The “Marsh Hawk” Conundrum
Julian Hough (all photos by author unless otherwise noted)
Gripper! Me holding a HY male, Northern Harrier, Cape May, NJ, USA, September 1990. Who’d have thunk back in my 20s, that these awesome beasts would not only encumber me with headaches and sleepless nights, but also many ‘wasted’ hours in front of a computer that I can never get back!
With all the current ‘hudsonius hysteria’, I hope the following may be of interest and is put forth here, not as an authoritative, in-depth identification piece but as an interesting resource, especially for those lucky enough to have seen the one of the putative HY (Hatch Year=juvenile/first-year) Northern Harriers that have graced Ireland and Norfolk recently. If anything, it is to present a pictorial expansion on criteria currently being discussed to help separate these two species/sub-species.
A typical HY male, Connecticut, October. Streaking on the underparts is variable. The sides of the breast and flanks are lightly streaked, but typically heavy streaking is absent from the central belly as is often shown by many cyaneus. Although some birds can show pencil thin-streaks on the lower belly, you don’t want your hudsonius to have thick streaking in that area!
It all began for me back in 2008 when I posted a request on the Surfbirds forum http://www.surfbirds.com/forum/showthread.php?t=4463 asking for information on ‘rufous-plumaged’ juvenile Hen Harriers (C. cyaneus). It was to solicit information that might provide insight into what features might be useful in separating these individuals from vagrant juvenile Northern Harrier (C. c hudsonius or C. hudsonius?)– an identification issue I had been interested in from my autumn experiences in Cape May, NJ, USA. These warm-plumaged juv cyaneus were often described as variants, but a perusal of books and online galleries show that these juvenile birds are not as uncommon as was previously thought. Documenting how these birds might be separable from vagrant hudsonius was a logical first step in attempting to solve the problem. I had no idea at the time, that such interest in this race/species would soon go “Super-Nova”.
Anyway, fast forward to 2009 and a hudsonius-like harrier seen on North Ronaldsay by Alex Lees, Paul Brown and John Bell kicked off all sorts of interests in the same arena. http://www.freewebs.com/punkbirder/orangeharrier.htm. Described as a veritable flying “Terry’s Chocolate Orange” it seemingly sported a nice quota of field marks suggestive of hudsonius. The essential reference was John Martin’s excellent paper in BB that documented the first acceptable juvenile on Scilly in 1982. From the available photo-evidence of the North Ron harrier, it was apparent from a rarities committee perspective that it might fall short of meeting criteria necessary to nail it as a hudsonius. It was this bird, and correspondence with Alex Lees, John Martin, John Bell and Martin Garner, that instigated talks about what features were valid and consistent in proving a Northern Harrier in a vagrancy context. I am also lucky enough to live 10 minutes from one of the best hawk watching spots in New England and get to see good numbers of “Marsh Hawks” each autumn. I was able to photograph quite a few.
Another typical HY male, Connecticut, January. Taken at sunset, the bird is saturated by the setting sun. Note the ‘boa’ effect extending around under the chin and streaking most notable on the flanks, not central belly.
Is three two too many??
Eerily, in October 2010, sharp-eyed Irish birder Tom Kilbane found a bird at Tacumshin. Nicely photographed by Killian Mullarney, it was as perfect candidate and ticked all the pre-requisite boxes. Cool! It seemingly could be done! Within weeks, photos surfaced of another bird at Kilcoole, Ireland that looked equally convincing but additional information was not forthcoming. Then, in what might have seemed a cruel twist of fate another individual was claimed in Norfolk (Mark Golley, Stuart White) that seemed destined to tar and feather these ‘good’ birds. One bird, awesome! two…err, OK,…. but THREE birds in almost as many weeks seemed to defy logic. England winning the World Cup again was more likely! Probability and common sense dictated three hudsonius in one fall (after an absence of 28 years) couldn’t be true ? Surely this east coast individual was the “I told you so cyaneus” – the one individual that would reinforce the notion that maybe we didn’t quite have a grip on just how difficult telling cyaneus from hudsonius could be. In the face of improbable odds, the photos of the Norfolk bird again ticks all the right boxes and appears as good a hudsonius as any other claim – kudos to the finders for putting out their suspicions in the face of such improbability! So, on the face of it, the only explanation is that there seems to have been a small arrival of Marsh Hawks this fall, -an hypothesis that could be superficially supported by weather patterns and the discovery of other Nearctic vagrants in 2010. Or, we are all just going completely insane!!
The final coup de grace in this drama was when Mark Newsome posted photos of a male bird he had photographed in Durham in February 2009. (http://www.birdforum.net/showthread.php?p=1992494#post1992494) It proved to be an adult male Northern Harrier – the first undisputed male for the Western Palearctic and reaffirmation that these birds do have the stamina and wing-loading to make it across the Atlantic.
HY female (left), HY male (right) Cape May, October – note dark brown iris in female and bluish-grey in HY male. The extent of white around eye is often broken at rear. HY Northern Harriers invariably show well-marked streaks across upper breast but others can be almost uniform below. (Photos: Alec Humann, left, R. Studholme, right)
Field marks-are there any useful ones?
John Martin’s BB paper (also a chapter in ‘Frontiers in Birding’), which still stands the test of time, laid out the criteria most observers use for reference. Other features of potential use in separating hudsonius were recently discussed and included; the width of the middle dark bar on the underwing secondary coverts; the prominence of the dark boa and the number of dark bars on the longest three primaries. Examining photos, I also had noticed independently the propensity for hudsonius to lack streaks on the undertail coverts – unfortunately a feature also shown by some cyaneus.
HY male, Cape May, NJ, September (same bird as in header photo) – note dark, chocolate upperparts and “Terry’s Chocolate Orange” outer tail feathers and wing coverts.
In an effort to validate and quantify some of these features, I had enlisted the help of Paul Napier and the Raptor Banding Project at Cape May, who kindly agreed to collect data and take some photos. To them, particularly Robert Studholme, I owe big thanks and to Alec Humann for use of their images. The image below shows the features that were analyzed.
The following are summarized comments from data collected on 40 (25 male and 15 female) HY Northern Harriers banded at Cape May, New Jersey in October 2010.
- Primary bars (excluding the dark tip) on P9-7 varied on both male and female. Males averaged 6 bars (lowest 5, highest 7) while females averaged 5.6 bars (lowest 5, highest 8).
- On the males, the middle secondary bar was always significantly narrower, but in females it varied with some females having a broader bar equal to A and C, especially on S4 – 6.
- In the hand, the undertail covert feather shaft streaking was obvious on almost all the males* but this streaking was absent on the females.
* These shaft streaks almost certainly undetectable in normal field conditions.
HY (sexes unknown) – note variation in primary barring, width of the dark secondary bar (B) and how many dark secondary bars are visible. These photos show the amount of primary barring is variable; typically 5-8 (average 6) excluding the dark tip and is not really useful in isolation. One cyaneus with 6 bars has been documented from Orkney (photographed by A. McGeehan)
HY male (left) and HY female (right). note rich cinnamon undertail coverts/vent that lack obvious dark streaking shown in many cyaneus. Some HY males show a darker feather shaft as shown, but these should not be visible in the field. While many cyaneus show more distinct brown or blackish streaks here that are visible in the field, some can show clean undertail coverts.
It’s interesting to note that out of the 40 birds trapped, 25 of them were males (62.5 %) and 15 were females (37.5%).
A glance through my (limited) photo collection shows that of the birds I could age from my photos (on eye colour) most were males. Photographing random birds at random times suggested a higher proportion of males to females.
It is interesting to compare the above features with those of the current claimed hudsonius. Personally, I had gone backward and forwards on whether I thought I could “do” them, especially as it is obvious that some cyaneus can be so similar as to make the identification in many field condition very difficult, if not impossible.
HY male, Connecticut, January. Note pattern of underpart streaking and middle secondary bar. This bird is well lit from below by light reflected off snow and appears less saturated.
Since many of these features may be difficult to accurately note in the field, obtaining photo-documentation seems a pre-requisite for a claim of any putative hudsonius. In illuminating discussions in private and on Bird forum and Surfbirds Forum, http://www.surfbirds.com/forum/showthread.php?t=4463 it had become clear that this issue is difficult at best due to the lack of any single diagnostic field mark. Identification seems only possible using a suite of characters and only the “classic” birds will prevail. In a vagrancy context, they are the raptor equivalent to ‘smithsonianus’ Herring Gulls!
HY, Connecticut, October. A more uniformly patterned bird with only 4 -5 apparent bars on the outermost primaries. What would you do with this in Europe!!
Continued research and documentation will create a more informed (and at the same time, probably confusing) picture. More research into cyaneus and determining how many birds can actually show a similar suite of features is needed. A careful examination of photos of some of these pseudo-hudsonius shows them to be lacking in some aspects and we must take care not to muddy the identification waters unnecessarily.
HY, male, Connecticut, November.
Based on current knowledge, the criteria used for identifying hudsonius is certainly being sharpened and may yet prove to be a moving goalpost. Future data may need to be reformed, revised and validated under more scientific controls. Until then, based on what we have, birds conforming to the suite of characters described above should be taken seriously. The recent claims (including the North Ron bird in my opinion) have been thought-provoking and the finders of these birds deserve applause for having their wits about them to bring to light their presence which is not an easy task out in the field!
And finally…an “easy “one. Adult Male Northern Harrier, Connecticut, November. Colloquially known as “Grey Ghosts”, adult males are exquisite. They are more marked above than cyaneus with a thick, black trailing edge on the underwing and small brownish-orange markings on the upper flanks and undertail coverts. Younger adults have a more brown-washed head (often appearing more “hooded”) and are often more extensively spotted.
Thanks to Alex Lees, John Martin, Martin Garner, Mark Golley, Killian Mullarney, John Bell, Jerry Liguori and Bill Clark for illuminating and educational discussions on this topic. Big kudos to Paul Napier and the Cape May Raptor Banding group. Special thanks to Martin Garner for allowing me to hijack his educational blog.