The Snowy Owl’s Supper, a Pellet Mini-Mystery

Tim HealyBehavior, Bird Sightings, Birding, Identification, Mammals, Mystery Birds, Science1 Comment

My fondness for Snowy Owls is well-documented. I consider myself incredibly fortunate to live in a corner of the continent where sightings of these nomadic raptors are an annual occurrence. I’ve spent many a winter’s day trudging about on the barrier beaches of Long Island in search of Snowies. It was through such scouting efforts that I honed my field craft skills, gradually growing from a curious kid into a proper birder. Nowadays, my non-birding friends are quick to turn to me when they want to see an owl in the wild. I’ve managed to successfully connect a number of interested parties with Snowy Owls over the years, providing awesome looks at remarkable birds from a respectable distance.

Most recently, my coworker Max accompanied me down to the South Shore for a February break owl prowl. While exploring the shoreline, I stumbled upon a surprising discovery: a 3-inch-long pellet lying on the sand. A preliminary assessment revealed several obvious bones surrounded by a mix of fur and feathers. Based on the pellet’s size and shape, the apparent combination of mammalian and avian remains, and its location on the beach nearly 100 feet from the dunes and far from any substantial vegetation or proper perches, I knew it had to be a casting from a Snowy Owl. This was a rare opportunity to learn more about the eating habits of our visiting owls, and I wasn’t about to pass it up! I tucked my treasure into a napkin and pocketed it before continuing down the coast. We eventually did locate the owl itself, hunkered down at a well-hidden roost where it was protected from the high winds. Max was duly impressed when we finally found our quarry. The rest of the day’s birding was perfectly pleasant, but I couldn’t wait to get home!

After sterilizing the pellet by baking it in an aluminum foil wrap, I began the painstaking process of dissection. Taking care not to break or lose any of the components, I gingerly pulled the pieces apart and began organizing them on a blank sheet of paper. Dozens of bone fragments and feathers gradually emerged from the mass of matted roughage. Even with a cursory glance at the external surface, it was readily apparent that the pellet contained evidence of at least two different organisms, and the skeletal elements revealed by my examination showed marked differences in form and structure. Once I had excavated all of the body parts, I set about trying to identify them. 

Many of the bones mined from this casting clearly belonged to a small mammal of some sort: the classic staple of owl pellet inspections. A dentary bone with a substantial gap between the molars and the large incisors revealed that the expired creature could only be a rodent or a rabbit, and its diminutive size ruled out the latter possibility. More detailed measurements supported my suspicions that the jawbone was too small for a squirrel or a rat. Noticing its rather robust appearance, I developed a working hypothesis about its origin. My tentative hunch was confirmed by Nick Tepper, a fellow member of the ever-amusing Redpolling Facebook group who has a great deal of practical expertise in identifying skulls from owl pellets. In addition to differing in overall shape from a mouse’s jaw, this specimen showed cheek teeth that were specialized for grinding up stalks of vegetation. Considering how common the species is among the dune grasses on the barrier islands, it comes as little shock that this Meadow Vole wound up in the clutches of a hungry Snowy Owl.

The feathers proved a little bit less obvious to name at first. Unlike the myriad keys, guidebooks, and other resources for identifying mammal bones found in owl pellets, there really aren’t any databases for analyzing matted, partially digested plumes. I did notice that they seemed appropriately proportioned for a medium-sized bird, and many of them showed a prominent dark spot at the tip. Considering that these feathers were probably ingested as the owl fed on the meatier parts of the catch, I knew they had to be from species with speckling on the breast or belly. I shared images online alongside the photos of the bones, hoping that one of my friends might have some insight to offer.

It was former Cornell colleague Teresa Pegan who first cracked the mystery, pointing out that these patterned pennae were perfect for Northern Flicker. Taking a closer look with this new information in mind, I realized that the shafts showed diagnostic yellow pigment, which I had previously disregarded as potential discoloration. Flickers are rather common among the pine stands and brushy areas on the barrier beaches, but I must admit that I did not consider this species an obvious prey candidate. That being said, Snowies are notably agile and more willing to make aerial chases in comparison with most other owl species. They have both the power to take down herons or geese and the finesse to snag buntings or larks. I suspect that the unfortunate woodpecker was probably taken in flight on its way to or from a roost tree. This was exactly the caliber of surprise I was wishing for with this investigation!

The pellet produced a number of other bits and bones, some of which were too fragmented to assess properly. Several articulated vertebrae can probably be attributed to the flicker carcass, based on their overall size and the honeycomb structure visible at the edges. A proportionally smaller limb bone may well belong to the vole, as I’d consider it unlikely that three separate meals would be represented in this single casting. Some of the specific incomplete elements will undoubtedly have to remain unidentified. All in all, however, I am positively thrilled that I was able to glean so much information from this fortuitous discovery.

Snowy Owls are among the world’s most recognizable and beloved birds, but there is still much to be learned about their general ecology. Research undertakings such as Project SNOWstorm have unveiled a great deal about the behavior and biology of these tundra predators over the past few years, including in-depth reports about annual movement patterns for specific individuals. Revelations about the varied diets of wintering owls have been among the most intriguing developments. Although they specialize in hunting lemmings during the High Arctic breeding season, Snowies down south have been documented scavenging dolphin carcasses, fishing for aquatic prey, and outflying birds of all kinds to seize them in midair. In addition to the pellet’s irrefutable evidence of a flicker feast, I also came across three separate gull carcasses along a relatively short stretch of beach during my recent visit. It’s certainly possible, if not probable, that the owl was responsible for these kills as well.

I still find myself delighted by the overall serendipity of this encounter. The long odds of finding the pellet by pure happenstance, combined with the recognizable and fascinating remains uncovered therein, made this little investigation a truly memorable experience. I’m not certain I’ll ever have another chance to take such a intimate, personal look into the life of one of my favorite animals, but I am simply thankful to have been presented with the opportunity in the first place. It’s an even greater pleasure that I learned something genuinely surprising in the process. The next time I see a Snowy Owl contentedly snoozing atop a windswept dune, the thought of it deftly plucking a fleeing flicker out of the sky is sure to bring a smile to my face. Nature, as ever, is full of unexpected spectacles.