A Northern Saw-whet Owl (NSWO) is a small, primarily nocturnal owl, roughly 8” tall with a streaked chest and a distinctive white V stretching from above its eyes to the top of the beak (the cere). Weighing about as much as an American Robin, these owls can be found in a variety of woodland habitats, although they seem to prefer areas with coniferous forests.
This year, we had the pleasure of hosting a NSWO raising a clutch in one of our larger nestboxes. Here’s how our experience with this surprise visitor unfolded.
March 15, 2012
Given our warm and snow-free March, I decided to do an early pre-season check of all of our nestboxes, to see if any needed repairing and to apply an initial coat of soap to the ceiling and sides of the interiors (an attempt at deterring paper wasp nest-building). As I approached one of our larger boxes, I glimpsed a blur of white at the box’s entrance hole. Figuring some chipmunk had dragged something odd into the box, I went to check it out. About 20 feet away, I realized it wasn’t some weird nesting material at the entrance hole—it was a NSWO! Holy cow! (Click on any photo to see a larger version of it; use your “back” button to return to this page.)
Understanding why we had an appropriately sized box for this diminutive raptor on our property requires winding the clock back a few years. Beginning in January, 2009, we heard a male NSWO calling nearly every evening in our area. (Click here and scroll down a bit to hear a clip of this “advertising” call.) When we realized he was sticking around, Zell built a few larger boxes, based on plans from the Internet. He mounted the new boxes in areas from which we heard the owl calling. Alas, that fellow called until early May but apparently never attracted a female. At first, I thrilled at hearing his call. After about 3 months, I mostly just felt bad for his effort, all for naught.
We had no hint of any NSWO in 2010 or 2011, but we just left the larger boxes where they were. In mid-February, 2012, we started hearing another NSWO calling in our area. I had mixed feelings—part excitement for the possibility, part dread of another fruitless 3 months of calling. The last we heard him was in early March. I thought he perhaps had been a faster learner than the 2009 bird and had moved on. Honestly, I was a bit relieved.
And then, the little cat-like face watched me from the entrance hole a couple of weeks later.
Never having had a NSWO in a nestbox, I wasn’t quite sure how to deal with monitoring. In fact, I didn’t even know if the owl had simply been using the box for a daytime roosting spot or if it might be a female starting a nest. On this week’s box check, I opened the door very slowly. Peering back at me—a NSWO. Not the best photos ever, but I think we had caught each other by surprise. Okay—a likely nester. I e-mailed a man whom I had met a few years earlier and who rehabs and monitors mountain owls in the Rocky Mountain National Park area (and author of a recent book on small mountain owls) to ask his opinion. He indeed thought she was probably getting ready to nest.
As my dog and I approached the box for the next check, the female popped up to the entrance hole. Present and accounted for. In the photo below, she was watching the dog, who was lying politely in the shade off to the side. I didn’t open the box—just headed out of the area.
The NSWO wasn’t at the entrance hole as we approached the box. I tapped lightly on the box—no response. I cracked the box open to find her in a prone position with several prey items along the edge of the box. The clues seemed to indicate that she was incubating eggs and the male had been dropping off meals for her. Interesting pelts on the dinner menu—they don’t look like deer mice, which is one of the common prey species and which are plentiful of our area. Perhaps a white-throated woodrat?
At this weekly check, the NSWO left the box when I was still more than 30 feet away. My presence had disturbed her more than I was comfortable with. I saw that she had flown to a nearby tree. I quickly opened the box, counted 4 eggs (and 2 freshly delivered deer mice—yum!), snapped a photo (below, left), and headed out. As I left the area, the female moved to the tree opposite the box, watching/not watching me (below, right). I vowed to leave her to incubate in peace.
NSWOs lay eggs at about 2-day intervals. Since the female starts incubating before the entire clutch is laid, the owls don’t all hatch at the same time (unlike most songbird species, where the female starts incubating after the entire clutch is laid and the hatchlings usually emerge within the same day). I didn’t know precisely when she had started incubating, so I decided to err on the side of caution and figure it was today. Owl eggs hatch in about 30 days; the female stays on the nest pretty much 24/7 until the youngest nestling is feathered and can keep itself warm on its own (referred to as “thermoregulation”)—approximately 18 days after hatching, according to Birds of North America Online. So I stayed out of the area of the box for the next 6 weeks. I had no idea I had so much self-control.
Today was the day. I kept an eye on the entrance hole as I approached the area. I could see a little face peeking around the edge of the entrance hole (below, left). So—at least one nestling! I stopped until it dropped down to the floor of the box and then approached the box. Opening the door slowly, I saw the 2 nestlings near the edge of the opening move a bit to the back of the box. I didn’t even take the time to count heads (although I could see at least 3) or look in the box carefully. Instead, I took a photo and closed the box quickly. When I uploaded the photo, I could see 3 nestlings and 1 unhatched egg at the front of the box (below, right). My guess was that the kid on the left was the oldest; the one on the right, the middle “child;” and the one tucked in the back, the youngest. I sent the photo to the rehabber/monitor, who confirmed this aging. He also said that he suspected the oldest likely fledged a day or so after the photo and that the other 2 would follow it shortly. Perfect timing on my part!
Northern Saw-whet Owl population—+3. Bird geek girl—grinning from ear to ear!
I was looking forward to checking out whatever might remain at the bottom of the empty nestbox at today’s check. Much to my surprise, one nestling remained in the box. As I thought about it, I could see that the youngest might still be in the box 7 days later, assuming the youngest nestling hatched from the last-laid of the 4 eggs. Since the nestlings fledge in the same order and temporal spacing in which they hatched, the oldest might have fledged Sunday/Monday; the next, Tuesday/Wednesday; the next (had the unhatched egg hatched), Thursday/Friday; the youngest, Saturday/Sunday. (This check was on a Saturday.) So—one last glimpse of an owlet before it launched into the world.