Data Zone
Justification of Red List category
This species is thought to be undergoing a moderately rapid population decline. Therefore, it is listed as Near Threatened.
Population justification
Partners in Flight (2019) estimate the population to total 7,000,000 mature individuals.
Trend justification
This species has undergone a large and statistically significant decrease over the last 40 years in North America (-71.2% decline over 40 years; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven [Sauer et al. 2017]). Partners in Flight (2019) suggest a current population decline of ~24% throughout the species's range across the stipulated ten year period, thus an ongoing decline of 20-29% is estimated here.
This species is a widespread breeder across much of the U.S.A. and Mexico, extending into southern Canada in the breeding season. Northern populations are migratory whereas those in the south of the range are generally resident (Froehly et al. 2019).
This species occupies a variety of habitats generally associated with open areas and short vegetation (Yosef and International Shrike Working Group 2017). This includes parkland, pastures, open woodland, orchards and agricultural land with hedgerows and perching sites (such as fences) and impaling sites for storing food (e.g. barbed wire or vegetation with thorns/spines) (Yosef 1996, Yosef and International Shrike Working Group 2017). Shrike habitat typically includes four 'common elements': 1) foraging areas, typically bare ground and exposed rock, 2) nesting sites, usually small trees and shrubs, 3) perching sites, and 4) impaling sites, often barbed wire, thorns of sharp branches (Pruitt 2000, A. Chabot in litt. 2020). The species typically feeds on arthropods, amphibians, and small mammals, birds and reptiles, such as the Thamnophis sirtalis infernalis (Hughes 2019, Yosef 2020).
Several ideas have been presented that may account for declines in this species (see Lymn and Temple 1991), including pesticides (Anderson and Duzan 1978), fire ant presence in wintering habitats (Lymn and Temple 1991), West Nile Virus (Bertelsen et al. 2004, Smallwood and Nakomoto 2009) and habitat fragmentation and loss, particularly through conversion to agricultural land. The Loggerhead Shrike has been evidenced to be significantly more abundant in better connected areas of suitable habitat (Froehly et al. 2019) whilst occupancy significantly increases in areas with greater than 15-25% habitat suitability (A. Chabot in litt. 2020). Migratory connectivity is known to be greater in western L. ludovicianus populations where the impacts of habitat loss on populations are thought to be reduced, hence western populations may be at comparatively less risk than eastern populations (Chabot et al. 2018). Habitat loss and fragmentation are therefore thought to only be of regional significance, hence in other locations additional factors must be responsible for limiting Loggerhead Shrikes and driving the witnessed declines (Brooks and Temple 1990, Froehly et al. 2019). The species may have also been persecuted and shot in the past, but this has likely reduced (Yosef 1996). While the use of certain pesticides is now prohibited in U.S.A. the potential effects of other threats may be likely to continue into the future (Pruitt 2000, COSEWIC 2014). Collisions with vehicles contribute to the species's decline as roads display a number of essential habitat features; 29% of all L. ludovicianus winter mortality in Virginia has been attributed to collisions on roads (Blumton 1989). Furthermore, intraspecific competition on wintering grounds between migrants and resident shrikes that occupy territories year round likely contributes to the decline of obligant migrant populations of Loggerhead Shrike in north-eastern North America (Brooks and Temple 1990; Cade and Woods 1997; Pruitt 2000; COSEWIC 2000). Loss of habitat in wintering areas may exacerbate competition (Lymn and Temple 1991). Extreme local weather conditions have been implicated in declines as a result of high nest failure rates (e.g., nest abandonment or loss of young birds during cold wet breeding seasons, especially with heavy rains [Pruitt 2000]) and such threats may increase as stormy conditions are exacerbated under a changing global climate (COSEWIC 2014, Environment Canada 2015a). Predation of shrikes by a variety of species, including cats, raccoons, crows, magpies, and several raptors has been observed (Blumton 1989; Wiggins 2004) but the significance has not been evaluated. Predation by feral cats (Felis catus) impacts the endemic subspecies L. l. mearnsi on San Clemente Island, California, U.S.A. (Gustafson et al. 2020).
Conservation Actions Underway
The Loggerhead Shrike is protected in Canada, Mexico, and the USA under the Migratory Birds Convention Act (COSEWIC 2014). Under Canada’s Species at Risk Act, the Prairie subspecies (L. l. excubitorides) is currently listed as Threatened, while the Eastern subspecies (L. l. migrans) is listed as Endangered (COSEWIC 2014). The species was incorporated into the Canadian Wildlife Service's Operation Grasslands Community (Yosef 1996) whilst a targeted recovery strategy was developed and implemented in 2015 for subspecies migrans in Canada, aimed at re-establishing a viable population of the subspecies in Canada where less than 100 wild individuals remain (Environment Canada 2015a). This species has been successfully reared in captivity with captive-reared juveniles released to augment populations in Ontario and Quebec (as well as San Clemente Island, California); over 400 juveniles released between 2001-2010 with ~76% of such individuals thought to survive from release to migration initiation (Imlay et al. 2010, Nichols et al. 2010, Lagios et al. 2015). A species recovery plan also exists for subspecies excubitorides in Canada (Environment Canada 2015b) whilst the subspecies is included in multi-species action plans for southwestern Saskatchewan (Environment and Climate Change Canada 2017) and the Grasslands National Park (Parks Canada Agency 2016). The North American Loggerhead Shrike Working Group was established in 2013 to undertake 'multi-jurisdictional research and conservation efforts for Loggerhead Shrike and their habitat', guided by the Loggerhead Shrike Conservation Action Plan (Loggerhead Shrike Working Group 2017). Accomplishments so far include a tri-national colour banding program, predictive occupancy and distribution modelling, developing standardised protocols for shrike surveys and monitoring, and broad-scale surveys and monitoring through the community science program, 'Shrike Force' (Loggerhead Shrike Working Group 2017, J. Steiner in litt. 2020). Banding and radio-tagging is underway in Mexico to explore local movements and habitat utilisation (J. Steiner in litt. 2020). This species has been successfully reared in captivity with captive-reared juveniles released to augment populations on San Clemente Island, California and in Ontario, Canada (Imlay et al. 2010, Nichols et al. 2010, Lagios et al. 2015) and this action is considered significant in securing the long-term persistence and re-establishment of Loggerhead Shrike populations, particularly throughout the north-eastern portion of its range (L. Steiner in litt. 2020).
Conservation Actions Proposed
Monitor the species to get clear estimates of population size and trends across its range. Investigate any possible further threats to this species that could be contributing to population declines, including investigating whether other pesticides could be affecting the species and how the impact of habitat loss and fragmentation on the species varies regionally (Environment Canada 2015a). Investigate the species's ecology, including work on its migration and its wintering locations, competition with other species and dietary requirements (see Yosef 1996, Environment Canada 2015a). Potentially further reduce the use of pesticides, and restore areas of habitat for the species (see Yosef and International Shrike Working Group 2017).
Text account compilers
Everest, J.
Contributors
Chabot, A., Ekstrom, J. & Steiner, J.
Recommended citation
BirdLife International (2024) Species factsheet: Loggerhead Shrike Lanius ludovicianus. Downloaded from
https://datazone.birdlife.org/species/factsheet/loggerhead-shrike-lanius-ludovicianus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.