"Males potentially gain a portion of the family territory, the ability to come back home easily if things do not work out, and perhaps even assistance with acquiring a nearby territory," said Janis Dickinson, lead author of the study and associate professor of natural resources at Cornell University.
She added, "It is also possible that familiarity with the area makes them more competitive for and aware of newly open vacancies nearby, so that they can find mates more easily. Sons also commonly mate with females that have been attracted into their winter groups, which may be an advantage over a vagabond lifestyle."
Dickinson explained to Discovery News that she and her colleague, Andrew McGowan, selectively removed mistletoe shrubs in oak tree bluebird territories. The birds usually eat bugs during the spring and summer months, but mistletoe berries are their primary food source from October until spring.
Only eight percent of sons overwintered with their parents in areas when the berries were removed, while half of all bluebird males continued to stay with their parents when resource wealth, in this case mistletoe berries, was left untouched by the researchers.
