Birder’s Notebook Northern Shrike: A window into the life of an unusual carnivorous songbird
It was a happy moment on April 22 when I first heard the bizarre beeps, trills and warbles of a northern shrike back on its breeding territory at Banner Creek. The next day, I heard two shrikes singing duets of odd notes and noises and saw the little black-masked predators perched separately on willow tops and wires, watching for prey.
The pair wasted no time. By April 29, they had built a bulky new nest in a willow, close to where shrikes have nested the last few years and the female was already incubating eggs.
I expected northern shrikes to inspire a Birder’s Notebook article over the winter, but it was the first time in memory that a shrike never crossed my path during the cold, dark months in Nome. I only know of two midwinter sightings in the Nome area and none were seen during the Christmas Bird Count, which is unusual.
Most shrikes usually do fly south, leaving the Seward Peninsula for the winter when their prey becomes scarce. However, a few hardy hunters typically remain, making themselves quite noticeable with their loud calls, prominent perching to scan for prey and flashy blackand-white feather pattern in flight. Interestingly, shrikes disappeared even before the heavy rains in late December created a thick coating of ice over the snow, sealing off the voles and shrews they depend on. It was almost as if they knew tough times were coming.
Though not a common bird in the region, shrikes breed widely across the Seward Peninsula in semi-open habitats with a patchwork of scattered spruce trees or tall shrubs. River bottoms and margins between forest and tundra are good places to find them.
The birds usually select a spruce or tall willow for their nest, placing it in a crotch where willow branches fork or on a spruce branch next to the trunk. The male brings nesting materials and the female assembles them, creating a deep, open cup made of twigs and lined with layers of ptarmigan feathers, hair, moss and grasses, creating a well-insulated cradle for eggs and nestlings in early spring cold spells.
A large clutch of six to nine eggs is typically laid, one egg per day. Only the female has a bare patch of skin on her abdomen for warming the eggs (brood patch) and she alone incubates the eggs and broods the nestlings. The beginning of incubation is not predictable but begins before the clutch is complete. Thus, hatching occurs over a several-day period and some nestlings are larger than others.
During my observations of family life of the neighborhood shrikes, the male has been a good provider and is very attentive to his incubating mate. On most of my watches, he has delivered bite-sized pieces of vole or shrew to the female several times an hour as she sat on their eggs. Sometimes the two call softly to each other when the male is perched on a nearby lookout waiting for prey.
When food is abundant, shrikes kill more than they can eat and store the excess for later in a cache away from the nest. Prey is hung from branch forks or impaled on a sharp object. Once the prey is firmly secured, the bird pulls pieces off with its bill. This habit has earned the shrike the name of “butcher bird.”
Incubation lasts an average of about 17 days. The female broods the nestlings for about 10 days, continuing to rely on the male for food for herself and the chicks. When the young are able to maintain their own body temperature, she, too, hunts and both parents feed and protect the chicks.
When there is a large brood of chicks, the nest appears to overflow and the bigger chicks are often seen perched on the rim. They fledge about 20 days after hatching.
Once fledged, the family stays together for over a month in a loose, noisy group. The parents offer protection and food as the juveniles learn to hunt for themselves. At first, they catch insects and spiders on the ground, gradually learning to snatch voles or shrews and finally to catch flying insects and small birds in flight.
Shrikes are carnivores and do not eat vegetable matter. They are skillful hunters that use an impressive variety of techniques to capture insects, small mammals and birds. They scan for prey from open or concealed perches, using both direct flight and stealth to snatch their quarry with either their feet or bill. They also hover and pounce and flick their white wing-patches to startle insects into flight.
Once a mammal or bird is captured, a shrike quickly disables it by severing the spinal cord with a quick bite to the neck, inserting the sharp, pointy tip of the upper bill between the neck vertebrae. Shrike bills are similar to those of some raptors. If shrikes capture bees and wasps, they remove the stinger before eating them.
Northern shrikes are a northern species and are found in southern Canada and the Lower 48 states only during the winter months. Because much of their range is remote and uninhabited, little is known about their overall population status or trend, yet these interesting birds are listed as a species of low conservation concern.