Image 7573: Red-necked Stint, New River, Coos County, Oregon, 27 August 2011 by Greg Gillson.
On July 12, 2011, Dave Lauten and Kathy Castelein discovered a small sandpiper that they initially identified as a Semipalmated Sandpiper (Calidris pusilla), a rather rare, but regular migrant through the Pacific NW. One oddity, though, it lacked partial webbing between the toes. In other words, the supposed Semipalmated Sandpiper was not semipalmated! With some prompting by Shawneen Finnegan, Dave and Kathy re-identified the bird as a Red-necked Stint (Calidris ruficollis) in non-breeding plumage.
If a Semipalmated Sandpiper without semipalmations raised eyebrows, the new identification even more so! There are very few North American records south of Alaska of Red-necked Stint (primarily an Asian Arctic breeder that winters in Australia). Most records are either juveniles or breeding-plumaged adults. The plain non-breeding, or "winter," plumage is very difficult to identify.
The Oregon Shorebird Festival in Charleston, Oregon, gave me an opportunity to see this bird. To do so required a 3 mile hike on loose sand and for me to remove my shoes and role up my pants legs to wade a creek!
Even then, the bird was no slam-dunk to identify. I observed carefully and took notes--even though I also took photos. Photos alone are often not enough to document a rare bird. Sometimes the photos don't show the salient identification features. Worse yet, sometimes shadows or odd angles or exposure or color settings can misrepresent the actual appearance in the field! And this bird didn't let me get close and the wind was making my shots unsteady and a bit blurry.
The following is an edited version of my report to the Oregon Rare Bird Records Committee. Such a rare bird report needs to describe the bird so that others can "see" it in their mind and identify it themselves based on the description of the bird alone, and not the reputation of the birder.
Rare Bird Report
End of Fourmile Road, south of Bandon, then north on New River to nearly due west of Hoffer Lane.
New River, Coos Co.
27 August 2011
In view about 30 minutes from 50 to 150 feet, with 8x binoculars, Canon Xti with 100-400 zoom (through the lens magnification of about 12x), borrowed Russ's 40x scope for 5 minutes.
With Tim Rodenkirk, Tim Shelmerdine, and Russ Namitz after pelagic trip.
General: Obvious Calidris sandpiper: compact body, rounded head on short neck, wings to the end of short tail. Bill short for a sandpiper, legs black. Approximately 6-7 inches from bill tip to tail tip. Gray above, white below, non-breeding plumage.
Habitat and behavior: Shallow tidal river behind ocean dunes. Spent most of time with Western Sandpipers (all 350 were juveniles) foraging in an inch or less of water, with entire bill submerged, or resting on small sandstone ridge of about 8 inches in height with small potholes of water, where it may have been able to get out of the wind. Consistently was the aggressor against all juvenile Western Sandpipers of both sexes.
Image 7542: Red-necked Stint (second from right) amid juvenile Western Sandpipers. Note size equal to Western Sandpiper, neckless and humpbacked. [click all photos for larger views]
Size and shape: Appeared as large as Western Sandpipers with which it associated. It was consistently differently-shaped, however, so it was difficult to compare overall length. The bird appeared pot-bellied and neckless, accentuated by a humpbacked look that gave it a very round appearing body [Image 7542 and 7578]. Thus, the bird was fatter, belly to upper back, than the Western Sandpipers, but not as long. On the few occasions when it moved near Least Sandpipers it was significantly larger and bulkier.
Image 7578: neckless, hunchbacked, good angle to judge tapered bill shape
Head and bill: Eye dark, entire head very pale gray and without strong contrasting patterns. The eyebrow stripe was faint but fairly wide, and appeared to go over the bill, barely contrasting with a slightly darker (brownish tinged or faintly streaked?) crown and darker lores. Ear coverts generally pale but a small post-ocular brownish feather or two in the center of the ear coverts at some angles. Bill short, as shortest Western Sandpiper male (shorter than >95% of male Western Sandpipers). Bill tapered (more so than typical Semipalmated Sandpiper and similar to Western Sandpiper), with a slight constriction just before the tip and slight droop. [Image 7578 is a bit soft in focus but shows the bill length and shape best. Image 7574 best shows the ear coverts.]
Image 7574: ear coverts, breast collar
Underparts: White and unmarked from chin to vent except for a blurry patch on the sides of the upper breast and, at certain angles, photos [Image 7574] reveal a narrow very faint gray (complete?) collar across the breast.
Image 7570: P9 molted?
Underwing: The bird stretched and raised its wings once and I was able to get a photo [Image 7570. Note that bill tip is behind sandstone and appears blunt.]. The wing linings, including axillars, were entirely white and the flight feathers and tertials were silvery gray underneath with no pattern. I count only 9 primaries with perhaps a slight gap between the outer two primaries on both wings, perhaps indicating P9 is shed, if so then near the end of wing molt. Molt of the flight feathers would confirm the age as an adult.
Image 7573: good view of back, scapular, and tertial feather patterns
Back and wings: The rounded back feathers appeared mostly gray with pale browner centers and thin white tips. The messy scapulars were gray with brownish shaft streaks becoming wider, grayer (less brown), and darker on the inner scapulars. The tertials were darker grayish-brown, darker toward the feather shaft, white on the edges, wider white on the tip. [Image 7573 shows mantle feathers clearly, but dark shadow in water makes bill tip appear odd.]
My photos are ambiguous as to length of primaries compared to the tail. In many of the photos the tertials cover the primaries completely, and the tail is not clearly visible in any photo (except when wings raised). The primaries certainly do not fall short of the tail tip. In one photo  it appears as if the tail end and wing tips are equal.
Image 7559: compare end of tail to wing tips.
Legs and feet: Black. Exposed tibia noticeably short compared to Western Sandpipers. Often only the tarsus emerged from the feathers of the round fat belly. The toes were clearly unwebbed in several scope views. Photos didn't really catch the toes at an advantageous angle, though webbing can clearly be seen on accompanying Western Sandpipers with no hint of such on any photo of the stint.
Voice: I heard the bird call as it flushed once. It was clearly different than Western's “jeet” call or Least's raspier “kreet” call. I described it as a rather smooth, drawn out “churrr.” On all of the Macaulay Library recordings I found only one call of Semipalmated Sandpiper that is similar (http://macaulaylibrary.org/audio/3124 time stamp 26-29 seconds). What I heard is NOT the short rough “chrrt” call of Semipalmated Sandpiper that is most common (http://macaulaylibrary.org/audio/3116 time stamp 50-54 seconds). The Red-necked Stint has a call similar to what I heard: http://macaulaylibrary.org/audio/63771 time stamp 37 and 48 seconds; and http://www.xeno-canto.org/recording.php?XC=61957 the very first call. Thus, the call I heard could match either Semipalmated or Red-necked Stint.
Similar species: Western Sandpiper, Semipalmated Sandpiper, and Little Stint in non-breeding plumage are the only contenders.
Most (>95% of males in my experience) Western Sandpipers have longer bills. Westerns show longer legs, longer neck. Non-breeding plumaged Westerns show more streaking and contrast on the crown and sides of the breast. Westerns have obvious partial webs that this bird clearly did not. Voice does not match.
The observed bird was much larger than Least Sandpiper, thus also Little Stint. The bill on the observed bird is probably thicker than any Little Stint. Voice does not match.
Image 7549: blunter looking bill shape in this photo compared to other photos
I believe that the bill on the observed bird is more tapered than Semipalmated Sandpiper. Several of my photos seem to show blunter bill [Image 7549]. But I also have a couple other photos with more pointed looking bills [7553, 7578]. The posture of the observed bird is extremely different than the taller aspect with longer legs and neck that I associate with Semipalmated Sandpiper. The non-breeding plumage photos I have seen of Semipalmated Sandpiper do not show the strongly contrasting shaft streaks and white feather edges to mantle feathers. The observed bird clearly did not have webbed toes. However, at least one recording of Semipalmated Sandpiper has a call similar to calls of Red-necked Stint, and similar to what I heard.
Semiplamated Sandpiper is variable, but differs with the observed bird in plumage color and contrast of the mantle, bill thickness and shape, webbing between toes, neckless, humpbacked, and pot-bellied aspect of the observed bird, and apparent length of tibia.
Image 7553: tapered bill
You may find a previous article, ID Challenge: Western Sandpiper and Semipalmated Sandpiper, of interest.