It’s a Hard-Knock Life

Juvenile Northern Saw-whet OwlsThere isn’t much else in the world that’s cuter than a baby Northern Saw-whet Owl. I should know; I handled dozens of them over the course of my doctorate research. Between their huge, blue, soulful eyes and the round, fluffy, ewok-like body, they’re guaranteed to evoke an ‘aww’ out of even the hardest-boiled egg of a person.

Still, most people will never have the opportunity to see one, at least not in their juvenile plumage. They’re notoriously hard to find.  Northern Saw-whet Owls nest in old tree cavities, moving into empty woodpecker holes and other crevasses in rotted out trunks. To study them more closely, researchers put up nest boxes in the hopes of coaxing them into more accessible real estate. It’s a lot easier to climb a ten-foot ladder up to a nest box than to have to figure out a way to get 25 feet up into a poplar or worse, a hydro pole.

Even once they’re out of the nest, they’re difficult to spot. Being not much bigger than a coffee mug full-grown, these little owls rely on camouflage to stay safe in the forests and woodlots where they make their home.  Their first line of defence when threatened is to go stock still against a tree trunk or in a mess of branches. It’s a very effective manoeuvre.  Adult saw-whets have stripes of brown and white on their breast feathers and spots on their heads that break-up their profile, helping them melt into the shadows. I can’t tell you how many times I’ve tracked a radio-tagged bird to their daytime roost and still couldn’t spot the little guy among the leaves. The brilliant white V on the forehead of juvenile birds is to help parents find their mouths in the dark of a nest cavity. Still, in daylight, this natural beacon manages to blend into the dappled sunlight on the foliage.

Adult Male Northern Saw-whet Owl

Adult male Northern Saw-whet Owl blending into the background.

So, any time I get to spend with these little guys is a treat, one that I never take for granted. It’s always such a pleasure to get to observe their individual personalities up close.

Don’t let their size and adorable expressions fool you. These are tough little birds. They have to be. Life for a Northern Saw-whet Owl is hard from day one. Females lay their eggs two days apart, but start incubating before they’ve completed the clutch. As a result, you end up with a nest full of young where the oldest may have a ten day head start on life over the youngest. In years where the small mammal population is high, the provisioning males can make their nightly quota of about seven or more prey items a night, making it possible for all the young to make it out of the nest. However, in years where food is scarce, that age difference suddenly comes into sharp relief and it’s not uncommon to find only one or two of the oldest nestlings surviving out of a clutch of 4-6.

Even if they make it out of the nest, life doesn’t get much easier. After a month crammed into the nest hole with mom and all their siblings, you’d think these newly-fledged saw-whets would want to move on and take advantage of their new-found freedom as quickly as possible.  However, despite having fully-feathered wings by the time they leave the nest (unusual for owls), juveniles tend to hang around the homestead for another month or so. They spend their days tucked away in the shadows in nearby trees and their nights calling insistently for food deliveries from their already beleaguered father, their mother having taken off around the time the oldest hit 21 days for a much-needed break.  During this post-fleding period, young saw-whets practice flying and refine their hunting skills.

Eventually, it’s time for them to strike out on their own into the great unknown. It’s actually a great unknown for us researchers as well. Despite a number of long-term banding programs for the species all over North America, we still don’t have a very good handle on saw-whet owl movements outside of the breeding season.

So every year, my colleagues across the country and I will keep adding new nest boxes and checking the ones we have, spending as much time as we can peering into the lives of these adorable and enigmatic owls in the hopes that one day we might unravel a few more of their mysteries.

* If you would like to entice owls to your backyard, let me know, and I’ll send you the plans for building a nestbox.

Flying with Dinosaurs

Canada goose and dinosaurSince the beginning of January, I’ve had the pleasure of teaching a second-year Chordate Zoology course at the University of Winnipeg. Having taken it at a different school as an undergrad and having taught the labs several years ago, the material isn’t exactly new. However, it’s been a wonderful way to rediscover the fascinating story that is the evolution of vertebrates.

First and foremost, it’s reminded me that we see dinosaurs just about everyday, flitting through the trees, soaring high overhead and gliding across a glassy pond. They’re all around us, bringing colour and music to our world.

Because of my grounding in zoology, the concept that birds are dinosaurs is not new to me, nor is it difficult to understand. However, I imagine for many people it’s a bit of a challenge to make the mental leap from a chickadee flitting among the leaves to a giant Tyrannosaurus rex thundering along a Cretaceous plain.  Still, whether you can see the resemblance or not, the genetic relationship is undeniable. A spectacularly rare discovery in 2007 of intact collagen protein in the fossil leg bone of a T-Rex allowed researchers to compare the amino acid chains within with a database of species we already have sequences for. It turned out that of all the possibilities, from mammals to reptiles, the sequence was most closely related to the collagen sequence of a chicken. This discovery probably would’ve left good ol’ Colonel Sanders with nightmares!

Even without the molecular connection, you can still see the family resemblance. Birds are descended from a lineage of dinosaurs known as Theropods, swift, bipedal predators, like Velociraptor, Deinonychus (pictured above) and the aforementioned T. Rex. While the ones most people are familiar with, thanks to Jurassic Park, are the large, ferocious creatures, most of this lineage were rather small, adapted for running and pouncing on their prey. These adaptations for speed and agility can still be seen in the skeletons of the last remaining dinosaurs, the birds.

They walked on two legs, their limbs swinging back and forth on the fulcrum of a pelvis that looked like part of a bicycle. Over time, that pelvis shifted, the individual bones fusing and getting stonger to withstand the strain brought by high speeds while maintaining its light weight. In fact, weight reduction was the order of the day in the evolution of birds from their theropod ancestors. Bones, overall, got smaller, lighter, hollowing out into tubes that were, and still are, reinforced by thin struts called trabeculae. The pectoral girdle got both smaller and in some ways, more rigid. Where the scapulae were freed up to allow the arms to swing out like flapping wings, the clavicles fused, forming the furcula (wishbone) and the sternum developed a deep keel, giving more space for what eventually became flight muscles to attach.

Still, the most striking feature these dinosaurs had in common with the ones we see today was feathers. That’s right, Creighton missed that little detail. Many theropods, Velociraptor included, had feathers. They started out as long, thin fibers that offered the minimum of insulation, gradually developing into the differentiated flight, covert and down feathers we know now. They appeared at least 160 million years ago, long before Archaeopterix (the first official bird) and even non-avian theropods like Velociraptor and Deinonychus. Paleontologists have found them in numerous species, including a small chicken-like theropod (the whole protein thing is making sense now) named Anchiornis. They’ve even managed to determine the colour of the feathers by examining the shape of the melanosomes (tiny pockets of pigment) preserved in the fossilized remains.

As more and more of these characteristics are teased from the fossil record, I can’t help but hope that one day my field guide to birds includes a section on the species that paved the genetic way for the spectacular diversity we see today.

I’m Learnin’ to Fly

Osprey practicing flightI’m always on the lookout for wildlife, even when I’m driving 100 km/h down a highway. My sister used to always get annoyed at my penchant for pointing out hawks circling overhead or braking suddenly to check out some mergansers along the lakeshore.

Well, the other day, my wandering eyes paid off. I spotted frantic flapping atop a hydro pole and had to pull over. It was definitely worth the stop, as I found myself watching a couple of juvenile Ospreys testing out their wings under the watchful eyes of their parents.

Over and over again they flapped furiously, gaining loft, but holding onto the branches of the nest like a ballerina would a barre. It was truly an amazing moment to witness.

Birds aren’t born knowing how do fly, just like humans aren’t born knowing how to walk. First off, it takes time to develop the enormous pectoral muscles needed to create and sustain the thrust required to get them off the ground and keep them in the air. Although most species lighten the load with hollow long bones and lungs that extend into air sacs throughout much of the body, the muscles responsible for flapping their wings make up 25-35% of a bird’s mass. These take time to develop; how much varies from species to species.  In Osprey, it’s nearly two months.

During that time, they practice, flapping and fluttering awkwardly and sometimes falling altogether. In some species, parents encourage the process by landing farther and farther from the nest with each food delivery, forcing their offspring to come out of their safe haven.

That fragile period in a bird’s life known as fledging is a bit of a behavioural tug-of-war between the demands of the young and the desires of the parents. It’s really not all that unlike human parents trying to get their grown up children to move out. Young birds don’t really want to leave the nest. I mean, why would you? You’re relatively safe, cozy and mom and dad bring you food several times a day. Sure, it gets a little cramped being crammed in there with your siblings and your room isn’t always the cleanest, but you don’t have to go out and work for your food. What’s not to love about that?

The thing is, parent birds need a break by the time young are ready to fledge. They can lose a significant amount of their body mass as a result of the energetic demands of feeding and protecting their offspring. Some species still have time in a season to raise a second brood, potentially doubling their genetic payoff. So, they want to get the kids off and into the world as soon as possible. Scientists have been studying this clash of wills for a long time now, measuring the costs and benefits on both sides of this ‘parent-offspring’ conflict.

When that conflict is resolved depends a lot of the species. Small songbirds usually only spend a couple weeks in the nest and then another couple of weeks following mom and dad around, figuring out how to feed themselves, but still begging for a handout whenever they can. For raptors, the period is much longer; osprey can take up to 17 weeks to become independent. It takes time to learn the art of hunting your own prey.

Young raptors learn by watching and again, through practice. I’m sure that for each generation of raptor there are mice and fish out there who’ve had a few years shaved off their lives from the terror of a near miss by a rookie owl or osprey careening towards them.

Still, they eventually get it right. They have to; at some point, mom and dad decide that they’ve invested enough into this generation and cut the chord. Because, regardless of the species we all must stand on our own two feet.