During 1996, nestlings in single nests of White Wagtail and Nuthatch were daily measured (maximum wing chord) and weighed (body mass to nearest 0.1 g). White Wagtails openen their eyes at day 5 (half open). Nuthatches at day 12 (hatching day = 0). Primaries started to protrude from the blood shafts at day 6 in White Wagtails and at day 9-10 in Nuthatches. Exact measurements are summarised in Appendix 1.