London, Apr 30 : Female starlings with a testosterone top-up compete ruthlessly for nesting sites but when it comes parental care, they give it a miss, according to a new study.
The latest research may offer clues as to why females in general do not have as much testosterone as males, say researchers.
The spotless starlings are better defenders of the nest, and can be killed or seriously injured as a result, reports New Scientist.
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 their young.
The scientists suggest that high levels of testosterone may work to a female's advantage where competition for nesting sites is fierce, but reduce reproductive success elsewhere.
The research will be published in a forthcoming issue of The American Naturalist.