Suburban Apex Predator, and the F-117 Barn Owl

Note: I had a hard-drive scare yesterday* and, for a couple hours, thought I’d lost the >90% complete draft of this post. I was totally, totally bummed. So I went over to Co-worker Matt’s office to commiserate, and ended up “telling” him the post. After I told him, Matt- who knew pretty much nothing about Owls beforehand- seemed genuinely into my “story-post” and impressed and interested by owls**. And then I realized that I didn’t feel so bad anymore, because at least 1 person had “read” and enjoyed the post. Just then the IT guy came over to Matt’s office looking for me; they’d recovered my drive.

*Yeah, that’s right- I blog on my work laptop. Oh, don’t get all sanctimonious on me; you’re probably reading this post on yours.

**Or maybe he was just yanking my chain to try and make me feel better. Whatever.

The Post

We moved into our current home in the Spring of 2002. When you move into a new neighborhood, you tend to notice all the little things- people out walking, how people maintain their yards, which houses have dogs that bark at you when you walk/run past, etc. One of the first things I noticed in our neighborhood that Spring was all the rabbits.

Our old neighborhood didn’t have rabbits, or if it did, I never noticed them. But here they seemed to be everywhere, and out not just in the early morning, but oftentimes right in the middle of the day. Awesome Wife and I joked that it was because now that we’d moved “uptown”, the neighbors didn’t let their dogs run free., and that if just one dog got out of its yard and roamed free for a weekend, the rabbits would probably disappear.

A few years passed. In early summer of 2005 a neighbor’s kid caught sight of a large owl perched on high up in a tall Blue Spruce next door. We spotted it almost every day for a couple of weeks. Sometimes it would hoot, and once or twice it spread its massive wings and flew off while we watched, probably annoyed by the neighborhood kids hanging out and chattering under its perch. After a couple of weeks it disappeared altogether, and we didn’t see it again. I wondered if all of our attention scared it away.

A few months later, in early Fall 2005, I was pedaling my bike home from a ride. I rolled down the little hill where I regularly used to spot rabbits out on a lawn and realized I hadn’t spotted a single rabbit in the neighborhood in, well, months. In fact I hadn’t seen one, since… that owl showed up.

I didn’t see rabbits again in our neighborhood until this past Spring. Over the Summer I’d see them out now and again, initially just around dawn, but later in the Summer out in the daytime as well. Rabbits aren’t particularly remarkable in a suburban neighborhood, but the kids like wildlife and would point them out to me, each other and their friends. Then last week, a neighbor’s kid* spotted this guy in the Elm** out front, the first one we’d seen in the ‘hood in over 5 years.

*Different kid, different neighbor, but same house. We’ve seen four families in that house- loved the first, didn’t care for second or third, love the fourth. Sort of a cool full circle thing. AW and I are getting all kind of serene and Zen-like with respect to problematic neighbors. We don’t get upset; we just out-wait ‘em. Eventually they all move away or die.

**Which I blogged about in this post. I don’t mean just the species; I mean specifically this tree.

The Great-Horned Owl, Bubo virginianus, is super-easy to ID. If you’re in the Western hemisphere and you see a big owl with ear-tufts, it’s a Great-Horned (GH Owl). And chances are, if you live in a suburban or rural setting anywhere in North America, you’ve already seen one. Its range is huge, from Alaska to Argentina. In fact, everywhere I’ve blogged about in the Western hemisphere- Maine, California, Mexico, Costa Rica, even Brazil- I’ve been within its range. Like many animals with huge ranges, the GH Owl is a generalist, in this case a generalist hunter. GH Owls of course hunt rabbits and mice, but you might be surprised how many other things they eat. Snakes, lizards, squirrels, rats, shrews, bats, moles and other birds. OK, so they eat a lot of different things, so what? Tell me something I don’t know.

OK, here’s something you might-not-maybe didn’t know: If you live anywhere in suburban or rural North America, there’s a good chance that the GH Owl is the single most bad-ass, toughest, fearsome predator that routinely passes through your yard. Don’t believe me? Here we go.

Know what else they eat? Raccoons. That’s a pretty big meal for a predator that only weighs 3-4 lbs, but GH Owls routinely kill prey 2-3 times their mass. What’s that? You’re still not impressed? Get this: GH Owls are more or less the only predator that routinely hunts skunks. That’s not all- they regularly hunt armadillos and even porcupines!* Wait- there’s more! GH Owls regularly hunt other birds, and not just cute little songbirds, but big birds- like ducks, swans and seagulls. That’s not all- GH Owls regularly hunt other birds of prey, including Red-Tailed Hawks and Peregrine Falcons**.

*Sometimes they do so by grabbing the porcupine out of a tree and dropping it to its death. I know that bobcats kill porcupines (on the ground) by going for the face, but don’t know if owls do this as well. I should mention though that in researching this post I learned that hunting/devouring porcupines does not always end well for the GH Owl. I covered porcupines BTW in this post, and bobcats in this one, with (admittedly lame) additional video footage in this post.

**I haven’t done a proper post about Falcons, but covered their hunting prowess and tactics last year during Pigeon Week. Man, it is like I have a post for everything.

In fact, GH Owls regularly hunt other owls, including every other owl species in North America except the (larger) Snowy Owl. GH Owls typically hunt by perching still from a high vantage point, then swooping down onto their prey. Since their eyes don’t move within their sockets, having a neck that can rotate around up to 270 degrees serves them well. But GH Owls can also hunt in other ways, including standing in shallow water to hunt small fish. And GH Owls have a bad rap with chicken farmers, as they’ve been known to actually walk inside coops to kill chickens. Before leaving their roster of prey, it’s worth mentioning that GH Owls also successfully hunt domestic cats and even on occasion small dogs.

Tangent: You can’t help reading about B. virginianus’ range of prey without wondering what it would be like to be attacked by them. Do GH- or any owls- ever attack humans? The answer is yes, though I’m unaware of any doing so fatally*. GH- and other owls- will defend nests vigorously, and may attack visitors, researchers or others who molest them. Then there are the cases where the owls apparently attack people well away from their nests. On Vancouver Island there have been a number of attacks on runners and hikers by Barred Owls, Stix varia**. And a rogue GH Owl attacked several cross-country skiers last year in Bangor, Maine. It’s thought that these owls might be mistaking human head-hair for small mammal prey.

*I came across this claim, which sounds like a stretch.

**The Barred Owl BTW, seems to be a significant threat to the endangered Spotted Owl, whom it typically out-competes for habitat/nesting sites. Interestingly, it also hybridizes with the Spotted.

But would a GH- or any other owl- deliberately hunt a small child? There’s no record of it, and human toddlers exceed the 2-3x body-mass metric. But what about outside of North America?

The closely-related Eurasian Eagle-Owl, Bubo bubo looks a lot like a GH Owl, with ear-tufts and everything. But it’s bigger- up to 9 ½ pounds- and has been known to take deer fawns as big as 22 lbs*. Now we’re approaching toddler territory, though I’m unaware of any such hunting attacks.

*Wikipedia says up to 37 lbs(!), but every other source said up to 22…

But there used to be even bigger owls. Until around 10,000- and maybe as recently as 8,000- years ago, the Cuban Giant Owl, Ornimegalonyx sp., inhabited that island. Ornimegalonyx stood over 3 ½ feet tall and weighed over 20 pounds. Its wings were small, as was the keel of its sternum, suggesting it either flew only for short distances or not at all, and its legs were longer than a typical owl’s. Ornimegalonyx may have run after prey on the ground, or leapt from treetops. In any case, it was big enough to take a kid. Even though humans were in the New World 8,000 – 10,000 years ago, they don’t appear to have made it to Cuba until more like 5,000 – 6,000 years ago, meaning giant running owls likely never chased Taíno children through tropical jungles. But then again, the mandible of what was apparently a similarly gigantic late Pleistocene owl turned up some years ago in Georgia, so maybe…

The GH Owl’s primary weapon is its talons, which are kind of interesting in that they are semi-zygodactylous. Zygodactylous feet have 2 toes facing forward and 2 backward, in contrast to the standard passerine (perching bird) architecture of 3 forward, 1 backward*. (pic below, not mine)In GH Owls, the fourth toe is reversible, allowing it to shift between a 3 forward- 1 backward, or anisodactylous, to a 2 forward- 2 backward zygodactylous configuration (pic below, not mine**). The 3-1 config is used for perching, but the 2-2, which provides a greater coverage area, for hunting.

*We covered zygodactylous feet last year when we looked at Roadrunners. Seriously, everything.

**Captain Obvious, here…

For most prey, the moment of contact is the moment of death- they never know what hit them. The talons of B. virginianus are incredibly powerful, able to crush bones with a gripping force of up to 500 pound per square inch. For comparison, a human grip generates a maximum force of some 80 psi, the bite of a German Shepherd roughly 250 psi, that of a Rottweiler 325 psi, and a human bite around 150 psi.*

*This is why you can open twist bottle caps with your teeth more easily than you can with your hand. Not that you should ever do so.

Side Note: These figures were surprisingly difficult to obtain* and make sense of, so take them with a grain of salt. Psi is not the same as bite-force; a Rottweiler’s bite has more force than a GH Owl’s grip, but the surface area of the latter’s talons is tiny in comparison. The important point is that, for something that looks rather thin and inconsequential, the talons of a GH Owl are incredibly powerful.

*Which is fair enough, when you think about it. Wouldn’t you hate to be the grad student tasked with getting the wolf or pit bull riled up enough to bite whatever measuring instrument they use with maximum force?

Back to bite-force, wolves and coyotes have much stronger bites than comparatively-sized domestic dogs*, with the exception of special breeds such as a Pit Bull, whose bite is phenomenally powerful. The bites of hyenas, lions and tigers are stronger still, in another category of force altogether.

*So I’m really glad that coyote in Emigration did not manage to connect with my right cheek.

Owls also have exceptional vision. Their eyes (pic left, not mine) are as big as ours*, but many times more powerful- even in full daylight. Most owls can sight a mouse in the grass about 5 times further away than we could make out any object of that size, and in darker conditions the difference is even more dramatic. The eyes of owls are ringed by specialized feathers that reflect/direct light into the pupil, and their retinas are packed with light-sensitive rod cells, enabling them to fly and hunt in what looks to us like near-total darkness.

*Which is proportionally like our having baseball-sized eyes.

But perhaps even more impressive than an owl’s sight is its hearing, which is highly sensitive, particularly in frequencies around that of rustling grass. An owl’s ears are asymmetric; the GH Owl’s right ear is set slightly higher up on its head, and positioned at a slightly different angle. This makes an owl’s hearing more sensitive to position and direction of sounds than ours. Barn Owls in fact can hunt effectively in absolute darkness by sound alone, flying around and landing on prey with accuracies of a fraction of an inch. (I don’t believe GH Owls can quite do this.)

Side Note: BTW, the GH Owls “ear tufts” are nothing of the sort. Though they look like the part of the outer ear that is technically the pinna (the outer, visible part) on a person, dog or cat, birds have no pinnas* (pic right = actual GH Owl ear, not mine). The avian ear does have specialized feathers, called auricular feathers, that serve to direct sound into the ear canal, but GH ear tufts aren’t those either. They’re display feathers, and have nothing at all to do with hearing. We’ll get more into avian ears in the next post.

*Pinnae? Pinnum? I’m never really sure.

Tangent: Let’s pause here for a second. Hopefully by now you’re convinced that the GH Owl- along with many other owls- is a totally Way Badass Predator. It’s for sure more bad-ass than hawks, and maybe even eagles. I didn’t appreciate how bad-ass until researching this post. Oh, I knew they were effective hunters and such, but…porcupines? Armadillos? Cats? And I guess I was surprised because they just don’t look that mean, but rather kind of wise and serene, and well “nice.”* Like, say you were an animal and you lived in a Watership Down**-type universe, where all the animals could talk to each other and you were lost and had to ask another animal for directions. Wouldn’t you be inclined to ask the wise old owl? But no- don’t do it! Because even though he looks so benevolent, he’s really like this hyper-effective, terminator-esque Silent Killing Machine!

*And then there’s “Owl” of the Winnie the Pooh*** gang, and the USFS’s “Woodsy (“Give a hoot, don’t pollute!”) Owl, and even the wise old cheater-Owl (“How many licks does it take…?”) on the old Tootsie-Pop commercials. All of these guys come off as slightly-addled, geriatric, harmless softies. Couldn’t we have just one seriously bad-ass owl in popular culture?

**I love that book.

***Still think that bear should have pants.

I’m not the only guy suckered by the owl’s serene face: think about birds of prey in our culture. The Bald Eagle is our national symbol; it’s on the presidential seal and the quarter, and eagles grace the seals and flags of numerous other countries. We have sports teams named after eagles and hawks. Our military flies the F-15 Eagle and the Blackhawk Helicopter. Know what the much-vaunted F-117 “Stealth Fighter” is officially named? The “Nighthawk”. A Nighthawk- which I’ll mention just below in a moment, and is not at all closely-related to actual hawks- is a cool little bird, but it’s not even really a nocturnal hunter, so much as it is crepuscular, meaning active around dusk/dawn. And you know what it hunts? Bugs. And it’s a little, inconsequential thing; hell, I’ve nearly run over them multiple times night-riding. Our nation’s baddest-ass techno-night-fighter-jet shouldn’t be named after a little birdie that flits around eating bugs. No, it should be the F-117 “Barn Owl”, because the Barn Owl is truly a bad-ass nocturnal predator.

But there’s no fighter-jet, no attack helicopter, no presidential seal, no flag, no heat-seeking missile either named after or with an owl on it. That’s BS. A few years from now, when I found the state of Wasatch*, the GH Owl will be our state symbol.

*I’ll have to cover this one in another tangent in another post, but briefly, it’s for Salt Lake and Summit counties to secede from Utah (West Virginia-style) and form a new state. Economically it’s a total winner for the new state, and would improve everything from class sizes to social justice to open space protection. The constitutional issues involved are thorny, but not insurmountable. I tell you what, I am always cooking up something…

The “faces” of owls are vaguely disk-like in profile, making them almost instantly distinguishable from nearly all other birds. The disk-profile is also thought to direct and optimize sound reception. Speaking of other birds, what are owls related to?

Owls have been around for something like 60 million years, and became widespread during the Eocene. Today, the owls, order Stirigiformes, include 2 families: the True Owls, Stirigidae, which includes the GH Owl and oodles other interesting species, and the Barn Owls, Tytonidae. For a long time it was unclear where exactly owls fit in the family tree of birds*, but they appear to be most closely-related to the order Caprimulgiformes- the Nightjars, Nighthawks, Frogmouths and Oilbirds.

*One theory was that they were more closely-related to hawks. The owl-like face of the Northern Harrier, Circus cyaneus, seems now to be an example of convergent evolution- not close kinship.

Side Note: Nighthawks, specifically the Common Nighthawk, Chordeiles minor, is on my slightly-embarrassing list of things-I-researched-and-meant-to-blog-about-but-never-got-around-to-doing-so. (Pic right, not mine*). They’re cool little birds which fly around close to the ground at dawn and dusk hunting insects, and are common in the foothills and high rangelands bordering the Wasatch. On several night-rides this Fall I came upon them suddenly, just sitting in the middle of the trail shortly after dark. As I rolled toward them they’d alight, and then fly in my bar-light-beam, staying just 10 or so feet ahead of me for a few seconds as I followed them down the trail. My plan was to get this on helmet-cam for a post, but I was never able to work out a light/cam configuration that captured the action.

*BTW, this is exactly how they look when you come across them in the evening just sitting in the middle of the trail- squat and squint-eyed, almost kind of smug-looking…

I’ve never been able to get decent night-time helmet-cam video. I’ve tried all different light/cam bar/helmet combinations, but the results are always the same- a small circle of white light in a field of blackness:

Believe it or not, that clip was made with both bar and helmet lights going full-blast- I could see fine. Around the same time I experimented with a bar-mount for the cam. Noise was always a problem, as you can hear in this clip:

I was able to partially damp the rattle with multiple rubber-bands, but it was still there. The lower-level video looked faster and better captured the lean-angle of the bike, which was cool, but I found the video quality sort of frenetic and annoying, and switched back to helmet-mount.

Their next closest relatives are the Turacos, order Musophagiae, a funky-looking group of semi-zygodactylous-footed, fruit and bug-eating African birds, and after them, our old friends, Swifts and Hummingbirds.

I mention this not only because I’m always interested in what’s related to what, but also because this roster of the owl’s closest cousins rings a couple of bells from previous posts. Oilbirds and Swifts (specifically some Asian swiftlets) are the only 2 birds known to have accomplished another awesome hearing-feat: echolocation*. Isn’t that interesting.

*Which we looked at last summer in bats. It’s like… Oh yeah, I said that already.

We’ve looked at lots of differences between birds and mammals in how they’ve tackled the same problems, including vision, song, respiration, sex determination, “nursing” and thermoregulation. It’s time to check out their ears.

Next Up: The awesome saga of the middle ear.

Note About Sources: My standard sources for every bird-related post include Kaufman Field Guide to Birds of North America and the Cornell University lab of Ornithology All About Birds website. Additional info came from Phylogeny and Classification of Birds: a Study in Molecular Evolution, Charles G. Sibley & Jon E. Ahlquist, The Origin and Evolution of Birds, Alan Feduccia, Tracking & the Art of Seeing: How to Read Animal Tracks and Sign, Paul Rezendes, the Owl Pages website, the Exploring Nature Educational Resource website, the Colorado Division of Wildlife website, ChaCha (don’t ask), negah28.info, BirdsnWays.com, CubaHeritage.org and Wikipedia. Several of the photos in this post were provided courtesy of Hunky Neighbor.