Variation in Avian Brain Weights with Special Reference to Age

Abstract

Weights and other measurements of the brain are available for a number of Old World species of birds (see Portmann and Sutter, 1940; Portmann, 1942, 1946-1947, 195.5, 1959; Sutter, 1943; Stingelin, 1957, 1960). Few data are available for New World species. Hancock (1887, 1888) has given brain weights for a few North American species, and there is a list of weights of organs presented by Crile and Quiring (1940) which includes some data on brains. In a study of weight characteristics of nocturnal migrants, we noted (Graber and Graber, 1962:86) that immature specimens of passerine birds had heavier brains than adults. The nature of this difference between adult and immature birds de- served investigation, and we determined to pursue the problem whenever additional specimens became available. Thus, a large kill of nocturnal migrants at television towers in central Illinois in September, 1962, was a stimulus for this study. It is the purpose of the study to shed light on two questions particularly. (1) What is the nature of the difference between the adult and immature brain, and (2) does the age variation in the brain have potential utility in ageing populations of birds?