Because only few yearling females and no yearling males were capable of breeding in the low phase of the vole cycle (Table 1), most of the population level analyses were performed for the data from the increase and decrease phases of the vole cycle. In the increase and decrease phases of the vole cycle, the partners of yearling males had the latest and the partners of 3-year-old males the earliest laying date when the age of the female was controlled for [F3,155 = 3·90, P = 0·01 (Bonferroni-corrected 6× contrasts: P = 0·006) in the increase phase and F3,256 = 2·64, P = 0·05 in the decrease phase, no interactions with female age, Fig. 2]. Male age was not associated with the laying date of their partners in the low phase of the vole cycle (F2,33 = 0·56, P = 0·58, Fig. 2) or during the weakly cyclic period (F3,59 = 1·19, P = 0·32). Laying date was not related to female age (F3,33 = 1·00, P = 0·40 in the low, F3,155 = 0·39, P = 0·76 in the increase, F3,256 = 0·81, P = 0·49 in the decrease and F3,59 = 0·16, P = 0·92 in the weakly cyclic phase of the vole cycle). Territory quality did not have obvious effect on laying date when it was added into the anova-model as a factor (for territory quality, F4,122 = 0·99, P = 0·42 in the increase phase and F4,219 = 1·46, P = 0·22 in the decrease phase, no interaction with male or female age).
Three-year-old females had the largest and 1-year-old females the smallest relative clutch size in the increase phase of the vole cycle (F3,149 = 4·05, P = 0·008 (Bonferroni-corrected 6× contrasts: P = 0·006), but not in the low and decrease phases (F3,31 = 0·24, P = 0·86 and F3,246 = 0·79, P = 0·50, respectively, Fig. 3) or during the weakly cyclic period (F3,65 = 0·61, P = 0·61). There were no differences in clutch sizes between the partners of different-aged males (F2,31 = 0·53, P = 0·60 in the low, F3,149 = 0·41, P = 0·74 in the increase, F3,246 = 0·09, P = 0·96 in the decrease and F3,65 = 0·13, P = 0·94 in the weakly cyclic phase of the vole cycle). Territory quality had no obvious effect on the clutch size in the increase phase (for territory quality F4,118 = 1·65, P = 0·17, no interaction with male and female age).