It is amazing what one can see out of the corner of an eye.

Peripheral vision is a godsend for naturalists because so often creatures are not where (or even what) one expects. This was brought home to me this afternoon driving home from Sapporo. A red traffic light gave me the chance to watch some dusky thrushes feeding in a rowan tree; the thrushes were making short work of the bright red berries hanging in clusters beneath heavy caps of snow.

Pulling forward, intent on the thrushes, I had passed a largish lumpy shape in a tree to my left before my brain kicked in with information from what my eyes, via peripheral vision, had already registered. My mind was saying “It couldn’t be,” while that brief image had looked suspiciously like a pheasant.

Pheasants are not native to Hokkaido, and because I was not expecting to see one at all, let alone halfway up a rowan tree, I had trouble registering the reality that my eyes had so briefly recorded. So I turned and parked, and my suspicions were confirmed. A female ring-necked pheasant was quietly and unconcernedly sitting on a snow-draped branch, picking delicately at the chandeliers of red berries. It was the first of its kind that I remembered seeing up here.

I suppose I should have a sticker on the back of my car reading “Danger: Driver is birding,” or some such, because I just can’t help watching for wildlife as I drive. Only 10 minutes before seeing the pheasant, I had been gawking at an adult white-tailed eagle that flew casually toward me just above the road. I was forced to wrest my eyes from it because the already packed snow surface ahead of me had glazed to an ice sheet, and my attention really was demanded elsewhere.

It is surprising what one sees while driving, perhaps because one’s attention and concentration is heightened by the demands of vehicle control. On the way back from a visit to Cape Nosappu on Hokkaido’s Okhotsk shore, back in November, I caught a glimpse of a pale gray, long-tailed form as it flicked away. Had it looked dark and been flying over trees I would have ignored it as a migrant brown-eared bulbul, but this was in open country and bulbuls don’t often perch on fences up here.

It took only seconds to confirm my suspicions; the bird had not flown far and had perched again on a prominent fence bar. This was a shrike, and a rare one at that. Sometimes in winter great gray shrikes, o-mozu, visit Japan, and that was what my peripheral vision had found.

Shrikes are a fascinating group of birds, and the great gray is one of the larger species found in the northern hemisphere. They most often appear in Japan during winter, between November and March, though sometimes seen during spring and autumn migration. My November bird had perhaps just arrived and was moving along the coast still before heading inland.

If you’ve never seen a shrike, but know the common brown-eared bulbul of Japan, it is of similar size, with an equally long tail, but is a very much more powerful bird. Its wings and tail are black while its body is a pale blue-gray, almost appearing white in strong light.

Shrikes all share a feature which really sets them apart: a broad black line from the base of the bill across the face through the eyes to the ears. They appear to be wearing a “don’t mess with me” mask, though there is more of the fierce highwayman about them than of Zorro.

The shrike’s arching, hooked beak is an immediate clue to its behavior. This is a predator, and a ferocious one at that, which will willingly hunt other birds its own size.

Unlike most predators, which kill mainly to satisfy their immediate hunger, the shrike will kill beyond its requirements. It finds a suitable perch, a tree or post that affords it a wide view across open habitat, and there it sits, seemingly relaxed and appearing almost to be asleep, for long periods. In fact, though, it is highly alert, constantly watchful for prey that moves. Once spotted, the prey is snatched from the air or pounced upon on the ground.

It is then that the hooked beak it put to use. Whereas some raptors, such as sparrow hawks and eagles, strike with their feet, shrikes dispatch their prey with a bite to the neck at the base of the skull before dismembering it.

Shrikes are also known as butcher-birds (their Latin name Lanius actually means butcher), from their habit of taking their surplus prey to thorn bushes, or even barbed wire fences, and impaling it there for later use. Regularly used, such places can hold a macabre collection of rodents, large insects and small birds. Sometimes, though, the shrike may not remember to return. It is a strange sight to see one of these shrike’s larders, a mortuary of partly mummified remains.

One feature makes the study of shrikes particularly easy. Since they consume prey with indigestible hard parts, not all of which they remove before they eat, that leaves them with something of a problem. In order to be able to fully digest bone, fur or chitin, they would need an immensely powerful digestive system that they just couldn’t afford to carry around with them, weight being at a premium. Like other raptors, and many insectivores, they solve the problem by retaining the indigestible matter, compacting it and then coughing it up as a hard pellet.

Last November’s shrike had flown to a conspicuous perch that made it possible to show it clearly to my passengers, none of whom had seen a shrike before. While describing the gory details of its behavior I noticed it making minute bobbing movements of its head, subtly stretching its neck and weaving its head from side to side. From an anthropomorphic perspective, it looked decidedly uncomfortable. It was clear what was about to happen: the casting of a pellet.

Owls are particularly well known for this, and I’ve visited nesting sites of barn owls in Britain where heaps of pellets had accumulated over the years below the nest. In open country it is more difficult to see pellets, and I was just in time to alert my companions before the shrike gaped, retched two or three times with its beak open, and suddenly produced a pellet that fell to the ground. It was all over in an instant, and immediately the shrike, clearly relieved, shook its head, looked about and flew off — perhaps in pursuit of more prey.

A search beneath the spot where it had been perching turned up the pellet: a shiny black oval of compacted prey remains.

It is one thing to be able to identify a species that one observes, but it is far more fun to observe something of their intimate behavior, and I owed my observations of the shrike’s pellet-producing behavior, like the sight of the pheasant feeding on berries nearly 3 meters up a rowan tree, to a chance movement caught by the corner of my eye.