GROWTH AND SEXUAL DIMORPHISM OF THE BOAT-TAILED GRACKLE

At hatching, male and female boat-tailed grackles (Quiscalus major) are similar in size. By day 12, just before fledging, they differ in manus and tarsal lengths, tarsal thickness, and weight, but not in culmen, primary remex 7, and tail lengths. Male and female nestlings attain asymptotic weights of 102.4 g and 65.6 g, respectively, at a rate faster than predicted from the general passerine pattern. These asymptotes are only 54.8% and 65.3%, respectively, of adult weight. The combination of a faster growth rate and an asymptote below adult size means that grackles fledge sooner than would be expected for the general passerine pattern. Clutches of 3 eggs hatch asynchronously; the hatching of the 3rd chick does not decrease growth rate of the early-hatching chicks. Third-hatched young fledge at weights significantly below those of early-hatching young. Compared to males hatching from the 1st or 2nd egg, males from the 3rd egg require several more days to attain sizes larger than females.