The Wilson Journal of Ornithology 128(2):268–277, 2016
OCCURRENCE AND TAXONOMY OF ARCTIC WARBLERS
(PHYLLOSCOPUS BOREALIS) SENSU LATO IN NORTH AMERICA
JACK J. WITHROW,1,4 DANIEL D. GIBSON,1 YURI GERASIMOV,2
NICKOLAY GERASIMOV,2 ALEXANDER SHESTOPALOV,3 AND KEVIN WINKER1
ABSTRACT.—We reviewed the taxonomic status of Arctic Warblers (Phylloscopus borealis) sensu lato occurring
in North America following the splitting of the complex into three species by the American Ornithologists’ Union (Chesser
et al. 2014). We used phenotypic and genetic markers to assess the status of this species complex in North America
and identified Arctic-type warblers occurring in the Aleutian Islands as Kamchatka Leaf Warblers (P. examinandus). This
species occurs at least occasionally through the Bering Sea, to the Alaska mainland, and as far east as arctic Canada.
Measurements of Arctic and Kamchatka Leaf warblers were found to differ by only a small degree, offering no simple
diagnostic characteristics. In addition, we recommend maintaining the long-recognized Alaska subspecies P. b. kennicotti
as a synonym of P. b. borealis. Received 19 February 2015. Accepted 18 September 2015.
Key words: Alaska, Arctic Warbler, Kamchatka Leaf Warbler, Northwest Territories, Phylloscopus examinandus, Russia.
The recent splitting of the Arctic Warbler into
three species by the American Ornithologists’
Union (Chesser et al. 2014) – Arctic Warbler
(Phylloscopus borealis), Kamchatka Leaf Warbler
(P. examinandus), and Japanese Leaf Warbler
(P. xanthodryas) – based on differences in
morphology, song, and mitochondrial DNA (Saitoh
et al. 2008, 2010; Alström et al. 2011), prompted
us to review and clarify the status of these forms in
North America. Spring and fall migrants through
the western and central Aleutian Islands had
been phenotypically identified as belonging to
one of the larger Asian-breeding taxa (Gibson and
Byrd 2007), and not as examples of the supposedly
smaller Alaska-breeding birds, historically discussed as P. borealis kennicotti (Hellmayr 1934,
Gabrielson and Lincoln 1959, Gibson and Kessel
1997). In part because of the morphological
similarity of the taxa formerly maintained within
P. borealis, the identification and taxonomic status
of the complex in general and of the migrant birds
occurring in parts of western Alaska has been
complicated and inconsistent (see Hartert 1920;
Portenko 1938, 1973; Ticehurst 1938; Vaurie 1954,
1959; Dement’ev and Gladkov 1968; Ornithological Society of Japan 1974, 2000; Williamson 1976;
Gibson 1981; Watson 1986; Bairlein et al. 2006).
1
University of Alaska Museum, 907 Yukon Drive,
Fairbanks, Alaska 99775, USA.
2
Kamchatka Branch of Pacific Institute of Geography,
Far East Branch of Russian Academy of Sciences, Pr.
Rybakov, 19a, Petropavlovsk-Kamchatsky, 683024, Russia.
3
Research Institute of Experimental and Clinical Medicine, Novosibirsk, 630559, Russia.
4
Corresponding author; e-mail: [email protected]
Furthermore, the sole record of an Arctic Warbler
from high-arctic Canada had been assessed as
P. b. borealis, because it was “too large to be of
the Alaska race” (Godfrey 1966:305). We clarify
the status of the Arctic Warbler complex in North
America using genetic and morphometric data.
METHODS
We sequenced the cytochrome oxidase subunit
b gene (cyt b), in whole or in part, for a total of
26 individuals considered to be (or likely to be)
from populations other than those breeding in
Alaska or individuals likely to provide comparative value: 14 collected in the western Aleutian
Islands, two from St. Lawrence Island, one
from St. Matthew Island, two from mainland
Alaska, six from Kamchatka, Russia, and one
from Canada (Appendix A). These sequences
were compared to published sequences (Saitoh
et al. 2010, Alström et al. 2011; see Appendix B)
representing the three species formerly recognized
as constituting the Arctic Warbler to confirm the
identity of North American specimens.
We extracted DNA from frozen and ethanolpreserved tissues with a DNeasy tissue kit
(QIAGEN Inc., Valencia, CA, USA) by following
the manufacturer’s protocol. Polymerase chain
reaction (PCR) amplifications were performed
using cyt b primers H16065 (Helbig et al. 1995)
and L14970 (Leisler et al. 1997) following the
protocols in Withrow et al. (2014). PCR thermal
regime started with 6 mins at 96uC followed by
4 cycles of 92uC for 2 mins, 56uC for 30 secs, and
72uC for 40 secs and a further 24 cycles of 92uC
for 20 secs, 50uC for 30 secs, 72uC for 40 secs.
268
Withrow et al. N ARCTIC WARBLERS IN NORTH AMERICA
PCR cleanup and sequencing were done at the
High-Throughput Genomics Unit (University of
Washington, Seattle, USA), using an ExoSAP
cleaning process, cycle-sequenced using BigDye
chemistry on an ABI 3730KL high-throughput
capillary sequencer (Applied Biosystems Inc.,
Foster City, CA, USA) using the same primers
as initial sequencing. We aligned and edited
the sequences with Sequencher 4.7 (Gene Codes
Corp., Ann Arbor, MI, USA) and archived them in
GenBank (Appendix A).
For older specimens (see Appendix A) for which
frozen tissues did not exist, DNA was extracted
from specimen toe pads, again using a DNeasy
tissue kit and following the manufacturer’s protocols except that the elution step used just half
the volume to obtain a higher concentration of
DNA. PCR amplifications were performed on skin
material following Alström et al. (2011; U. Olsson,
in litt. 2014). These primers were TGCCTAGTTACACAAATCGTCACA (exam1F) with reverse
primer AGGCGGTTGCTATTAGGGTCAGTA
(exam1R) and an overlapping section with forward
primer CAATGGCGCTTCCTTCTTCTTTAT
(exam2F) and reverse primer TGTTTGATCCC
GTTTCGTGTAGTA (exam2R). PCR thermal
regime started with 5 mins at 95uC followed by
four cycles of 95uC for 30 secs, 60uC for 30 secs,
and 72uC for 30 secs, then four-cycles of 95uC
for 30 secs, 58uC for 30 secs, 72uC for 30 secs,
and finally 36-cycles of 95uC for 30 secs, 56uC for
30 secs, 72uC for 30 secs, ending with 72uC
for 5 mins. This protocol resulted in a diagnostic
,480 bp fragment near the beginning of the cyt b
gene. All sequence data were visualized and compared to other published sequences using a medianjoining haplotype network (Bandelt et al. 1999) as
implemented in Network Publisher (Fluxus Technology Ltd., Suffolk, United Kingdom).
Published phenotypic comparisons between
examinandus and borealis (sensu stricto) are
effectively lacking, because most authors since
Ticehurst (1938) have treated examinandus as
a synonym of xanthodryas (Vaurie 1959, Williamson 1976, Watson 1986, Bairlein et al. 2006;
but see Saitoh et al. 2008), the most phenotypically
distinct member of this complex, resulting in
exaggerated reported differences because examinandus is phenotypically intermediate between
xanthodryas and borealis (Ticehurst 1938,
Saitoh et al. 2008). Traditionally and more recently, differences between borealis and examinandus/xanthodryas were determined by size as
269
much as by plumage coloration (Ticehurst 1938,
Vaurie 1954, Gibson 1991, Saitoh et al. 2008).
We assessed size differences using statistical
differences (t-tests); however, because this method
can be hard to interpret and is influenced by sample
size (Nakagawa and Cuthill 2007) we also used
a percent overlap of populations that allowed us to
estimate the number of birds falling in the zone of
equivocal measurements. To do this, we assumed
population measurements were normally distributed and calculated the percentage of birds falling
below the 97.5 percentile of examinandus and
above the 97.5 percentile of borealis, i.e., those in
the zone of overlap for all but the most extreme
5% of a population. Using both methods maximizes the utility and interpretability of our data
for field and in-hand identifications of borealis and
examinandus.
JJW measured 29 examinandus and 27 borealis
for bill length (nares to tip), bill width (at distal
end of nares), and wing chord (sensu Winker
2000; see Appendix C), measurements reported to
be representative or indicative of differences
between these taxa (Vaurie 1954, Saitoh et al.
2008). Two birds from Amchitka Island at USNM
were measured by Brian Schmidt, and the Canada
bird was measured by Michel Gosselin (for a total
of 32 examinandus). Birds whose species status
was not confirmed by sequencing were all taken
in June, July, or August from known breeding
sites in Alaska or Kamchatka (our northernmost
Russian specimen was taken at 56.35u N) and were
thus assumed to represent borealis or examinandus,
respectively. Our sample consisted of 44 males,
9 females, and 6 individuals of unknown sex.
Plumage variation was examined by eye under
full-spectrum lighting against a neutral-gray
background by JJW, KW, and DDG, although
sample sizes of uniform age, season, sex, and
preparation were small (see Appendix C).
RESULTS
Our cyt b haplotype network (Fig. 1) clearly
shows that all of the sequenced Aleutian Islands
birds are examinandus. In addition, one individual from St. Matthew Island in the northern Bering
Sea and one from Old Chevak on the YukonKuskokwim Delta had examinandus haplotypes
(Fig. 1, 2). High-arctic Canada’s extralimital record also turned out to be examinandus. In contrast,
the two specimens from St. Lawrence Island
and one from Fairbanks had borealis haplotypes.
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THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 128, No. 2, June 2016
FIG. 1. We constructed a haplotype network by using 82 sequences from three species formerly constituting Arctic
Warbler, sensu lato; see Appendix A and B for details. White represents Phylloscopus xanthodryas, dark gray P. borealis,
and light gray P. examinandus. Black circles and areas denote sequences generated for this study. Small open circles denote
unsampled haplotypes. Circles are proportional to the number of individuals with that haplotype; the number of individuals
with a given haplotype is presented if more than one.
No birds showed haplotypes associated with the
Japanese Leaf Warbler.
Bivariate plots of wing chord vs. bill length
(Fig. 3) showed two relatively distinct clusters.
Wing chords
SD 5 2.77)
SD 5 2.97)
(t 5 5.95, df
of examinandus (mean 69.1 mm,
and borealis (mean 64.6 mm,
were significantly different
5 56, P , 0.001). Bill lengths of
FIG. 2. Sampling distribution of Phylloscopus xanthodryas (open circles), P. borealis (dark grey circles), and
P. examinandus (light grey circles) based on haplogroup association (see Fig. 1) used to assess the genetic affinities of
North American records. North American records of P. examinandus show a clear pattern of spring over-shoot migration.
Withrow et al. N ARCTIC WARBLERS IN NORTH AMERICA
271
FIG. 3. Wing and bill measurements of 32 P. examinandus and 27 P. borealis. See Appendix C for
specimens examined.
examinandus (mean 7.5 mm, SD 5 0.40) and
borealis (mean 6.6 mm, SD 5 0.36) were also
significantly different (t 5 8.15, df 5 56,
P , 0.001). Bill width (data not shown) also
showed differences, with examinandus (mean
3.12 mm, SD 5 0.16, n 5 24, range 2.9–3.5) and
borealis (mean 2.68 mm, SD 5 0.16, range
2.4–3.0) again showing significant differences
(t 5 9.57, df 5 49, P , 0.001), with little
overlap between the specimens (some examinandus had damaged bills, hence the smaller sample
size). Although significant, these differences are
small. The percentages of birds falling in the areas
of overlap were high. Wing chord showed the
most overlap, with 65.3% of individuals displaying equivocal wing measurements. Percentages
were lower for bill length (34.4%) and bill width
(23.5%); both would approach or exceed 50% if
the full range of variation (99% or more) was
considered. In an attempt to use all measurements
to diagnose individuals, we summed wing chord,
bill length, and bill width into a single value.
The combined measurements had an estimated
overlap of 43.8%, similar to the actual overlap of
20 of 51 (39.2%) shown by our birds (Fig. 3).
Females averaged smaller than males (data not
shown), and the percentage overlaps when only
males were considered were (53.6%), (50.3%),
and (24.5%) respectively.
Putative color differences between taxa within
the old Arctic Warbler complex have usually
been prefaced by adjectives that suggested
minute differences, and in the birds visually
examined we found individual plumage variation to be greater than any other differences
between examinandus and Alaska borealis (see
Appendix C).
DISCUSSION
Kamchatka Leaf Warblers are intermittent
spring (date range 1–22 June) and casual fall (date
range 16 Sep–23 Oct) migrants in the western
Aleutians, occasionally reaching as far east as the
central Aleutians (Amchitka Island; Kenyon 1961,
Gibson and Byrd 2007). All Aleutian specimens
known to us of “Arctic” warblers are examinandus.
Echoing Gabrielson’s own hesitance, we are
inclined to dismiss his sight report of an Arctic
Warbler from St. Matthew Island (Gabrielson
1944, Gabrielson and Lincoln 1959, Winker et al.
2002), especially because the specimen taken by
him at Brooks Lake on the Alaska Peninsula
and widely reported (Gabrielson 1944, Cahalane
1959, Gabrielson and Lincoln 1959) as an Arctic
Warbler is instead an Orange-crowned Warbler
(Oreothlypis celata; USNM 591957, examined
DDG). Thus, the only record from St. Matthew
Island, 11 July 1985, is of examinandus. A record
from Old Chevak on the Yukon–Kuskokwim
River Delta on 5 July 1975 is of examinandus.
One fall specimen from Nunivak Island appears
to be P. borealis (Swarth 1934; CAS 30761,
examined DDG), although we did not sequence the
bird. In the Pribilof Islands Arctic-type warblers
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THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 128, No. 2, June 2016
TABLE 1. Records of Kamchatka Leaf Warbler (Phylloscopus examinandus) in North America arranged by date. All
locations except for the first one are in Alaska. The United States National Museum is abbreviated USNM, University of
Alaska Museum as UAM, and Canadian Museum of Nature as CMN. Ad 5 adult, HY 5 hatch year, unk 5 unknown.
Voucher number
Age, sex
Date
Location
CMN 35173
USNM 465415a
USNM 465421a
UAM 7053
UAM 3583a
UAM 4876a
UAM 3692a
UAM 5248
UAM 5343
UAM 11451
UAM 17665
UAM 17702
UAM 18003
UAM 18004
UAM 27030
UAM 27032
UAM 27031
UAM 27029
UAM 28150
UAM 28149
UAM 24554
UAM 27636
Ad, =
unk, =
unk, =
Ad, =
Ad, =
Ad, unk
Ad, =
Ad, =
Ad, =
Ad, =
Ad, =
HY, R
HY, =?
HY, =
unk, =
HY, =
HY, =
unk, R
HY, =
HY, unk
HY, unk
HY, =
21 July 1949
17 October 1957
23 October 1957
5 July 1975
13 June 1977
18 July 1978
25 September 1978
11 July 1985
9 June 1986
5 June 1999
10 June 2002
20 September 2002
11 October 2002
11 October 2002
19 September 2005
24 September 2007
24 September 2007
27 September 2007
27 September 2007
29 September 2007
11 October 2007
26 September 2010
NW Territories, Prince Patrick I.
Aleutian Islands, Amchitka Island
Aleutian Islands, Amchitka Island
Yukon-Kuskokwim Delta, Old Chevak
Aleutian Islands, Attu Island
Aleutian Islands, Buldir Island
Aleutian Islands, Shemya Island
St. Matthew Island
Aleutian Islands, Attu Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
Aleutian Islands, Shemya Island
a
Denotes that bird was not sequenced for cyt b and is assessed as examinandus based on a combination of measurements and probability (P. borealis is unknown
in the Aleutian Islands).
are intermittent or very rare in spring and fall
(Thompson and DeLong 1969; S. Schuette, in
litt., 2014). No specimens exist from these
islands, where either species might occur. On St.
Lawrence Island, Arctic Warblers are regular
migrants (see Lehman 2005). Both Murie (1936)
and Friedmann (1937) discussed such migrants as
“P. b. kennicotti,” and the two UAM specimens are
indeed P. borealis, thus, this species clearly
reaches and departs Alaska via the Bering Strait
region. The only New World record of examinandus outside of Alaska is from Mould Bay, Prince
Patrick Island, Northwest Territories on 21 July
1949 (Godfrey 1966; see Table 1). South and east
of Alaska there are no Arctic-type warbler records
from British Columbia (Campbell et al. 2001),
Washington (Wahl et al. 2005), or Oregon (OBRC
2014), but Sinclair et al. (2003) listed one
hypothetical record of presumed “P. b. kennicotti”
from northern Yukon Territory. California has
eight accepted records of Arctic-type warblers
but still lacks a specimen (Hamilton et al. 2007,
Pike et al. 2014; date range 7–28 September)
and currently treats it as a taxon pair (Arctic/
Kamchatka Leaf Warbler), and there is one report
from Baja California, Mexico (Pyle and Howell
1993; 12 Oct).
Despite statistically significant differences between borealis and examinandus in all three
measurements, reflecting mean differences in size,
the degree of overlap suggests that while some
extreme individuals may be identified, a substantial
percentage will show equivocal measurements
and thus be impossible to diagnose as one species
or the other. Furthermore, it should be pointed
out that the bill width measurement is extremely
sensitive to inter-observer variation, because less
than half a millimeter separates the taxa, a problem
also noted by Portenko (1973). Based on these
data, measurements alone will identify only a small
percentage of birds, and differences are too small
to be instructive in the field. Of course, with birds
of known age and sex, measurement overlaps
among individuals of the same category between
the two species will be less, but without a specimen, such information is usually unavailable.
Our morphometric results differ from Saitoh et al.
(2008), who discriminated between the species
using a size-based principal component analysis.
However, their limited sample size (6 borealis,
Withrow et al. N ARCTIC WARBLERS IN NORTH AMERICA
13 examinandus), failure to quantify the size of
their observed differences and thus its robustness
when extrapolated to larger sample sizes (populations), inclusion of measurements from both live
and museum specimens (Winker 1993), and use of
a measurement not available from most specimens
(total head length) make their results less than
definitive and not directly comparable to our data.
It is useful here to also consider the validity and
history of the long-recognized Alaska subspecies
P. b. kennicotti. In his original description, Baird
(1869:314) described kennicotti, from a single
specimen, as a species only marginally separable
from the Willow Warbler (Phylloscopus trochilus),
stating “if not a distinct species then, as a permanent
geographical variety of P. Eversmanni [5P.
trochilus]”. Ridgway (1904) discussed Alaska
birds as P. borealis kennicotti using a series of
seven birds, but he compared them to birds from the
Commander Islands and Petropavlovsk (P. examinandus), in retrospect an inappropriate comparison. Ticehurst (1938:132) was able to examine
only two birds identified as kennicotti and so did
not judge its validity himself, including it despite
reservations communicated by James L. Peters that
it was “a rather unsatisfactory race.” Portenko
(1938), working with only one Alaska specimen,
did not recognize kennicotti, but later (Portenko
1973), after examining more material, recognized
it based on narrower bill widths, dismissing
Vaurie’s (1954) color differences. Vaurie
(1954:18), working from 30 specimens, accepted
kennicotti based on a smaller (shorter and
narrower) bill and “probably valid color
difference[s],” an opinion that was followed by
most subsequent authors (Williamson 1976, Watson 1986), until Saitoh et al. (2008) and Alström
et al. (2011).
The Bering Strait does not appear to be
a significant barrier to gene flow (Reeves et al.
2008) or song type (Matsuda 2002, fide Saitoh
et al. 2008) in Arctic Warblers, and Phylloscopus
warblers in general exhibit extreme morphological conservatism. Based on the evidence to date,
we agree with Alström et al. (2011) that it is
probably a better working hypothesis to consider
kennicotti as a synonym of borealis (whose
type locality is the [northern] Sea of Okhotsk),
until series of taxonomically useful material
from either side of the Bering Strait are collected
and can be compared. Other authors have treated
borealis (sensu stricto) as monotypic (e.g.,
Ticehurst 1938, Williamson 1976); however,
273
given disagreement on this issue (e.g., Vaurie
1954, Watson 1986), substantial amounts of
genetic structure in this mtDNA clade (Reeves
et al. 2008, Alström et al. 2011), and a lack thus
far of adequate population genetic analyses and
a modern range-wide phenotypic evaluation, it is
premature to consider the case of subspecies
within the Arctic Warbler as a whole to be
resolved.
Few Old World passerines have successfully
colonized North America, and most of these nest in
disturbed, low brush, or alpine habitats. Arctic
Warblers (sensu stricto), generally preferring
shrubby, partly forested nesting habitat, have
a larger North American range than all but the
Northern Wheatear (Oenanthe oenanthe), which
probably colonized the continent from both the east
and west (Bairlein et al. 2012). Both Arctic and
Kamchatka Leaf warblers breed on the Kamchatka
Peninsula, but their ranges there in relation to one
another are not well known. They occur within at
least 320 km of one another (e.g., an Arctic from
59.1uN [Alström et al. 2011]; a Kamchatka Leaf
from 56.35uN [UAM specimens]) suggesting they
may be parapatric, because most authorities do not
describe a break in distribution on the Kamchatka
Peninsula, so from an ecological perspective the
two species probably could occur together in
North America as well. Given that the Kamchatka
Leaf Warbler is a regular, if intermittent, spring
migrant through the Commander and Aleutian
islands (Johansen 1961, this paper), it certainly has
the potential to colonize North America. However,
it appears to prefer shrubby areas in and near forest
of greater stature than the Arctic Warbler (KW,
pers. obs.). Thus, like many Old World taxa, the
Kamchatka Leaf Warbler may be too far removed
from suitable New World breeding habitat to
successfully colonize.
ACKNOWLEDGMENTS
Brian Schmidt at the Smithsonian Institution, Washington
D. C. provided measurements of the two Amchitka Island
specimens at USNM. Michel Gosselin at the Canadian
Museum of Nature, Ottawa, provided measurements and
a toe pad cutting of the Canada specimen. Urban Olsson
provided primer sequences and protocols for sequencing of
toe pads. Kyle Campbell generated four of the sequences
used. CRDF provided support for Kamchatka fieldwork (and
we thank Irene Lerman for her invaluable support in making
that possible), and the Friends of Ornithology provided
funding for the molecular work. Finally, we thank Paul
Lehman and an anonymous reviewer for helpful comments
on a previous version of the manuscript.
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LITERATURE CITED
ALSTRÖM, P., T. SAITOH, D. WILLIAMS, I. NISHIUMI, Y.
SHIGETA, K. UEDA, M. IRESTEDT, M. BJÖRKLUND, AND
U. OLSSON. 2011. The Arctic Warbler Phylloscopus
borealis – three anciently separated cryptic species
revealed. Ibis 153:395–410.
BAIRD, S. F. 1869. Phyllopneuste kennicotti Baird:
Kennicott’s Warbler. Transactions of the Chicago
Academy of Science 1:313–314.
BAIRLEIN, F., P. ALSTRÖM, R. AYMÍ, P. CLEMENT, A.
DYRCZ, G. GARGALLO, F. HAWKINS, S. MADGE, D.
PEARSON, AND L. SVENSSON. 2006. Family Sylviidae
(Old World warblers). Pages 492–709 in Handbook
of the birds of the world. Volume 11. Old World
flycatchers to Old World warblers (J. del Hoyo, A.
Elliott, and D. A. Christie, Editors). Lynx Edicions,
Barcelona, Spain.
BAIRLEIN, F., D. R. NORRIS, R. NAGEL, M. BULTE, C. C.
VOIGT, J. W. FOX, D. J. T. HUSSELL, AND H.
SCHMALJOHANN. 2012. Cross-hemisphere migration
of a 25 g songbird. Biology Letters DOI: 10.1098/
rsbl.2011.1223.
BANDELT, H.-J., P. FORSTER, AND A. RÖHL. 1999. Medianjoining networks for inferring intraspecific phylogenies. Molecular Biology and Evolution 16:37–48.
CAHALANE, V. H. 1959. A biological survey of Katmai
National Monument. Smithsonian Miscellaneous
Collections 138(5):1–246.
CAMPBELL, R. W., N. K. DAWE, I. MCTAGGART-COWAN,
J. M. COOPER, G. W. KAISER, A. D. STEWART, AND
M. C. E. MCNALL. 2001. The birds of British
Columbia. Volume 4. Passerines. University of British
Columbia Press, Vancouver, Canada.
CHESSER, R. T., R. C. BANKS, C. CICERO, J. L. DUNN, A. W.
KRATTER, I. J. LOVETTE, A. G. NAVARRO-SIGÜENZA,
P. C. RASMUSSEN, J. V. REMSEN JR., J. D. RISING, D. F.
STOTZ, AND K. WINKER. 2014. Fifty-fifth supplement
to the American Ornithologists’ Union Check-list of
North American Birds. Auk: Ornithological Advances
131:CSi–CSxv.
CHIKUNI, K., N. MINAKA, AND H. IKENAGA. 1995.
Molecular phylogeny of some Passeriformes, based
on cytochrome b sequences. Journal of the Yamashina
Institude for Ornithology 28:1–8.
DEMENT’EV, G. P. AND N. A. GLADKOV (EDITORS). 1968.
Birds of the Soviet Union. Volume 6. Israel Program
for Scientific Translations, Jerusalem, Israel.
FRIEDMANN, H. 1937. Further additions to the known
avifauna of St. Lawrence Island, Alaska. Condor
39:91.
GABRIELSON, I. N. 1944. Some Alaska notes. Auk 61:
105–130.
GABRIELSON, I. N. AND F. C. LINCOLN. 1959. The birds of
Alaska. Stackpole Co., Harrisburg, Pennsylvania, USA.
GIBSON, D. D. 1981. Migrant birds at Shemya Island,
Aleutian Islands, Alaska. Condor 83:65–77.
GIBSON, D. D. 1991. Old World genera (Phylloscopus,
“Locustella”). Pages 16–19 in The known birds of
North and Middle America. Part II (A. R. Phillips,
Editor). A. R. Phillips, Denver, Colorado, USA.
GIBSON, D. D. AND G. V. BYRD. 2007. Birds of the Aleutian
Islands, Alaska. Series in Ornithology 1:1–351.
GIBSON, D. D. AND B. KESSEL. 1997. Inventory of the
species and subspecies of Alaska birds. Western Birds
28:45–95.
GODFREY, W. E. 1966. The birds of Canada. National
Museum of Natural Sciences, Ottawa, Canada.
HAMILTON, R. A., M. A. PATTEN, AND R. A. ERICKSON
(EDITORS). 2007. Rare birds of California. Western
Field Ornithologists, Camarillo, California, USA.
HARTERT, E. 1920. The birds of the Commander Islands.
Novitates Zoologicae 27:128–158.
HELBIG, A. J., I. SEIBOLD, J. MARTENS, AND M. WINK.
1995. Genetic differentiation and phylogenetic relationships of Bonelli’s Warbler Phylloscopus bonelli
and Green Warbler P. nitidus. Journal of Avian
Biology 26:139–153.
HELLMAYR, C. E. 1934. Catalogue of birds of the Americas
and the adjacent islands. Part 7. Zoological Series of
the Field Museum of Natural History 13(7):1–531.
JOHANSEN, H. 1961. Revised list of the birds of the
Commander Islands. Auk 78:44–56.
KENYON, K. W. 1961. Birds of Amchitka Island, Alaska.
Auk 78:305–326.
LEHMAN, P. E. 2005. Fall bird migration at Gambell, St.
Lawrence Island, Alaska. Western Birds 36:2–55.
LEISLER, B., P. HEIDRICH, K. SCHULZE-HAGEN, AND M.
WINK. 1997. Taxonomy and phylogeny of reed
warblers (genus Acrocephalus) based on mtDNA
sequences and morphology. Journal für Ornithologie
138:469–496.
MURIE, O. J. 1936. The birds of St. Lawrence Island,
Alaska. University of Alaska Miscellaneous Publications 2:361–376.
NAKAGAWA, S. AND I. C. CUTHILL. 2007. Effect size,
confidence interval and statistical significance: a practical guide for biologists. Biological Reviews 82:
591–605.
OLSSON, U., P. ALSTRÖM, AND P. SUNDBERG. 2004.
Non-monophyly of the avian genus Seicercus (Aves:
Sylviidae) revealed by mitochondrial DNA. Zoologica
Scripta. 33:501–510.
OREGON BIRD RECORD COMMITTEE (OBRC). 2014. Official
checklist of Oregon birds, April 2014. Oregon Birding
Association, Lincoln, OR, USA. www.orbirds.org/
checklist2014.pdf (accessed 17 Nov 2014).
ORNITHOLOGICAL SOCIETY OF JAPAN. 1974. Check-list of
Japanese birds. Fifth Edition. Ornithological Society
of Japan, Tokyo, Japan.
ORNITHOLOGICAL SOCIETY OF JAPAN. 2000. Check-list of
Japanese birds. Sixth Edition. Ornithological Society
of Japan, Tokyo, Japan.
PIKE, J. E., K. L. GARRETT, AND A. J. SEARCY. 2014. The
38th annual report of the California Bird Records
Committee: 2012 records. Western Birds 45:246–275.
P ORTENKO , L. A. 1938.
(Phylloscopus borealis) [New observations
on the Arctic Warbler]. Izvestiya Akademi Nauk SSSR
Otdelenie Matematicheskikh i Estestvennykh Nauk
5/6:1051–1056.
Withrow et al. N ARCTIC WARBLERS IN NORTH AMERICA
PORTENKO,
L.
A.
1973.
[Birds of the
Chukotski Peninsula and Wrangel Island].
2
[Part 2]. Izdatel’stvo “Nauka” Leningradskoe Otdelenie, Leningrad, USSR.
PYLE, P. AND S. N. G. HOWELL. 1993. An Arctic Warbler in
Baja California, Mexico. Western Birds 24:53–56.
REEVES, A. B., S. V. DROVETSKI, AND I. V. FADEEV.
2008. Mitochondrial DNA data imply a steppingstone colonization of Beringia by Arctic Warbler
Phylloscopus borealis. Journal of Avian Biology
39:567–575.
RICHMAN, A. D. 1996. Ecological diversification and
community structure in the Old World leaf warblers
(genus Phylloscopus): a phylogenetic perspective.
Evolution 50:2461–2470.
RIDGWAY, R. 1904. The birds of North and Middle
America. Part 3. Bulletin of the U. S. National
Museum 50(3):1–801.
SAITOH, T., P. ALSTRÖM, I. NISHIUMI, Y. SHIGETA, D.
WILLIAMS, U. OLSSON, AND K. UEDA. 2010. Old
divergences in a boreal bird supports long-term
survival through the ice ages. BMC Evolutionary
Biology 10:35 doi: 10.1186/1471-2148-10-35
SAITOH, T., Y. SHIGETA, AND K. UEDA. 2008. Morphological differences among populations of the Arctic
Warbler with some intraspecific taxonomic notes.
Ornithological Science 7:135–142.
SINCLAIR, P. H., W. A. NIXON, C. D. ECKERT, AND N. L.
HUGHES (EDITORS). 2003. Birds of the Yukon
Territory. University of British Columbia Press,
Vancouver, Canada.
SWARTH, H. S. 1934. Birds of Nunivak Island, Alaska.
Pacific Coast Avifauna 22:17–64.
275
THOMPSON, M. C. AND R. L. DELONG. 1969. Birds new to
North America and the Pribilof Islands, Alaska. Auk
86:747–749.
TICEHURST, C. B. 1938. A systematic review of the genus
Phylloscopus. British Museum, London, UK.
VAURIE, C. 1954. Systematic notes on Palearctic birds.
Number 9. Sylviinae: the genus Phylloscopus. American Museum Novitates 1685:1–23.
VAURIE, C. 1959. The birds of the Palearctic fauna,
a systematic reference: Order Passeriformes. H. F. &
G. Witherby Ltd., London, UK.
WAHL, T. R., B. TWEIT, AND S. G. MLODINOW (EDITORS).
2005. Birds of Washington: status and distribution.
Oregon State University Press, Corvallis, USA.
WATSON, G. E. 1986. Phylloscopus borealis. Pages 241–
242 in Checklist of birds of the World. Volume 11
(E. Mayr and G. W. Cottrell, Editors.). Museum of Comparative Zoology, Cambridge, Massachusetts, USA.
WILLIAMSON, K. 1976. Identification for ringers 2. The
genus Phylloscopus. Second Edition. British Trust for
Ornithology, Tring, United Kingdom.
WINKER, K. 1993. Specimen shrinkage in Tennessee
Warblers and “Traill’s” Flycatchers. Journal of Field
Ornithology 64:331–336.
WINKER, K. 2000. Obtaining, preserving, and preparing bird
specimens. Journal of Field Ornithology 71:250–297.
WINKER, K., D. D. GIBSON, A. L. SOWLS, B. E. LAWHEAD,
P. D. MARTIN, E. P. HOBERG, AND D. CAUSEY. 2002.
The birds of St. Matthew Island, Bering Sea. Wilson
Bulletin 114:491–509.
WITHROW, J. J., S. G. SEALY, AND K. WINKER. 2014.
Genetics of divergence in the Northern Saw-whet Owl
(Aegolius acadicus). Auk: Ornithological Advances
131:73–85.
276
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APPENDIX A. Cytochrome-b sequences generated in this study with voucher number, fragment length, GenBank
accession number, and location.
Voucher number
Phylloscopus examinandus
CMN 35173a
UAM 7053a
UAM 5248a
UAM 5343a
UAM 11451
UAM 17665
UAM 17702
UAM 18003
UAM 18004
UAM 27030
UAM 27032
UAM 27031
UAM 27029
UAM 28150
UAM 28149
UAM 24554
UAM 27636
UAM 29471
UAM 29476
UAM 30464
UAM 30463
UAM 30462
UAM 30461
P. borealis
UAM 5620a
UAM 14874
UAM 6940
a
Fragment bp
GenBank accession #
Location
491
491
481
461
1011
982
1009
1010
1010
1011
1011
982
1011
982
982
1000
982
982
982
1011
1011
1011
1011
KP245890
KP245894
KP245891
KP245892
KP245882
KP245875
KP245876
KP245877
KP245878
KP245879
KP245881
KP245895
KP245880
KP245897
KP245898
KP245887
KP245896
KP245873
KP245874
KP245883
KP245884
KP245885
KP245886
Prince Patrick Island
Old Chevak
St. Matthew Island
Attu Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Shemya Island
Kamchatka, near Petropavlovsk
Kamchatka, near Petropavlovsk
Kamchatka, near Esso
Kamchatka, near Esso
Kamchatka, near Klyuchi
Kamchatka, near Apacha
491
982
474
KP245893
KP245888
KP245889
St. Lawrence Island
St. Lawrence Island
Fairbanks, Alaska
These five birds were sequenced from toe pads.
APPENDIX B. Cytochrome b sequences used for comparison in the haplotype network and their sources.
GenBank accession number
Sources
Phylloscopus examinandus
AB362424 – AB362434, AB362436, AB362434, HQ243661.
Saitoh et al. 2008, Alström et al. 2011.
P. borealis
AB362435 – AB362446, AB362461, AB362462,
Helbig et al. 1995, Richman 1996, Olsson et al. 2004,
AB530997 – AB531003, AY635052, HQ243657 – HQ243660,
Saitoh et al. 2008,, Alström et al. 2011.
L77143, Z73484.
P. xanthodryas
AB362447 – AB362458, AB362465, AB362466, D38316,
Chikuni et al. 1995, Saitoh et al. Alström et al. 2011.
HQ243662, HQ243663.
Withrow et al. N ARCTIC WARBLERS IN NORTH AMERICA
277
APPENDIX C. Specimens measured for construction of Fig. 1. Unless otherwise noted, all specimen numbers
are University of Alaska Museum (UAM; available on Arctos arctos.database.museum/home.cfm). The specimen
from Canadian Museum of Nature (CMN) was measured by Michel Gosselin. The two specimens from the
Smithsonian Institution (USNM) were measured by Brian Schmidt. Bold numbers indicate that the individual was
sequenced and correspond with those in Appendix B.
Alaska/Canada, P. examinandus
3583, 3692, 4876, 5248, 5343, 7053, 11451, 17665, 17702, 18003, 18004, 24554, 27029, 27030, 27031, 27032, 27636,
28149, 28150, USNM 4654115, USNM 465421, CMN 35173.
Kamchatka, P. examinandus
29471, 29472, 29471, 29474, 29475, 29476, 30461, 30462, 30463, 30464.
Alaska, P. borealis
723, 2419, 2762, 3149, 3295, 3296, 3298, 3837, 4115, 4296, 4299, 5620, 6571, 6940, 6992, 7364, 7366, 7371, 7372, 7373,
7375, 13972, 14874, 18682, 20151, 34059, 34708.