August 11, 2016
Black-billed magpies and American crows, both members of the clever corvid family of birds, have adapted comfortably to life in urban and suburban communities. In Jackson Hole, Wyoming, the two species often nest nearby each other in backyards and parks. Nesting near their much larger crow cousins affords magpies a margin of extra safety from a common enemy—ravens, an even larger corvid species.
"Ravens are notorious nest raiders," said Rhea Esposito, an educational program leader at the Cary Institute of Ecosystem Studies. During her graduate work at the University of Louisiana at Lafayette, Esposito studied how birds associate during nesting season. Smaller birds sometimes nest near larger species to benefit from their more aggressive defense against predators. Research has tended to focus on the protection side of the relationship. But what about competition? Do magpies pay a food penalty for nesting near larger rivals? Or do the smaller birds compensate with bold pursuit of new food sources?
To find out which of the two corvids were more intrepid snack scouts, Esposito presented breeding pairs with a set of Cheetos challenges. She will present her results today at the 101st Annual Meeting of the Ecological Society of America in Fort Lauderdale, Florida, during a session on animal Behavior.
"Cheetos are not the healthiest food, but the birds like them a lot," said Esposito. "And because they are bright orange, it was really easy to observe when the birds completed the task."
Esposito set out Cheetos near nests and settled in to watch the birds fly down to investigate. Magpies moved on the unfamiliar food an average of 20 seconds faster that crows, which eyed the orange treats with more suspicion, pausing longer before picking them up. Once having identified Cheetos as food, however, crows were more apt to steal.