Darwin, a Northern saw-whet owl. Image taken at the San Francisco Zoo.
Alright, remember this little guy? Darwin? I promised a while ago that I would write more about saw-whet owls once I got settled up here in Oregon. No more teasing, here’s the real deal.
I mentioned before that Darwin is with the San Francisco Zoo because he was hit by a vehicle. You’ll notice that his left wing hangs low because it healed incorrectly. This is not uncommon. Birds of all sizes are hit by vehicles more often than most people realize.
Anyway, Darwin is a full grown Northern saw-whet owl. While the females are a bit bigger than the males, this is about how large they get and you can see by the hand he’s standing on, that’s not very large. He was the only raptor at the Animal Resource Center (ARC) that was so small, we couldn’t handle him while wearing a glove because his tiny feet would have trouble gripping around a thick glove. Including his equipment, his weight hovered around 85-95 grams. So, while this isn’t the tiniest species of owl, they are pretty small.
Darwin stepping off of the scale after being weighed. Image taken at the San Francisco Zoo.
It’s probably because they are so small that I have a hard time imagining them as the serious predators that they are. I have a hard time imagining little Darwin catching full grown mice or voles. But that is in fact what they eat. (Although they catch adult mice, they usually can only finish about half a mouse in a sitting, so they just cache the other half until later.) When there is an abundance of mice, these guys are all business. They will catch up to six mice in a row, one right after the other, without stopping for a bite. Then they will just cache the excess food in safe places for later. Imagine this little owl catching six mice in a row! Now if it’s winter, all of this stored food might freeze. So, when they are ready to eat it, they thaw it out by “brooding” it, or sitting on the frozen carcass like they would an egg!
And yes, even when with a piece of mouse flesh hanging from his mouth, Darwin is still ridiculously cute.
Darwin, eating a piece of mouse. Image taken at the San Francisco Zoo.
Look at those eyes! I mean seriously, here it almost looks like he’s holding a heart:
Darwin eating. Image taken at the San Francisco Zoo.
Still, during the mating season this little hunter will take it up a notch. The female in the pair will brood the young and incubate the eggs and clean out the nest. She will leave the nest only for a few minutes each night. The male’s job is to bring her and their young food and he will often go overboard in his duties. During egg laying, the female might have up to 24 surplus carcasses around her. One of the reasons these birds don’t reuse the same nest is because of the rotting prey remains that are still there after the young have fledged. So when I said earlier that this little bird is a serious hunter, I was not exaggerating.
Aside from being a fearsome predator, Darwin also has a few things in common with all owls in general. Here are a few facts about owl biology:
-They actually have 14 bones in their neck (twice as many as people or giraffes do). This is why they can swivel their head 270 degrees in either direction! Since their eyes are so large, they can’t shift their eyeballs around in their sockets like we can, so in order to see to their sides and behind them, they have to rotate their whole head, and they can.
-They’re the only birds that lower their top eyelid when blinking, which to me makes them look like the old Chuck-e-cheese singing robots. It’s a very distinct movement and they often do it when they are swallowing.
-Looking at their eye biology, they have a lot of rods (which detect light) and not a lot of cones (which detect color). This means that they are one of the few birds that probably don’t have great color vision. They can see well in low light though.
-Since they are nocturnal, it probably makes sense that they have an excellent sense of hearing. Their ears are actually located on the exact opposite sides of their head, except one is slightly higher than the other. This allows them to triangulate exactly where a sound is coming from, even if they can’t see it.
Now, just one more picture of adorable Darwin:
Darwin, focused on a piece of food nearby. Image taken at the San Francisco Zoo.
Backyard Zoologist 