Sunday, January 16, 2011

The Butcherbird

Yesterday marked the sixth annual Ohio Ornithological Society winter raptor field day at the Wilds. Twas rather a balmy day by January standards in a wide-open 10,000 acre former strip mine in Muskingum County, Ohio. Here, my group basks in the nearly Floridian low 30's temperatures as they scan for Golden Eagles (we saw one, albeit at great distance).

It never fails to amaze me how many people come out for this gig. We had 120 birders this year, and some years there have been 150. Of course, two years ago we did have some last minute cancellations and a few no-shows. It's possible that the minus 12 degree temperatures had something to do with folks begging out.

A big thanks to Marc Nolls of the OOS and all of the expert birders who volunteer their time to organize this extravaganza and lead the field trips. Major props go to Nicole Cavendar of the Wilds and her staff for hosting us as they do every year. Not only does the Wilds open up and heat the normally shuttered restaurant for us to repair to at lunch time, this year they took everyone behind the scenes into the rhino and giraffe houses.

Between the birds and mammals, this field trip sported quite a diversity of observations.
There are lots of small rodents darting through the grasses at the Wilds, and their enemies are many. This is a female American Kestrel, and she was actively hunting a meadow right in front of our group. Whenever she'd spot suspicious movement, the kestrel would hover in place as if tethered to a string. We saw more kestrels than in recent years, and I am hopeful that the birds are claiming more of the nest boxes that were installed a few years ago.

Another raptor noted for wind-kiting is the Arctic-breeding Rough-legged Hawk, and we saw many of the patchy light morph birds such as the one above. Fewer, at least for our group, were the ebony dark morph Rough-leggeds, one of the world's most striking raptors in my estimation.

However, it was this distant speck that probably thrilled everyone more than any of the other feathered predators. Perched at treetop level, around 1:00 in the photo, is a Northern Shrike, one of the most violent songbirds to ever evolve. Northern Shrikes are not common birds in Ohio, and become downright rare south of the counties that buffer Lake Erie. However, this is at least the sixth year that one has been found in this location, and there was another in a distant corner of the Wilds yesterday.

Classic shrike posture: perched horizontally, tail out, and eyes and head constantly awhir as it seeks victims. Once a shrike takes to the wing, watch out! They've got a very strong, fast flight and really cover the ground. Fast flurries of wingbeats are interspersed with pauses during which the bird starts to drop like a rock. Thus, their flight is quite undulating and woodpecker-like, or perhaps suggestive of a rabid oversized goldfinch on steroids and with a penchant for murder.

Should you be a weaker animal, you'll do very well to stay out of sight of one of these beasts as we shall see.

Classic edge habitat and the sort of country favored by shrikes. Open fields, shrubby successional areas, and interspersed stands of larger trees. And very importantly, plenty of suitable cache shrubs. Such as that bushy Autum-olive, left center, which will play into this story.

Photo: Marek Szczepanek via Wikipedia Commons.

Marek's excellent photo was taken in Poland. The Northern Shrike has a broad breeding distribution across the northern reaches of North America and Eurasia. Shrikes move southward as need be in winter to find food. We've got another, far scarcer shrike in Ohio - the Loggerhead Shrike. Loggerheads are far more southerly in distribution and experienced a boom and bust cycle in eastern and midwestern North America. Now that they've largely gone bust, only one or a few are found each year in Ohio.

Anyway, this photo shows why a nickname of the shrike is "butcherbird". This shrike's hapless mouse victim has been firmly impaled on a thorn, and that's how these homicidal songbirds roll.

Purple and brown denote the breeding distribution of Northern Shrike in North America. Our Ohio birds have certainly come a long way, and it'd be interesting to know where they come from. East or west of Hudson Bay? As shrikes can be long-lived for a songbird, it'd also be interesting to know if this Wilds bird or some of the others that show up at the same places each winter in Ohio are the same individuals.

As word of the shrike spread among the eight groups that were out canvassing the Wilds, more people stopped by to admire the bird. One of the trip leaders, Jason Larson, observed the shrike rocket into an Autumn-olive shrub with a furry bundle. After the bird left, he sped over and discovered its somewhat grisly cache.

Shrikes are well known for capturing and killing all that they can, which in the olden days of rampant anthropomorphism led to them being branded as wanton killers; evil scourges among otherwise delicate and golden-voiced songbirds. I'm sure that many a shrike has been offed by old-time naturalists incensed by the highly predatory habits of these feathered Vlad the Impalers.

The reason that shrikes go on killing sprees is to stock the larder for lean times. Cold northern winters can be tough to survive, and if a tasty vole presents itself, the shrike would be foolish not to take advantage, even if it is still sated from the previous meal. So, the excess plunder is hung in dense shrubs where it less likely to be discovered by ground-roaming mammals. The shrike will return to the cache later and devour its victim.

It must have been a sight, that shrike trundling through the air lugging this fat meadow vole. A plump vole can weigh about 50 grams; the shrike weighs but 65 grams. That's an extraordinary feat of strength!

A shrike is certainly not an animal to be trifled with. They will attack nearly anything up to their size or even larger. There are reports of shrikes going after birds up to the size of Blue Jays and even Rock Pigeons. If the shrike gets the advantage, it'll snap the cervical vertebrae of its victim with a crushing pinch of its powerful bill. If that happens, its game over for the prey and that's a merciful thing considering how it'll later be dealt with.

A common belief is that shrikes impale their victims because their feet are too weak to hold it, so the bird wedges the morsel between some twigs or hangs it on a thorn and then tears it asunder. I don't know about this. Any songbird that can carry a chubby meadow vole that nearly matches it in weight can't be that weak in the feet. It may be that the shrike's short legs and body dimensions just make it difficult to grasp the prey in its feet and simultaneously reach it with its bill.

Once the victim has been secured, whether by thorn, barbed wire, or lodged between twigs, the shrike is free to use its raptorlike hooked bill to tear into the prey. While such manners may seem gruesome, the shrike has merely evolved a wonderfully efficient method of dealing with its food.

Let's just be grateful that shrikes aren't the size of condors or we'd all be in trouble.


Nicole said...

That's amazing about the shrike. It looks like a cute little songbird!

Nina said...

The neatest thing about seeing the shrike (since he's relatively small and stayed a bit of a distance away) was seeing his cache--realizing that the cool things you usually only read about in books can really be observed firsthand if you're in the right place, and at the right time!

Skunk-cabbage and an icy waterfall

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