Answer
For both cases, a study looking into the fitness of the males has been done. In Iguanas, the sexually more attractive largest individuals were less able to keep their energy intake at the necessary levels as smaller individuals. The longer tailed widowbirds were less able to forage for food and ended up with worse body conditions than shorter clipped individuals.
These two extreme examples might imply that sexually selected features are often detrimental to the health of the individual, making high sexual achieving males less fit for survival.
Work Step by Step
For both cases, a study looking into the fitness of the males has been done. In Iguanas, the sexually more attractive largest individuals were less able to keep their energy intake at the necessary levels as smaller individuals. The longer tailed widowbirds were less able to forage for food and ended up with worse body conditions than shorter clipped individuals.
These two extreme examples might imply that sexually selected features are often detrimental to the health of the individual, making high sexual achieving males less fit for survival.
