INTRODUCTION The black-and-blue jays constitute four allopatric species: Cyanocorax melanocyanea, the Bushy-crested Jay, C. sanblasiana, the San Blas Jay, C. yucatanica, the Yucatan Jay, and C. beecheli, the Beechey or Purple-backed Jay. Since Ridgway's publication (U.S. Natl. Mus., Bull. 50, Pt. 3:313-317, 1904) it has been recog- nized, but only generally, that plumage and soft part character- istics in these jays are complex, with definitive (i.e. non-molting, at least temporarily stabilized) stages in at least juvenile, first- year, and adult age groups. My studies reveal that ontogeny of plumage and soft part coloration in these species is more elaborate than previously supposed by anyone. One can accurately dis- tinguish juveniles, first-, second-, and third-year subadult classes without reference to weight or mensural characteristics but rather on distinctive plumage and soft part color differences. As a part of my long range studies of comparative biology of these jays, I collected specimens and kept birds in captivity to observe the details of ontogenetic changes of external morphology and their timing. I also gathered information from museum study skins. A knowledge of changes in plumage and soft part color of these birds was necessary to understand the role of age n the complex social structure of these jays. What follows, therefore, is a descriptive analysis of stages and changes in external morphology, based on specimens and captive live birds. DESCRIPTIVE ANALYSIS Cyanocorax melanocyanea Juvenile.--(Fig. 1A.) head, nape, and breast dull blackish-gray; mantle and remainder of underparts dull neutral gray, the back with scattered blue feathers. Upper surfaces of wings dull blue, reetrices deeper blue with a violet wash. Under surfaces of wings grayish-white to light neutral gray; under surfaces of rectrices dusky neutral gray. Bill dull yellowish-horn, developing brownish tip just before fiedging. Brownish color gradually spreads over one-third of the bill distally. Inside of bill white. Tarsus and toes deep neutral gray to blackish-gray, with some dull horn color on toes. Iris dark brown or blackish-brown. First prebasic (= postjuvenal) molt stage.--(Fig. lB.) This in- volves only the body. Bill particolored, showing horn color mainly FIGURE 1. Schematic representations of some key stages in the development of plumage and external soft part coloration in three species of jays. See text for full explanation. Line 1: Cyanocorax melanocyanea. A. Juvenile. B. First prebasic molt stage. C. First-year stage. D. Second-year and adult stages. Line 2. C. sanblasiana nelsoni. E. Juvenile. F. First-year stage. G. Second- year stage. Note: Third-year stage not illustrated. H. Adult. Line 3. C. yucatanica. I. Juvenile. J. First-year stage. K. Second-year stage. L. Third- year and adult stages. in basal half and along tomium, with the remainder blackish-brown. Body as above with various numbers of dull black feathers re- placing the gray ones. First-year stage.--(Fig. 1C.) Birds of the first brood (social flocks raise two successive and overlapping broods) have completed change to first-year plumage by early December. By mid-January, soft part coloration also stabilizes. Plumage essentially like that of adults but less glossy in general. Bill horn colored on basal one- third to one-half of lower mandible and extreme basal circumnasM area; remainder dull black. Iris dark olive-tan. Legs dull black with irregular edgings of horn, and toe pads horn colored. Inside of bill dull white. An irregular amount of horn color persists on the basal portion of he upper and lower mandibles through the first year, decreasing by March o he poin where it is hardly visible in he field. The iris may lighten slightly to pale olive an or dull yellowish-horn color. By late May iris color is greenish-yellow in some individuals. Second prebasic (= first postnuptial) molt stage.--Plumage in- distinguishable from hat of adult (see Ridgway, op. cit.). Bill solid black exteriorly, but considerable white inside with black beginning to spread along the edges and median line. Iris greenish- yellow as compared with pure yellow of adult. Second-year stage.--Data incomplete. Probably full adult plu- mage and soft par color (Fig. 1D.) except for inside color of bill, since one captive a the time of hird prebasic mol had pure yellow irides and largely black inside the bill. Full adult stage.--(Fig. 1D.) Plumage as described by Ridgway (op. cit.). Iris brigh yellow, bill black inside and out, arsi and oes black with horn edgings and toe pads. Cyanocorax sanblasiana elsoni  Juvenile.--(Fig. 1E.) Similar to juvenile C. melanocyanea, but wih head and body feathers blacker and a prominent frono-nasal crest developing in nestlings before feathers are unsheathed. Legs dull brown and bill slightly more yellowish and withou a dark tip. Inside of bill white. Iris dark brown. Two fully grown captive juveniles with well developed crests showed first signs of bill darkening--a distal lateral spot of black on the upper mandible. First prebasic molt-stage.--Molt develops first on body, hen on head. The two captive juveniles mentioned above fledged on 25 June and began first prebasic mol about 14 September. Black area on bill spreading over distal par of upper mandible. Molt complete by I November. First-year stage.--(Fig. 1F.) There is a gradual change in bill color hrough he firs year, and it is individually variable. In one bird on 26 December, new areas of black appeared in circumnasal area, and the disal one-fourth of he bill was black. In he oher bird, on he same dae, he black was restricted to he extreme bill tip, the remainder of the bill remaining yellowish-horn color. Through he first year of life he bill remains largely pale. The inside of the bill remains white through he firs year of life. Tarsi and oes are now dull greenish-yellow, as they remain throughout life. While this paper was in press, I became aware of a paper by John Davis (Condor, 62: 215-219, 1960) containing an important discussion of iris color and its ontogeny in C. sanblasiana. The data of Davis make it necessary for the remarks herein on this species to be restricted to the race nelsoni; in the nominate race the iris color apparently becomes yellow early in the first year of life! The two first-year captive San Bias Jays each passed through a partial prealternate (= prenuptial) molt involving, so far as I determined, only the feathers of the head. Such a molt has not been described previously for any corvid, and I have not detected it in any other jays. I also do not know if it is characteristic of the species. When more data are available the character and possible significance of this molt will be discussed elsewhere. At this time, I would welcome from readers any information on prealternate molts in jays. Pre-second-year stage.--Shortly before the second prebasic molt, in August and September, some individuals have acquired almost completely dull black bills, except for the area of horn color on the sides of the lower mandible, just above the tomium, or irregular small areas or pale color elsewhere. By the onset of molt in mid- September, the two captives had completely dark bills exteriorly. However, two individuals, obtained at one year of age in June, still showed markedly particolored bills while molting in September. Second prebasic molt stage.--This is a complete molt resulting in deeper blue and black featbering, the black becoming glossy and indistinguishable from that of the adults. The crest is greatly reduced in number of feathers, but those that remain are long and still prominent, although directed slightly more posteriorly in normal carriage. If the bill is exteriorly particolored, it remains white inside except for a pronounced tomial margin of black. As the bill becomes black outside, the inside also becomes partly black (Fig. 3A). However, during the second year of life it remains distinctly particolored--never black or black xvith slight traces of white. The iris remains dark brown. Second-year stage.--(Fig. 1G.) Following the second prebasic lnolt, from late November and afterward, birds generally have completely black bills exteriorly, particolored interiorly, and long sparse crests. Over this period the iris gradually pales to olive brown in some individuals but remains dark brown in others. Second-year birds are at least sometimes sexually mature, since a female captive of this age laid eggs in my aviary. Third prebasic (= second postnuptial) molt stage.--Generally ths molt reduces the crest to its final repeating state. This may be characterized by no crest or one or two wispy feathers, which even adults may possess. The bill becomes solid black inside and out, except that some individuals probably retain for life some es- tremcly small areas of white. Third-year stage.--This is a stage no[ previously described. In it the iris remains dark brown to olive brown, but otherwise the bird is indistinguishable from the adult (Fig. 1. Intermediate to G and H.). A female, acquired in July 1970 at the end of the second year of life, then went through the third prebasic molt and ex- ternally did not change in appearance. By January 1972 when the bird died, the iris was slightly lighter in color (olive). Fourth prebasic (= third postnuptial) molt stage.--I have held no captives that made the transition from third-year stage to full adult stage, which differs only in that the iris becomes yellow. It is possible, but unlikely in my opinion, that birds remain in the dark-eyed stage for longer than three years. I presume that the irides become fully yellow sometime about the fourth prebasic molt. The female mentioned above, whose irides were becoming paler at death in January 1972, supports this presumption. Full adult stage.--(Fig. 1H.) Except for one characteristic this stage has been described adequately by Ridgway (op. cit.). He and all subsequent authors have thought that the sexes are alike. They are, however, distinguishable by iris color: males have green- ish or olive yellow irides and females have pure yellow irides. A person not aware of this subtle difference would probably term the iris color of both sexes yellow and thus museum specimens with accompanying data on soft part colors are usually not of much help in substantiating this claim. I base it upon three adult males and eight adult females. The three males were birds taken in the wild. Three of the females were taken in the wild and five were captive birds. Once familiar to the observer, this character can be used to sex adults with a binocular in the wild! Study of these same 11 birds in addition to another male and three female captives over two years of age and two museum skins of males indicates a non-overlapping size difference between the sexes as well. Females weigh from 91.3 to 110.3 g and males from 117.0 to 123.0 g (details in Table 1). From data on weights of two captives taken at fiedging and studied for slightly over one year, it is not safe to age birds of this age by weight. These two captive juveniles varied in weight from < 100 g to > 130 g, although on a given date the male always weighed more than the female. Cyanocorax yucatanlea Except for the juvenile stage and post-juvenal molt stage, the description below is based primarily on a group of six captives obtained in April 1968 from a bird dealer in Merida, Yucatan. These included two full adults, two birds almost two years old, and two birds almost one year old. These were kept captive until early 1972. Juvenile.--(Fig. 1I.) Head and body white, remainder of dorsal surfaces grayish-blue. Ventral surfaces of wings and tail dull gray; rectrices, except middle pair, white-tipped. Bill, tarsi and toes pale yellowish with pinkish flesh tones. Inside of bill white. Iris dark blackish-brown. First prebasic molt stage.--Molt involves only body and head feathers. Prior to molt or accompanying it there is increased yellow pigmentation of the tarsi and toes, bill, and fleshy eye ring. First-year stage.--(Fig. 1J.) Entire head and body deep black. Bill tarsi, toes, and fleshy eye ring yellow. Inside of bill white. Mantle blue with glaucous overtones (these overtones differ sub- Tm,: 1. Weights in grams of San Blas Jays (Cyanocorax sanblasiana) demonstrating sexual size dimorphism. Specimen Males Females JWH-768 ad. JWH-766 ad. Live-trapped ad. MVZ-137777 MVZ-115620 2nd yr? JWH-765 ad. JWH-767 ad. (JWH-782 ad.)* (JWH-779 ad.) (JWH-814 ad.) (Discarded ad.) (Discarded ad.) MVZ-136220 ad. Live-trapped (JWH-780 2 yr. old) (JWH-788 1 yr., died at 2 yrs.) (1 yr. old, no specimen saved) 120. 122. 123. 117.0 121. 92 2 112 5 102 0 102 0 110 3 98 9 107 2 99 9 108 2 92 6 101.6 (102.2) 91.3 *Specimens in parentheses were captives. specifically in the two races, yucatanica and rivularis). Upper surface of wings dull blue. Tail purplish blue. Ventral surface of wings and tail deep gray, and rectrices, except middle pair, white- tipped. Since rectrices are retained from juvenal plumage, the white tips may wear completely away long before the second prebasic molt. In June at the earliest, or as late as August, some dark "shadows" may appear on the bill, but the bill remains essentially yellow, and further progress toward the particolored condition does not occur until September. Then blackish pigment begins to appear around nasal openings and on the rami of the lower mandible. Second-year stage.--(Fig. 1K.) Full adult plumage. Bill highly variable but at first still almost completely yellow and by March becoming black and yellow particolored. Tarsi and toes yellow, as they remain through life. At about two years of age, some indi- viduals are wholly black-billed, others retaining markedly parti- colored bills. Yellow eye ring may show some black interruptions at any time in the second year. At least by the third prebasic molt FGUR: 2. Schematic representation of some key stages in the development of plumage and external soft part coloration in a jay, Cyanocorax beecheli. See text for full explanation. A. Juvenile. B. First-year stage. C. Second-year stage. D. Third-year and adult stages. period and usually by the age of two years, the ring is lmost completely black with one to several small yellow interruptions. The progress in blackening of bill nd eye ring is usually not bi- laterally symmetrical. Third-year stage.--A bit of yellow may persist on the eye ring and on the bill well into the third year, at least to November, but by January it is gone. In the erly part of the third year the first blackening of the inside of the bill begins to occur. On 27 November one bird showed several isolated centers of black pigment in the upper mandible (Fig. 3B left) nd by 8 May these hd joined to include over 50 per cent of the inside blck (Fig. 3B right). Fourth-year stage.--(Fig. 1L.) By this stage the bills of ll birds are black exteriorly. Variable small amounts of white my remain on the nside upper mndible, but in general the inside of the bill is blck, and aging individuals t this stage by vriable amounts of white is not safe. All six cptives were identical in soft prt and plumage color in spring 1972. Cyanocorax beecheil No cptives of this species hve been rised from known first- year age through significant ontogenetic changes. However, several captives hve been retained for over two years of life nd although they were not of known age at acquisition, the changes of soft prt color occurred as predicted from their estimated ges. The Moore Laboratory of Zoology collection has n excellent series of skins depicting the following stages: lte juvenile. first prebasic molt, what my almost certainly be considered first-year, second prebsic molt, early nd late second-year, nd full adult. From these speci- mens, we may construct the following picture. Juvenile.--(Fig. 2A. Like juvenile of C. sanblasiana, but bird much larger nd with prominent erect supraorbital crest. Breast blck, rther sharply delimited from the gray abdomen. Bill yellowish horn, trsi nd toes dull horn, inside of bill white, iris probably dark brown (see first-year stage). Frovir: 3. A. Schematic drawing of the head of a subadult Cyanocorax san- blasiana nelsoni, showing outwardly particolored bill and largely white interior marked witk isolated patches of black. The bill becomes black inside and out in the adult. B. Inside of bill of tkird-year stage subadult C. yucatanica skowing progress in blackening of inside of upper mandible from 27 November (left) to 8 May (right). First prebasic molt stage.--Onc specimen, dated 12 August (MLZ 30877). Only body feathers involved, mantle becoming purplish-blue, and head, nape and underparts black. Molt of body feathers proceeding from head posteriorly. No changes in color of bill, tarsi, or toes. First-year stage.--(Fig. 2B.) Plumage like full adults (Ridgway, 1904: 316). Bill tarsi, and toes yellow, iris dark brown (from color transparency reference). Inside of bill white. A prominent erectfie crest persists through life. This description apparently holds for the entire first year of life, since an 8 June specimen (MLZ 15303) that is undoubtedly a bird of the previous year shows no soft part color changes. Second prebasic molt stage.--One specimen (MLZ 11714) taken 31 August is in heavy molt nd is acquiring the parficolored bill. FGv 4. Schematic drawing of heads of two specimens of Cyanocorax beecheil, showing progress of blackening of bill in second-year stage from October (left) to May (righ. Second-year stage.--( Fig. 2C.) The distinctive particolored bill condition persists irregularly through most of the second year. An 11 October specimen (MLZ 9601) has over 80 per cent of the bill black externally and greenish-yellow irides. A specimen taken 5 October (MLZ 11757) has a similar bill, whereas a 10 May speci- men (MLZ 28201) still has the bill only $0 per cent black (Fig. 4). The bill remains white inside. Third-year stage.--Except for persistent white inside bill, in- distinguishable from adults (Fig. 2D.). Iris yellow. Rarely a bird in the third year shows traces of horn color on the outside of the bill near base. In one captive this seemed to be stabilized and to bear no relationship to age. Fourth-year stage.--(Fig. 2D.) Full adult. Inside of bill black (minute amounts of white may persist and stabilize, having no apparent relationship to age). Iris yellow. A WORD OF CAUTION An examination of large numbers of specimens of black-and-blue jays will almost always reveal anomalous specimens not conforming exactly to any one of the foregoing descriptions. Rarely, nearly adult birds may show not only some white remaining inside the upper mandible but also anywhere on the outside of the bill. One specimen of C. sanblasiana in the British Museum (Natural History) has faintly white-tipped rectrices, a condition characteristic of first year C. yucatanica, but so far as I know unique in C. sanblasiana. Readers are thus warned that anomalies must be viewed within the context of other features characterizing each stage of ontogeny. SUMMARY Plumage and soft part color changes from juvenile to full adult are described for the four allopatric black-and-blue jays, Cyanocorax melanocyanea, sanblasiana, yucatanica, and beecheii. These descriptions include accounts of the definitive stages as well as transitory phases and their approximate timing. In general, individual specimens in which soft part coloration has been noted or preserved can accurately be aged to within a few months up to the fourth year of life after which the full adult character is established and maintained. In C. melanocyanea stages through only the second year of life can be distinguished consistently from the adult. Over the first three to four years of life iris color changes from dark brown or black to yellow, except in C. yucatanica in which a yellow eye ring in the first year gives way to black and the iris is always dark brown. Bill color changes from horn or yellow in the first year to black by the end of first year (melanocyanea) or by three years of age. A prominent frontonasal crest disappears gradually from the first year to virtual absence in adulthood (sanblasiana) or by the first year plumage (beecheii). A prominent erectile crest persists in C. beecheii. Crests in the other two species are very short at all times. In yucatanica juveniles have pure white head and body feathers and white-tipped rectrices (which persist through the first year of life). A third-year stage is described for sanblasiana (like adult except for dark irides). Birds immediately subadult can be distinguished from adults by the white interior of the upper mandible. In sanblasiana there is sexual size dimorphism from about age two years onward and sexual dichromatism in iris color of adults. Males have greenish-yellow irides and females have pure yellow irides. ACKNOWLEDGMENTS Students at Occidental College helped gather information for this study and among these I wish to thank especially David Welton, Bruce Steele, and Michael Oliver. Dr. Ralph Raitt aided me greatly by reading and commenting on the manuscript. The American Philosophical Society, the American Museum of Natural History, and Occidental College provided funds to support the investigations, and I am grateful to these institutions. The Los Angeles County Zoo and its curator of birds, Mr. Frank Todd, graciously loaned two living birds for observation. I also thank Dr. Ned K. Johnson, Museum of Vertebrate Zoology, University of California, Berkeley, for supplying weight data on specimens in his care. Moore Laboratory of Zoology, Occidental College, Los Angeles, California 90041. Received 12 November 1972, accepted 29 December 1972.