Maximum likelihood estimates for covariate parameters in the global model examining the relationship between the probability a bird tested positive during the breeding season (April 1 to September 30) and the variables shown.

DBZ (days below zero) is the cumulative number of days during the previous overwintering season that the mean temperature was less than zero and IAP is the interval apparent prevalence during the previous overwintering season. Hatch Year is the effect size relative to after-hatch-year birds, Age Unknown is the effect size relative to known age birds, Female is the effect size relative to males, Sex Unknown is the effect size relative to known sex birds, and all species effects are relative to the mallard. MLE is the maximum likelihood estimate of the parameter and 2.5 percent and 97.5 percent define the 95 percent confidence interval around the MLE based on profile likelihoods. All values are on the logit scale; however, exponentiation of these estimates provides an odds ratio interpretation of the effect size.