Let me take you back again to the sunny forest at the North End Trails near Cable, WI. A colorful line of thirty students, several parents, and a couple of teachers – all on snowshoes purchased with a grant from the Wisconsin Environmental Education Board – stretched out behind me on the trail.
The students could sense that the hike was almost over, and I’d already reassured some that it was all downhill from here. I was looking ahead to my next stop at the fox station, and eavesdropping on the students’ excited conversations behind me, when a teacher called out, “Hey, Miss Emily, there’s a dead mouse in this tree!”
Well, that stopped me in my tracks. “Are you serious!?” I called back, nearly bursting with excitement. “That’s awesome!” I stepped out around the students and started tromping through the deep snow back to where she stood. I waved to the kids in the front of the line to turn around and walk back with me.
There, nestled in the delicate fork of two sugar maple twigs, just above my eye level, was a very dead mouse. “That’s awesome!” I said again, probably striking fear into the hearts of the parents who were wondering how someone this weird came to be leading their children through the woods.
And then I started to explain: this mouse was most likely stored here by a bird called a Northern Shrike. When shrikes are able to catch more food than they need in a day, they store it for later use. Sometimes they’ll impale prey on thorns, or barbed wire fences. When those aren’t available, the fork in a twig will do.
Stored prey provides the shrike with food security, and will eventually get eaten when the hunting is poor. A male shrike with abundant prey impaled throughout his territory has a better chance of attracting mates and fathering successful nests, but this bird probably wasn’t worried about attracting mates. Breeding takes place north of 50 degrees latitude around the globe (that’s northern Canada). In winter, shrikes migrate only as far as necessary to find food, which often means they come to Wisconsin!
Surprisingly, these skilled predators are songbirds. Being songbirds, shrikes lack the sharp talons of raptors like hawks and owls. Being songbirds, shrikes have another weapon. Like the winged Sirens of Greek mythology, shrikes sing sweetly to attract other songbirds.
Once prey are lured in, shrikes attack with a solid blow, then finish the job by biting the neck, shaking, or repeated knocks to the skull with their sharp beak. Impaling prey on thorns or sticking them in forked twigs may seem brutal, but it is also a practical way to compensate for having delicate songbird feet that cannot grip food during dinner.
Sporting a black bandit-mask on their gray heads, Northern Shrikes look the part of a feathered villain.
More than half of a shrike’s diet is small rodents like mice and voles. Right now, most of those tasty little critters are safely hiding beneath a foot of snow in the subnivean layer. This unlucky mouse must have been caught running on top of the snow, above the relative safety of the subnivean zone. While foxes and owls have enough mass to break through the crust and dig for tunneling mice, shrikes do not have that ability.
We hadn’t seen a single mouse track on the snow in our two days of field trips, so this mouse might have been caught and stored a few days ago, before the last storm. It certainly looked a tad dehydrated.
After snapping a couple photos, I snowshoed back to the head of the line and kept the group moving. I’m not sure what those kids (or teachers and parents) thought of our discovery. A gross oddity? A cool animal sign? A scientific curiosity? In any case, the naturalist in me is thrilled to find evidence that a shrike is visiting our woods. I’m not the least bit sad that there is one less mouse running around, especially since it came to such an educational end.
“…And you know theirs is a decent task in the scheme of things – the hunters, the rapacious plucking up the timid like so many soft jewels. They are what keeps everything enough, but not too many…” –Mary Oliver from Bowing to the Empress.
For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.
Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com