Why do birds migrate? Seasonal food scarcity finds study
March 1, 2007
A new paper attempts to answer the age old question of why birds migrate. The authors, Dr. Alice Boyle and Dr. Courtney J. Conway of the University of Arizona, argue that birds are driven to fly long distances due to seasonal food scarcity.
“It’s not just whether you eat insects, fruit, nectar or candy bars or where you eat them — it matters how reliable that food source is from day-to-day,” said Boyle. “For example, some really long-distance migrants like arctic terns are not fruit-eaters.”
Their findings are based on computer analysis of 379 species of New World flycatchers from the suborder Tyranni, a group that includes kingbirds, flycatchers, phoebes, becards, manakins and cotingas. The researchers found that food scarcity was the most important factor in predicting the migratory behavior of a species.
A royal flycatcher shows his stuff. This homebody is content to stay put in Costa Rica year-round. Photo copyright 2004 Alice Boyle.
“Food availability is the underlying process, not diet and habitat,” said Boyle. “If you are faced with food scarcity, you have two options. You can either forage with other birds or you can migrate.”
Boyle and Conway found that forage in flocks are less likely to migrate.
“Flocking can be an alternative way to deal with food shortages,” explained Boyle, since a group of birds is more likely to find food than a lone individual.
This article used quotes and information from a news release from the University of Arizona.