Owls and shrikes

hunters on the wetlands

On a damp morning at the end of November, I wandered out on the wetlands near the golf course. There were rumors of short-eared owls foraging in the meadows and I hoped to watch one in action. They commonly pass through the Juneau area on their seasonal migrations, especially in the fall (I think), and occasionally a few may stay the winter.

Short-eared owl. Photo by Kerry Howard

Some short-eared owls that nested in western and Interior Alaska were marked and followed to their wintering areas. Most of the marked birds went south on the east side of the Rockies, but some went along the coast. Winter quarters were spread from Montana to Texas and California to Kansas. Spring migration routes seem to be less well known.

About those short ‘ears’: they are not for hearing at all. They’re just little tufts of feathers that can be erected, presumably as some sort of social communication. The functional ears are asymmetrically placed on the sides of the head, which helps with pin-pointing prey locations.

Short-eared owls are open-country birds, nesting and hunting in tundra and grasslands. Unlike many owls, they often hunt during the daylight hours. Their main prey items are voles and other small mammals, often swallowed whole, but they also capture birds, commonly tearing off the wings before swallowing. Undigested remains are coughed up as pellets (so handy for curious naturalists who like to know what they were eating).

Shortears hunt chiefly by coursing low over the meadows, occasionally hovering for a closer inspection. The wings look big compared to a relatively small body, and indeed this species has low wing-loading. That is the body mass (technically, not quite the same as weight, but close enough for many purposes) divided by the wing area. Those long, broad wings carry an owl smoothly and gracefully over their hunting grounds. The low wing-loading is said to enhance aerial agility, allow better hearing while in flight, and reduce detection by prey.

Owl spotting wasn’t good that morning, though lots of hopeful photographers were out there. I didn’t see an owl in flight or perched on a stump but, guided by some friends, I saw one that had been dead for a few weeks. This bird apparently had been shot by some yokel with more ammo than brains—a wanton, useless act of vandalism that—in addition– certainly reduced potential pleasures for wildlife watchers of all sorts. The body was carefully tucked up in a niche under a stump, maybe just to hide the evidence, but I’d like to think that someone had sympathetically said Rest In Peace.

That was a sad finding, but there was also a good sighting—of a northern shrike. It perched on the long-stranded stumps and logs (with their lovely gardens of lichens and mosses), moving from one to another. Shrikes commonly hunt from elevated perches, most often in non-forested habitats. They eat mainly arthropods (e.g., beetles, grasshoppers, and bees from which they remove the stinger and venom gland—or at least the experienced adults do) in summer. However, in winter they eat more small mammals and birds, often killing these vertebrates with a neck bite. Shrike bills are stout and armed with not only a sharp hook, but also two smaller teeth on the upper bill that have matching notches on the lower bill—the better to break necks, tear flesh, and crack the exoskeletons of insects. Most prey is swallowed whole or in large pieces, but shrikes are said to lack crops, so they cough up undigested remains quite frequently.

Northern shrike. Photo by Kerry Howard

Shrikes are sizable songbirds that can catch prey larger than themselves. They are often called butcher birds, presumably for their habit of wedging or impaling prey; this helps hold the prey for dismemberment and also stores food for later consumption. In fact, the name for the genus of shrikes is Lanius, from a Latin word for butcher. There are reports of nest sites surrounded by scattered stashes of impaled prey, a larder for feeding chicks.

Shrew, stashed by a northern shrike. Photo by Gina Vose

This species of shrike nests in shrubby, semi-open habitats all across the north, beyond the boreal forest. They migrate south for the winter and are then found widely scattered across the country. Occasionally they exhibit population irruptions, when large numbers of them appear in some winters, at least in some areas. Such irruptions in other species are commonly related to food shortages, but for shrikes, the reasons behind the irruptions are not clear. Here, we see shrikes only occasionally, mostly on migration but sometimes in winter. The shrubby flats on the shores of Mendenhall Lake and the wetlands offer the right sort of habitat locally. Seeing this one was a treat. Its mostly gray plumage is not fancy, but the black and white patches on wings and tail were flashed conspicuously when it flew. Then it looked like a different bird altogether.

Lakeside findings

needle ice, a starving shrike, and early-bird willow buds

Sometime in mid-January, after a nice cold snap, the temperatures soared into the fifties; even near the glacier it was in the balmy forties. Near the visitor center, sidewalks and trails were slick with ice. A friend and I were headed for a walk on the beach, and we were glad we’d brought our ice cleats.

As we walked down the ramp from the first parking lot, we saw that the pond on the right had a very low water level—the little beaver dam that helps to form that pond was gone. Unfortunately, the lower water levels exposed an area along one shoreline where sockeye spawn. That exposure probably meant that eggs in those redds were killed when temperatures plummeted into the single digits for days at a time, earlier in the winter. Although lots of water was coming down Steep Creek, it didn’t add much to this pond but went into the lake by another outlet.

Once we reached the beach, walking was less slippery but very crunchy. Needle ice had created towers and chasms and a mini Grand Canyon as the thin needles grew up into cold air, perhaps fusing together as they grew. The low brush on the sand flats was liberally decorated with wind-blown gull feathers, both long flight feathers and fluffy body feathers, as if there had been a molting party on the beach.

A large, much battered, log had arrived on the beach. It had been standing in the forest not too long ago: it still had small colonies of moss and lichen, as well as scars from bark-chewing porcupines. We guessed that this old hemlock had travelled from Nugget Valley, down over Nugget Falls, before arriving here. A similar log, probably part of the same tree, had landed not far away, along with a smaller tree with smashed roots. We don’t often see big timbers washed up on this side of the lake. The heavy winter weather, with winds and rains, may have brought the tree into the creek and over the falls; a temporary high water level had stranded the broken trunk on the beach.

In among some bushes at the edge of the beach, we found a dead female northern shrike. The keel on the sternum (breastbone) was very pronounced, indicating that it had little stored fat and may have been starving. However, there was some blood on the face, and when we skinned the head, we found hemorrhage in the skull; there was also some internal bleeding in the abdominal cavity. This bird probably hit a window somewhere, got a concussion, but somehow managed to fly away before it gave up the ghost. We speculated that perhaps it had been chasing another bird (to eat it!) so vigorously that it failed to notice a window—this is something other predatory birds sometimes do too.

shrike-sketch-hocker
Sketch by Katherine Hocker

Shrikes come to us sometimes on migration or in winter, and we see them on the sandy flats near the glacier or out on the edges of the wetlands. They favor semi-open, shrubby habitats, often sitting on top of a bush while looking for tempting prey. They are predators, capturing insects and birds, often on the wing, as well as small mammals. They sometimes capture birds as large or larger than themselves, such as robins and jays. Birds are often captured by grabbing them with the feet, but other prey are more often captured with the bill. The upper bill has a sharp hook at the end and two small ‘teeth’ on the edge of the bill, not far behind the hook. Hook and teeth no doubt help in dispatching a captured prey animal: vertebrates are typically killed by biting through the neck, while insects are generally just crunched up. Sometimes called ‘butcher birds’(in fact their genus name, Lanius, means butcher in Latin), shrikes often impale dead prey on thorns or barbed wire, or in branch forks, to be eaten on the spot or later.

Another interesting find was a beaver-cut branch of feltleaf willow on which the catkins had lost their bud-covers and expanded into nice, fluffy pussy-willows. January is normally too early for this willow to flower, even though it is the earliest one to do so in the spring. We inspected several trees of this species along the lakeshore and found just a few fat buds and two partially open catkins. So the branch we found was well ahead of those that were still on their trees, perhaps as a trauma response to being cut. Plants can respond to damage by releasing enzymes and proteins that produce changes in undamaged parts of the plant; in some cases there is an accelerated development of reproductive organs.