Warbling vireos and Colorado eBird

[greatg...@aol.com]

All:

With the split of Warbling Vireo into two species (Eastern Warbling Vireo [EWVI] and Western Warbling Vireo [WWVI]), eBirding has become much more difficult and problematic, and we Colorado birders get to be the guinea pigs for learning about the distributions of the two species on the Colorado plains. While there are pre-existing data, there are nowhere near enough, as few birders cared about the subspecies Warbling Vireo (Eastern) and Warbling Vireo (Western).

The first and most intractable problem is that there are NO consistent plumage color or pattern differences between the two species. Western TENDS toward the grayer end with a darker crown, and Eastern TENDS toward the brighter end with a paler crown, but the overlap in plumage tone is virtually complete. Western has a shorter, thinner bill than does Eastern, but the usable in-hand differences are in the half-millimeter range, something that will be nearly useless in field conditions.

The primary take-home message from this post: Recordings of SINGING birds provide the only truly definitive documentation. Not calling birds. Not whining birds. Singing birds, and singing birds singing full songs. That means that all of our phones’ audio recorders will be getting a workout come May. That also means that non-singing birds are essentially unidentifiable, and should be recorded as “Eastern/Western Warbling Vireo” (or some such entry).

Because there are relatively few definitively identified records of either species on the Colorado plains, where the two species meet and overlap, we don’t know the true extent of either species’ breeding distributions there. Yes, the farther east one goes, the more likely it is that EWVI is the breeding species, and WWVI is more likely as one approaches the foothill edge. West of the foothill edge, all breeders are WWVI… probably. Both species are suspected to breed at Barr Lake S.P., and if they hybridize there or elsewhere where the two species meet, then virtually all bets are off when it comes to definitively identifying even singing warbling vireos. Additionally, the extremities of the two species’ breeding ranges probably differ greatly between the South Platte drainage and the Arkansas drainage. The same is true for many “eastern” species of birds, such as Red-bellied Woodpecker, Bell’s Vireo, Baltimore Oriole, and Indigo Bunting, all of which breed much farther west in the South Platte drainage than in the Arkansas drainage. More on this, below.

As I noted in the first sentence, the reason I am posting in this venue is to give everyone birding on the Colorado plains next spring and summer a heads-up as to how the Colorado eBird filters will be dealing with this worst-ever bird-ID conundrum to visit the state’s birders.

eBird filters provide a framework for the abundance (or lack thereof) for all species occurring in a given filter region (e.g., Adams County, Crowley and Otero counties, and the San Luis Valley’s five counties). Those filters are what cause entries to flag or not (see eBird Data Quality : Help Center for more on that eBird process). Individual species have upper limits on the number of individuals that can be submitted to eBird from a particular location, beyond which the entry will flag for relatively atypical abundance for limits of 1 or greater, or will flag for rarity for a limit of zero.

[Those interested in a deeper dive into the hows and wherefors of Colorado eBird filters, check out Colorado & Wyoming eBird: Stone Age to Industrial Age: The evolution of eBird's filter system. For other aspects of eBird relative to Colorado, check out the blog housing the above-linked essay: Colorado & Wyoming eBird

Stone Age to Industrial Age: The evolution of eBird's filter system Did you ever wonder why eBird asks for details about a report of American Dipper from Adams County, Colorado, bu...

Colorado & Wyoming eBird Everything eBird for Colorado and Wyoming, from the keyboards of the region's eBird reviewers

.]

I return you to our regularly scheduled programming.

Front Range, Wet Mountains, and Sangre de Cristos and west – This is the only portion of the state that is/has been simple to create the eBird filter limits that will govern which species will be available on filters: All filters from these areas will allow Western Warbling Vireo at various limits of >0 during the seasons of typical occurrence (on a gross scale, May through September). Somewhat unfortunately, all foothill-edge counties in Colorado straddle the foothill edge, so those counties (Larimer, Boulder, Jefferson, Douglas, El Paso, Pueblo, Huerfano, and Las Animas) will also have Eastern Warbling Vireo on those filters, but with the limit set to zero on each. That means that any reports of Eastern Warbling Vireo in those counties will require documentation of the occurrence.

Colorado’s eastern edge (Sedgwick, Phillips, Yuma, Cheyenne, Kit Carson, Kiowa, Prowers, and Baca counties): These filters will have limits of >0 for Eastern Warbling Vireo from arrival to the end of the breeding season (probably May through mid-August), but will have 0 limits for Western Warbling Vireo (the species may be a casual or rare migrant through these counties, as the species breeds in the Black Hills of South Dakota and may traverse eastern Colorado to and fro).

Western portions of the Arkansas River drainage on the plains (Elbert, El Paso, Lincoln, Crowley, and Otero counties): Eastern Warbling Vireo will have limits of 0 in all seasons and all counties. Because we CO birders are not sure of the distributions of the two species in Crowley and Otero, BOTH species will have a limit of 0 all year; documentation will be required, even in migration, when Western Warbling Vireo is probably a fairly common spring (and fall) migrant.

Eastern portions of the South Platte River drainage on the plains (Logan, Morgan, and Washington counties): The expected breeding species here is Eastern Warbling Vireo, but in Washington, possibly only along the South Platte and at Prewitt Reservoir. Western Warbling Vireo is probably of reasonably regular occurrence as a spring migrant. EWVI will have non-zero filter limits from May through early August, but WWVI will have filter limits of 0.

The problem children (Weld, Adams, and Arapahoe counties): As I noted earlier, both warbling vireo species have been noted singing at Barr Lake (Adams Co.) during the breeding season. Thus, in Adams County, both species will have filter limits >0 from May to early August, but both filters will have 0 limits in the fall (essentially after 7 August). I strongly suggest providing recordings for reports of either species in the county so we can begin to fully understand the breeding distributions and the relative abundances of the two species. In both Weld and Arapahoe counties, the filter limits of both species will be 0, so documentation for both will be required.

Hopefully, eBirders will provide a lot of recordings this coming spring and summer, so that the various Colorado eBird reviewers can better understand the two species’ spring and summer occurrence patterns. That would provide those reviewers the opportunity to refine filters for subsequent breeding seasons.

Tony Leukering

Denver, CO

eBird blog

eBird commentary

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[tom none]

If the two "species" hybridize where they overlap, might we dealing with a cline. Maybe the western birds can't breed with eastern counterparts, but are interfertile at the relative edges of their respective ranges.

Have fun,

Tom Curtis

[Jake Shorty]

To add to Tony's great walkthrough, Denver County also sits in the awkward overlap between species, and with limited records of either. For now, Denver proper will follow the pattern of Weld and Arapahoe counties, using a year-round zeroed filter. It's most responsible to use the slash designation when you can't get a song recording, or even if you do and you're unsure about it! 

Thanks!
Jake

[Ted Floyd]

Hey, all. As Tony says:

The primary take-home message from this post: Recordings of SINGING birds provide the only truly definitive documentation. Not calling birds. Not whining birds. Singing birds, and singing birds singing full songs. That means that all of our phones’ audio recorders will be getting a workout come May. That also means that non-singing birds are essentially unidentifiable, and should be recorded as “Eastern/Western Warbling Vireo” (or some such entry).

Agreed, but I might add a few points:

1. The Merlin Bird ID app, once it goes through mandatory training, will probably get fairly good, but far from infallible, at separating the two warbling[-]vireos. However... ;-)

2. It is good to understand a few quirks about the mind of Merlin. For starters, Merlin "thinks out loud" as it chugs along listening to three-second cuts of audio. A huge number of people don't know this. Merlin is actually rather like a human in this regard. Picture, oh what the heck, me and Tony listening to a "solitary vireo" in the Boulder foothills in May. The bird gives a bunch of "classic" Plumbeous song elements, but then the 14th sounds more like a Cassin's, and Tony says, "Interesting...that was closer to Cassin's than to Plumbeous." Tony doesn't mean that the bird suddenly turned into a Cassin's Vireo. He just means that it gave a single song element that was Cassin's-like. Merlin does that, too! Imagine that you're out and about, and you get Merlin output like this: Western, Western, Western, Western, Western, Eastern, Western, Western, Eastern, Western. That doesn't necessarily mean that both warbling[-]vireos are present. Rather, it means that the app is "thinking"—and that, Leukering-like, it's remarking on how the 6th and 9th songs sound Eastern-like. Which isn't the same thing as saying it is an Eastern.

3. Don't ever, ever, say in your eBird notes, without discussion, that an ID is supported by Merlin. If I were an eBird reviewer—oh, wait, I actually am—I would summarily reject any problematic ID "supported" by the one-word throwaway "Merlin." The only thing more egregious than that is the one-word throwaway "photos." In the same way that you would, needless to say, indicate "photos," and then upload said photos (I can't believe I even have to say that), it is totally fine to say "Merlin," if, and only if, you also include the audio recording. And that's the great thing about Merlin. It makes recordings of everything you listen to! (Including your grumblings about the propellerheads at Cornell, or your ex, or me and Tony, or the person who raided the fridge and took the last slice of Velveeta® you were so looking forward to). Just put the audio there and, sooner or later, Eric DeFonso or Nathan Pieplow or someone will validate the ID.

4. Make long recordings! Yes, there is a sort of "classic" Eastern and also a somewhat "classic" Western, but there are many, many 'tweeners. (Same as with Plumbeous and Cassin's vireos.) Fortunately, warbling[-]vireos during the breeding season sing their heads off, and they sing loudly. Record for at least a minute, upload the recording, and wait around for Eric and Nathan & Co. to do their thing.

5. If possible, upload photos or video. Tony takes the cautious view that photos alone are insufficient for making the call, and I think that's largely correct. (And it's distinctly different from the multitudes of self-proclaimed experts on social media suddenly and confidently ID'ing as Eastern the birds in seemingly all photos of extraseasonal warbling[-]vireos in the East.) That said, a good photo or video may well support the ID as one singing warbling[-]vireo or another.

And, hey, look at it on the bright side: None of us has to worry about any of this at all for at least four full months.

Ted Floyd

Lafayette, Boulder Co.

P. s. Warbling[-]vireos because the orthography is a total cluster. AOS has them as Eastern and Western warbling-vireos, whereas eBird has them as Eastern and Western warbling vireos. The four-letter code overlords follow AOS, not eBird, in these matters, so the birds are officially EAWV and WEWV, respectively. Here's an idea for a New Year's resolution: Just don't use four-letter codes.

P. p. s. Remember MYWA, the butterbutt, the Myrtle Warbler. Okay, but what about Mangrove Yellow Warbler? ;-)