The Red-tailed Hawk (Buteo jamaicensis) is one of the most widespread and recognizable raptors in North America. This medium-sized buteo occurs across much of the continent, occupying a variety of habitats including forest edges, grasslands, deserts, and urban areas. The Red-tailed Hawk exhibits a high degree of geographic variation in plumage and size, with several subspecies recognized.
Overview of Red-tailed Hawk Taxonomy
The Red-tailed Hawk belongs to the avian order Accipitriformes and the family Accipitridae. Until recently, most taxonomic authorities recognized two primary subspecies groups within B. jamaicensis:
- The B. j. jamaicensis group – This includes larger, darker-colored birds found across eastern North America.
- The B. j. calurus group – Smaller, paler birds found in the western part of the continent.
However, recent genetic research has revealed that this dichotomous treatment is likely an oversimplification. In particular, findings indicate that western Red-tailed Hawk populations exhibit a high degree of genetic structure and likely represent multiple distinct subspecies. As such, more modern taxonomic treatments recognize a greater number of subspecies, with some authorities delineating up to 19 unique subspecies of Red-tailed Hawks across North America.
Eastern Red-tailed Hawk Subspecies
In eastern North America, most recent taxonomic treatments recognize six subspecies of Red-tailed Hawks:
- B. j. jamaicensis – The nominate subspecies; occurs across eastern Canada and the northeastern United States. This is the darkest-colored form.
- B. j. abieticola – Found across southeastern Canada and the northeastern U.S.; slightly paler than jamaicensis.
- B. j. borealis – Breeds across northern and eastern Canada; smaller and paler than more southern forms.
- B. j. krideri – Occurs across the Great Lakes region and into the central U.S. Lighter than borealis but darker than western forms.
- B. j. harlani – Found in the prairie regions; the lightest eastern form.
- B. j. fuertesi – Resident on the Florida peninsula; similar in color to jamaicensis and krideri.
These subspecies intergrade extensively across transition zones where their ranges contact one another. However,they can typically be distinguished based on geographic location and plumage characteristics such as color saturation and tail banding patterns.
Western Red-tailed Hawk Subspecies
In western North America, taxonomy remains actively debated with 11-14 potential subspecies described. Commonly recognized distinct forms include:
- B. j. calurus – A small, pale desert form found across the interior southwest U.S.
- B. j. alascensis – A richly-colored subspecies resident across coastal Alaska.
- B. j. fumosus – A melanistic form found along the northwest coast.
- B. j. socorroensis – A resident of the Revillagigedo Islands off Mexico.
- B. j. lucasanus – Found in the Channel Islands of southern California.
- B. j. pallescens – Occurs across the southern portions of California.
In addition, some authors delineate forms such as B. j. montanus, B. j. caurinus, and B. j. regalis found across other parts of western North America. More study is needed to clarify the taxonomic status of these potential subspecies.
Hybrid Zones Between Subspecies
Across zones of contact between the recognized subspecies, various degrees of intergradation and hybridization occur. Notable hybrid zones exist between:
- B. j. abieticola and B. j. borealis in southeastern Canada
- B. j. borealis and B. j. calurus in the Great Plains
- B. j. calurus and B. j. alascensis in British Columbia
- B. j. harlani and B. j. calurus in the southwestern U.S.
The presence of these hybrid zones makes definitively distinguishing some subspecies difficult, especially for migratory populations that may traverse multiple typical subspecies ranges over the course of a year.
Summary of Recognized Subspecies
To summarize, while taxonomy continues to evolve, most recent treatments recognize around 16-19 subspecies of Red-tailed Hawks in North America, with 6-7 subspecies occupying eastern North America, and 10-12 found in western parts of the continent. The table below outlines the primary recognized subspecies and their geographic distributions:
| Subspecies | Range |
|---|---|
| B. j. jamaicensis | Eastern Canada and northeastern U.S. |
| B. j. abieticola | Southeastern Canada and northeastern U.S. |
| B. j. borealis | Northern and eastern Canada |
| B. j. krideri | Great Lakes region and central U.S. |
| B. j. harlani | Great Plains |
| B. j. fuertesi | Florida |
| B. j. calurus | Interior southwest U.S. |
| B. j. alascensis | Coastal Alaska |
| B. j. fumosus | Pacific Northwest Coast |
| B. j. socorroensis | Revillagigedo Islands, Mexico |
| B. j. lucasanus | Channel Islands, southern California |
| B. j. pallescens | Southern California |
Conclusion
In conclusion, most recent taxonomic treatments recognize between 16-19 subspecies of the widespread Red-tailed Hawk across North America. Further research using modern genetic techniques may continue to refine the delineation of different subspecies and add to our understanding of geographic variation in this adaptable raptor. However, the currently recognized subspecies provide a good framework for understanding the diversity of plumage, size, and habitat associations exhibited by Red-tailed Hawk populations across the continent.
