Sunday, January 12, 2014

Northern Shrike - Plum Island - 1/11/14


Northern Shrike

For decades, I've been enchanted with Northern Shrikes.  Today, I enjoyed another encounter while searching
for winter raptors.

The Latin name for the Northern Shrike is Lanius excubitor, meaning "the butcher, sentinel or watchman".  Shrikes are usually observed alone on a prominent, lofty perch ready, waiting and watching.  A few years ago in Cambridge, I attended a presentation on migration by Dr. Reuven Yosef, Director of the International Birding and Research Center in EilatIsrael.  Dr. Yosef's doctoral research was on shrikes.  I was delighted with the opportunity to chat with him about Northern Shrikes after his presentation.  In the trusted Princeton Field Guide's Birds of Europe, the Northern Shrike is referred to as the Great Grey Shrike.  Is that because the upright posture of a perched Great Grey Shrike on the edge of a field is similar to that of the Great Grey Owl?  

The shrike is not a vegetarian nor a master of grains.  It's aided by a cutting or tomial tooth on the upper bill which severs the spinal cord, partially paralyzing its prey. Then the shrike carries the prey, sometimes as heavy as itself, in its feet.  Smaller prey items are transported in its bill.  It then retires to a spot to dismember and to impale its quarry on a thorn or to skewer it on barbed wire or to wedge it into a forked branch.  They kill more prey than they can consume.  It was thought that this roving bird was a malicious, heedless killer; however, careful observation revealed that they store excess prey to eat later.  Their larder for future use is an adaptation for surviving a time of scarcity of prey or days when weather conditions aren't favorable for hunting.  They have an excellent memory and are able to retrieve prey items many months later. 

Northern Shrike by Phil Brown


Descriptions of Northern Shrike:

Pete Dunne uses an American Kestrel or a Northern Mockingbird as an example of their size.  The pale, pearly gray backed passerine has a stripe above the eye. The cheeks, chin, throat and chest are white.  The mask is a deep, black streak that extends from the forehead through the eye to the ear coverts on its large head.  The bill is nearly black with a pale area at the base of the lower mandible.  It's a hooked bill with a tomial tooth.  There are rictal bristles at the base of the bill, aiding them in capturing insects.  In Chris Leahy's The Birdwatcher's Companion, bristles are described as "...hair-like feathers that project over the gape from above".  Their wings are blunt, short and black with a white patch and white wingbars. The scapulars are white, and the wingspan is 14 inches.  The tail is long and black with white outer feathers.  David A. Sibley's field guide states their weight  at 2.3 oz!  This is a fierce, predatory, robin-sized passerine that hunts like a hawk; its legs, feet and claws are black and powerful.

On Plum Island, I've seen Northern Shrikes hover like a kingfisher, then undulate like a flicker.  I've witnessed them jerking their tails most probably to help with balance in the wind.  It seems that they also twitch just prior to taking flight.  I've observed them pounce on their prey.  With my scope maxed out, I've scrutinized tree perches looking for the shrike's favorite branch, its watchtower, hoping to find the nearby, hidden storeroom or a regurgitated pellet on the ground below 
with no success.

Dr. Yosef shared so much about shrikes with me.  He encouraged me to invest the time observing them in winter  ~  where else but at my favorite outdoor classroom on that Essex County barrier island that brims with lessons on birds and their behavior. I hope I'll be fortunate enough to see a shrike's deep, bulky nest in a boreal spruce, an alder thicket or a creek-side willow in Canada or Alaska in some future breeding season...  

Good birding,
Sue

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