PARENT SESSION
Oral Session #71: Animal Population Ecology. Presiding: J. Dooley.
Thursday, August 9, 2001. 1:00 PM to 4:15 PM. Hall of Ideas J.
Optimal group size and Northern Bobwhite coveys.
Williams, Christopher1, Lutz, Scott1, Applegate, Roger2, 1 2
ABSTRACT- Northern bobwhite (Colinus virginianus) form social units, called coveys, during the non-breeding season (approximately September - April). Although, the maintenance of covey size has been observed, little has been offered as to the evolutionary advantage of this behavior. Therefore, we investigated: 1) the existence of an optimal covey size, 2) the effect of migration in maintaining an optimal covey size, 3) the individual survival and covey fidelity in relation to covey size, and 4) the effect of group size on mass change. We conducted research on twelve independent 640 ha study areas in east central Kansas between 8 November - 31 January, 1997-00. Analyses was conducted on 386 radio-collared individuals comprising 137 groups. Covey size did not differ among or within years and averaged 10.98 (SE ± 0.22) individuals. Optimal covey size was promoted by improved individual survival, high group fidelity, and low movement. Small groups (< 7 individuals) had lower individual survival and group fidelity. Consequently, small coveys used increased movement to create or join larger groups where survival was higher. Large groups had lower individual survival, increased movement, and reduced feeding efficiency. It is possible density dependent feedbacks lowered larger coveys to optimal size. Our results suggests the regulation of optimal covey sizes could be promoted to buffer environmental stress through group thermoregulation, improve feeding efficiency and/or improved competition for scarce resources, and/or improve individual survival.
KEY WORDS: bobwhite quail, optimal group size, Allee Effect