Table 1. Top general linear models that explain variation in spring migration behaviour of juvenile and adult wood thrushes.

Dependent variable	Factors retained in top model	Estimate±standard error	t	P
Spring departure date	Age (J)	7.93±2.91	2.73	0.009
	Sex (M)	−10.88±2.89	−3.76	<0.001
	Breeding latitude	0.74±0.38	1.96	0.057
Spring enter U.S.	Age (J)	9.02±2.66	3.39	0.001
	Sex (M)	−10.57±2.53	−4.17	<0.001
	Breeding latitude	1.02±0.34	2.98	0.005
Breeding arrival date	Age (J)	13.97±2.66	5.25	<0.001
	Sex (M)	−11.58±2.53	−4.57	<0.001
	Breeding latitude	1.12±0.34	3.03	0.002
Spring migration duration	Age (J)	7.73±2.74	2.81	0.008
Longitude entering N.A.	No significant factors	-	-	-
Spring migration distance	Breeding latitude	79.78±26.81	2.98	0.002
	Breeding longitude	−107.49±25.81	−4.16	<0.001
Spring migration speed(distance/migration duration)	Age (J)	−80.70±33.99	−2.37	0.023

Letters in brackets indicate the base category for that estimate, i.e. J = juvenile, M = male. Full models for all variables included age, sex, breeding latitude and breeding longitude. We also included an interaction term for age and sex, although it was not significant in any model.