Tracking class finds sign of shrike

In a recent Audubon tracking class, the feature attracting the most interest and excitement was not a track in the snow, but something dead up in a tree. A sharp-eyed participant happened to look up, and saw a dead, dessicated mouse draped over a twig. Only birders would get excited about that. Four or five avid birders pooled their knowledge about the significance of a dead mouse draped over a twig.

It was the sign of the Northern Shrike.

Also known as the butcher-bird, it is a robin-sized gray-and-black bird that lives much of its life in the Arctic tundra. It is a songbird, most nearly related to the vireos. The shrike preys mostly on mice and voles, but occasionally kills and eats small birds, such as chickadees and sparrows at feeders.

The shrike has a hooked bill and a relatively large head compared to that of the robin. This indicates that the shrike’s bill has much musculature backing it up. Its bill can sever the spinal cord of a mouse between two vertebrae. But its small feet are only good for perching on a twig. Hawks have large powerful talons; shrikes do not.

That is why they impale their prey on a thorn, or wedge it in the crotch of a twig – so they can pull it into pieces of a size they can swallow. An empiricist in the tracking class gently lifted the mouse off the twig, and found that it indeed was impaled on a thorn.

Shrikes are uncommon and are found in Maine only in the winter. Maine is their balmy respite from the Arctic winter. Avid birders watch for them every winter. Shrikes are easy to spot – look for a big field with some shrubs. Look at the top of every shrub for a horizontally perched small bird with a relatively large head. That’s your shrike.

An avid Maine birder may typically find from none to 10 shrikes in a winter. A Christmas Bird Count’s total of shrikes for the day may be zero to 10 Shrikes also, depending how many fields are in the count’s 15-mile circle, and how many birders they have. It also depends on the year – some years voles and lemmings are abundant, some years less so.

Shrikes fascinate and thrill birders, probably because of their rarity and their unusual habits. Shrikes also appall feeder-watchers who get to see a shrike in action.

The tracking class did not see the shrike, just the sign. But, we can all wonder about it. Why did the shrike leave the mouse for so long? Will it come back? If not, why not?

For information on Fields Pond Audubon Center, call 989-2591.