Cellular structure of adipose tissue in birds

In a randomly collected sample of 91 wild and captive birds, in which there is no significant correlation between fatness and body mass, the total number of adipocytes is proportional to (Body Mass)^0.68 . The adipose tissue of larger birds consists of proportionately fewer adipocytes; therefore, the adipocytes of larger birds are larger, in relation to the fatness of the specimens, than those of the smaller species. The cellularity of the adipose tissue of predominantly carnivorous birds does not differ from that of mainly herbivorous species. The adipocytes in the abdominal cavity and around the thigh are on average 29% larger than those in the superficial and clavicular depots; however, these site-specific differences were variable and were statistically insignificant in many of the specimens. The size of the adipocyte complement is highly variable even among specimens of a single species and similar body mass, suggesting that in birds the number as well as the volume of adipocytes might increase or decrease as the adipose tissue expands or shrinks.