The Case of the Mysterious “Might-be-a-rare-bird”

Birders as a whole, can be quite passionate about their bird lists. While we still thoroughly enjoy the activities of our common sparrows and finches, it’s the rare birds that really fuel our obsession. We live for that next new addition to our beloved list. The subtleties and nuances that separate a rare species from the more common ones, can provoke a splendid detective case where every detail becomes a critical piece of evidence. As the case for a rare bird is built, the facts can sometimes be obfuscated by what we want to see. Sometimes the facts may be not be as relevant and we suspect them to be. This is especially true when photographic records are obtained second-hand.

JIM! – Check your email…

The game is afoot.
And so it began, a text with 4 short words. A text that would result in 3 1/2 hours of field work, and a few more hours of research and detective work behind the computer.

Map Link to the San Joaquin River National Wildlife Refuge

Some birders, new to the obsession, had noticed an unusual bird mixed in with the usual suspects out at the San Joaquin River National Wildlife Refuge, west of Modesto. The bird in question superficially looked similar to a regular winter resident of any wet habitat, the Greater Yellowlegs. But this bird just didn’t look like the others nearby. It didn’t have the long, pointy-tail look, the legs were a bit off-color (peachy) and the base of the bill seemed pale. They knew enough to try and get some good photos of it and then to send them to someone that had more experience. And so, the novice birders sent their evidence to a veteran valley birder.

As in a court case, the images were now second-hand evidence, as the veteran birder had not actually seen the bird. While images of a bird can be quite helpful, there are some caveats to this value. Distant birds, combined with low quality lens’s or digital zooming can distort size and color. As can the position of the sun relative to the photographer and the subject. The experienced birder knows the importance of when to broadcast a rare-bird sighting and when not to. Birders have been known to immediately book flights to chase down the rarest of sightings and the miss-reporting of a rare species can deal a blow to the reporter’s reputation (not to mention the waste of money…). In this case, the evidence seemed sufficient to warrant a limited broadcast to some of the locals in hopes they might gather more evidence to support a potential rare bird.

With only the location known and two poor images, I raced out the door, yelling to my wife, “be back later…” In route to the refuge I got a phone call from Salvatore Salerno explaining a little more about “the bird.” First a little background about the usual “Tringa” sandpipers vs the rare ones.

Greater Yellowlegs belong to the Genus Tringa and are common throughout the valley in any wetlands, ponds, lake shore or flooded field from August through May. Less common is the Lesser Yellowlegs which is more of an uncommon spring and fall migrant, with a few individuals sticking around in winter. The rarest of Tringa shorebirds include the Spotted Redshank, Marsh Sandpiper and Wood Sandpiper, and it was the possibility of the mystery bird being one of the latter that got us all motivated.

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Historical records of the three rare Tringa species are
– San Joaquin County has a record of Spotted Redshank (5 total CA records)
– Marsh Sandpiper (2 CA records) one in the valley, and
– Wood Sandpiper (3 CA records) with none in the Central Valley.

There were three pieces of evidence from the photos that seemed to point to the possibility of a Spotted Redshank; short-primary projection, light-base of the bill and peach-colored legs. Fortunately, the weather was beautiful and it was a short walk from the parking lot to where the bird was seen. As a photographer, I have many “Squirrel” moments and am readily distracted by any bird that will pose long enough for me to snap a few shots. Today was no different and as I walked to the flooded field, I couldn’t help but stop and shoot a couple dozen images of the Sandhill Cranes as they were constantly flying around the area.

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I made a mistake when I ran out the door to get here as quickly as possible, and I failed to grab my telescope. I knew instantly that this was going to be a tough stake-out. There were dozens of Greater Yellowlegs as well as one or two Lesser Yellowlegs. And they were all a bit too far out to get good photos of.

I scared up a flock of Green-winged Teal as I walked around the pond.

A short time later, Sal appeared (no telescope either) along with Daniel Gilman who fortunately did have one. As were continuously looked at first one yellowlegs, and then another, and another, we delved into a discussion about the possible rarities, and what we needed to observe to make a solid case of identification. Using the Sibley iPhone App, we looked at images and listened to each suspect’s call.

We never saw anything that resembled what we thought could be a rarity and after a bit, Sal and Daniel departed. I decided to take advantage of the gorgeous weather and I walked as far as I could along the nature trail. I was serenaded by California Towhees, California Thrashers and Wrentits.

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I couldn’t go very far down the trail as the refuge staff had posted closed signs a short ways down the trail. I’m not sure if this is permanent or a by-product of the government shut-down.

On the way back to the parking lot I had a Blue-gray Gnatcatcher make its buzzy call right next to me and I got a decent shot of it.

On the ride back into town, I got a call from Sal commenting that more in-depth analysis of the photos revealed that the mysterious “Might-be-a-rare-bird”, was after all, not quite so rare. It was deemed to be a first winter Lesser Yellowlegs. A winter sighting of a Lesser Yellowlegs was definitely uncommon, but not something to be added to the great list of rarities.
While I didn’t get to add a new rare bird to my list, I had a very enjoyable walk in nature, got a few photos and learned a lot about the rare Tringa shorebirds of California.