Breeding time, clutch size, dimensions and intra- and interclutch variation were measured in 612 egg clutches of F. coelebs during the past 100 yr. Egg-laying starts on average 4 days earlier in Denmark and southern Sweden than in southern Finland, and 4 days earlier the last 3 decades than around the turn of the century, probably due to the spring climate amelioration. No latitudinal trend in clutch size was found. Mean-egg volume decreased from the south to the northeast, as did male wing length. Mean egg volume increased with the progress of the breeding season, but the correlation was not stable, for clutches with large mean egg volume are presently laid early in the season more frequently than before. Egg shell thickness varies between and within some regions, and also among clutches collected before the use of pesticides. Replacement clutches exceed 1st clutches in mean egg volume, but the number of eggs per clutch remains the same until very late in the season. Selective forces shaping the breeding strategy of chaffinches of different ages and sizes were discussed.