Lanius borealis borealis in the Western Paleartic

Taxonomy

English name: Lanius borealis borealis > American Northern Shrike

Other taxa borealis: Lanius borealis sibiricus / Lanius borealis funereus / Lanius borealis bianchii / Lanius borealis mollis


Identification

Bland head pattern, little or no supercilium and dark mask behind eye often only weakly present

Upperparts brownish-grey with well developed brown-ochre (yellow) on tips of feathers, most obvious on upperparts and on flanks. Intensity of brown variable. Broad rich buff fringes and tips to greater coverts when fresh. Fringes wear off but broad tips remain into winter, broader then the white fringes in excubitor. Pale rump patch more prominent than many first-winter excubitor. Some first winter female excubitor mooted as similarly ‘brown and barred’, though more research required.

Underparts, weak ochre brown tint with very obvious brownish transverse striations on sides of throat, cheeks, breast, belly and to variable degree in ventral region.

Scapulars brownish-grey with weak paler tips.

White primary patch relatively small maximum length: 53. 4-69.5 mm

No white secondary patch, though beware broad pale tipped greater coverts can almost mimic a secondary patch.

Tail feathers variable, often have the least amount of white. Black extensive with up to half  of T6 black.

Biometrics: tarsus length apparently averages shorter in sibiricus than in excubitor.

* Very similar as Lanius borealis sibiricus with tendency to have more grey tones admixed with brown on the upperparts and less of a brown wash below.


Distribution of  Lanius borealis borealis

lanius-borealis-borealis-map

Largest of the two Lanius species that breed in North America, the Northern Shrike is a species of boreal affinity across the Holarctic, nesting widely but sparsely in the taiga and taiga–tundra ecotone. In the Nearctic, the Northern Shrike breeds from Labrador and Quebec to western Alaska, and many, but not all, individuals migrate south to southern Canada and northern United States during late fall and early winter. Winter irruptions are common, with peaks generally occurring every 3–6 years, but the reasons for such movements (e.g., cyclical small mammal densities) are little understood. In some years, individuals are found as far south as Arizona, New Mexico, Oklahoma, Missouri, Virginia, and Maryland.

The Northern Shrike feeds on larger prey than the similar, and more southerly distributed Loggerhead Shrike (Lanius ludovicianus), especially during winter months, when their diet consists of a higher percentage of vertebrate prey (birds and mammals). The Latin binomial, Lanius excubitor, means “butcher watchman,” an apt name for this capable and alert predator that impales its prey on thorns, barbed-wire fences or wedged in forks of branchlets. Laniushave a strong, sharp, hooked bill with a small falcon-like “tooth” (tomium) on either side of the upper mandible and a corresponding notch in the lower mandible. They are commonly observed perched atop a tall tree or shrub, surveying the landscape, where they appear innocuous and non-predatory. However, should a flock of finches or starlings fly overhead, they will actively pursue them. Although they are not strong direct flyers, they are persistent, and will often follow prey into thick bushes. They have been known to take down birds larger than themselves, including robins, jays, and doves. Although not noted for their song, they can sing rhythmic and complex songs, and are capable mimics. Both sexes are commonly heard singing in late winter (February–March), especially on sunny days.

Nearctic populations exhibit some geographic variation, with the western subspecies (L. excubitor invictus) being slightly heavier, paler overall, and with more white in the tail than the central/eastern subspecies (L. e. borealis). Palearctic populations (L. e. excubitor) are quite variable and may include more than one species (Harris and Franklin 2000). Because this species is uncommon in the Nearctic and breeds in remote, sparsely populated regions of North America, they are less well-studied than the more southerly Loggerhead Shrike (Yosef 1996) and Palearctic populations of L. excubitor, both of which nest closer to population centers (Kuczynski et al. 2010). Studies on excubitor in the Nearctic are summarized chronologically below.

Miller 1931c investigated the systematics and natural history of North American shrikes and laid the groundwork for future investigations. Davis 1937a began a series of studies on the cyclic and irruptive winter movements of shrikes, based on data from Christmas Bird Counts, that has continued to the present (Cade 1967, Davis 1974e, Davis and Morrison 1988, Atkinson 1995, Petersen and W. E. Davis 1997, Hess 2000, JDP). Bent 1950 summarized both published and unpublished information on the natural history of the Northern Shrike. Cade 1962 and Cade 1967studied the hunting behavior and food habits both on its breeding grounds in Alaska and its winter haunts in upstate New York and produced the only paper on breeding biology in the Nearctic (Cade and Swem 1995). Atkinson 1991, Atkinson 1993, Atkinson 1997, Atkinson and Cade 1993studied overwintering ecology and food habits in Idaho. Recently, Brady and Paruk color-banded over 90 individuals overwintering in northern Wisconsin and studied territory size, plumage differences (Brady et al. 2009), and determined resting metabolic rates (Paruk et al. 2015). Otherwise, information about the Northern Shrike in North America is widely scattered in often obscure literature as short notes or segments in faunistic and ecological accounts.

Texts above from The Cornell Lab of Ornithology


Records of (possible) Lanius borealis borealis in the Western Palearctic

American Northern Shrike (Lanius borealis borealis) 1st-winter

18th October 2015: Lighthouse valley, Corvo, Azores

19th October 2015: Caldeirao, Corvo, Azores

read

borealis 1Photograph © Vincent Legrand

borealisPhotograph © David Monticelli


Tail patterns Lanius borealis borealis from the collection of Naturalis Biodiversity Center, Leiden

This drawings are part of the collection of BCP (Black Code Project)

?: ? / Old Collection, North America (128032)

1863: adult / Labrador (128033)

1863: adult / Labrador (128034)

?: male summer/ Wisconsin (128035)

1870: juvenile, Cambridge, Mass. (128036)

1872: male / Boston (128037)

 


Pictures of Lanius borealis borealis outside the Western Paleartic

Canada:

borealisPhotograph © Samuel Belleau


Broughton / Cape Breton, Canada / 24-06-2006

broughton 2006 borealisPhotograph © unknown


References

Birding Frontiers; Challenge series Winter– Martin Garner, 2015

The Cornell Lab of Ornithology: https://birdsna.org/Species