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A Western Sandpiper (and Purple Finch and Sharp-shinned Hawk) conundrum

August 15, 2011

I love eBird. I will sing its praises from here to the end of the earth and continue the, mostly futile, attempt to get old-time North Carolina birders to enter their sighting into what I hope will be a great repertory of bird information, elegantly cataloged and universally available.  But even eBird, in its infinite usefulness, isn’t perfect.   The obvious concern with those who initially criticize eBird, at least in my experience, has to do with the rare species vetting protocol.  But rest assured, the rare bird concerns are well in hand.  The system by which sightings are filtered and notable reports are flagged and checked by a local reviewer is really great.  The vast majority of properly reported rare birds are correctly dealt with, and the incorrect reports are weeded out accordingly many times with a friendly exchange.   I can vouch in my experience as a eBird reviewer and with reviewers from elsewhere, that quality control, and birder outreach, is a priority for us.  No, for eBird, this biggest conundrum has to do with not rare cryptic species pairs.  This is the problem that keeps eBird reviewers up at night.  Well, not up at night per se but certainly furrowing our collective brows when we look at our carefully calibrated eBird-generated bar charts.

What I mean by these not rare cryptic species are those for which neither species is particularly rare, one is certainly more common than the other, and the two can easily and frequently be mistaken for each other.  The most obvious example is the Cooper’s/Sharp-shinned Hawk complex. Throughout the near entirety of the continent both of these similar species are present, but generally one is far more frequently encountered than the other.  For most of us it’s the Cooper’s Hawk that’s most common, but because Sharpies are not particularly unusual, there are no grounds by which they deserve to be flagged in the eBird database.  But small male Cooper’s Hawks are easily mistaken for Sharp-shins, especially given a less than ideal look at the bird, and I’m convinced, taking into account my own experiences birding in North Carolina, that Sharp-shinned Hawks are over represented, perhaps significantly so, in the eBird records.  But I don’t see a way to fix this beyond putting the eBird reviewer in the position of being inundated with dozens of Sharp-shinned Hawk records every week.

The same can likely be said for Purple and House Finches as well, though generally a regular check for Purple Finches on checklists that do not include House Finches is enough to get rid of the most egregious errors.  In all cases, these are all well-intentioned reports, and while it’s not the eBird reviewers’ place to play list police, there’s no way to completely eliminate the problem.  But I’m trying.  Take my most recent concern, Western Sandpipers.

I took this shot in Carteret Co, NC in May 2008. Slim-tipped curved bill, chestnut ear patch, front-heavy posture? Yup, classic Western.

Calidris sandpipers offer the birder no shortage of problems generally, but the Western/Semipalmated duo is widely regard as the most sinister of the bunch.  Semipalmated is a common fall migrant through the Piedmont of North Carolina, and outside of the tiny, yellow-legged Leasts and massive Pectorals, they’re the default peep.  But Western is a regular migrant as well, and it’s a good day when a central North Carolina birder can go out to a mudflat and find one Western on which they can hang their hat.  Maybe two.  Almost never more than five.   In fact, the pre-eBird gold standard for distribution and abundance in the Triangle, an amazingly thorough abundance chart created by long-time Triangle birder Will Cook (.pdf), suggests five is an exceptional count.

That’s not to say it can’t happen, birds do seem to exist just to surprise us sometimes, but by and large if you’re finding yourself picking up more than a few sandpipers that seem to be showing Western-ish tendencies, it’s probably a good idea to back up, take a second look, and really try to make that convincing argument to yourself as to why these birds aren’t within the range of Semipalmated.  Because most likely they will be.

Now this isn’t a post that seeks to provide ways to differentiate Western from Semipalmated Sandpiper, there are other places that can offer that my birders who have generally have far less trouble with it than I do (here’s a really good one by shorebirder extraordinaire Cameron Cox), nor is it the North Carolina eBird reviewer opening a can of “I told you so, so there” on obviously well-intentioned birders, but the principles of indeterminacy should inform your observations here. And if the reports of four to eight(!) Western Sandpipers I’ve recently received are any indication (all reported at a site I hit up weekly without finding these birds), people are possibly jumping the gun a little bit.

Or maybe I’m just peeved I haven’t come across a Western Sandpiper this year. In any case, I’ve tightened up the filters a little bit – they were set a bit too loose – and sent out some requests for information.  We’ll see what I turn up.  We’ll see whether the same needs to be done for the Hawks and Finches.

UPDATE: Turns out the eight Western Sandpipers was a mis-entry.  The correct count was one, which makes a lot more sense.

One Comment
  1. August 16, 2011 7:54 am

    I am constantly surprised at how often not uncommon birds I have never or rarely seen in my home county show up on eBird in my home county. I often forward the sightings I notice to my local eBird reviewer with a request that he ask about them to see what the reporter has to say. It is a weakness of eBird but a necessary weakness, I guess. That is, unless the reviewers become the bird police.

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