The relationship of the size of a second nest as a function of the size of a previous year's nest in blue tits (Cyanistes caeruleus) in Wytham Woods, Oxfordshire, UK. We collected data in April–May 2001–2003. These data are from females that bred more than once in the study period and used different nest boxes in each nesting attempt, n = 149 nests from 79 females. The line of best fit represents the variation explained by female identity as calculated from linear models with and without female identity included, χ2 = 7.55, p = 0.006, R2 = 0.615; the grey shaded area shows 95% confidence interval.