identical plumage


Saw-whet owl banding season is upon us! So for the next six weeks, I will probably be spamming you guys with Cute Owl Content (to balance out a down-swing in fanart content, since my drawing time is going to be halved until nearly Thanksgiving.)

(click to embiggen, obviously. I’m the one in the red plaid.)

The background: this is part of an ongoing scientific study that’s been gathering data on saw-whet owl migration in North America for the past, like, 15 or 20 years.  There are a few hundred banding stations across the United States and Canada.  The saw-whet owl is (obviously) a very small North American owl that largely breeds in the boreal forest in Canada, and then the majority of the owls migrate south for the winter.  (Some stay in their nesting territories; some choose to stay and breed at lower latitudes.) They migrate as far south as Alabama, to the best of our knowledge (I’m not aware of anyone setting up nets any further south? Very few make it that far south, most seem to prefer to go about as far as Virginia.)  If you put up mist-nets at night and play the male’s toot-toot-toot (repeat infinitely) call, you can get owls to come down and check it out and get in the nets.

Unlike songbirds, saw-whets are kind of peripatetic migrators, at least on their southern trip.  They fly for a bit, stop, and can pause in a midway spot for days, even weeks, before deciding to move on.  (Some decide not to move on at all, and over-winter in a place where they find good prey numbers.)

The banding project has gathered data on thousands of owls (all our data gets put into a centrally-available database), over time revealing things like migration patterns (which is how we know that they move in fits and starts; and that they have several fly-ways that they seem to stick to year to year) and demographic information.  Besides putting a band on them, we take weight and size measurements, and also make some broad determinations about age based on feather age and molt patterns.  Way back at the start, someone did the tests necessary to determine the sex of about a thousand saw-whets, and from that was able to plot out the size and weight range of males and females.  (Their plumage is identical.  Like most raptors, females are a little bit larger than males; unfortunately, the size disparity isn’t usually great enough to tell by sight, although after a while you do get a feel for when you have a particularly small owl in hand.)

The two dark photos above are us using blacklight to age feathers.  Most of the time you can do it by eye – newer feathers are darker – but when it’s very tricky, we use the blacklight. There is a chemical in new feathers called porphyrin, which glows pink under blacklight.  It fades as the feather ages, so old feathers look entirely blue.  The owl above was just for demo purposes, and as a hatch-year bird had all new feathers, so it doesn’t look that dramatic.

About 80% to 90% of the owls we catch are females.  The majority that we catch were also hatched that spring, and after that the numbers dwindle to second-year birds, and some who are clearly older than hatch-year or after second-year but it’s hard to tell exactly how old.  (Life expectancy in the wild for saw-whets is 4-6, I think; but there are individuals who have lived to age 19 in captivity.)  Their numbers fluctuate in boom-bust cycles (possibly linked to prey boom-bust cycles in their breeding territories, but I don’t know that anyone has yet done the studies to try to determine that); so some years you get very few owls, and some years you get lots of owls.

Anyway, that’s the short of it!  But feel free to message me if you want to find out more details.

I’ve been volunteering with this for about 6 years, I think.  If you live in the U.S. or Canada, you might check to see if there is a banding station in your area.  Many banding stations run programs where the public can come see what it’s all about.  (I got involved by attending such a demo, and then started volunteering.)

So yes, this is a Very Serious Scientific Study, Really.  But I think you can look at the pics and see why some of us gladly give up half of our nights (or more) in October and part of November, every year.  (You do have to be – excuse me – a night-owl for this; on slow nights I get home at midnight; on busy nights it’s been 2am, and that’s only because we called it quits, not because the owls stopped coming.)