Variability in Levels of Blood Uric Acid in Five Species of Birds

Abstract

OUR preliminary studies on serum uric acid in birds showed the existence of diurnal differences in concentration. Therefore, it seemed appropriate to study the factors associated with these differences. This work is based on 123 birds of four species : Carpodacus mexicanus, Lophortyx californica, Passer domesticus and Zonotrichia leucophrys. The birds were housed individually at temperatures ranging from 22 to 26° C. on a daily photoperiod of 5 hr. To test a non-flying bird, week-old chicks kept at 33° C. in a brooder on a 5-hr, photoperiod were used. Water consumption was measured to check the degree of hydration prior to obtaining blood samples. Blood sera were analysed colorimetrically¹. Activity was induced by (a) placing the birds in a cylindrical cage 8 in. in diameter and 24 in. in length and forcing them to hop by slowly rotating the cage at 6 r.p.m. with an electric motor for 2½ hr. or by (b) releasing them in mid-air in an empty room illuminated by dim red light. The birds were not attracted by the red light, although we had previously observed them flying towards any stray white light when they were permitted to fly in a darkened room. Because it was impossible to keep the birds flying in the dim red light for more than a few minutes, they were picked up at the end of each flight and re-released a sufficient number of times to give the approximate equivalent of 10 min. continuous flight.