A balanced diet, exercise and reduced stress not only can lead to a longer life, but also better reproduction, according to a new study by a team of researchers, including one from Arizona State University, on barn swallow nutrition and mating habits.
The study shows that swallows who maintained a positive antioxidant balance over the course of their breeding season were those who produced the most young.
The results of the study are presented in the February 25, 2010 issue of PLoS One, a journal of the Public Library of Science, in the article "Positive carotenoid balance correlates with greater reproductive performance in a wild bird." The study was led by Rebecca Safran, an assistant professor in ecology and evolutionary biology at University of Colorado in collaboration with Kevin McGraw, an associate professor in the School of Life Sciences at Arizona State University. Co-authors include Colorado doctoral students Matthew Wilkins and Joanna Hubbard, and project volunteer Julie Marling.
Little seems to be easy for the North American barn swallow. The pint-sized bird travels thousands of miles to its nesting grounds and then almost immediately upon arrival engages in its courtship and mating rituals. If successful in these activities, the barn swallows then need to feed, warm and protect their offspring.
While working at a seemingly exhausting pace, it turns out that the strongest of the barn swallows are not only up to the task, but they excel at it. The reason: The leaders of the pack "have a prime 'management system' for antioxidants," said McGraw. "Even after completing the arduous tasks of migration and reproduction, these intense breeders still find themselves carrying a surplus of antioxidants to combat additional challenges."
"Our results indicate these top-of-the-line barn swallows are less stressed and have higher functioning immune systems," added Safran.
The antioxidants that McGraw and his colleagues studied are carotenoids - plant compounds like lutein and beta-carotene found in fruits and vegetables. These compounds often are sold as human nutrition supplements.
In a variety of animals, these carotenoids can have potent free-radical-quenching and immune-boosting activity. "Whether the stud birds are acquiring more carotenoids from food or having to use less to keep their bodies healthy, they're clearly successful at keeping levels high while out-reproducing their competitors."
While several other studies have examined how carotenoid levels in animals are linked to health and other aspects of fitness at single points in time, the new study is the first to consider how an individual's temporal change in carotenoid levels is associated with its evolutionary fitness.
Conventional wisdom, McGraw explained, is that vigorous activities such as migrating thousands of miles, courtship, nesting and reproduction should deteriorate the physiological state of animals like swallows.
"Among a variety of animals, reproduction can compromise health and decreased health can inhibit reproduction," McGraw said. "But here we show that, among the best barn swallows, they're able to both keep carotenoid levels high and breed the most. Thus, we don't find clear support for a health/reproduction trade-off among wild animals."