Table 4. Logistic regression models of variation in avian influenza virus (AIV) seroprevalence for greater white-fronted geese sampled in Alaska, USA, 2008–2010.

Greater white-fronted geese (n = 1150)
Models	k a	AICb	ΔAIC	ωi b
Age + Sex	2	1540.13	0.00	0.59
Site + Age+ Sex	5	1542.61	2.48	0.17
Site + Year + Age + Sex	10	1542.91	2.78	0.15
Year + Age + Sex	7	1543.71	3.58	0.10

^a k  =  number of parameters in model.

^bThe best approximating model has the lowest Akaike's Information Criterion (AIC) value and the highest model weight (ω_i), relative to others in the model set.

Models examine the effects of location (site) and/or year, while controlling for sex and age (adult vs. subadult).