Pinyon Jay Gymnorhinus cyanocephalus
Version: 2.0 — Published March 19, 2020
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The Pinyon Jay is medium-sized, crestless, and 26–29 cm in total length (Northern Arizona University Vertebrate Museum specimens; n = 11). The bill is more sharply pointed and tail is shorter than other jays (tail was about 102 mm in adults from northern Arizona , but slightly longer in New Mexican birds ). Adult (Definitive Basic) plumage is entirely dull blue, except the chin, throat, and breast are streaked whitish; the inner webs of the primaries are black. Sexes are alike, except the crown is slightly deeper blue in males than females, and the bill averages longer in males (adult male, mean 35.34 mm; adult female, mean 33.18 mm; 13). The mouth lining and bill of adults are black. Juveniles have uniformly mouse-gray plumage whereas first-year birds in Formative Plumage are similar to adults but average duller and have narrower and grayer retained juvenile wing and tail feathers. There is slight geographic variation, populations in the eastern portion of range generally being paler and averaging shorter and more curved bills than those in the western portion of range.
The Pinyon Jay is easily distinguished from all other sympatric jays by a combination of the overall blue color, shorter tail, and lack of crest. Woodhouse's Scrub-Jay (Aphelocoma woodhouseii) and Mexican Jay (A. ultramarina) have blue upperparts but contrastingly whitish to grayish underparts. Steller's Jay (Cyanocitta stelleri) and Blue Jay (C. cristata) have crests and black markings on the head.
Pinyon Jay social organization also differs from those of other sympatric jays (14, 15). The species is extremely social. It is rarely observed individually, except sometimes during irruptions. It forages ubiquitously, often walking (not hopping) on the ground. Vocalizations are variable, but contact call Kaws, Racks, and Krawks are unique and common. During autumn, it can make long-distance flights in large flocks.
The Pinyon Jay has 10 primaries (numbered distally, p1 to p10, with the outermost, p10, reduced in length), 9 secondaries (numbered proximally, s1 to s9, and including 3 tertials, s7–s9 in passerines), and 12 rectrices (numbered distally, r1 to r6, on each side of the tail). Geographic variation in appearance is slight (see Systematics: Geographic Variation); the following molt and plumage descriptions pertain to all subspecies. No geographic or sex-specific variation in molt strategies have been reported.
See Molts for molt and plumage terminology. The following is based primarily on detailed plumage descriptions of Ridgway (16), Bent (17), Oberholser (18), and Goodwin (19); see Pyle (20) for age-related criteria. Sexes show similar appearances in all plumages. Definitive Plumage is assumed following Second Prebasic Molt. Some color terms follow those of Ridgway (21).
Present primarily in April–August, in the nest. Pinyon Jay hatchlings are naked (12); no natal down has been described. For a description of growth and development of hatchlings, see Breeding: Young Birds .
Juvenile (First Basic) Plumage
Present primarily May–September. Plumage is predominantly grayish. Body-feathers are mouse-gray; however, the final feathers to emerge on the lateral regions of the spinal tract, as well as additional feathers to the loral, malar, and auricular areas, can be contrastingly bluer, perhaps the result of hormonal color-deposition changes with age. Pitelka (22) referred to these feathers as “adventitious feathers” in juveniles of the California Scrub-Jay (Aphelocoma californica). Nasal, orbital, frontal and auricular regions, and lores, are dull blackish slate. Upperwing secondary coverts show narrow white tips when fresh. Wings and tail appear bluish dorsally and dark slate gray ventrally, with whitish tips when fresh, the bluish-gray brighter and bluer than the rest of the upperpart plumage; rectrices are narrow and tapered (Figure 138 in 20); remiges have clove-brown inner webs. Underparts are slightly paler than upperparts, slate gray (with bluish or brownish cast), becoming distinctly whiter on the lower abdomen. The whitish feathers of the bib (see Definitive Basic Plumage) are not distinct because feathers of the adjacent malar and postauricular regions are pale blue.
"First Basic" or "Basic I" plumage from Humphrey and Parkes (23) and some subsequent authors; see revision by Howell et al. (24). This plumage is present primarily August–July and is similar to the Definitive Basic Plumage except duller and grayer overall. Formative body feathering is rather easily distinguished from the mouse-gray feathers of juveniles and Flax Flower Blue (deep bright blue) feathering of adults. Retained juvenile rectrices of Formative Plumage are narrow and tapered (Figure 138 in 20), increasingly paler Clove (medium brown) with wear, vs. duskier in Definitive Basic Plumage. Primary coverts are relatively grayish to brownish and usually without bluish fringes; replaced inner upperwing lesser, median, and greater coverts are bluer, contrasting with retained juvenile outer coverts (most birds replace many to all lesser and median coverts and 0–3 inner greater coverts, but some can replace all secondary coverts); tertials and up to 3 additional inner secondaries can also be replaced, are contrastingly new and bluish.
Definitive Basic Plumage
This plumage is present primarily August–July. Crown is deep (Cyanine) blue; malar area is light (Cobalt or Azure) blue and body feathering a pale (Flax Flower Blue) blue, except for the white bib. The bib has a series of feathers that begins at the base of bill, occupies the gular region and extends ventrally to the midbreast region. Structurally, the feathers are not unusual. Bib length is correlated with age and sex; birds in Formative Plumage (n = 86) have smaller bibs (mean 21.8 mm) than those in Definitive Basic Plumage (mean 29.5 mm; n = 179, P < 0.01), and males (n = 89) have significantly larger bibs (mean 29.4 mm) than females (mean 24.7 mm; n = 65, P < 0.01; B. Marshall, unpublished data). This variation may be used for individual recognition. Freshly molted birds can be identified by their possession of pale, loose barbs at margins of body feathers. Barbs wear off by spring. Rectrices are square and truncate (Figure 138 in 20); upperwing coverts, tertials, and secondaries are uniformly blue (without contrasts of Formative Plumage); inner webs of remiges blackish and outer webs blue.
Molt and plumage terminology follows Humphrey and Parkes (23), as modified by Howell et al. (24, 26). The Pinyon Jay exhibits a Complex Basic Strategy (cf. 24, 27), including complete prebasic molts and a partial-to-incomplete preformative molt but no prealternate molts (28, 13, 18, 29, 20; Figure 2).
Prejuvenile (First Prebasic) Molt
Complete, primarily April–July, in the nest. The following is from Bateman and Balda (12) and Ligon and White (13). Rapid growth of primaries occurs from 8–25 d; rectrices grow fastest at 12–40 d. Also, at day 8, dorsal body feathers, secondaries, and coverts are small pins; rectrices are tiny white brushes. At day 15, nestlings are dorsally well feathered, but the undersides of wings and abdominal region are largely bare. All remiges are sheathed basally for about one-eighth of their lengths; associated coverts are also growing at this time. Rectrices are sheathed for about 20% of their length. Feathers of the anterior spinal tract are nearly fully grown, but posteriorly they are still growing. Feathers of the mid–coronal region measured 11 mm, feathers of the cervical region were 27 mm, dorsal feathers were 30 mm, pelvic feathers measured 19 mm, and uppertail coverts measured 28 mm. Active feather growth in most or all feather tracts continues after fledgling at 21–23 d; the greater underwing coverts are absent at fledging but grow rapidly thereafter. By 42 d, the rectrices were still incompletely grown, the outermost averaging 88.8 mm. By 56 d, all feathers are fully grown.
"First Prebasic" or "Prebasic I" molt of Humphrey and Parkes (23) and some subsequent authors; see revision by Howell et al. (24). Partial to incomplete, primarily June–September, on summer grounds. Molt is initiated at about 60 days of age, but the age at which molt begins varies. The extent of molt also varies, depending on the time of year the bird hatches. The majority of individuals replace most to all body feathers (including small feathers of alar and caudal tracts), most upperwing lesser coverts, no to most median coverts, 0–3 inner greater wing coverts, and 1–2 feathers of the alula, but no tertials. Birds hatched early during the year replace more feathers, including up to all upperwing median and greater coverts, six inner secondaries, and sometimes one or two central rectrices (13).
Second and Definitive Prebasic Molts
Complete, primarily June–September, on summer grounds. Timing is highly variable and influenced by previous events in the breeding cycle. When breeding is early, birds molt early, and when breeding is late or nonexistent, birds molt late. Nonbreeding, 1-yr-old males are the first in a flock to initiate molt (Second Prebasic), followed by adult males (Definitive Prebasic), 1-yr-old females (Second Prebasic), and lastly adult females (Definitive Prebasic). Ligon and White (13) summarize this complex issue as follows: Molt appears to be primarily influenced by photoperiod, but may be modified directly or indirectly by a shortage of food that will suppress, retard, or prohibit breeding, influencing the timing of molt. In the southwestern United States, molt usually commences between 1 May and 10 June.
Primaries are replaced distally, p1 to p10, secondaries replaced proximally from s1 and proximally and distally from the central tertial (s8), and rectrices probably replaced distally, r1 to r6, on each side of tail, with some variation in sequence possible. The first secondaries to drop are s8, s9, and s1, in that order, the s1 often not shed until p4 is molted. Then s2, s7, s3, and s4 are dropped, with s5 and s6 being the last secondaries to molt. Tail molt is initiated soon after p4 is molted. Up to four pairs of rectrices may be growing at the same time. Upperwing greater wing coverts are molted simultaneously before the first secondaries are lost, and primary coverts are dropped with the corresponding primary. Body molt begins between the loss of p3 and p6 and can continue after molt of p10 is completed. The last of the body to molt is the spinal tract. Completion of molt may take 60–80 d in an individual.
Bill and Gape
The bill is bone colored to gray in nestlings, with a bright-red mouth-lining and yellow at commissural points. By 18 weeks of age, the bill is black. The bill and mouth are black in adults, except adult females during the nonbreeding season, when they may be a dull gray. During the first year the roof of the mouth probably changes to white and then mixed grayish and white, becoming black in adults, as in other jays (30). Seasonal variation in bill length (bills are shorter in fall and winter) may be attributed to mechanical wear on the bill due to eating different foods (13). Nares are featherless and exposed.
Iris is chocolate brown in yearlings and adults.
Legs and Feet
Legs and feet are tan to pink in nestlings, black in adults.
See Table 3 for measurements from New Mexico. In all populations, males average slightly larger than females, with overlap. Wings are relatively long and pointed for a southwestern jay, showing modest sexual dimorphism (Table 3), with the outer primary measuring about 59 mm in birds from northern Arizona (12).
At three sites in New Mexico from 2005–2014 (various times of year), bill depth was measured from the top of the maxilla to the bottom of the mandible at the widest part (the base) of the closed bill. Mean bill depth of adult females was 10.5 mm ± 0.62 SD (range 9.2–12.0, n = 34) and that of adult males was 11.15 mm ± 0.64 SD (range 9.7–12.9, n = 50) (KJ, unpublished data).
Mass measurements below were taken from live birds in the Flagstaff, Arizona, Town Flock. For young birds (measured during first autumn): males, 104 g ± 1.35 SD (n = 30); females 106 g ± 2.61 SD (n = 8). For adults (measured at all times of year): females, 99 g ± 0.68 SD (n = 66); males, 111 g ± 0.68 SD (n = 66), a highly significant difference (P < 0.0001). Seasonal changes in mass are not known, and no other population has been measured for seasonal changes in mass.
At three sites in New Mexico from 2005–2014 (at various times of year), mean mass of adult females was 98.95 g ± 7.6 SD (range 85–115, n = 33) and mean mass of adult males was 108.12 g ± 6.2 SD (range 94–123.4, n = 52) (KJ, unpublished data).