Thyroid Development in Precocial and Altricial Avian Embryos

ABSTR•CT.--Histological criteria indicate that thyroid glands are organized into follicles at about the same time of incubation in Japanese Quail (precocial) and Ringed Turtle Dove (altricial) embryos, but dove thyroids develop more slowly, are much smaller and are much less active than quail thyroids by the time of hatching. These results indicate thyroid readiness for participation in early endothermic responses of precocial hatchlings, and relative thyroid inactivity in young ectothermic altricial nestlings.--Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061. Accepted 12 April 1976.