and fat depositions. Many data points are collected, and an effort is made to determine how much fatty reserves the birds have built up. If it looks like the bird is enjoying this inspection, it probably is. Saw-whets seem to respond to touch in much the way that a house cat does: hooding their eyes and pushing into one's finger as if to urge the holder to continue the stroking.

Few birds are as mellow as saw-whets. For the most part, they make no attempt to struggle or otherwise indicate displeasure; mostly just staring curiously at their captors. After all, most of these owls have probably never seen people, coming from the wilds of the vast boreal forest as they do. Furthermore, saw-whets have low metabolisms and are not high-strung or fidgety, which probably serves them well to conserve energy.

The odd black light test. Porphyrins in the feathers can help reveal the age of the bird, and these compounds glow pink when exposed to black light. These is a hatch-year bird; porphyrins fade with age and become less pronounced on older individuals.

Deb came along on this Friday evening outing, and got the opportunity to witness a few Northern Saw-whet Owls up close and personal, and learn about the fascinating morphology of owls up close and personal. Well over a thousand people have been exposed to the marvelous but mostly unwitnessed life of owls at this banding operation.

One aspect of owl morphology that saw-whet banders quickly become acquainted with is powerful talons. Small as these micro-hooters may be, their talons are sharp as hypodermic needles and those little - although proportionate to the bird, huge - feet are strong indeed. Woe to the mouse that falls victim to one of these predators, and double woe to the careless bander whose finger is seized.

Now that's an ear! Proportionate to the size of their skull, saw-whets probably have among the largest ears in the animal kingdom. Not only are they big, but saw-whet ears are doubly asymmetrical. Each ear is shaped slightly differently than the other, and the ears are also offset from one another. These adaptations allow the bird's "micro-processor" to better triangulate on sound and almost instantly calculate the precise location of prey in utter darkness - even a vole moving under the snow.

The eyes of a Northern Saw-whet Owl are enormous; the pair can comprise up to 5% of the bird's head! Big eyes coupled with double the number of rods and cones that you or I have allow the owl to see well in the dimmest of conditions.

Once the hapless mouse has been located, it'll never hear its cute grim reaper coming. The leading edge of the foremost primary flight feathers are "fimbriate", or fringed with soft comblike extensions. These serve to muffle the sound of flight, and are the reason that owls are silent fliers.

Before long, it's time to release the owl back into the dark woods. We put it in a soft bag, and walk it to the base of the hill, near where it was caught. By then, it's been in the dark for ten minutes or so and its eyes have re-acclimated to the nighttime forest. Oftentimes, the banders will place the owl on the outstretched arm of a visitor, to let the owl fly off on its own terms. The little fellow above was set on my arm, where it sat... and sat... and sat. It was a good seven minutes before the little hooter finally set sail, flitting up into the cover of a nearby red cedar tree.

An enormous side benefit of Northern Saw-whet Owl research is the opportunity to expose people to the little owls. Most people have not only never seen one, they did not even imagine that such a beast existed. The chance to see a saw-whet up close, and learn firsthand about their various morphological and behaviorial aspects that I discussed above wins many converts to birds, nature, and conservation.

The bulletin board above is one of several in the research lab, and they are papered over with newspaper articles, stories from magazines, and above all, notes from kids who have visited. The latter crowd is especially important, if we want to grow a new crop of conservationists. Seeing a magical little owl that seemingly appeared miracously from the gloom of the nighttime forest is sure to make an impression, and I'm sure that some of the saw-whets capured at this station have served as "spark birds" for budding young conservationists-to-be.


--S. said...

Great post! I love the photos -- beautiful and informative.

Jim McCormac said...

Thank you!

Gaia Gardener: said...

Wonderful post! Thank you. I've wondered how common some of these little owls are, given their relative "invisibility".

russell said...

I am a long time reader of your wonderful web-site and have a question for you. In previous posts you have mentioned how Saw-whet owls and screech owls(and possible others)are silent fliers due to their fimbriate feathers. My question is are these owls still silent fliers on thick/foggy mornings when the sound of other birds flying movements are more audible?

Jim McCormac said...

Thanks for reading, Russell! From my limited field experience of being in close proximity to wild owls under the conditions that you describe, I would say that yes, they still are totally silent.

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