ARCTIC WARBLER (Phylloscopus borealis) sensu lato or alternatively
ARCTIC/KAMCHATKA LEAF WARBLER Goose Lake State Park Lake County, Oregon 19 September 2020 9:20 AM
OBSERVER: Shawneen Finnegan WEATHER: Sunny in the low 50s with haze from forest fires OPTICS: Swarovski 8x42 EL binoculars
OBSERVATION: Dave Irons and I began birding soon after sunrise at Goose Lake State Park. After checking around the campground we proceeded to State Line Road. Appropriately named it forms the boundary between California and Oregon.
We next explored the area west of the railroad tracks at the very southwest corner of the park. For the exact location please see the screenshot below that I took off my phone when trying to make sure we were in Oregon vs. California. We estimated we were about 30 feet north into Oregon.
Dave had followed me into the tall grass amongst various willow patches when a bird moved in front of me. I immediately said “Oh god, Dave, there is an Arctic Warbler. It’s straight ahead.” Dave looked at it briefly before taking two photos. At that point the bird disappeared into the very dense and large willow thicket never to be seen again. We looked the rest of the day and well into the following day with help of various birders.
DESCRIPTION: I spotted an Old World warbler that was plain olive green above and whitish below. It had a bold, long whitish supercilium that flared slightly behind the eye juxtaposed by the dark eyeline that extended from the lores to the post ocular area. The other thing I keyed in on was the single thin pale lower wing bar, typical of Arctic. While it has a tiny upper wing bar it often doesn’t show. Structurally it was short tailed. No vocalizations were heard.
There are a number of other greenish Phylloscopus warblers but they have bolder wing bars, crown stripes, some with browner coloration or other features that distinguish them from Arctic. California officially added Yellow-browed Warbler (P. inornatus) in 2020 but Yellow- browed shows two very bold wing bars.
Two things happened to support this incredibly brief sighting.My recognition of it as an Arctic Warbler and Dave’s quick photographic capture. All transpired in perhaps 10 seconds. It gave us very little time to study the bird so the photos provide the best support.
The most likely North American species that this bird might be confused with is Tennessee Warbler. We have extensive experience with Tennessee Warblers that are more lime green above with bright white undertail coverts. Their facial pattern is far less contrasty and the supercilium is nowhere near as bold or flared at the back. One might wonder if it was a vireo of some sort but it was much smaller overall, the bill was much slimmer and lacked a hooked tip, not to mention it had a wing bar. And given the olive cast and slight wing bar, other browner and/or more heavily marked species of North American wood-warblers were eliminated. Before the day was over we had received positive feed back from Jon Dunn and Paul Lehman who have seen who knows how many Arctic Warblers in Alaska over the past 25-30+ years, plus many other respected and experienced birders on the ABA’s Rare Birds page. It was mentioned multiple times that one needed to record the call to conclusively identify whether it was P. borealis or P. examinandus. As noted in Withrow et al. size differences between the species offers “no simple diagnostic characteristics.”
TAXONOMIC DISCUSSION: Arctic Warbler was split into three species based on morphometrics and vocalizations in 2011 by Alstrom et al:
1) Arctic Warbler (P. borealis) breeding from Scandinavia to Alaska 2) Kamchatka Leaf Warbler (P. examinandus) breeding in south Kamchatka, Sakhalin and northeast Hokkaido. 3) Japanese Leaf Warbler (P. xanthodryas) breeding in Japan except Hokkaido.
From the literature cited here the most informative one was Withrow, et al. I have inserted a map from this article showing the distribution of sampled individuals.
All records from the Lower 48 have fallen between 6 September and 12 October.
On 26 January 2015 the California Bird Records Committee changed all their Arctic Warbler records to Arctic/Kamchatka Leaf Warbler (P. borealis/examinandus) on the main and review lists. https://californiabirds.org/changelog.asp
California has accepted 9 records of this species pair. There is one record from Baja California on 12 October 1991 and one from Nevada on 9 September 2016. Per the Rare Birds of California the CBRC could not assign a subspecies to the first record which was captured, measured and photographed on 13 September 1995 given no vocalizations had been recorded. The 10th record was found in Orange County, CA the day after ours. Having listened to all the calls on Xeno-canto the calls had we heard it we would have been able to separate these two as they are noticeably different. I anticipate the OBRC will be equally challenged to determine how to quantify this record as they other records committee.
Presumptively this bird is a nominate Arctic Warbler due to the lack of proven records of Kamchatka Leaf Warblers in the lower 48, but given its lack of vocalization it will be probably never be resolved.
SCREEN SHOTS:
These show just how close this bird was to the California border. I took the left screenshot from my phone immediately after seeing the bird to determine exactly where it was relative to the border. The right one shows the habitat and the red line is the fence/border.
LITERATURE CITED:
Alstrom, P., T. Saitoh, D. Williams, I. Nishiumi, Y. Shigeta, K. Ueda, M. Irestedt, M. Bjorklund, And U. Olsson. 2011. The Arctic Warbler Phylloscopus borealis – three anciently separated cryptic species revealed. Ibis 153:395–410.
Pyle, P. and S.N.G. Howell. 1993. An Arctic Warbler in Baja California. Western Birds 24:53-56. https://www.birdpop.org/docs/pubs/Pyle_and_Howell_1993_An_ARWA_off_Baja_California.pdf
TINSMAN, J and M. Meyers. 2019. Nevada Bird Records Committee Report for 2017. Western Birds 50(1): 2-15. ARCTIC WARBLER Phylloscopus borealis (sensu lato) (1, 1). 2016-044, Warm Springs Natural Area (Clark), 9 Sep 2016. B. Zyla (P, V; Figure 7). First record for Nevada. https://archive.westernfieldornithologists.org/archive/V50/50(1)-p002-p015.pdf
Withrow, J.J., D.D. Gibson, Y. Gerasimov, N. Gerasimov, A. Shestopalov, and K. Winker. 2016. Occurrence and taxonomy of Arctic Warblers (Phylloscopus borealis) sensu lato in North America.The Wilson Journal of Ornithology 128(2): 268-277. ARWA-2020-01 (Arctic Warbler) 1st round voting December 6, 2020
Accepted, Species Unresolved: 9 Not Accepted: 0
ACCEPTED, SPECIES UNRESOLVED Verified: I agree with Finnegan's reasoning and assessment that, lacking vocalization, it is not possible to determine between two possible species: - Kamchatca Leaf Warbler (P. examinandus) - Arctic Warbler (P. borealis) The bird is undoubtedly a Phylloscopus old world warbler. Tennessee Warbler is ruled out by the strong dark flared supercilium behind the eye and yellowish tinge on the undertail coverts. The lack of bold wing bars and crown stripes rules out other Phylloscopus warblers.
Kamchatka Leaf Warbler This is a great find; it coincides with two other Arctic-type warblers (one in Orange County, CA, and one in Lincoln County, OR) that same month. Shawneen's detailed report helps to rule out all but these two species - Arctic and Kamchatka Leaf - which, as she notes, are indistinguishable if not heard. The dark eyeline and pale supercilium extending well behind eye, dull olive cap and upperparts, single pale wingbar, and dirty white underparts are unique for this species pair. Tennessee should have less of a supercilium behind the eye and should be either grayer or lime-green without a wingbar; Wood would lack a wingbar and show yellowish on the face; Dusky browner without wingbar; other smaller Phylloscopus warblers like Palla's Leaf and Yellow-browed have very unique plumages.
Arctic Warbler, Kamchatka Leaf-warbler, and Japanese Leaf-warbler The photographs clearly show a phylloscopus warbler consistent with the former Arctic Warbler and the observer describes the distinguishing features that eliminate other North American Warblers and other possible phylloscopus warblers, such as Dusky. Arctic Warbler was recently split into three species that can only reliably be distinguished by song as far as I can tell, although in-hand measurements may also be diagnostic. Either way, there is insufficient evidence here, as the observer noted, to determine which of the three closely-related species this bird is, although given the proximity of the breeding range of Arctic in Alaska, this bird is very likely that species.
Arctic Warbler/Kamchatka Leaf Warbler (Phylloscopus borealis/Phylloscopus examinandus). I agree ith an identification of Arctic-t pe Warbler and feel that both Dave and Sha neen provided ver concise, informative, and well worded descriptions as to why this bird is a Phylloscopus species. I also agree that the best course of action at this given time is to list this as a species unresolved Through researching this species comple I agree that all three Arctic-t pe Warblers are unable to be reliably distinguished from one another morphologically. Even though this was likely an Arctic Warbler, I feel that without an audio recording, or a description of vocalizations heard, there is no way to be completely certain of the ID. In any event, an incredible discovery and wonderful to see one documented in Oregon.
Arctic/Kamchatka Leaf Warbler I appreciate the excellent write up and documentation by Shawneen and Dave. I see no reason to doubt that this is a phylloscopus warbler as so thoroughly discussed in their write up. I believe their documentation plus the photo eliminates other possible warblers and vireos. Many experts familiar with this species have also confirmed that this is a phylloscopus warbler. The expected species is Arctic but without a voice recording or having heard it calling the two are impossible to separate by sight alone.
Arctic Warbler, Kamchatka Leaf warbler, other Phylloscopus sp. My reason for including "other Phylloscopus species" among the possible review is that Dave's photo shows white margins on the tail, a feature I have not found mentioned, nor illustrated in discussions of Arctic, Kamchatka Leaf, or other species. I am puzzled that this apparently was not mentioned by Jon Dunn nor Paul Lehman, so maybe it's not a big deal? BTW nothing else in the photo suggests that this could be an artifact of lighting conditions. Strong backlighting, for example can give birds' tails the appearance of white edges, but nothing else in the photo suggests strong backlighting.
An outstanding discovery by Shawneen and amazing fast camerawork by Dave. Great teamwork for a new state record. And well done to keep the bird (barely!) within Oregon. California has enough of them already. The riteups together ith the photo leave no doubt that this bird is an Arctic-type Warbler. At least among all the Phylloscopus species that are known to have occurred in North America, the photo fits the three taxa recently split Arctic Warbler (P. borealis), Kamchatcka Leaf Warbler (P. examinandus), and Japanese Leaf Warbler (P. xanthodryas) while I think safely ruling out the others. As the observers note, the only reliable way to tell these three species apart, apparently, is by their vocalizations, so it is a shame that no call notes were heard. Given this situation, I feel we cannot accept this bird as any one of these three ta a even if Arctic ma be e think most likel I m afraid this bird is destined to be a slash So to me the two options to consider would be Arctic/Kamchatka (on the basis that Kamchatka is believed to be much more likel to reach Oregon than Japanese or Arctic Kamchatka Japanese on the basis that e can t reall rule out Japanese, regardless of how unlikely it might be). Kamchatka Leaf Warbler has at least reached the ABA Area but I am unclear on hether there s much understanding of ho far a Japanese Leaf Warbler might wander, relative to a Kamchatka. It might be useful to hear the reasoning of the California Committee when they opted for a two-way slash option instead of a three-way slash option for their records. With a bit of additional information along these lines I d be read to choose bet een these t o options for ho to pigeonhole this record.
It is clearly an Arctic or Kamchatka Warbler. I propose that it be accepted as "Arctic Warbler type".
Arctic or Kamchatka Leaf Warbler, if we accept as two species.
I know there will be some suggestion that it is species unresolved, but since the only one of the three that has occurred in the lower 48 the presumption must be that this is an Arctic Warbler.
Phylloscopus sp. (e.g., Arctic Warbler, Two-barred (Greenish) Warbler, Yellow-browed Warbler) The photo suggests that the supercilium extends to the bill. That and the, actually fairly prominent, posterior wingbar suggests this could be a Two-barred Warbler. (Hey, but I only know these from books.) In any case, I don't think there's enough to ID this to a particular phylloscopus species.
Definitely a member of the Arctic Warbler superspecies, but according to current knowledge, they are almost impossible to tell apart physically. Since no vocalization was heard, this bird cannot be identified to species. Candidate species therefore are Arctic Warbler, Kamchatka Leaf-Warbler or Japanese Leaf-Warbler.
Arctic Warbler and Kamchatka Leaf Warbler This bird is likely to have been an Arctic Warbler, but since no vocalizations were heard, Kamchatka Leaf Warbler must also be considered since experts find it very difficult to separate these two species from from each other from visual evidence alone. Japanese Leaf Warbler looks very similar to the bird in the photograph, but it generally has a brighter wash to the face and the underparts than this bird had. The fact that this bird had only a single wingbar eliminates many of the Old World Warbler species including Yellow- browed Warbler. The photo clearly eliminates all expected North American warbler species. I agree with the observers that it would be best to accept this bird as a Arctic Warbler/Kamchatka Leaf Warbler.