A Possible Avian Analogue of the Scrotum

Abstract

While in their normal position the air sac systems of Brewer''s blackbird (Euphagus cyanocephalus) were injected with a latex soln. The viscera were studied over 2 successive seasons of the testicular cycle and it was found that the testes move a short but important distance downward and backward so that during the warm spring months while spermatogenesis is in progress the testes become enveloped between the 2 dorsal folds of the abdominal air sacs. A late spring or summer testicular regression occurs. The insulating properties of the air sacs provide enough relief to allow reproduction before collapse of the gonads takes place.