Hi there!

Welcome to northernredtails.wordpress.com. This site consists of several pages:

Homepage: The page that you’re currently viewing. eBird: This page provides a link to view current abieticola Red-tailed Hawk sightings and also, a step-by-step guide to selecting abieticola Red-taileds when uploading field data. Submit Images: A page designated for information on how and where to submit your images. Gallery: A place where we showcase a variety of Red-tailed Hawk photographs, including those sent in by visitors of this page. References & Further Reading: This page provides all of the current published information on abieticola Red-taileds, as well as some websites and articles that are worth checking out. Contact: A page consisting of both our emails, as well as the email for this site. Thank you for dropping in. We hope that you find this blog site both informative and stimulating.

The idea behind this blog site is to provide readers with an in-depth online resource for information on Northern Red-tailed Hawks (abieticola). The layout, design, and flow of this site was strongly influenced by the content on another WordPress site: BC Red-tails (http://bcredtails.wordpress.com/). In late August of 2014, I fired off an email to Jerry Liguori and mentioned how I thought having ALL the available resources, many of the best images, first-rate identification pointers, etc. on a single site would be a good idea. Luckily, he agreed, and, well, here we are.

So, what is a Northern Red-tailed Hawk (abieticola) and when and where can one observe one?

Northern Red-tailed Hawks were first described by Todd (1950) he noted a population of Red-tailed Hawks distinct from other Red-taileds in the east by their rich coloration and heavy streaking. Todd described this population breeding in the boreal forest of Quebec and Labrador east of Hudson Bay. Dickerman and Parkes (1987) described the range of abieticola as existing throughout the spruce/fir belt from Alberta east to the Maritime Provinces. Classic individuals of abieticola are quite distinct from borealis, and more similar in appearance to typical examples of calurus. In calurus, typical light morph adults show bold, rufous-tinted, extensive markings to the underside, multiple tail bands, a dark, faintly mottled upperwing, and dark throat (Liguroi 2001). Typical examples of abieticola show a noticeably dark head in which streaks “dribble” out from the sides of the throat and onto the upper breast, deep brown back (on average, noticeably darker than typical borealis), and extensive belly band composed of globular streaks which, in some individuals, forms a solid band which is “pinched in” at the center, and grows in width towards the flanks. The base color, especially throughout the upper breast, is more buffy/orange-toned in coloration than what is seen with typical borealis Red-taileds. The tails of adult abieticola are quite similar to borealis though Todd (1950) described the subterminal band as being thicker. This was not found to be a reliable field mark when Dickerman and Parkes (1987) investigated abieticola; they found extensive overlap in subterminal width when comparing adult borealis and abieticola specimens. Dickerman (1989) stated that adult abieticola from the western population can show ancillary barring along the tail, though it is important to note that the extent of ancillary barring and thickness of the subterminal band vary within and among subspecies populations (Liguori 2001). I was able to observe an adult specimen on 1 December 2013 which showed ancillary barring along the tail and a thick, black subterminal band.

It is cautioned by North American raptor experts, Jerry Liguori and Brian Sullivan, that there is great overlap in plumage of juvenile Red-tailed Hawks among several subspecies and many specimens’ subspecific origins are better left safely undetermined. A classic juvenile abieticola is similar to a juvenile borealis but more heavily-marked, showing a dark brown head, a marked throat (though, sometimes, unmarked) which is demarcated by heavy malar streaks, “dribbling” of dark brown from the nape area into the upper breast and more extensive bellyband. Sometimes, this band is thinnest at its center and increases in girth towards the flanks (Ruddy 2014).

For an in-depth study on abieticola, please see Jerry Liguori and Brian Sullivan’s excellent paper (2014). To note, there are plenty of excellent sources of information available within the References & Further Reading page. (JR)

There are a lot of unknowns re: abieticola. Are they a heavily-marked form of Eastern Red-tailed Hawk (least controversial theory) or a distinct subspecies, showcasing a distinct geographical distribution isolated from borealis Red-taileds (most controversial theory)? Birds, such as the Red-tailed Hawk, lack specific defined geographic ranges that signify the end of one subspecies range and the start of another; making the line drawn on subspecies regions far from black-n-white. Given that the Northern Red-tailed Hawk (B.j. abieticola) originates from the seemingly endless swath of boreal forest that extends, nearly uninterrupted, from the northeastern US to the Alaskan coast, interbreeding with Krider’s in areas of the northern Great Plains, with the Western race in states and provinces that border the east side of the Rocky Mountains, and with the Harlan’s race throughout western Canada to parts of Alaska, is inevitable and has been documented. That said, it is still possible to identify many birds to subspecies that fit the defined criteria, and it is possible that abieticola is a proper candidate for subspecies status, but there are clinal and introgression factors to be considered when approaching subspecific ID of Red-tails. Take, for instance, an example of subspecific ID of Great Horned Owls. In Ontario, virginianus is the breeding subspecies throughout southern Ontario. As one heads NW to eastern Manitoba, there is a tendency towards lighter, grayer colored individuals, and, as one heads NE to northern interior Quebec, there is a tendency towards darker, more saturated deep brown plumages. At a certain point, geographically speaking, “classic” examples of the described subspecies (subarcticus in the NW and heterocnemis in the NE) are found. However, clinal and introgression factors are abound throughout that geographical journey northward to the breeding grounds of those “classics.” One can admire the genetic influence of the tendency towards those plumage characteristics while studying skins within a museum collection. Many do not fit neatly into the ascribed subspecies characteristics (M Gosselin, 2014, pers. comm., November). So, as a cautionary note, if you should take to the wonderful pursuit of Red-tailed Hawk study (or, if you’re already there!), there are specimens that cannot be safely identified to subspecies level. However, many migrant and winter resident abieticola are field recognizable, and distinct from “typical” Eastern (borealis) and “typical” Western (calurus) Red-tailed Hawks in plumage.

Overall, the authors of this blog site believe that more study is needed throughout much of abieticola’s breeding range to make a case for classifying it as an accepted subspecies. However, in order to continue to generate useful discourse, and for the sake of simplicity, it’s suggested that birders continue to use the English name, Northern Red-tailed Hawk, and Latin name, abieticola, without, perhaps, necessarily implying deeper connections such as subspecific status, etc, more so in simply keeping with a name that is used to describe heavily-marked Red-taileds throughout the east as described by Todd (1950 & 1963) and studied by Dickerman (1987), Pittaway (1993), and Liguori (2001 & 2014). “Classic” examples are quite distinct from Eastern (borealis) Red-taileds, and are consistently observed in southern Ontario and the northern and central states throughout the fall and winter. However, come late March through to late April, like clockwork, abieticola Red-taileds resume their enigmatic dispositions as they begin to leave their wintering grounds and vanish into the boreal forest throughout, primarily, regions in northeastern USA and central and northeastern Canada.

– Jerry Liguori & Jon Ruddy

 General abieticola-related Questions:

  • Migration WAVES: Do Red-taileds identified as abieticola appear in waves, suggesting population? Or do waves of migrant Red-taileds reveal a high degree of variation and general scattering of phenotypes? This question is an exciting one because 1) The usefulness of careful field observation is a powerful tool in this instance and 2) The popularity of Digital Photography, Photo Sharing, Facebook, Flickr, etc makes Citizen Science an immensely useful resource for developing a rich database of information from which experts can glean from as they continue to develop their working hypotheses with regards to abieticola as a form or subspecies of Red-tailed Hawk.
  • Are abieticola geographically separate from other subspecies of Red-tailed Hawks?
  • What is the prevalence of interbreeding with borealis and kriderii in the southern and eastern parts of their range, and calurus and harlani in the west?
  • What is the extent of their wintering range?
  • What is the extent of their breeding range?
  • Regarding morphometrics, are abieticola in any way distinct?
  • Are there dark morph abieticola Red-taileds?



Jerry Liguori: jerrylig@hotmail.com

Jon Ruddy: accipitriformes@gmail.com

Site: bjabieticola@gmail.com



4 thoughts on “Home

  1. Hi Lionel:

    Very interesting. Thanks for your note!

    By “dark RT’s” are you referring to heavily-marked Red-taileds or dark in the traditional sense of the word, as in, dark morph?



  2. Some great pics: I noticed of the 27 or so photos groups that a “herringbone” structure or pattern is closely associated with the blobs/tear-drops and often stitched together( frontal view-belly-band area): from strong to faint in the area of the belly-band. Its rarely seen by me and occasionally photograohed. I reside in the Kelowna, BC area where primarily calurus and harlani are seen. I will watch for the aforementioned pattern and document when possible.


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