Thyroidectomy of nestling starlings appears to cause neotenous sexual maturation.

Nestling starlings (Sturnus vulgaris) were thyroidectomized, in the wild, when 8 days old. They were later brought into captivity and hand reared on a daylength of 16h light: 8h darkness per day. Thyroidectomy dramatically affected somatic development so that even at 23 weeks of age these birds retained the physical characteristics of approximately 3-week-old euthyroid birds. Nevertheless, they appeared to be healthy and were active. Despite retaining juvenile features, these thyroidectomized birds became sexually mature. In males, testicular growth began at 8 weeks of age and by 23 weeks both males and females had well developed gonads.