Table 3.

Best-fitting models under Akaike Information Criterion (AIC) model selection. Outbreak locations from 2003 to 2009 (n = 26) are compared with random points (n = 26). Variables include outbreak latitude (Lat), poultry density (Dens), utilization distribution for satellite-marked wild ducks (BBUD), urban areas (Urban), cropland (Crop), water, and wetlands. Number of parameters (k), AIC score, AIC difference (ΔAIC), likelihood, and AIC weights are reported. Models with biologically significant AIC scores are indicated (*).

Model	Description	k	AIC	ΔAIC	Likelihood	AIC weight
1	Lat+Dens*	3	66.48	0.00	1.00	0.36
2	Lat+Dens+BBUD*	4	67.85	1.38	0.50	0.18
3	Lat+Urban+Crop+BBUD	5	69.04	2.57	0.28	0.10
4	Lat+Crop+Dens+BBUD	5	69.39	2.91	0.23	0.08
5	Lat+Water+Wetland+Dens	5	69.97	3.49	0.17	0.06
6	Lat+Urban+Crop+Dens+BBUD	6	70.05	3.57	0.17	0.06
7	Dens	2	71.62	5.14	0.08	0.03
8	Lat+Water+Urban+Crop+Dens+BBUD	7	71.64	5.16	0.08	0.03
9	Lat	2	71.71	5.23	0.07	0.03
10	Lat+Water+Wetland+Crop +Dens	6	71.85	5.37	0.07	0.03
11	Lat+UD	3	72.59	6.11	0.05	0.02
12	Lat+Water+Wetland+Urban+Crop+Dens+BBUD	8	73.51	7.03	0.03	0.01
13	Lat+Urban+Crop+UD	5	74.14	7.66	0.02	0.01
14	Full model: Lat+Water+Upland+Wetland+Urban+Crop+Dens+BBUD	9	74.20	7.72	0.02	0.01
15	Lat+Water+Wetland+Crop	5	76.70	10.21	0.01	0.00
16	Urban+Crop+Dens+BBUD	5	77.58	11.10	0.00	0.00
17	Null model	0	82.41	15.93	0.00	0.00