Harlan's Hawk (1 Viewer)

[Richard Klim]

Ref. Clark, W.S. 2009. Extreme Variation in the Tails of Adult Harlan's Hawks. Birding 41 (1).
http://www.aba.org/birding/v41n1p30.pdf
http://www.aba.org/birding/v41n1p36w1.pdf

Clark's concluding paragraph:

"I am currently at work on a manuscript addressing the taxonomic status of Harlan’s Hawk, so I’ll not comment here on that subject. Suffice it to say, Harlan’s Hawks are unique among raptors for the extreme amount of tail variation that they show."
​

Could Buteo harlani soon be split again...???

Richard

 

[l_raty]

It certainly will be interesting to see how things turn out, but... I'm not sure that identifying a taxon as "unique for the extreme amount of variation it shows" is a very good starting point to split it...
Note that the taxonomic issues with Harlan's Hawk don't end with the "species vs. not-a-species" question. The dark harlani phenotype has also been regarded a color morph in the past, thus we arguably also might have a "subspecies vs. not-a-valid-taxon" question.

Riesing et al. (2003 - http://www.bird.at/fileadmin/user_upload/Redaktion/pdf/buteophyl.pdf) found two clades of mtDNA in B. jamaicensis.
One was present in samples from Jamaica (jamaicensis) and eastern N America (borealis), as well as in a harlani (taken in N Dakota, though - thus outside the breeding range of the ssp).
The other was present in samples from western N America (calurus) and Mesoamerica (costaricensis), but also in a borealis from New Jersey. (This second clade is also what they found in the two South-American Rufous-tailed Hawks B. ventralis they sampled.)
This is suggestive of an east+north vs. west pattern of differentiation - quite classical in N American birds - but the sample sizes are really small, and more data would be necessary to confirm this.

Alternatively, if N America was colonized following two distinct pathways (one from a Caribbean refugium, through eastern, then northern N America, the other from a Mesoamerican refugium, through western N America), it may be conceivable that these could both have ended, and met, in the range of harlani. Thus if harlani is so variable, what about it being something like a krideri-calurus intergrade/hybrid swarm?

L -

 

[Richard Klim]

It certainly will be interesting to see how things turn out, but... I'm not sure that identifying a taxon as "unique for the extreme amount of variation it shows" is a very good starting point to split it...
Note that the taxonomic issues with Harlan's Hawk don't end with the "species vs. not-a-species" question. The dark harlani phenotype has also been regarded a color morph in the past, thus we arguably also might have a "subspecies vs. not-a-valid-taxon" question.

You're right Laurent - I was being highly speculative. Perhaps Clark's manuscript will indeed be a discussion of possible colonisation models, as per your comments.

Richard

 

[mb1848]

But is krideri a valid subspecies? Quoting The Birds of the Salton Sea: " Its status as a valid subspecies is debatable. Red-tailed Hawks exhibiting this phenotype apparently do not occupy a distinct breeding range but rather occur "only in association ...with borealis or calrus" (Taverner 1936) Because a valid subspecies must have a distinct, exclusive breeding range, Taverner treated krideri as a white morph of borealis.

 

[Richard Klim]

But is krideri a valid subspecies?

Indeed. Preston & Beane 1993 BNA Online also references Taverner:

"Buteo jamaicencis "krideri". Probably not a valid subspecies; unclear if breeding range exclusive of other races exists. When compared with adjacent races, "kriderii" exhibits only a dilution or suppression of color, varying greatly among individuals (Taverner 1936). Distribution and taxonomic status require thorough examination. Presumably intergrades with all adjacent races. Winters from S. Dakota and s. Minnesota south to Arizona, Louisiana, and central Mexico. Scattered reports of extremely pale individuals from much of se. U.S."​

Clark himself notes in his 2001 Raptors of the World:

"Whitish individuals found sparingly on Great Plains throughout range of borealis and formerly regarded as separate subspecies ('krideri'), but in fact merely pale morph of that race."​

Richard

 

[Richard Klim]

Clark himself notes in his 2001 Raptors of the World:

That should have read: Ferguson-Lees & Christie 2001.

Richard

 

[Richard Klim]

Clark's concluding paragraph:

"I am currently at work on a manuscript addressing the taxonomic status of Harlan’s Hawk, so I’ll not comment here on that subject."
​

Could Buteo harlani soon be split again...???

BNA Online has a fully revised species account for Buteo jamaicensis Red-tailed Hawk (Preston & Beane, 18 May 2009). The Systematics section notes:

"Twelve subspecies in two groups: Harlan’s Hawk (B. j. harlani), formerly treated as a distinct species (Peters 1931, Am. Ornithol. Union 1957) -- and may yet prove to be given limited interbreeding with neighboring populations where ranges meet (W. S. Clark pers. comm.) -- and all other "typical" Red-tailed Hawks."
​

Richard

 

[Richard Klim]

AOU2009 Philadelphia

Clark, W S 2009. Taxonomic status of Harlan's Hawk. 127th Stated Meeting of the AOU.

Abstract:

"Harlan’s Hawk (Buteo harlani) has been considered by the AOU as either a species (1886-1891, 1944-1973) or as a subspecies of Red-tailed Hawk (B. jamaicensis) (1898-1944, 1973-present). The two lumpings lacked taxonomic justifications, whereas the separation in 1944 was based on published plumage differences. From examining more than 2000 museum specimens, I have found that Harlan’s are always diagnosable by plumage and by the shorter extent of bare tarsi. These taxa differ in frequency of color morphs, tail coloration and pattern, body plumage by age, behavior, and markings on the remiges. Harlan’s Hawk plumages are highly variable, much more so than in other Buteos. Rufous in the plumages of many adults, apparently the only reason for the lumpings, will be shown to be due to ancestry, not to interbreeding. No valid cases of interbreeding were found; all such alleged cases were in the breeding range of Harlan’s and were based on misidentified adults. Harlan’s Hawk should be again considered a species, as it differs greatly from Red-tailed Hawk, and its inclusion in that taxon has never been justified."​

Richard

 

[njlarsen]

Thanks Richard

Niels

 

[Mysticete]

would be nice to see some molecular data for these species...

 

[Birdbrainjwc]

I totally agree with Richard Klim, I do also believe the Harlan's Hawk should be a seperate species.

Here in Montana, we get good numbers of them in the winter months, and they are FULLY identifiable from the "normal" Red-tailed Hawks. They even have a slightly different body shape, and structure. They are a bit more compact, like a Broad-winged Hawk. They are even more shy, and flighty. Almost hands down, the Harlan's will fly from a telephone pole before a "normal" Red-tailed Hawk would. I am not sure it this is just habit, or they are consious of there dark coloration contasting with the white landscape.

I would like to see them split, they are a beautiful and unique Buteo.

 

[Richard Klim]

I totally agree with Richard Klim, I do also believe the Harlan's Hawk should be a seperate species.

Here in Montana, we get good numbers of them in the winter months, and they are FULLY identifiable from the "normal" Red-tailed Hawks. They even have a slightly different body shape, and structure. They are a bit more compact, like a Broad-winged Hawk. They are even more shy, and flighty. Almost hands down, the Harlan's will fly from a telephone pole before a "normal" Red-tailed Hawk would. I am not sure it this is just habit, or they are consious of there dark coloration contasting with the white landscape.

I would like to see them split, they are a beautiful and unique Buteo.

Well, I was just reporting Bill Clark's paper.

Seeing Harlan's Hawk was certainly one of the highlights of a trip to Alaska a few years ago (after an earlier unsuccessful search on a brief winter visit to Texas). A very distinctive bird.

Richard

 

[Richard Klim]

Liguori & Sullivan 2010. Comparison of Harlan's with Western & Eastern Red-tailed Hawks. Birding 42(2): 30-37.
http://www.aba.org/birding/v42n2p30.pdf

Liguori & Sullivan 2010. A Study of Krider's Red-tailed Hawk. Birding 42(2): 38-45.
http://www.aba.org/birding/v42n2p38.pdf

More photos:
http://www.aba.org/birding/v42n2p5w1.pdf

Richard

 

[tomjenner]

Bill Clark showed me some of his photos of hundreds of individuals he photographed on passage in Alaska. Although there was a lot of variation there was also a very distinctive patterning to the tails. He has also photographed hundreds of specimens showing similar patterning. This was a couple of years ago, so I don't remember the details. He seemed very convinced of the separation, but it seemed (at the time at least) to be more based on plumage characteristics than anything else and I wondered if that would be sufficient to justify a split. I look forward to seeing the arguments in his final paper.

Tom

 

[Richard Klim]

Hull et al 2010

Hull, Mindell, Talbot, Kay, Hoekstra & Ernest 2010. Population structure and plumage polymorphism: The intraspecific evolutionary relationships of a polymorphic raptor, Buteo jamaicensis harlani. BMC Evol Biol 10:224.
http://www.biomedcentral.com/content/pdf/1471-2148-10-224.pdf

[Supports continued treatment of harlani as a ssp.]

Richard

 

[jmorlan]

Bill Clark was a speaker last November at the "Central Valley Birding Symposium" where he presented his arguments for splitting: [FONT=Arial,sans-serif]"Harlan's and Red-tailed Hawks: their taxonomy, differences, and field identification." [/FONT]It was a long paper with a lot of morphological data. Essentially he was able to show that the supposed hybrids were actually pure Harlan's.

The reaction from the the folks I spoke to, including one member of the AOU Check-List Committee was that they were unconvinced. One person told Clark that he had made an excellent case that harlani is a good subspecies. Clark had no evidence of assortative mating in areas of contact or overlap which is what the AOU is looking for.

My take was that he started his program with the hypothesis that harlani is a good species and then focused on any and all evidence, especially morphological differences which supported his conclusion. It did not appear to be particularly balanced or objective.

I've questioned the maps by Wheeler in "Raptors of Western North America" which show Harlan's overlapping in breeding range with typical Red-tailed. I corresponded with Wheeler on this, and he has thorough data on these nests, but no satisfying evidence that the birds were correctly identified. I brought this up during the Q&A after Clark's presentation and he also questions those maps.

What's interesting is that if those maps were correct, they would represent the strongest evidence for harlani as a biological species. One member of the audience reported an apparent contact zone in British Columbia and Clark seemed interested in following up on that.

Clark also argued that krideri was merely a white morph of harlani. With recent studies of krideri on the breeding grounds by Liguori and Sullivan (cited earlier) that seems unlikely.

 

[Kirk Roth]

Hull, Mindell, Talbot, Kay, Hoekstra & Ernest 2010. Population structure and plumage polymorphism: The intraspecific evolutionary relationships of a polymorphic raptor, Buteo jamaicensis harlani. BMC Evol Biol 10:224.
http://www.biomedcentral.com/content...148-10-224.pdf

[Supports continued treatment of harlani as a ssp.]

I find it disappointing that the article doesn't address Clark's claim of a lack of interbreeding between harlani vs. alascensis/borealis/calurus. Indeed, Clark is formally cited twice: once for his field guide and for his article in Birding. Oddly, his article is cited as "in press," despite Liguari's later Birding article getting a full citation. Some lazy editing there! But at any rate, I feel that its a bit irresponsible for the Hull article not to discuss Clark's findings, despite Clark's assistance to their field work.

Unless I'm mistaken, the article uses the same mtDNA markers that have been used in other hawk analyses. This seems an odd convention to me - as if hawk DNA only varies in 17 particular spots. All of this just before the article states "These data suggest that the Mc1r locus in B. jamaicensis is not responsible for breast color variation or the variable melanin-based
plumage patterns observed in B. j. harlani." To me, this seems to mean "we studied several genes, but not the ones that make harlani distinct." If the analysis instead honed in on melanin-related genes, I would expect the data to show either a closer relation between harlani-calurus (contra Hull's results) or perhaps more distinction, depending obviously on the mechanisms of melanism between the two taxa.

I'm trying to say that it would seem a real possibility that Hull's analysis could have missed key genetic pieces. The article addresses this with a half sentence on the last page: "Potential mechanisms include: 1) a B. j. harlani-specific gene or gene-complex, or 2) particular environmental, temporal, or physiological conditions within the B. j. harlani range interacting with the standard B. jamaicensis genotype without involvement of a unique B. j. harlani
genotype." I bring this up because even a single gene can cause biological speciation, and frankly I have a hard time accepting that mtDNA and microsatellites change in constant rates, along all taxa, such that it can be the basis for such bold statements as the Hull paper makes about speciation and lack thereof.

One other note about point #2 in the quote in the paragraph above - For this scenario to be true, some sort of phenotypically plastic gene would have to be present in harlani and borealis, but not alascensis. Unfortunately, alascensis was excluded in this study, leaving out an important piece of the puzzle.

Too bad we can't get a good study limited to Alaska and northwest Canada, integrating ecological, morphological, and genetic data. But I suppose that would put Harlan's Hawk researchers out of a job.

Clark also argued that krideri was merely a white morph of harlani. With recent studies of krideri on the breeding grounds by Liguori and Sullivan (cited earlier) that seems unlikely.

One of our understandings of Clark's remarks is incorrect. The last I heard from him, he admitted to not knowing what exactly the true krideri morph is. However, I can attest that a great many winter "krideri" reported here in the midwest end up being light morph harlani, especially juveniles.

 

[jmorlan]

One of our understandings of Clark's remarks is incorrect. The last I heard from him, he admitted to not knowing what exactly the true krideri morph is.

When was that? My understanding is based on his presentation in November 2009 at CVBS.

It would not surprise me that he might have changed his mind in view of more recent publication such as that of Liguori and Sullivan.

 

[Kirk Roth]

When was that? My understanding is based on his presentation in November 2009 at CVBS.

It would not surprise me that he might have changed his mind in view of more recent publication such as that of Liguori and Sullivan.

Going through my correspondence, it was actually in '08, so go figure. While digging around, I found this link:

http://www.globalraptors.org/grin/downloads/RRF2008_Annual_Meeting_Abstracts.pdf

On page 6 is an abstract from Bill explaining that most Krider's he examined in museums were misidentified light-morph Harlan's.

I do feel that the diagnosis of a Krider's hawk is problematic. Bernard Hoopes' type specimens are both juveniles, so a weak argument could be made that an adult Krider's is an undefinable entity. All I can speak for is the midwest, but a great many observers here aren't even aware that light-morph Harlan's even exist, plus many leucistic but otherwise typical borealis get passed off as Krider's. In this sense, at least some "Krider's" are indeed Harlan's or typical borealis.

To tie this all together - in light of Liguori and Sullivan's description of Krider's breeding range, I don't think a Krider's could possibly be Harlan's, unless the definition (and range) of a Harlan's were changed quite a bit. This makes for an interesting supposition, however, if you'll be kind enough to follow: The Hull paper uses borealis from Wisconsin for genetic sampling, which is not too far from Minnesota and Iowa, where Krider's seem to have been reported widely (not least of all from Krider himself in "Forty Years Notes of a Field Ornithologist"!). IF Krider's = Harlan's and IF Hull's data includes some Kridersy genes in the borealis sample, then there would be no difference between the gene sets. Now, these are big and likely false "ifs," but it makes for some fun food for thought, doesn't it?

 

[Richard Klim]

AOU2009 Philadelphia:
Clark, W S 2009. Taxonomic status of Harlan's Hawk. 127th Stated Meeting of the AOU.

Bill Clark was a speaker last November at the "Central Valley Birding Symposium" where he presented his arguments for splitting:
"Harlan's and Red-tailed Hawks: their taxonomy, differences, and field identification."
It was a long paper with a lot of morphological data.

Anyone know when/where Clark's taxonomy paper will finally be published?

Richard