The Discovery

It was 6:30 am and I found myself, once again, at the southern part of the San Joaquin River National Wildlife Refuge, west of Modesto. The previous morning I had started a run of point counts as a part of the Least Bell’s Vireo monitoring program with the US Fish & Wildlife Service. In 2006, Least Bell’s Vireos had been found to be breeding on the refuge after more than fifty years without records of breeding in the Central Valley. Since then, there has been a yearly effort to monitor and document their presence on the refuge.

Bells Vireo | Photo by Andy Reago & Chrissy McClarren

I had made a mistake and missed a point count location the day before, so I had returned to pick up at the last correct spot. I had inadvertently left my map at home, so I was waiting for my wife to send me a digital copy. While I waited, I was standing outside my car, swatting away mosquitos and enjoying the sounds of the birds singing all around me.

There were lots of Marsh Wrens calling with their vociferous gurgling, rattling trill. Red-winged Blackbirds were singing their odd conk-la-lee call. Amongst the continuous chorus of these marsh birds was the occasional witchety-witchety-witchety call of the Common Yellowthroat and the odd, discordant squawk of the Common Gallinule. Then the bass section kicked in when the American Bittern began its deep booming pump-er-lunk, pump-er-lunk call. The combined orchestra was quite cathartic on this beautiful morning and I felt far from worries in the calming presence of nature.

I had glanced one more time at my phone to see if the map had arrived when I heard it — a somewhat muted cof-cof-cof-cof-cof drifted across the marsh from several hundred yards away. My consciousness immediately questioned the veracity of what my ears were trying to communicate. Cupping my hands behind my ears like a big antenna, I strained all my senses for a second offering of that call. And then it repeated, more clearly this time, or perhaps because of the heightened state of my auditory receptors: cof-cof-cof-cof-cof and again, cof-cof-cof-cof-cof.

The adrenaline surged through me as I realized that not one, but two males were calling from different locations. I crept carefully and quietly along the road, trying to get closer to my prey. And then I saw them! One flew up from the tules and then a second one chased after it quite closely, not 60 feet from where I stood: two LEAST BITTERNS. Somehow, while looking for one “Least” species, I had found another!

IMPORTANT DISCLAIMER
White Lake is a fragile habitat and is not currently open to public access. Please visit the Merced National Wildlife Refuge which has public access to a walking trail, appropriately called The Bittern Trail. Least Bitterns have been observed in this location during spring migration.
https://www.fws.gov/refuge/merced/

The excitement I felt came from knowing that the sighting of a Least Bittern anywhere in northern California has been extremely rare for decades. Birders eager to add the species to their checklists often had to venture to southern California, where the birds could be found at the Salton Sea and along the Colorado River.

Least Bitterns are a California Species of Special Concern whose numbers have declined severely in the Central Valley since 1945. They qualify as a Species of Special Concern due to their population declines and range retractions. There are only a handful of Least Bittern sightings in Stanislaus County, and a pair at this protected location at this time of the breeding season, screamed of potential nesting.

Least Bittern at the Green Cay Wetlands in Boynton Beach FL | Photo by Jay Paredes

The refuge manager Eric Hopson, was as excited as I was about the discovery, and immediately visited the location where he recorded video with the two males calling softly in the distance. He related that the 2 males continued to sing continuously for most of that day. My follow-up visits the next morning revealed that at least 3 Least Bitterns were currently exploring the rich habitat of the refuge but singing only sporadically. One week later the only sound coming from them was the kek-kek-kek call given while on a nest. Ironically, I was searching for the Least Bell’s Vireo, another threatened species, when I found the bitterns.

TAXONOMIC CONNECTIONS

Least Bitterns belong to the Ardeidae family that also includes herons, egrets and other bitterns. There are 68 bird species included in this family with 8 species found locally. They range from the giant Great Blue Heron, to the elegant Great Egret.

The Least Bittern is not the only bittern species that occurs in the valley. The much larger American Bittern is much more likely to be observed in our nearby wetlands. The American Bittern however, is much larger than the diminutive Least. While their habitat is similar, their niches are quite distinct. While the larger American Bittern wades methodically along the shallow water and grassy edges, the Least Bittern discretely picks it way from tule to tule, grasping the reeds with its claws like a Marsh Wren as it squeezes its narrow body through the dense vegetation.

Least Bittern | Photo by Steve Arena USFWS

The Least Bittern’s scientific name is Ixobrychus exilis. Ixobrychus is from Ancient Greek ixias, a reed-like plant and brukhomai, to bellow. Exilis meaning little, slender.

DESCRIPTION

With 16 species of Bitterns worldwide, the Least Bittern is one of the smallest herons in the world. They’re stylishly attired in hues of chestnut, cream, and black, with the male more ornately colored than the female. Because of its habitat choice, it often goes unseen except when it flies, but its cooing and clucking call notes are heard frequently at dawn and dusk and sometimes at night. Like other bitterns, they eat fish, frogs, and similar aquatic life.

Least Bittern at Great Meadows NWR| Photo by Steve Arena

DISTRIBUTION & HABITAT

Least Bitterns migrate from their wintering grounds in Northern Mexico and Baja California in mid-April, with nesting starting in mid-May and fledglings appearing in early June. Until very recently, Least Bitterns had become extremely rare in the San Joaquin Valley, primarily due to loss of their wetland habitat. Remnant populations have bred in the Sacramento Valley over many years, but recent breeding records for the San Joaquin Valley are extremely scarce. The San Joaquin County bird checklist shows the species as extirpated there. Least Bitterns niche of choice is along the edge of the vegetation over deep water because they mostly climb in reeds rather than wading. Restoration of habitat such as has taken place on the San Joaquin River National Wildlife Refuge is thought to be a major factor in their return to the Valley.

Least Bittern on Nest | Courtesy of Missouri Department of Conservation

The Gem of the San Joaquin River – Refuge Extraordinaire

The vision of the San Joaquin River National Wildlife Refuge is quite clearly stated in the Draft Comprehensive Conservation Plan.

“This Refuge will conserve and restore the area’s native habitats, maintaining its role as an important riparian corridor for natural resources within the state’s Central Valley. It will emphasize management of native wildlife and the necessary actions that focus on the recovery of Federal and State listed endangered/threatened species and other species of special concern, and protection and/or enhancement of migratory bird resources.”

It was no accident that the Least Bitterns happened to choose this area to raise their young. Eric Hopson and his staff have worked closely with scientists and consultants to recreate the deep water permanent marsh habitat that once extended along the length of the San Joaquin Valley.

And Now, the Rest of the Story

Thus far, with barely a week’s worth of observations, it’s exciting to see how this will play out. Based on the lack of mating calls and the observance of several on nest kek calls, it is possible they are incubating eggs. Stay tuned for a follow-up report at the end of the breeding cycle in mid-July. It’s the “Least” I can do!

IMPORTANT REMINDER

White Lake is a fragile habitat and is not currently open to public access. Please visit the Merced National Wildlife Refuge which has public access to a walking trail, appropriately called The Bittern Trail. Least Bitterns have been observed in this location during spring migration.

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.

Lesser Yellowlegs
Greater Yellowlegs

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.

Photograph of a Marsh Sandpiper — Marsh Sandpiper – Photographed in Yolo County

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.

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.

Photograph of a Greater Yellowlegs — Greater Yellowlegs

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

Photograph of Green-winged Teal in flight — Green-winged Teal

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.

Photograph of Sal Salerno and Daniel Gilman watching birds

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.

Photograph of the Pelican Nature Trail — Pelican Rd Nature Trail

California Thrasher
Wrentit

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.

Photograph of the Pelican Rd Nature Trail with closed signs — Area Closed

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.

Tag: San Joaquin River National Wildlife Refuge

When One Least Leads to Another