Growth Rates of Cranes Reared in Captivity

Abstract

Abstract We measured eggs, incubation periods, growth of chicks, and masses of adults of 10 species of cranes at the Bronx Zoo and the International Crane Foundation. Growth rate constants of Gompertz equations fitted to the data varied between 0.034 and 0.057/day. These values were 50-90% of those for altricial birds of comparable adult mass, and were considerably greater than those of other precocial species, such as galliforms. Rates of growth intermediate between altricial and precocial species are consistent with the fact that crane chicks, although precocial, are brooded and fed by their parents during much of the early development period. Within species, asymptote (A) and growth-rate constant (K) of the Gompertz equations were negatively correlated, owing to their inherent relationship in the curve-fitting process. Masses of chicks during the first month after hatch were unrelated to the mass asymptote, but correlated strongly with the estimated growth-rate constant. The mass of the neonate was about 60% of the fresh mass of the egg. Egg mass was unrelated to subsequent chick mass during the first month, but correlated with the mass asymptote in two species when the relationship between A and K was accounted for statistically. Egg mass also was correlated with incubation period, fledging period, and the growthrate constant in isolated instances. Growth rate and asymptote among species were inversely related, as found among large samples of diverse bird species. The size of the egg relative to the mass of the adult was related inversely to adult mass, again consistent with patterns in other groups of birds. Fledging period was related strongly to the length of the incubation period and weakly to the asymptote to the growth curve, and it was unrelated to growth-rate constant of the Gompertz equation.