Southern Executioner I Reckon Id Hang Them Again
The desiccated lizard hangs lifeless on fence, impaled through the gut on a barbed-wire spike. A few meters away, a dead bee protrudes from another twist of metallic.
Who killed them? And why? As it turns out, this real-life murder mystery has a surprising avian culprit: the shrike.
As well known as butcherbirds, loggerhead and northern shrikes leave a culinary horror show in their wake. Both species regularly impale prey — often still live — on spikes, thorns, or spinous wire, and go out them there for days or weeks.
We dive into the fascinating story behind shrikes and their grisly table manners.
A Tale of Ii Killers
If you lot've e'er run across a small brute impaled on a fasten, odds are it was killed by a shrike. But which species? There are 2 types of shrike in North America, the loggerhead shrike and the northern shrike.
Both species are remarkably similar: they're about the size of a robin, with a dark, hooked bill, grayness trunk, and black-and-white wings. Both birds also have prominent white wing patches that are visible in flight and a black ring through the center.
Getting a good look at that band is key to telling the species autonomously: Loggerheads have a slightly chunkier body and a thicker band that covers the top of nib. Northerns take a slimmer band that narrows every bit it meets the bill, and does not cover height of pecker or go over centre. (For more shrike ID tips, check out this guide from Audubon.)
Left: A loggerhead shrike. Note the thicker middle band. Photo © cuatrok77 / Flickr. Correct: A northern shrike. Note the narrow centre band that doesn't extend over the eyes or above the beak. Photo © Mick Thompson / Flickr.
Another skilful way to tell the species autonomously is their range. Loggerheads are plant year-round in the lesser one-half of the continental United States, and in the summer they migrate north to the Rocky Mountain states and Midwest. (But not the mid-Atlantic or New England.)
Northern shrikes take, unsurprisingly, a more northerly range. In the summer they breed in Alaska and farther northern Canada, where the tundra meets the taiga. In winter they migrate south, ranging through the northern half of the continental Us. (They venture a flake further south in the western states, to around the Colorado-New Mexico border).
For birders living in the continental The states, here's the (very) quick dominion of thumb: if it's summer, y'all're definitely seeing a loggerhead. If information technology's wintertime and you alive in the south, probably a loggerhead. If it's winter and y'all live in the northward, it could exist either species so go a closer look.
Both species live in open up, brushy habitats like grasslands, prairies, desert scrub, and savannahs. Shrikes are as well common near homo evolution, where they inhabit agricultural fields, pastures, old orchards, riparian areas, golf courses, and even cemeteries. They're unremarkably seen forth roads, searching for prey forth the mowed strip of grass.
Anyone Hungry for Shish Kebabs?
Shrikes eat, well, just nigh anything. Loggerheads volition eat arthropods, amphibians, reptiles, minor mammals, and even other birds. They tend to eat more insects during the summertime breeding season, and then add a picayune more than diversity in winter. Northerns accept a slightly pickier palate, tending to swallow fewer reptiles.
Both species hunts like miniature raptors: they look on an exposed perch and spotter the ground below, diving downwardly on their prey from above. (Loggerheads volition also hover-hunt, like kestrels, or wink their wing patches to startle prey out of hiding.)
Then it gets gruesome.
Shrikes might hunt like raptors, but they lack talons to pivot their prey downward. And when you hunt prey almost as large equally yourself, that's a serious drawback. And then shrikes grasp prey in their hooked beaks and fly it to the nearest pointy object, like a cactus spike, branch, or barbed wire spike.
Then they impale the fauna to both immobilize and kill it. If at that place's zippo spikey at hand, shrikes will also wedge casualty in the crook of a tree branch.
The shrike can either pick its prey apart, fleck by flake, or leave it for later. These food caches are chosen "pantries" or "larders," and they provide a critical source of nutrient when prey is scarce in winter, or when the birds need extra nutrition during the summer breeding season.
Sometimes, caching prey also helps make information technology more than palatable. In the southern US, shrikes prey on the toxic lubber grasshopper, Romalea microptera. Leaving the insects out to dry for a few days allows the toxins to dethrone, making them safe to swallow.
The impulse to impale is hard-wired into shrikes, and people have even observed juvenile shrikes practicing by impaling leaves on tree branches virtually their nest. Ambrosial… sort of.
Come on Baby, Let's Do the Twist
Things get even more interesting when shrikes take on a big meal.
Loggerhead shrikes ofttimes hunt prey as large as themselves, so the birds have a special hunting method for taking down these supersized meals. Scientists discovered this unique technique by analyzing high-speed video of hunting shrikes to effigy out merely how they kill large rodents.
First, the shrike grabs the rodent from backside, clamping down at the base of cervix and pinching the spinal cord to paralyze the animal. Then the shrike shakes its caput back-and-forth to suspension the rat'south neck.
That might sound simple, until you lot acquire that the back-and-forth whipping motion generates accelerations of upwards to half-dozen thousand-forces, or equally Audubon describes, "roughly the same corporeality of forcefulness felt past passengers on high-1000 roller coasters, or the whiplash experienced by victims of low-speed, rear-end car crashes."
Yikes.
Shrikes Effectually the Earth
Northern and loggerhead shrikes are simply 2 of the 33 shrike species worldwide. Their family proper name, Laniidae, is derived from the Latin word for "butcher," and shrikes are also known every bit butcherbirds.
Most of the 33 species are establish in Eurasia and Africa; there are just two in North America and one in New Guinea. (Yous can notice several species of butcherbirds in Australia. These birds aren't shrikes, but they occupy a similar ecological niche.)
Nigh all shrikes live in open up habitats, and they all share the same general greyness / brown / black and white coloration.
An Uncertain Future
With killer hunting moves and a diverse nutrition, you might think that shrikes are relatively safe from threats. Recall again.
Loggerhead shrike populations are declining across much of their range. Data from the Northward American Breeding Bird Survey shows that, between 1966 and 2015, the species declined by almost 3 percentage a year. That works out to a cumulative decline of 76 percentage during the past l years.
Co-ordinate to the Cornell Lab of Ornithology, the population decline coincides with the increased use of chemical pesticides from the 1940s and the 1970s, perchance because the birds are eating pesticide-laced insects near treated fields.
Other threats to loggerheads include vehicle collisions when they chase near roads, the loss of hayfields and other pasturelands to development, other forms of habitat destruction, and changing prey populations due to livestock grazing.
We know much less about northern shrikes considering they are relatively rare and occupy such remote habitats.
Hopefully, scientists and conservationists can pinpoint the causes of shrike decline before it's besides late. Because — equally gruesome every bit it may seem — there's something wonderful about finding a fence line decorated with little bodies, and knowing that a shrike lurks somewhere nearby.
Source: https://blog.nature.org/science/2020/01/27/shrikes-meet-the-bird-that-impales-prey-on-spikes/
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