GROWTH, DEVELOPMENT, AND FOOD HABITS OF YOUNG PINON JAYS

DESPITE numerous reports of growth and early development in a variety of passerines (Banks, 1959; Anderson and Anderson, 1961; Willson, 1966; Ricklefs, 1967a; Holcomb and Twiest, 1968) relatively few such studies have dealt with members of the family Corvidae. Parmalee (1952) describes the growth and development of Corvus brachyrhynchos, and Pitelka (1945) gives valuable information on molt sequences and other age specific characteristics of early plumages in the genus Aphelocoma. Mewaldt (1956) published data on growth and development of Clark's Nutcracker (Nucifraga columbiana) and Crossin (1967) briefly described development of the Tufted Jay (Cyanocorax dickeyi) during the nestling and early postfledging period. Ricklefs (1967b, 1968a, 1968b) stresses the importance of discovering causes underlying the existing diversity of growth patterns in birds. He feels that comparative studies of growth will reveal much about the ecology of some species. This study provides quantitative and qualitative information regarding growth of one of the more unusual corvids. The Pition Jay (Gymnorhinus cyanocephalus), a highly social species, is one of the earliest nesting passerines in the north temperate region. Studies of young born during periods of inclement weather should reveal some factors influencing growth rates under adverse environmental conditions. The high degree of sociality of this species may contribute significantly to the pattern of growth and development of the young. METHODS This report describes the growth and development of young from a flock of about 250 Pition Jays nesting in an area of the ponderosa pine forest 10 miles northeast of Flagstaff, Arizona. Studies of the annual cycle and social behavior of this species initiated in February 1968 have continued through the 1971 breeding season (Balda and Bateman, 1971). Growth and development of young were of major concern during the first 3 years of study. Temperature data were obtained by a hygrothermograph on the study area. Precipitation (Table 1) in the form of snowfall was measured at Flagstaff PullJam Airport, 13 miles southwest of the nesting grounds at a comparable elevation. Differences in amount of snow received at the two areas are relatively minor. From February through June nests containing eggs and/or young were checked as often as prudent consideration of the parent birds allowed. the study area was normally visited from two to five times a week. It was not always possible to examine all nests at a given visit because of the large number of contemporaneously active nests, but we do have almost daily records of growth for some individuals during their nestling periods.

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