Plumages, Molts, and Structure

The Tawny-throated Dotterel has ten full-length primaries (numbered distally, from innermost p1 to outermost p10), 15–16 secondaries (numbered proximally, from innermost s1 to outermost s11–s12, and including 3–4 tertials, numbered distally, t1 to t3), and 12 rectrices (numbered distally, from innermost r1 to outermost r6, on each side of the tail). Plovers are diastataxic (8 Bostwick, K. S., and M. J. Brady (2002). Phylogenetic analysis of wing feather taxis in birds: Macroevolutionary patterns of genetic drift? Auk 119:943–954. Close ), indicating that a secondary has been lost evolutionarily between what we now term s4 and s5. Geographic variation in appearance slight and possibly clinal (see Systematics: Subspecies). The following covers both subspecies and is based primarily on descriptions in Goodall et al. (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ), Hayman et al. (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close ), Piersma and Wiersma (10 Piersma, T., and P. Wiersma (1996). Charadriidae (plovers). In Handbook of the Birds of the World, Volume 3 (J. del Hoyo, A. Elliott and J. Sargatal, Editors), Lynx Edicions, Barcelona, Spain. pp. 384–443. Close ), and Jaramillo (7 Jaramillo, A. (2003). A Field Guide to the Birds of Chile Including the Antarctic Peninsula, the Falkland Islands and South Georgia. Christopher Helm, London, UK. Close ), along with review of Macaulay Library images; see Pyle (11 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ) for criteria to determine age in related plovers. See Molts for molt and plumage terminology. Sexes similar in all plumages; definitive appearances assumed at the second basic and alternate plumages.

Natal Down

Present primarily in October–January (with geographic variation in timing; see Breeding: Phenology), on and near the natal site. Hatchlings are covered with thick down, patterned to be cryptic against breeding substrates (cf. ML385168951 ). Upperparts and wings mottled blackish, buff, tawny, and gray with darker patches on crown and sides of lower back. Underparts largely buff to tawny in hatchlings (ML509092381 ). As chicks age a second coat of down emerges that is less patterned, buff with sparser black mottling above and paler or whiter below.

Juvenile (First Basic) Plumage

Present primarily November–February. Similar to later plumages but duller, buffier, and less patterned. Upperpart feathers broadly fringed buff creating a scaled appearance. Throat only tinged or washed tawny, often sparsely mottled dark. Gray breast feathers fringed pale when fresh, creating scalier appearance. Black patch on abdomen absent or reduced and indistinct. Body feathers uniform in quality, without contrasts in feather generations or wear due to protracted molts. Juvenile flight feathers narrower and more tapered or rounded at the tips than formative and basic feathers, fresh at a time of year when older birds show abraded feathers.

Formative Plumage

Present primarily February–September. Formative Plumage similar to Definitive Basic Plumage but averages duller, with duller tawny throat and often less black feathering to the abdomen (beware fresh basic birds can have buff fringing to these feathers); some individuals can show brighter throats, e.g., the formative bird in ML339641551 . Formative Plumage best identified by retained juvenile flight feathers. Based on examination of Macaulay Library images, some birds may retain at least a few outer upperwing secondary coverts, the outer greater coverts worn and brownish with narrower fringing, contrasting with replaced newer and more brightly fringed formative inner and lesser coverts. One to three tertials and 1–2 central rectrices can be replaced, contrasting with adjacent juvenile feathers. Otherwise, juvenile primaries, primary coverts, secondaries, and rectrices appear to be retained, relatively narrow, brownish, worn, and not showing molt clines indicating replacement (see below).

First and Definitive Alternate Plumages

Present primarily September–January. Similar to Formative and Definitive Basic Plumage, respectively, but back feathers and some to all scapulars (at least) replaced, brighter and edged tawny to rufous-orange, contrasting with more worn and browner, formative or basic feathers, with larger scapulars and wing coverts. Fewer feathers on average may be replaced in First compared to Definitive Alternate birds. Throat, breast, and abdomen brighter due to molt and feather wear; throat brighter tawny and nape and breast feathers silvery gray; First Alternate Plumage continues averaging duller than Definitive Alternate Plumage. First and Definitive Alternate Plumages are separated using criteria related to flight feathers described under Formative and Definitive Basic Plumage; retained juvenile outer primaries and rectrices become relatively more abraded and brown as compared to basic feathers.

Definitive Basic Plumage

Present primarily September–January. Plumage reported to vary more by individual than by sex, with some birds being tawnier while others are grayer. Head square looking with large eyes; crown and nape gray; mantle, rump, and wing coverts beige with much broad black central streaks forming marked and bold variegation; uppertail coverts tawny with black bars; tail buff to pale gray with black bands (cf. middle image below and ML530855201 ). Sides of head prominently patterned with wide buff supercilium, buff to whitish subocular stripe, and distinct thin dark eye-line from lores to nape, widening posteriorly; lower face below buff subocular brownish-gray to clay colored. Primaries and secondaries dusky blackish with pale buff bases forming wing stripe in flight. Chin and throat tawny, varying in brightness but usually duller than in alternate plumages in part due to buff feather fringing. Breast pale gray (connecting to gray nape); flanks grayish to rich tawny; lower underparts clay colored, paling to whitish ventrally and on undertail coverts, with distinct black patch on abdomen. Underwing coverts mostly whitish with some gray (see center image below); buff wing stripe visible on flying bird from below (cf. ML482452551 ).

Definitive Basic Plumage separated from Formative Plumage by basic scapulars and upperwing coverts uniform in wear and quality, basic tertials uniform in wear with adjacent secondaries, basic primaries uniformly darker, fresher, and broader at tips. Molt clines occur from more worn inner to fresher outer primaries and with darker outer secondaries contrasting with more worn inner primaries due to time lag in replacement between these feathers. Rectrices uniformly broader, less tapered at the tips, and fresher than retained juvenile rectrices of Formative Plumage.

Molt and plumage terminology follows Humphrey and Parkes (12 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76:1–31. Close ), as modified by Howell et al. (13 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: A review of molt and plumage homologies. The Condor 105:635–653. Close ). Under this nomenclature, terminology is based on evolution of molts along ancestral lineages of birds from ecdysis (molts) of reptiles (14 Pyle, P., S. N. G. Howell, D. I. Rogers, and C. Corben (2024). Moult terminology: envisioning an evolutionary approach. Journal of Avian Biology 2024:e03169. Close ), rather than on molts relative to current breeding seasons, locations, or time of the year, the latter generally referred to as “life-cycle” molt terminology (15 Jenni, L., and R. Winkler (2020). Moult and Ageing of European Passerines. Second edition. Bloomsbury, London, UK. Close ; see also 16 Pyle, P. (2022). Defining moults in migratory birds: A sequence-based approach. Journal of Avian Biology 2022:e02958. Close ). The Tawny-throated Dotterel exhibits a Complex Alternate Strategy (cf. 13 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: A review of molt and plumage homologies. The Condor 105:635–653. Close ), including a complete prebasic molt, a partial preformative molt, and limited-to-partial prealternate molts in both first and definitive cycles.

Prejuvenile (First Prebasic) Molt

Complete, primarily November–February (with geographic variation in timing; see Breeding: Phenology), near the natal site. No detailed information on timing or sequence of pennaceous feather irruption and development.

Preformative Molt

Based on Macaulay Library images, the Preformative Molt is partial to incomplete, primarily December–March. It includes most to all body feathers (although some juvenile scapulars and perhaps rump feathers can be retained) and upperwing lesser and median coverts, some to most or all upperwing greater coverts, often 1–4 tertials and 1–2 central rectrices, but no primaries, primary coverts, secondaries besides tertials, or central rectrices. This extent for the Preformative Molt is typical of plovers that do not undergo long-distance migrations (11 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ).

First and Definitive Prealternate Molts

Examination of Macaulay Library images indicates that prealternate molts occur in the Tawny-throated Dotterel, primarily in August–November. As in many North American plovers (11 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ), these appear to include some to most head, upperpart, and breast feathers but few if any upperwing coverts or flight feathers (study needed on whether or not some lesser coverts, tertials, and/or central rectrices could be replaced). The First Prealternate Molts may average less extensive than Definitive Prealternate Molts, a pattern seen in many plovers and other shorebirds.

Second and Definitive Prebasic Molts

Complete, primarily December–March. Primaries are replaced distally (p1 to p10), secondaries replaced bilaterally from t2 or t3 and proximally from s1 and perhaps s5, and rectrices are generally replaced distally (r1 to r6) on each side of tail, with some variation occurring. Molt of outer secondaries (proximally from s1) and central rectrices usually commences about when p6 is being replaced. Location of molting grounds relative to breeding grounds at the population level or breeding territories at the individual level unknown. Few Macaulay Library images show birds in active primary molt, indicating that they may inhabit remote areas or become more furtive during the molting period. Images (see below) indicate that San Gregorio, Magallanes, Chile, is at least one area where prebasic molts can occur.

The following is based on descriptions in the the literature (17 Wagler, J. G. (1829). Beiträge und Bemerkungen zu dem ersten Bande feines Systema Avium. Isis von Oken 22: col. 645–664. Close , 9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close , 18 Johnsgard, P. A. (1981). The Plovers, Sandpipers and Snipes of the World. University of Nebraska Press, Lincoln, NE, USA, and London, UK. Close , 10 Piersma, T., and P. Wiersma (1996). Charadriidae (plovers). In Handbook of the Birds of the World, Volume 3 (J. del Hoyo, A. Elliott and J. Sargatal, Editors), Lynx Edicions, Barcelona, Spain. pp. 384–443. Close , 19 Couve, E., and C. Vidal (2003). Aves de Patagonia, Tierra del Fuego y Península Antártica. Editorial Fantástico Sur, Punta Arenas, Chile. Close ,7 Jaramillo, A. (2003). A Field Guide to the Birds of Chile Including the Antarctic Peninsula, the Falkland Islands and South Georgia. Christopher Helm, London, UK. Close ), along with examination of Macaulay Library images.

Bill

The bill is long, thin, and sharp for a plover, with the tip slightly inclined. At all ages it is dusky brownish to black.

Iris and Facial Skin

The eyes are exceptionally large, as if intended for nocturnal use (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ). At all ages, the iris is brown but appears primarily black in the field, especially at a distance.

Tarsi and Toes

Feet are tridactyl, with the toes unusually short (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ). In adults, legs and feet are pink, appearing to become brighter during pre-breeding and breeding periods than during molting and nonbreeding periods. In hatchlings, they are dusky with a pinkish wash, gradually becoming dusky pink in juveniles and dull pink (matching nonbreeding adults) during the first year. See images below and also those under Plumages.

Linear Measurements

Below, measurements are provided for each subspecies (nominate ruficollis and pallidus) where possible, and given as mean ± SD when known.

Total Length

• ruficollis: 25–29 cm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close , 20 Wiersma, P. (1996). Family Charadriidae (plovers): species accounts. In Handbook of the Birds of the World, Volume 3 (J. del Hoyo, A. Elliott and J. Sargatal, Editors), Lynx Edicions, Barcelona, Spain. pp. 411–442. Close ).

Wing Length

• ruficollis: 165.1 mm (17 Wagler, J. G. (1829). Beiträge und Bemerkungen zu dem ersten Bande feines Systema Avium. Isis von Oken 22: col. 645–664. Close ); 162.5 ± 1.72 mm (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ); 160–183 mm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close ).
• pallidus: 146.5–151 mm (21 Bond, J. (1955). Additional notes on Peruvian birds. 1. Proceedings of the Academy of Natural Sciences of Philadelphia 107:207–244. Close ); 146–152 mm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close ).
• Wing (flattened): females 148–180 mm; males 146–177 mm (18 Johnsgard, P. A. (1981). The Plovers, Sandpipers and Snipes of the World. University of Nebraska Press, Lincoln, NE, USA, and London, UK. Close ).

Tail

• 69–90 mm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close ).
• ruficollis: 82.55 mm (17 Wagler, J. G. (1829). Beiträge und Bemerkungen zu dem ersten Bande feines Systema Avium. Isis von Oken 22: col. 645–664. Close ); 74.2 ± 0.89 mm (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ).

Culmen

• 27–31 mm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close ). Females 33–38 mm; males 33–40 mm (22 Blake, E. R. (1977). Manual of Neotropical Birds. Volume 1: Spheniscidae (Penguins) to Laridae (Gulls and Allies). University of Chicago Press, Chicago, Illinois, USA. Close ).
• ruficollis: 30.9 ± 0.43 mm (9 Goodall, J. D., A. W. Johnson, and R. A. Phillipi (1951). Las Aves de Chile: su Conocimiento y sus Costumbres. Platt Establecimientos Gráficos, Buenos Aires, Argentina. Close ).

Tarsus

• 45–53 mm (1 Hayman, P., J. H. Marchant, and A. J. Prater (1986). Shorebirds. An Identification Guide to the Waders of the World. Croom Helm, London, UK. Close )
• ruficollis: tarsus 52.38 mm; bare part of tibia 11.11 mm; middle toe including claw, 17.46 mm (17 Wagler, J. G. (1829). Beiträge und Bemerkungen zu dem ersten Bande feines Systema Avium. Isis von Oken 22: col. 645–664. Close ).

Mass

• 120–169 g (23 Dunning, J. B. (1992). CRC Handbook of Avian Body Masses. CRC Press, Boca Raton, FL, USA. Close , 24 Christie, M., E. J. Ramilo, and M. D. Bettinelli (2004). Aves del Noroeste Patagónico: Atlas y Guía. Sociedad Naturalista Andino Patagónica and Literature of Latin America, Buenos Aires, Argentina. Close ); 120–154 g (20 Wiersma, P. (1996). Family Charadriidae (plovers): species accounts. In Handbook of the Birds of the World, Volume 3 (J. del Hoyo, A. Elliott and J. Sargatal, Editors), Lynx Edicions, Barcelona, Spain. pp. 411–442. Close ); 131 g (mean, n = 10 undetermined sex; 23 Dunning, J. B. (1992). CRC Handbook of Avian Body Masses. CRC Press, Boca Raton, FL, USA. Close ).
• pallidus: mean 115 g (range 111–118 g, n = 3, both sexes; 18 Johnsgard, P. A. (1981). The Plovers, Sandpipers and Snipes of the World. University of Nebraska Press, Lincoln, NE, USA, and London, UK. Close ).
• ruficollis: 132.5 g (25 Contreras, J. R. (1975). Características ponderales de las aves del parque nacional Nahuel Huapi y regiones adyacentes. Physis 34(88):97–107. Close ), 169 g (24 Christie, M., E. J. Ramilo, and M. D. Bettinelli (2004). Aves del Noroeste Patagónico: Atlas y Guía. Sociedad Naturalista Andino Patagónica and Literature of Latin America, Buenos Aires, Argentina. Close ), 133.0–142.5 g (26 Salvador, S. A. (2014). Peso de las aves del Departamento General San Martín, Provincia de Córdoba, Argentina. Biológica Naturaleza, Conservación & Sociedad 17:48–57. Close ). Adults, mean 133 g (range 120–145 g, n = 6, undetermined sex; 18 Johnsgard, P. A. (1981). The Plovers, Sandpipers and Snipes of the World. University of Nebraska Press, Lincoln, NE, USA, and London, UK. Close )