Mallard (Anas platyrhynchos) Science Article 6
abstract
The steroid hormone testosterone (T) mediates the expression of many secondary sexual characters, including behaviors which in.uence male reproductive success. Testes are one of the major sources of androgens, in particular of T. Although a positive relationship between testes size and T levels could be hypothesized, it has rarely been tested intraspeci.cally. We investigated this link in mallards (Anas platyrhynchos) using a double- antibody radioimmuno-assay to measure hormone levels and X-rays to determine testes size. Here, we report a positive correlation between both traits in a group of 13 drakes during the reproductive season
Angelika G. Denk and Bart Kempen rs, J Ornithol (2006) 147: 436-440