Download Is HARLAN`S HAWK a subspecies of Red

Is HARLAN’S HAWK a subspecies of
Red-tailed Hawk?
Review of publications that advocate such –
and why their taxonomic justifications are not
convincing
British Columbia
harlani
Washington
William S. (Bill) Clark
B. j. calurus
HARLAN’S HAWK:
described as Buteo harlani by Audubon (1830),
based on his Louisiana adult specimen.
Ornithological
Biography i:442-443.
Type specimen is in
the British Museum
British Natural History Museum
TAXONOMIC STATUS - history
1833-1891: Species: B. harlani
1891-1944: Subspecies of Red-tailed Hawk:
Buteo jamaicensis harlani, but without
taxonomic justification. AOU 2nd check-list 1891
1944-1972: Species: B. harlani, with
justifications given for separation. AOU 1944.
1972 to present: Subspecies of Red-tailed Hawk:
Buteo jamaicensis harlani, but without
taxonomic justification. AOU 1972.
1891: AOU check-list committee decided harlani
was a subspecies of the Red-tailed Hawk.
Apparently based solely on Ridgway (1890), who thought
a light-morph adult Harlan’s specimen was a hybrid, an
adult Red-tail with a Harlan’s tail.
Light-morph adult Harlan’s Hawk - Canadian Museum of Nature
Specimen was collected in late September in Iowa. I
was unable to locate it. Ridgway’s description fits many
adult light Harlan’s. But even if it had been a hybrid,
that does not make Harlan’s the same species, as many
hybrids exist between good species of Buteo.
However, Ridgway in 1895 still
treated Harlan’s Hawk as a species
on page 469 of his:
Ridgway, R. 1895. The Ornithology of
Illinois. Part I, volume II. Description
catalogue. State Laboratory of Natural
History. pp 469-472.
Included descriptions of both light and
dark color morphs of Harlan’s Hawks and
differences from Red-tailed Hawk.
1944: AOU reinstated B. harlani , citing
Peters 1931 & Taverner 1936.
Peters (1931) Check-list of the Birds of the
World treated B. harlani as a species, perhaps
based on the work of Kirk-Swann.
Taverner (1936) changed his mind (from
Taverner 1927) and argued why harlani is a
good species based on plumage differences.
Wood (1932) (not cited) described plumage
differences between 137 harlani specimens &
> 200 of B. jamaicensis and considered
Harlan’s a species.
AOU check-list committee cited three
publications to justify its 1973 decision:
1. Brown & Amadon. 1968. Listed harlani as a
race of jamacensis but stated that some
considered it a species.
2. Godfrey 1966. Birds of Canada. Listed
harlani as a race of Red-tail, no reasons given.
3. Van Tyne and Sutton. 1937. Paper
described new subspecies B. j. fuertesi.
State that they cannot differentiate between
juvenile dark calurus and harlani.
NONE offered taxonomic justifications for lumping
or rebuttals of separate species arguments given
by Taverner, Peters, and Woods.
Questioning of this decision
Dr. Richard Banks, then chairman of the AOU Check-list
committee, gave me copies of four letters regarding this
taxonomic decision.
Dr. Laurence Jerome wrote a letter in 1974 to the then
Chairman of the AOU check-list committee and pointed
out the lack of justification for lumping Harlan’s with
Red-tailed. He noted the lack of reference to Wood
(1932) and suggested that the committee review its
decision and urge studies to better understand the
taxonomy of this taxon.
Questioning of this decision
The Chairman wrote a long response to Jerome. He
offered no taxonomic justifications for this lumping
other than this was the accepted ‘taxonomic opinion.’
He referred to alleged interbreedings between the taxa
as a justification, but we now know that this happens
regularly between good species and is not in itself a
factor in taxonomy. He did not refute the differences
mentioned by Wood (1932) or Taverner (1937) nor
address the request for further studies.
Two other committee members, both eminent
ornithologists, also wrote letters to Jerome but offered
no further taxonomic justifications.
But Harlan’s Hawks consistently
differ from Red-tailed Hawks
harlani
Buteo jamaicensis calurus
British Columbia
British Columbia
My presentation listing all of the differences is
on The P-Fund’s GRIN web site. See next slide
for a summary and URL:
Harlan’s Hawk differs from Red-Tailed
Hawk, Buteo jamaicensis calurus, by:
1. Frequency of color morphs;
2. Adult plumage by color morph especially in tail
pattern and color;
3. Harlan’s adult & juvenile plumages are almost alike;
those of Red-tails differ; &
4. Extent of bare area on the tarsus.
5. Some behaviors.
For a presentation explaining these differences, go to:
http://www.globalraptors.org/grin/ResearcherRes
ults.asp?lresID=155
And scroll down to ‘Publications’ and click on
‘pdf’ after ‘Harlan’s Hawk differs…’
Treated as the same species most likely due
only to alleged records of interbreeding, as
this was the Biological Species Concept of the
time.
Mindell (1983) showed that Harlan’s had a breeding
range exclusive of Red-tailed Hawks, and concluded
that they were subspecies, based on the citations
above. He could just as easily used the same data to
consider Harlan’s a species.
Two citations given as ‘proof’ of interbreeding:
Taverner (1927) and Lowe (1968)
Both are based on Alaska breeding adults, with one
adult harlani & the other calurus, however both are
harlani.
’HARLAN’S IS A VALID SUBSPECIES OF REDTAILED HAWK’ Mindell (Auk 1983):
Mindell, when a grad student, surveyed for raptors along
rivers in west central Alaska for three summers. During
the 3rd summer, he noted the tail color of adult Harlan’s
seen and little else about their plumages (Dark and light
circles).
>10%
All
Mindell (1983)
He saw 82 adults in 3rd summer, of which 9 had some
rufous in their tails; he called these 9 intergrades
based on alleged interbreeding, but all of these were
most likely harlani.
He offered no proof of interbreeding, but cited Taverner
(1927) and Lowe (1968), nor did he present any good
taxonomic reasons to support his assertion that this is a
valid subspecies.
Mindell has since published monumental papers on
raptor phylogeny.
Important result of this paper:
ONLY HARLANI OCCURS IN THAT AREA OF ALASKA!
Mindell could also have used his results to justify
considering Harlan’s as a species.
Mindell (1983) cited for interbreeding:
Taverner (1927)
His alleged calurus
specimen breeding in
Alaska with a harlani
was, upon inspection,
also harlani (see
previous slide).
Same with other
alleged
interbreedings.
Taverner (1927): Family was collected on
the Chitina River, AK in July 1925
Chicks harlani
3 chicks
Canadian Museum of Nature
Adult male is not calurus. It is harlani, with
short bare tarsi, as are the 3 chicks.
Mindell (1983) cited for interbreeding:
Lowe (1978) thesis
U. Of Alaska
Actually harlani
MS
Lowes’ AK calurus & borealis breeding adults
differed from those seen elsewhere and were all
harlani that had some rufous or banding in tails
Plates 5 & 6 of Lowe’s Thesis
Lowe thought that the dark adult on the right
was an adult Western Red-tail, B. j. calurus.
But it is a rather typical dark-morph adult
Harlan’s Hawk. Lowe’s records of breeding
between harlani & calurus are not valid.
Mindell in Auk (1983) and Amer. Birds (1985)
believed that harlani was a Red-tail
subspecies, apparently based on his seeing
rufous in the tails and body plumages of
hawks in Alaska, which he thought meant that
they breeds freely with neighboring
jamaicensis.
Many adult
Harlan’s have some
rufous in their tails
but have no traits
of Red-tailed
Hawks of (other)
subspecies.
Alaska
Bob Dittrick
Mindell took three nestling Harlan’s
Hawks from interior Alaska
One was a typical
dark, one was light,
and the third was
black; all three were
pure harlani!
David Mindell
He noted rufous in the adult plumages of all
three hawks and concluded that there was gene
flow between harlani and B. j. calurus. That and
his observations of rufous tails in Alaska were
the basis for his two papers (1983 & 1985).
Adult plumage of Mindell’s light-morph
hawk
David Mindell
He noted the rufous in the tail and thought
this bird had calurus genes. But there are no
calurus traits on this hawk’s head, underparts,
or tail. It is a typical adult harlani!
Adult plumage of Mindell’s typical
hawk
David Mindell
He noted the rufous in the breast and thought
this hawk had calurus genes. But there are no
calurus traits on this hawk. It is a typical adult
harlani!
Adult plumage of Mindell’s dark hawk
The underparts of
this hawk were
uniformly blackish
David Mindell
He noted the rufous in the tail and thought this
hawk had calurus genes. But there are no
calurus traits on this hawk’s head, upperparts, or
tail.
All of these are pure Harlan’s Hawks
Another reason for lumping was that adult
Harlan’s can show rufous in their tails, that
this could only happen by interbreeding,
ignoring ancestry & hybridization.
Quite a few adult Harlan’s show rufous in
their tails & no traits of Red-tailed Hawk.
My presentation on extreme variation in
adult tails is available on The Peregrine
Fund web site GRIN: Go to
http://www.globalraptors.org/grin/Researcher
Results.asp?lresID=155
And scroll down to ‘Publications’, then click
on ‘pdf’ after ‘Extreme tail variation…’
Adult Harlan’s tails
can by gray or can
have some rufous
& are variable
British Columbia
MVZ
Adult Red-tails always have
all rufous tails with a
narrow dark subterminal
band and sometimes have
other narrow bands
Texas
It is possible that the rufous
in some harlani tails is due
to interbreeding.
A recent paper presented some results
from sampling DNA (but non-coding
areas) of Harlan’s and Red-tailed Hawks.
Hull et al (2010) Population structure and
plumage polymorphism: The intraspecific
evolutionary relationships of a polymorphic
raptor, Buteo jamaicensis harlani.
BMC Evolutionary Biology
They sequenced 17 microsatellite loci and 430
base pairs of mt-DNA control region of:
Western Red-tail (B. j. calurus)(CA & UT)
Eastern Red-tail (B. j. borealis)(WI)
Harlan’s Hawk (harlani) (AK)
*B. j. alascensis of se Alaska was not sampled
RESULTS: Mt-DNA & nuclear DNA between
Harlan’s Hawk and two subspecies of Redtailed Hawk differed, but only a little.
Hull et al interpreted their results to indicate
gene flow betweenthese taxa and concluded
that harlani is closer to borealis than to
calurus. They also concluded:
‘…our findings are inconsistent with the
historical description of harlani as a separate
species.’
In other words, they do not reject the
hypotheses that harlani is a separate species,
they just found no support for such in the
DNA they sampled.
Hull et al found no differences in the sequences
of Mc1r gene among these taxa (only one of
many genes that control for color),
and they suggested that differences in color
morph frequency (harlani mostly dark; other
taxa, mostly or always light) could be due to
environmental differences. (epigenetic and not
due to the many other genes that control color).
They did not address the differences in color
between harlani (black) and the others (brown)
nor that many other genes can control for color.
Hull et al. state: ‘The extent of variation makes
descriptions of definitive B. j. harlani characters
difficult and no diagnostic set of B j. harlani
plumage characters has yet been accepted
(Liguori & Sullivan 2010).’
However, Liguori & Sullivan do present characters
that distinguish harlani , as did Wood (1932).
Hull et al. did not address other differences in
plumage and morphology.
And also I do so in my presentation: ‘Harlan’s
Hawk differs…’ which was mentioned
previously but was not available to Hull et
al.
Hull et al included no discussion of the
differences in plumages between harlani and the
other taxa and did not cite Wood (1932), who
described some of these differences.
They cited Mindell (1983) for validation of
subspecies status of B. j. harlani.
Mindell (1983) cited Taverner (1927) and Lowe
(1978) for instances of interbreeding.
NONE OF THESE ARE VALID CASES OF
INTERBREEDING! Examination of specimens in all
instances verified that the alleged calurus and
borealis were in fact harlani.
Finally, Hull et al. conclude by recommending
many further investigations:
1. Determine the mechanisms influencing
plumage patterns in B. J. harlani, and
2. Identify the gene(s) responsible for
variation in the plumages of these taxa, and
3. Determine factors responsible for the dark
plumages, and
4. Perform a controlled study on environmental
influences on the plumage characters of
harlani.
In light of the above, this paper seems to ask
more questions than it answers.
The following articles are useful in
interpreting the results from Hull et al.
(2010):
Winker (2009) advocated using both phenotype
(results of natural selection) & genotype
(results of time and random mutations) to
evaluate speciation. Hull et al (2009) used only
genotype.
Humphries and Winker (2009) showed that for
nine species pairs of Beringia birds, Mt DNA,
nucDNA, and phenology gave conflicting
estimates of divergences due to separation by
the rising Bering sea.
Irwin et al. (2009) found that two taxa of
Eurasian buntings, Yellowhammers and Pine
Buntings, which have distinct plumages, had
nearly identical sampled mtDNA. They hybridize
in an extensive zone in western and central
Siberia.
No one
questions
that they
are both
species
However, variation in the nuclear gene CHD1Z
between them was comparable to that of other
species pairs.
Gay et al (2009) showed that for two speciespairs of gulls that had significant gene flow and
essentially identical mtDNA, they nevertheless
maintained their species distinctness in active
DNA, no doubt because of selection.
Glaucous-winged
Hybrid
Western
This is another case of DNA being almost alike in
two good species, & much closer than the DNA of
harlani & jamaicensis of Hull et al (2009).
Brelsford & Irwin (2009) found that two taxa of
Yellow-rumped Warblers had identical sampled
DNA, but used SNPS to find genetic differences
that they related to plumage differences between
them on both sides and across a hybrid zone.
They advocated two species.
Audubon’s
Warbler
Myrtle
Warbler
From
Sibley
They identified two nuclear loci (one sex-linked
and one autosomal) that showed fixed
differences across the hybrid zone, in a close
concordance with patterns of plumage
variation.
In many of these studies, the MtDNA was
identical or nearly so between the two species
reported, but in the results of Hull et al (2010),
the mtDNA was not identical.
Their results are:
For mtDNA: the various Φst are:
0.203* between harlani & calurus
0.059* between harlani & borealis
0.032* between calurus & borealis
* All three were significantly different.
Bottom line: it takes only a few differences in
important genes to reflect assortative mating
between taxa.
From Dice 1932: “According to the usual
geographic concept of subspecies employed
by zoologists, no two subspecies of the same
species should, except under extraordinary
conditions, occur in the same area; for if they
should occur together they would be
expected to interbreed and lose their
distinctness.”
Breeding Ranges
Harlan’s Hawks breed in Alaska, Yukon, nw BC,
and the far north of NWT. The ranges of five
(other) subspecies of Red-tails are shown.
Mixture
harlani
From Wheeler
2003, with
modifications
HOWEVER, Light-morph Harlan’s Hawks
are & have been breeding within the
calurus range in western Canada
Based on specimens, sightings, and
photographs taken at nests
Alberta
BC
HARLAN’S HAWKS ARE & HAVE BEEN
BREEDING WITHIN THE RED-TAILED
HAWK RANGE IN WESTERN CANADA
For a presentation explaining the extent of
overlap in breeding, go to:
http://www.globalraptors.org/grin/Resea
rcherResults.asp?lresID=155
And scroll down to ‘Publications’ and click
on ‘pdf’ after ‘Harlan’s Hawk are & have
been…’
And Red-tails occur in the Harlan’s
breeding range
Adult lightmorph calurus
sighted in late
spring and
summer
2X
April
X
Atlin
July
Red-tails in Harlan’s breeding range
Apparent Red-tailed Hawk nesting in Alaska. This adult
was nesting near the Hawk Count site at Gunsight Mt.,
AK. Brian Sullivan noted that it was a male breeding
with a light adult female Harlan’s. His plumage is
similar to Red-tails in NWT & Alberta (Sullivan 2011).
Adult ♀ was a
typical light adult
Harlan’s, with
whitish head,
underparts, &
upper tail. It was
the only light adult
seen by Brian that
trip.
Brian Sullivan
Dark Red-tailed X dark Harlan’s in se AK
Chuck Susie found a pair of dark adults
breeding near Klukwan, se Alaska in June
2013. The male was a dark-morph Harlan’s and
the female was a dark-morph red-tailed Hawk.
No dark morph is known for B. j. alascensis.
Chuck Susie
Adult male
Adult female Juvenile
One of two juveniles was decidedly Harlan’s Hawk
Some hybrids exist between Harlan’s & Red-
tailed Hawks, but there is no classic hybrid
zone, e.g., as shown by Glaucous-winged &
Western Gulls & Yellow-rumped Warblers and
other good species pairs.
From Gay et al
2009
Glaucouswinged Gull
Also, can two
subspecies be
breeding in the
same areas?
Hybrid
zone
Western
Gull
One possible scenario for the origin of harlani is
that it was isolated from jamaicensis during the
last glacial maxima, most likely in Beringia, &
evolved in isolation to look and act differently.
Nothing in the
Hull et al
(2009) results
rules out this
scenario for the
evolution of
Harlan’s Hawk.
Harlan’s Hawk
As the glaciers retreated, most likely secondary
contact occurred with one or more of the
subspecies of B. jamaicensis, with some resulting
hybridization.
If the resulting gene flow were unrestricted, then
one would expect that both forms would share
traits and look much more alike, most likely with
a hybrid zone between their breeding ranges.
Clearly this isn’t happening. Something is causing
the majority of Harlan’s to be dark and their
plumages to differ, and that most likely is
selection, either natural or sex-linked or both,
resulting in assortative mating.
Hybridization
Many good species hybridize, for a variety of
reasons. This is especially true in the genus
Buteo, in which many species pairs have been
reported hybridizing, some on a regular basis.
Red-tailed Hawks have been found to hybridize
with:
Swainson’s Hawks,
Red-shouldered Hawks,
Ferruginous Hawks, &
Rough-legged Hawks.
Hybridization
Hybridization between harlani and several taxa
of B. jamaicensis is happening, but it is not
resulting in the widespread mixing of
characters between them or in a classic hybrid
zone at the junction of their breeding ranges.
Further study of this hybridization will help us
understand the true taxonomic relationship
between these taxa.
HARLAN’S HAWK SPECIES STATUS
Harlan’s Hawk is clearly much more different
from the various subspecies of Red-tailed Hawk
than they are from each other.
Harlan’s Hawk differs from Red-tailed Hawk
more than any two subspecies of any other
raptor species.
The BOU (see below) and the adherents of the
Phylogenetic Species Concept both would have
no problem assigning species rank to Harlan’s
Hawk.
I plan to publish my findings on phenotypical
differences and will assist any and all analyses of
genetic differences .
Criteria for determining if a
taxon is a species
The American Ornithological Union (AOU) has
no criteria for judging species status.
But Helbig et al (2002) have published criteria
of assigning species rank that have been
accepted by the British Ornithological Union.
These are:
1. Are the taxa diagnosible?
2. Are they likely to retain their genetic and
phenotypic integrity in the future?
Criteria for determining if
Harlan’s Hawk is a species
1. Is Harlan’s Hawk diagnosably different from
Red-tailed Hawk?
The answer is a clear YES.
2. Is Harlan’s Hawk likely to retain its genetic
and phenotypic integrity in the future?
There are no reasons to assume that Harlan’s
will be subsumed into Red-tailed Hawk in the
primary breeding range of Alaska and Yukon, as
it has not done so in the past.
FUTURE RESEARCH
DNA researchers should locate and sequence the
genes that are causing these differences and
compare and relate their phenotypes and
genotypes to get a clearer understanding of the
taxonomic status of Harlan’s Hawk.
We also need to better understand why light
Harlan’s are breeding in the western Canadian
range range of calurus and why a few adult
calurus occur in the breeding range of harlani.
LITERATURE CITED:
AOU. 1973. Thirty-second supplement to the Check-list. Auk 90:414.
Audubon, J. J. 1830. Birds of America, Folio ed., Plate 86.
Brelsford, A., & D. Irwin. 2009. Incipient speciation despite little assortative mating:
the yellow-rumped warbler hybrid zone. Evolution 63-12: 3050–3060.
Brown L. H., & Amadon, D. 1968. Eagles, Hawks, and Falcons of the World. Vol.
2:606. McGraw-Hill, New York.
Dice, L. R. 1931. The Occurrence of Two Subspecies of the Same Species in the Same
Area. J. Mammalogy 12: 210-213.
Gay et al. 2009. Speciation with gene flow in the large white-headed gulls: does
selection counterbalance introgression? Heredity 102: 133–146.
Godfrey, W. E. 1966. The birds of Canada. Rev. ed. Natl. Mus. Nat. Sci. , Ottawa, ON.
Helbig, A. J., A. G. Knox, D. T. Parkin, G. Sangster, and M. T. Collinson. 2002.
Guidelines for assigning species rank. Ibis 144:518-525.
Hull, J. et al. 2010. Population structure and plumage polymorphism: The
intraspecific evolutionary relationships of a polymorphic raptor, Buteo jamaicensis
harlani. BMC Evolutionary Biology 10:224.
Humphries and Winker. 2010. Discord reigns among nuclear, mitochondrial and
phenotypic estimates of divergence in nine lineages of trans-Beringian birds.
Molecular Ecology 1-11.
Irwin, D. E., A. S. Rubtsov, and E. N. Panov. 2009. Mitochondrial introgression and
replacement between yellowhammers (Emberiza citrinella) and pine buntings
(Emberiza leucocephalus) (Aves: Passeriformes). Biol. J. Linnean Soc. 98:422-438.
Liguori, J., and B. L. Sullivan. 2010. Comparison of Harlan’s Hawks with western
and eastern Red-tailed Hawks. Birding 42:30-37.
(Continued)
LITERATURE CITED (Cont.)
Lowe, C. M. 1978. Certain life history aspects of the Red-tailed Hawk in central
Oklahoma and interior Alaska. MS thesis, U. of Alaska.
Mindell, D. P. 1983. Harlan’s Hawk is a valid subspecies of Red-tailed Hawk. Auk
100:161-167.
Mindell, D. P. 1985. Plumage variation and winter range of Harlan’s Hawk (Buteo
jamaicensis harlani). American Birds 39:127-133.
Peters, J. L. 1931. Check-list of birds of the world, vol. 1. Harvard Univ. Press,
Cambridge, MA.
Ridgway, R. 1890. Harlan’s Hawk a race of the Red-tail, and not a Distinct Species.
Auk 7:205.
Ridgway, R. 1895. The Ornithology of Illinois. Part I, volume II. Description catalogue. State
Laboratory of Natural History. pp 469-472.
Sullivan, D. 2011. Apparent Eastern Red-tailed Hawk nesting in Alaska. North American Birds
65(3) 1-4.
Sullivan, B. & J. Liguori. 2010. A territorial Harlan’s Hawk (Buteo jamaicensis harlani)
in North Dakota, with notes on summer records of this subspecies from the northern
Great Plains. No. Am. Birds 64: 368-372.
Taverner, P. A. 1927. A study of Buteo borealis, the Red-tailed Hawk, and its varieties
in Canada. Victoria Mem. Mus. Bull. No. 48 Biol. Series 13:1-25.
Taverner, P. A. 1936. Taxonomic comments on Red-tailed Hawks. Condor 38:6
Winker, K. 2009. Reuniting Phenotype and Genotype in Biodiversity Research.
BioScience 59: 657-665.
Van Tyne, J., and G. M. Sutton. 1937. The birds of Brewster County, Texas. Misc. Publ.
Mus. Zool. Univ. Mich. No. 37:20.
Wood, N. A. 1932. Harlan’s Hawk. Wilson Bull.44:78-87.
Thanks
The following people made helpful
comments on earlier drafts of this
presentation:
Richard Banks, Donna Dittman, Darren
Irwin, Jim Lish, Brian Millsap, Van
Remsen, Ildiko Szabo, Kevin Winker, &
Chris Witt.
David Mindell kindly shared his photos
and information. Bob Dittrick, Chuck
Susie, and many others freely shared
their photos of these taxa with me.
Thanks
I thank with great enthusiasm the many
curators and collection managers for
permission to look at and study their bird
specimens and for their freely given help,
especially the Canadian Museum of
Nature and Michel Gosselin, but also
Mark Robbins (KU) and Robert PrysJones (British Museum).
Theirs is a most valuable and important
resource for bird study.
THANKS FOR YOUR
ATTENTION
Thanks also to The Peregrine Fund (especially
Lloyd Kiff & Travis Rosenberry) for making this
presentation available on their Global Raptor
Information Network (GRIN) web site