Siberian (A. r. japonicus) versus American Pipits (A. r. rubescens, pacificus, alticola) in basic plumage continued...

Cin-Ty Lee

Contents:

Page 1 of Article click here

Page 2 of Article

Photo Page 1 (Siberian Pipits) click here

Photo Page 2 (American Pipits) click here

Plate of Rock Pipits by Brian J. Small click here

Plate of Water and Buff-bellied Pipits by Brian J. Small click here

Plate by Andy Birch click here

3.3.2 Siberian Pipit: migration and vagrancy
The Siberian Pipit has probably occurred as a vagrant to Italy and is regularly seen in the Middle East during migration and winter (Shirihai and Colston, 1987; Shirihai, 1996). At Eliat in Israel, Shirihai (1996) states that Siberian Pipits arrive during late October (earliest 22nd) and depart in March to early April (latest 10th). A peak of 60 during the winter of 1986/86 suggest that the Siberian Pipit may in fact overwinter in Israel. In Japan, the Siberian Pipit arrives in late October and November and departs northward in late March, with a few stragglers remaining into May. Wintering occurs as far south as Myanmar (Shirihai and Colston, 1987).

It is considered casual in Iwo Jima, Turkestan, and western Alaska (American Ornithologist’s Union, 1989). At least fifteen fall vagrants have been sighted in California, although supporting documentation has not been published for any of these sightings (McCaskie, 1990, 1992, 1997); all of the sightings occurred between 7 October and 23 November. According to McCaskie (1997), up to six Siberian Pipits were reported in fall of 1991, a "fall with far more than the average number of Red-throated Pipits." Monson and Phillips (1981) reported a specimen believed to be Siberian pipits, which was taken at Naco in northern Sonora, Mexico on June 6, 1958. If correct, this remarkable specimen would not only have represented the first record of Siberian pipit in North America outside of western Alaska but also the only record of a spring vagrant. Japonicus is considered to be a very rare transient in late fall to Hawaii (Pratt et al., 1987).

4. Molt
The timing and strategy of molt plays an important factor in determining the age of a bird and in controlling the variability in certain field marks (e.g., the appearance of the median and greater coverts). The molt strategy of American pipits has been studied by Pyle (1997a; 1997b) and that of the Water Pipit (A. spinoletta spinoletta) by Jenni and Winkler (1994) and Williamson (1965). We are not aware of any studies conducted on the Siberian Pipit or of any systematic study of molt strategies broken down by the American subspecies.

According to Pyle (1997a; 1997b), American Pipits go through a prebasic and a prealternate molt. The first prebasic molt occurs between July and September primarily on summering grounds. This molt is considered to be a partial molt, in which no to all median coverts are replaced, zero to four inner greater coverts are replaced (Pyle states that ~55 % of individuals replaced no greater coverts), and sometimes one to two tertials are replaced (in ~25 % of the birds). No rectrices are replaced. The first prebasic is followed by the first prealternate molt, which occurs between January and April, primarily on the wintering grounds or during migration. In the first prealternate molt, zero to four inner greater coverts are replaced, one to three tertials are replaced, and often one to two central rectrices are replaced. The second prebasic molt, after which the bird attains adult plumage, is complete. The adult prealternate molt is similar to the first prealternate. For comparison, the molt strategy of the nominate race of the Water Pipit (A. s. spinoletta) is very much like that of American Pipits, but its first prebasic molt differs in subtle ways. In its first prebasic, at most two greater coverts and at most three greater coverts are molted (Jenni and Winkler, 1994). Broadly speaking, A. s. spinoletta thus replaces fewer feathers in its first pre-basic molt than the American Pipits.

Knowledge of molt strategy may sometimes allow one to recognize first-fall birds using the presence or absence of molt limits in the median and greater coverts. Molt limits can be recognized by the contrast between juvenile and replaced feathers, the former tending to be more worn or having frayed feather tips by fall migration, and the latter tending to be fresher and brighter. As will be discussed below, the color and boldness of the tips of greater and median covert feathers are important field characters. However, first-fall birds that have replaced few to none of the median and greater coverts may exhibit substantial wear, potentially reducing the overall size and boldness of the wingbars. In contrast, fall adults having passed through a complete molt should be in fresh plumage.

5. Notes on field Identification in basic plumage (late August to late December)
The following discussion is broken down into key regions of the bird, which we think one should focus on when seeking an identification. In short, we find that the color and contrast of the median coverts; the size, color and shape of the malar stripe; the color of the underparts; the degree and size of streaking; the boldness of the eye-ring; and the color of the legs are important distinguishing features in basic plumage. The field marks discussed below are strictly valid only between late August and late January. We consider the period between late January and late March to be a gray zone, in which birds are undergoing a protracted prealternate molt, which may give rise to intermediate characters. Since the first pre-basic occurs on the breeding grounds, juvenile plumages are not likely to be encountered on wintering grounds or during migration, and are therefore not discussed here.

Siberian Pipit (Anthus rubescens japonicus) versus American Pipit

Size and overall coloration: The Siberian Pipit is the most distinctive subspecies of the Buff-bellied Pipit complex. Overall, it appears larger and bulkier than pacificus and alticola, and in side-by-side by comparison, its larger size relative to pacificus and alticola may be noticeable. The Siberian Pipit overlaps in size with rubescens. Siberian Pipits differ subtly from the American Pipits in having upperparts, which are dark olive brown, and underparts, which are whiter than the American Pipits. The sides and chest may occasionally be washed with buff, but typically the throat, center of breast, and belly are white, whereas these same regions on rubescens, alticola, and pacificus are generally buffy or off-white (although pacificus can be variably whitish beneath). Compared to the characteristically buffy rubescens and alticola, the Siberian Pipit appears very white below. The most significant overlap in overall coloration is with pacificus, which tends to be slightly grayer than rubescens and alticola. However, in most cases, the underparts of pacificus are buffy or gray rather than white.

Underpart streaking: The Siberian Pipit is heavily streaked below with long and thick streaks, which are dark brown in color (sometimes appearing black from a distance). The streaks extend noticeably along the flanks, more contrastingly so than rubescens. This feature is reminiscent of Meadow (A. pratensis) and Olive-backed Pipits (A. hodgsoni). The dark coloration of the streaks contrasts strongly with the white underparts, and they are also considerably darker than the gray-brown upperparts. Underpart streaking in the American Pipits are browner and lighter in coloration: compared to their buffier underparts, the contrast between the streaks and underparts is subdued. A subtle, but potentially distinctive feature of the streaks on Siberian Pipit is that the streaks tend to coalesce longitudinally, sometimes giving a "striped" appearance. This feature is likely to be most useful in distinguishing the Siberian Pipit from pacificus because the streaks on pacificus tend to be short and do not coalesce significantly, giving pacificus a somewhat spotted rather than streaked or striped appearance. Rubescens and alticola may show a slightly striped appearance, but the degree of coalescence between streaks is smaller.

Median wing coverts: The median coverts on the Siberian Pipit nearly always have white tips, whereas those of the American pipits are characteristically buffy, especially in rubescens. Moreover, due to "Siberian’s" grayer and darker upperparts and wings, the white-edged median coverts stand out as white upper wingbars. Even for Siberian Pipits which are slightly buffy below, we found that the upper wingbars appear white. The greater coverts (lower wingbars) on Siberian Pipit vary between whitish and buffy and are therefore not so diagnostic. On American Pipits, the color of the median and greater covert feather edges are both buffy. We believe that the color of the upper wingbar and the degree of contrast with the wings may be potentially diagnostic in the field for Siberian Pipit, but further tests in the field and on museum specimens are needed. It is possible that first-winter birds may have whiter tips to the median and greater coverts than adults.

Eye-ring: Both Siberian and American Pipits exhibit a white eye-ring. While the thickness or completeness of the eye-ring is quite variable in both subspecies, the eye-ring tends to stand out more on Siberian due to its overall darker upperparts.

Malar stripe: The malar stripe on the Siberian Pipit tends to be thick and dark, contrasting not only with the white underparts, but also with the grayish upperparts. The contrast between the malar stripe and the upperparts in the American Pipits is generally not as strong because the malar stripe is not as dark. Some American Pipits can have malar stripes approaching the darkness of those of the Siberian Pipit. However, we note that while the American malar stripes can be so pale as to be concolor with the upperparts, that of the Siberian Pipit is always contrastingly dark relative to the upperparts and underparts. In addition, the posterior end of the malar stripe on Siberian tends to be more solidly colored than the American Pipits. In the latter, the individual streaks making up the malar stripe can often be seen, this effect being most pronounced on pacificus than on rubescens and alticola. Another helpful feature is that the Siberian’s malar stripe bulges at its posterior end, often flaring into the side of the neck, reminiscent of Richard’s Pipit (A. richardi). While American Pipit can also display this feature, the degree of flaring is generally less significant, and in many cases, the posterior end of the malar stripe does not extend beyond the auriculars.

Leg coloration: Siberian Pipit has pink or pale brown legs, but never black. In general, American Pipits have dark gray to black legs. However, both authors have observed pacificus and rubescens with pale brown legs. In fact, to see several pale-legged pacificus’s in a small flock is not unusual. Thus, while pale-legs may signify a potential Siberian Pipit, the amount of leg-color variation in the American Pipits cautions against using leg-coloration as the sole basis for identification.

"American Pipits"
Here, we present preliminary notes on subspecific variation of the American pipits. We caution however that the entire spectrum of variation occurs, and therefore identification of the American pipits to subspecies may not be realistic. Our reasons for addressing this issue are not to master subspecific identification but to appreciate the degree of subspecific variation, thereby improving our ability to separate Siberian from American Pipits as a whole.

Rubescens tends to be the buffiest and largest of the three subspecies. The size difference is very subtle, but differences with pacificus, the smallest of the subspecies, might be noticed in the field during side-by-side comparison. Rubescens tends to have buffier wingbars than pacificus, and also tends to have an overall browner plumage than pacificus. Streaking on the underparts tends to be slightly more extensive than pacificus, which has a more spotted appearance. Rubescens may also have a slightly bolder malar stripe than pacificus (but not as bold as in Siberian). In addition, the streaks on rubescens tend to coalesce laterally in the upper chest region, sometimes forming a continous band on the chest. In pacificus, the streaks do not coalesce as much, giving a more spotted appearance.

Pacificus is the smallest and grayest of the three American subspecies. The streaks on its underparts tend to be small and short, and do not coalesce together laterally or longitudinally. This gives it a "spotted" rather than "streaked" or "striped" appearance. Median and greater covert feather tips range from gray to buff, but typically not as buff as in rubescens. Underpart coloration also ranges from gray to buff. Although not typically as buff as rubescens, this subtle difference seemed noticeable only in side-by-side comparison of museum specimens, where lighting conditions on all specimens can be made identical. This feature is unlikely to be reliable in the field or in photographs.

Alticola is intermediate in size between rubescens and pacificus. Its plumage more closely resembles that of rubescens because it generally has a buffy overall coloration, darker underpart streaking than pacificus, and buffy edges to the median and greater wing covert feathers. Like rubescens, the streaks on the upper chest appear to coalesce laterally, often forming a continuous band across the upper chest. We stress that these features of alticola are based solely on comparison of museum specimens. Identification to subspecies was based solely on range. We assumed that specimens collected in Texas during the winter, which appeared buffier than typical pacificus, were alticola. As such, we consider our notes on basic-plumaged alticola to be extremely preliminary, and potentially wrong. Further research is necessary to characterize alticola in basic plumage.

Conclusions
Field identification of the Buff-Bellied Pipit complex is difficult. While we believe that the Siberian Pipit can generally be separated in the field from the American subspecies using a combination of field marks pertaining to wingbar color, overall color, degree of streaking, thickness of malar stripe, boldness of the eye-ring, and leg color, field identification of the American complex to subspecies is still in its infancy. Nevertheless, we hope that the preliminary outline of plumage variation in the American Pipits brings us one step closer to this goal. Readers who wish to comment or add more information based on their own studies or experiences are encouraged to write or email the authors.

Acknowledgements
We thank Carla Cicero (Museum of Vertebrate Zoology, Berkeley), Kimball Garrett (Los Angeles County Natural History Museum), Ned Johnson (Museum of Vertebrate Zoology, Berkeley), Raymond Paynter (Museum of Comparative Zoology, Harvard University) for access to museum collections, and the Ernst Mayr library at Harvard for overlooking the many overdue books that we accumulated during the course of this study. We also thank Brian J. Small for generously sharing his own field observations and notes on the Buff-bellied Pipit complex and Ken Arber and Martin Birch for their input and support. We are indebted to a number of photographers (cited in figure captions) for donating their photographs to us.

Cin-Ty Lee
Department of Earth and Planetary Sciences
Harvard University
20 Oxford St.
Cambridge, MA 02138
ctlee@eps.harvard.edu