Loggerhead Shrike's Last Stand


Ron Pittaway


First published in the Toronto Ornithological Club Newsletter, March 2018, Number 275


HISTORY: It is a little known fact that the Loggerhead Shrike historically was absent from Ontario. Its range expanded into Ontario and Eastern Canada with the clearing of forests for agriculture. The first provincial record was near Hamilton in 1860. During the first half of the 1900s, shrikes nested fairly commonly in southern Ontario.

DECLINE: A population decline began in the mid-1900s and is now continent-wide. Doug Clarke (1972) was one of the first to comment on the disappearance of the Loggerhead Shrike in Ontario. During the first breeding bird atlas 1981–1985, the province’s breeding population was 50 to 100 pairs (Cadman 1987). By the second atlas 2001– 2005, most shrikes were confined to the Carden Alvar and Napanee area (Chabot 2007). Surveys by Wildlife Preservation Canada in 2017 found 26 breeding pairs and 60 fledged juveniles, plus 8 unmated birds. This more than doubled the 11 pairs in 2015 (lowest since 1991) and was a marked increase over the 18 pairs in 2016. Captive-bred released shrikes made up 17% of the wild population in 2017 (Wheeler 2017). The Loggerhead Shrike would be extirpated as a breeding bird in Ontario without the annual releases (128 juveniles in 2017) of captive-bred birds to augment the population.

CAUSES: The reasons proposed for the decline include habitat loss, road kills, pesticides, West Nile Disease, predation, and mortality during migration and on the winter range. Pesticides have not been shown to lower the reproductive success in shrikes (Yosef 1996) and Ontario pairs fledge healthy juveniles. Researchers in Ontario and elsewhere often remark that shrike numbers seem lower than the apparent carrying capacity of the habitat. Carden, Napanee, Manitoulin Island, Grey-Bruce, and Smith Falls all appear to have breeding habitat that is unoccupied by Loggerhead Shrikes.

CONCLUSION: If habitat isn’t limiting the breeding population of Loggerhead Shrikes, what is? Cadman (1987) and (Yosef 1996) reported that road kills were a significant factor in the shrike’s decline. The decline correlates strongly with the phenomenal increase in motor vehicles and roads in North America. The shrike’s habit of frequenting roadsides and swooping low to the ground for prey make it vulnerable to vehicle strikes. A study in Virginia found that road kills caused 29% of fall and winter mortality, second only to predation (Blumton 1989). During migration shrikes cross hundreds of busy roads twice annually. Road kills are almost certainly the overriding limiting factor now controlling shrike numbers in Ontario. Ontario’s Loggerhead Shrikes are now an isolated outpost population quite distant from the nearest and declining populations in the United States. Collisions with vehicles (not breeding habitat) probably are the principal factor limiting shrike numbers in Ontario. Shrikes would be gone as a breeding bird in the province without the annual releases of captive-bred birds by Wildlife Preservation Canada and its partners. Loggerhead Shrikes will soon be returning to Ontario. Get out and enjoy viewing them and other grassland specialty birds on the Carden Alvar.


Loggerhead Shrikes in hawthorn with impaled grasshopper.

Illustration by Christine Kerrigan



Blumton, A. K. 1989. Factors Affecting Loggerhead Shrike Mortality in Virginia. Master’s Thesis. Virginia State University, Blacksburg, VA.

Cadman, M. 1987. Loggerhead Shrike. In, M.D. Cadman et al., eds., Atlas of the Breeding Birds of Ontario. University of Waterloo Press.

Chabot, A. 2007. Loggerhead Shrike. In, M.D. Cadman et al., eds., Atlas of the Breeding Birds of Ontario, 2001–2005. Co-published by Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, Ontario Nature.

Clarke, C.H.D. 1972. Of Shrikes and Hawthorns. Ontario Naturalist 11(2).

Wheeler, H. 2017. Eastern Loggerhead Shrike Recovery. Issue 27. Wildlife Preservation Canada.

Yosef, R. 1996. Loggerhead Shrike. In, Birds of North America. Online. The Cornell Lab of Ornithology. Ithaca, New York.