PARENT SESSION
Oral Session # 83: Ecological Theory II: Modeling; Competition.
Presiding: C Brassil
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.
Individual variation in demographic traits of Florida Scrub Jays.
Kendall, Bruce *,1, Fox, Gordon2, Woolfenden, Glen3, Fitzpatrick, John4, 1 University of California, Santa Barbara, CA2 University of South Florida, Tampa, FL3 Archbold Biological Station, Lake Placid, FL4 Cornell University, Ithaca, NY
ABSTRACT- Our prior theoretical work has demonstrated that variation in demographic traits among individuals in a population can affect the uncertainty in the population's demographic fate that is associated with demographic stochasticity. In particular, when an individual's trait is drawn at random and is uncorrelated with traits of other individuals, then variation in mean fecundity may increase the uncertainty associated with demographic stochasticity in reproduction, but individual variation in survival probability has no such effect. In contrast, variation associated with cryptic population structure (so that individual traits are not entirely independent of one another) can reduce the uncertainty due to demographic stochasticity in survival, but may have no effect on fecundity. Here we quantify the magnitude and effect of individual trait variability in a well-studied population of Florida Scrub Jays from central Florida. These birds exhibit substantial individual variation in demographic traits associated with factors such as genotype, breeding history, territory quality, and the presence of helpers at the nest. Were we to ignore this population structure (which we might have to do in a small, poorly-studied population), we would introduce biases into our estimates of the magnitudes of demographic stochasticity. This in turn would bias our estimate of the extinction risk of the population.
Key words: Aphelocoma coerulescens, demographic stochasticity, social structure