Table 1. List of outcome and explanatory variables used in models examining demographic and spatiotemporal determinants of low pathogenic avian influenza virus infection in Blue-winged Teal in Canada and the United States, 2007–10.

Variable	Type	Definition	Description
AIV infection	Categorical, outcome variable	Positive suggests current infection based on RRT-PCR	Binomial outcome–positive or negative
Sex	Categorical, explanatory	Gender of bird	Female or Male
Age	Categorical, explanatory	Age of bird at capture	Hatch year (<1 year old, HY and SY) or after hatch year (>1 year old, AHY and ASY)
Year	Categorical, explanatory	Year of sampling	2007–2010
Flyway	Categorical, explanatory	Migratory flyway where sampling occurred [19]	Atlantic, Mississippi, Central, or Pacific
Latitude	Continuous, explanatory	Latitude of sampling location	Decimal degrees, standardized
Blue-winged teal stage of annual life cycle–“Season”	Categorical, explanatory	Stage of life cycle of BWTE [18]	July-August: Staging, End of Moult, Preparation for fall migration; Sept-Oct: Fall migration; Nov-June: Wintering, Spring migration, breeding period