Thogmartin, W. E., Roseberry, J. L., and Woolf, A., 2002, Cyclicity in northern
bobwhites: A time-analytic review of the evidence: in DeMaso, S. J., Kuvlesky, Jr.,
W. P., Hernandez, F., and Berger, M. E., eds., Quail V: Proceedings of the Fifth
National Quail Symposium: Texas Parks and Wildlife Department, Austin, TX, p.
192-200.

Abstract

Cyclical behaviorin wildlife populations, including northern bobwhite
(Colinusvirginianus), has long fascinated human observers. However, studies
examining cyclicity of bobwhite abundance have yielded contradictory results. We
reviewed evidence for periodic fluctuation in bobwhite abundance by studying 73
long-term time series. Ou raim was to discern with time-series techniques whether
cyclicity occurred in bobwhite abundance. We elucidated the frequency of occurrence,
geographical distribution, and potential mechanisms responsible for cyclicity.
Approximately one-half (n = 37) of the populations examined demonstrated cyclical
behavior, with a period varying between 4 and 17 yrs. True cycles, consistent,
significant fluctuations in abundance, were rare, occurring in only 3 time series. The
predominant form of periodicity was oft he phase-forgetting quasi-cycle type (n  =
34). This phase-forgetting may have contributed to previous contradictory findings of
cyclicity in this species. We reason cyclicity in bobwhite populations is caused by
aperiodic environmental perturbations interacting with density-dependence. Cyclic
bobwhite populations occupied the northern and western portion of the species' range,
where stochastic weather events regularly negatively influence bobwhite population
dynamics. Bobwhite populations were non-cyclic in the relatively consistent climate
of the southeastern United States, however, habitat fragmentation rather than climate
may have contributed to the absence of cyclicity in thi sregion.

Keywords

California quail, Callipepla californica, Colinus virginianus, density dependence,
environmental forcing, northern bobwhite, periodicity, phase-forgetting quasi-cycles