Figure 1.

Frequency distribution (%) and box-and-whisker plot showing the mean (ellipses), the median (lines), 5th and 95th percentiles and nonoutlier range of the size of the black breast tie of forest and urban male great tits. Mean (±SE) values of tie size for urban birds: 8.6 ± 0.23 mm and for forest birds: 9.3 ± 0.17 mm. The size of the black tie was measured as the width of the tie at the level of the clavicle (1992–2008).