What is the term for a mature female turkey?

The term for a mature female turkey is "hen." In avian terminology, especially concerning domesticated and wild turkeys, "hen" is specifically used to denote the adult female of the species. This term is widely recognized in both agricultural and wildlife contexts, making it the appropriate choice in this scenario.

The other terms provided refer to different species or genders. For instance, "gobbler" refers to a mature male turkey, not a female. "Jend" is not a recognized term in poultry terminology, and "peahen" pertains to a female peafowl, which is a completely different species altogether. Thus, understanding the specific terminology associated with different bird species is essential in animal science.