Female starlings with a testosterone top-up are better defenders of the nest, but skimp on parental care. The finding may offer clues to why females in general do not have as much testosterone as males.
The spotless starlings of the western Mediterranean compete ruthlessly for nesting sites, and can be killed or seriously injured as a result. When Jose Veiga and Vicente Polo at Spain’s National Museum of Natural Sciences in Madrid placed testosterone implants in 30 female starlings they found that these birds tended to be better at acquiring and holding onto their nests, but took less care of…
