Willet (1 Viewer)

I could only find one Willet thread, and it focused on convergent evolution in Tringa, so I am making a new one that is Willet-specific. I have a question about the Willet and the potential split of that species into two. Almost five years ago, David Sibley listed them (Eastern and Western Willet) as the most splittable of his 10 potential splits (http://www.sibleyguides.com/2010/04/the-next-10-north-american-bird-splits/). What is the status of any sort of taxonomic work on these two taxa? Has the AOU ever faced a proposal to split them? Does anyone have information on why they are still considered conspecific?

I have pasted some information below from BNA about the two groups, and it sounds good to me.

Information copied from BNA:
“
Two disjunct groups of breeding populations that differ in size (wing length, bill length and thickness, leg length, and body mass), plumage (especially Alternate plumage), vocalizations, breeding ecology, and to a large extent, winter ranges. These 2 groups are recognized as separate subspecies, C. s. semipalmatus and C. s. inornatus, referred to as Eastern and Western willet, respectively (see below). Both plumage and size appear to be more variable among Western Willets.
…
Eastern Willets discriminate between Eastern and Western songs, suggesting behaviorally facilitated reproductive isolation (Douglas 1998).
“

O'Brien 2006 (Subspecific identification of the Willet Catoptrophorus semipalmatus) suggests that a split may be appropriate.

The two subspecies are listed as 'distinctive subspecies groups' by eBird/Clements; and as 'distinct subspecies sometimes considered specifically distinct' by Dutch Birding.

But I don't think that AOU-NACC has considered a proposal to split them; and I'm not aware of any recent study proposing a split.

Everyone can pen a proposal to the NACC. If that is on your mind, the best place to start is with the question of: do the two subspecies meet anywhere? If they do, what happens at that location? Are there hybrids, if there are hybrids then how wide is the zone of hybridization, is there existence of evidence that hybrids fare less well than the pure individuals, etc.

Niels

njlarsen said:

Everyone can pen a proposal to the NACC. If that is on your mind, the best place to start is with the question of: do the two subspecies meet anywhere? If they do, what happens at that location? Are there hybrids, if there are hybrids then how wide is the zone of hybridization, is there existence of evidence that hybrids fare less well than the pure individuals, etc.

Niels

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The populations are actually allopatric - at least three states away from one another.

As insinuated before, this pair has been speculated over for years, but nobody has submitted anything to the NACC. I would imagine it is a low-hanging fruit for any splitter willing to gather the documentation and turn it in to them (in a well-organized, well-worded proposal, of course!).

cox1 data from BOLD. (Not really convincing...)

Kirk Roth said:

The populations are actually allopatric - at least three states away from one another.

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What about during winter, and if mixing then, what chance odd individuals migrating back with the 'wrong' [sub]species?

Any / many records of vagrants of either within the other's breeding range?

I don't see mention of Tobias scoring on HBW's site. While some taxa that were not split do have a score on their page, Willet does not (at least that I can see as a non-subscriber).

Nutcracker said:

What about during winter, and if mixing then, what chance odd individuals migrating back with the 'wrong' [sub]species?

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Western willets are regular on the east coast (at least in New Jersey) in winter and migration.

Jeff hopkins said:

Western willets are regular on the east coast (at least in New Jersey) in winter and migration.

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Thanks! What proportion of the total wintering Willets there, roughly?

Laurent-You are correct, that genetic data does not look convincing. Do you know of similar data for the Nelson’s/Saltmarsh Sparrow group? Somewhere, I have seen it hypothesized that the Willet groups split under the same(ish) circumstances as those two sparrows, so it would be interesting to see the sparrow genes.

In my opinion overall though, genetic data can more easily say that something is a species than something is not a species, unless you are following a strict application of the PSC. After all, if two taxa view themselves as different, but their genetics have not yet diverged, I would think they would be different species.

It is unfortunate that HBW does not list the scoring criteria for Willet on their website. Did they apply the Tobias criteria to all subspecies groups that they have done so far?

In looking around for more information on potential hybrids or vagrants, I came across an interesting discussion here: http://www.oceanwanderers.com/ONWillet.html The discussion was somewhat focused on field ID, but I thought it may be relevant to this thread.

As for wintering, I don’t think Eastern Willet is known to winter in the US, so I would assume that roughly 100% of wintering Willets in New Jersey would be western, but I would defer to local birders on this. (Jeff, do you have thoughts on this?) Maybe state records committees keep track of out-of-season eastern birds? That would be helpful. Looking at the records committee websites for Florida and Texas (the states I would guess would be most likely to host an overwintering eastern), they don't seem to have easy access to records to past occurrences of species, so I'm not sure if they keep track of it.

cwbirder said:

Somewhere, I have seen it hypothesized that the Willet groups split under the same(ish) circumstances as those two sparrows...

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O'Brien 2006 (cited/linked in post #2)...

Mitochondrial DNA evidence has shown Pleistocene glacial events to be responsible for both initiation and completion of speciation in numerous sister species pairs such as King and Clapper Rails, Nelson’s and Saltmarsh Sharp-tailed Sparrows, and Great-tailed and Boat-tailed Grackles (Johnson and Cicero 2004), species pairs with coastal vs. interior distribution patterns comparable to those of Eastern and Western Willets.

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cwbirder said:

It is unfortunate that HBW does not list the scoring criteria for Willet on their website. Did they apply the Tobias criteria to all subspecies groups that they have done so far?

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HBW/BirdLife don't even recognise the Willet subspecies as distinctive groups (so the Tobias criteria are unlikely to have been applied); H&M4 likewise.

cwbirder said:

Laurent-You are correct, that genetic data does not look convincing. Do you know of similar data for the Nelson’s/Saltmarsh Sparrow group? Somewhere, I have seen it hypothesized that the Willet groups split under the same(ish) circumstances as those two sparrows, so it would be interesting to see the sparrow genes.

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Data mainly from Walsh et al. 2011 [pdf], retrieved from GenBank--there are three nelsoni in the BOLD database, but no caudacutus. It's the same genetic marker.
The distance is not big, but at least here the two taxa form distinct clusters.

Nutcracker said:

What about during winter, and if mixing then, what chance odd individuals migrating back with the 'wrong' [sub]species?

Any / many records of vagrants of either within the other's breeding range?

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You're right - I should have specified that I was talking of breeding ranges.

I know that on the Texas coast, wintering inornata can be present before all the semipalmata have left, in fact I believe there are many photos of the two taxa next to one another.

I've never heard of one taxa simultaneously in the breeding range and breeding season of the other, although I would be very surprised if there weren't records out there of the semipalmata birds staying all year on some eastern beach (it is not uncommon for shorebirds to simply forego northern migration if they are injured or unhealthy). More interesting would be whether any Eastern Willet phenotypes had been recorded in Western North America.

l_raty said:

cox1 data from BOLD. (Not really convincing...)

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I wasn't aware of this work. Certainly makes Solitary Sandpiper look like the better split!

Kirk Roth said:

Certainly makes Solitary Sandpiper look like the better split!

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I recall a possible split of Cinnamon-dotted/Western from Pale-dotted/Eastern being mooted several years ago, but there doesn't seem to have been any recent discussion.

Kirk Roth said:

You're right - I should have specified that I was talking of breeding ranges.

I know that on the Texas coast, wintering inornata can be present before all the semipalmata have left, in fact I believe there are many photos of the two taxa next to one another.

I've never heard of one taxa simultaneously in the breeding range and breeding season of the other, although I would be very surprised if there weren't records out there of the semipalmata birds staying all year on some eastern beach (it is not uncommon for shorebirds to simply forego northern migration if they are injured or unhealthy). More interesting would be whether any Eastern Willet phenotypes had been recorded in Western North America.

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Thanks! As to injured birds summering on the wintering grounds, maybe also first-summers not old enough to breed?

One slight annoyance, no hope of an armchair tick for me if they get split, only had Western :C :-O

Kirk Roth said:

I wasn't aware of this work. Certainly makes Solitary Sandpiper look like the better split!

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Solitary Sandpiper was one of the early "provisional splits" suggested by barcoding of North American birds. See Table 2 in Kerr et al. 2007 [pdf].

I think this thread shows the limitations of DNA - a powerful clue but not always definitive. To me, Willet is still one of the most obvious potential splits in North America, regardless of what the DNA says. It just "feels" like two species, with differences in so many independent features - plumage, structure, behavior, voice, migration. And in the tree that Laurent posted I wonder if the data might be a little more favorable than they appear. The three semipalmata clustered with inornata are all from Florida, where both subspecies are common. Can those be verified as semipalmata?

I've spent quite a bit of time with Solitary Sandpipers since Kerr et al showed that big barcode difference, and there are some minor tendencies in plumage from east to west, but I still can't distinguish subspecies. Maybe I just haven't looked at the right details yet, but I suspect it's a situation like Mountain Chickadee or Common Raven, with a genetically differentiated group that still looks and acts just like the rest of the species.

With all due respect, I would suggest this thread shows the limitations of poor DNA data (not DNA data in general). Using a DNA sequence dataset from a single locus (the mitochondrial gene COX1) as evidence of the limited usefulness of DNA is akin to using a Pabst Blue Ribbon as evidence that beer is a tasteless beverage. The processes of mitochondrial introgression and deep coalescence are rampant and lead to serious bias in single-locus datasets such as the apparent mitochondrial DNA sequence datasets presented in this thread. [Mitochondrial introgression is the spread of a mitochondrial allele from one species into another, making the two look identical genetically, and may occur as a result of just one event of hybridization between the two in the last few million years. Deep coalescence is the presence of two genetic lineages in a single population and it can make it look as if there are two divergent things when really there is only one population of freely interbreeding individuals.] Mitochondrial introgression could easily produce the apparent genetic similarity of Willets in the presented dataset, and I would argue based on the observed phenotypic differences that this is the most likely explanation for the observed pattern (assuming phenotypically "pure" birds were sampled from the breeding grounds, as mentioned by David). Deep coalescence could easily produce the apparent deep split in Solitary Sandpiper in the previous document. Essentially, what it comes down to is we can have very little confidence in the results of mitochondrial (or other single-locus) datasets.

Thankfully, the recent shift to using tens to thousands of independent loci is solving these issues. A well-sampled genomic dataset can tell us everything up to and including the time since populations diverged, the extent to which populations interbreed, and (given enough work) the number of genetic changes responsible for observed phenotypic differences. This isn't to say that genomic datasets will overturn all of the results from mitochondrial data over the past 2.5 decades, but they will reveal the likely substantial number of cases in which mitochondrial trees were a result of recent introgression or deep coalescence rather than an accurate reflection of species history and divergence. Of course, even with genomic data, genetic datasets are no silver bullet and should always be combined with research on phenotype, behavior, etc., but they're definitely better than a PBR.

With regards to Willets, I believe a thorough study is being conducted currently with many loci and individuals sampled from the breeding grounds with appropriate vouchers for phenotypic data.

Mike

Nutcracker said:

Thanks! What proportion of the total wintering Willets there, roughly?

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I don't honestly know. I only know that westerns occur.