How do migrating birds solve the volunteer´s dilemma?

• Applicant: Dr. Bernhard Völkl
• Subject Area: Sensory and Behavioural Biology
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 208422747

A considerable part of the world wide bird population performs yearly long-distance migrations. One conspicuous feature of several larger bird species is their flight in V-shaped or echelon formation, which has been suggested to reduce energy costs. As not all birds in a formation can profit from the aerodynamic upwash to the same extent, a social dilemma arises around the problem which bird has to fly in the least advantageous leading position. Several game theoretic models can be formulated that will help to predict which individuals are more likely to lead a formation, how often leadership should change and which waiting time for the departure can be expected. In order to test these predictions we will monitor the flight behaviour of three flocks of juvenile bald ibis (Geronticus eremita) during their human guided autumn migration. All birds will be equipped with data loggers with high-precision GPS antenna, accelerometers and EMG sensors that allow us to evaluate the position of the birds within the formation and their energy requirements. Based on these estimates and indicators for the physical condition of the birds, we will specify the models and test them with the recorded data from the three migrations. It has been suggested that many cooperation problems in biology have the form of a volunteer's dilemma. Formation flight in birds is an outstanding example and a highly suitable model system for two reasons. First, the benefits from cooperating are substantial as juvenile birds that fall back and get lost in unsuitable habitat during their first migration are likely to experience severe fitness consequences. Second, thanks to improvements in sensor technology it is now possible to accurately measure energy expenditure and this, in turn, allows us to quantify the investment of the cooperating individuals during formation flight.

• DFG Programme: Research Grants