Larvae and Owl Pellets at Bell Top Elementary

My Bell Top stay resulted in a couple of interesting activities/observations that I’d like to share. The first was on one of the school yard ecology nature walks. A student discovered these interesting caterpillars, or so we thought. Because the larva reacted to disturbance by curling back their abdomens over their bodies, my initial reaction was that they were sawflies, which are actually a kind of wasp, but I wasn’t sure so I told the kids that I would have to do some RESEARCH. There were dozens of them eating gray birch leaves, leaving many bare leaf stems. Not going with my initial thought of sawflies, I went to Caterpillars of Eastern North America looking through all of the pages. No luck, so I perused the introduction and low and behold under the section entitled "Not Quite Caterpillars" I found a photo and description of the Croesus latitarsis sawfly. My initial reaction was right, we had found sawfly larvae!

The other activity that I want to share was Owl Ecology, a class I do for many schools. In this class I introduce students to the world of ornithology. I challenge them with the fact that they could be ornithologists studying owls in their own back yard and surrounding community. We start off with the fact that scientists ask questions. What questions would we ask to start off a study of owl close to home – what would those owls be and what habitat would they live.

I like to cover the three most common owls students might encounter, the Eastern Screech-owl, the Great Horned Owl and the Barred Owl. I throw in the Common Barn Owl since the pellets we dissect come from them (check out the Pellets Inc. website link). We chant the types of habitat these owls like – the Screech-owl “Woods and fields and woods and fields – and they don’t mind buildings”; Great Horned Owl “Woods and fields and woods and fields and they don’t like buildings” (at least not a lot of buildings like in a typical city) and the Barred Owl “ Woods and woods and woods and more woods”.

We talk about the calls the owls make and how we would keeps a science journal to record our data on where we find the owls. We discuss their hunting and feeding behavior, and how they produce pellets, the ball of fur and bones regurgitated by the owl after they’re meal. We then investigate the pellets to see if indeed mice are the most favored food (I present this as a hypothesis – “Mice, or rodents, are the number one favored food, shrews are second and tied for third are moles and small birds”. Students dissect pellets, two students per pellet using their hands, a paper clip unbent to serve as a probe, a scrap piece of white paper to work on and a double-sided information sheet (on one side are instructions and a mouse skeleton diagram, on the other side is a bone sorting chart showing the various bones, skull, jaw, fore limbs, shoulder blades, hip bones, hind limbs, vertebrae and ribs). I give them these basic clues as to what to look for and what kind of animal the owls ate (incidentally the pellets come from Barn Owls of the Pacific northwest areas of northern California, Oregon and southern Washington, purchased from Pellets Inc.) – an orange/yellow claw looking bone is not a claw, it’s a jaw of a mouse (actually a vole), a tiny beak like skull with very tiny purplish teeth is from a shrew, a relatively large skull with white teeth from front to back is a mole and birds have no teeth look for a beak and keeled breastbone.

The students dive into the dissection and soon you hear “What’s this?” reverberating around the room. We take time to tally our findings and see if my hypothesis is correct. We always find that mice/rodents are indeed the most often eaten food, sometimes shrews do come out in second place, sometimes we determine that we need more data to figure out if shrew are indeed second and moles and birds third. No matter what our discoveries are it’s an exciting class.