Release-day in relation to 1^st egg date.

<p>The relationship between the release day of female pied flycatchers from the aviaries and date of 1^st egg is shown for the three treatment groups. The duration between release from the aviaries and laying of the first egg varied from 2 to 19 days (all data points are above the x=y line) and declined with date, for each group. Each symbol indicates a nest, with separate regression lines for each treatment group. For graphical reasons, one data-point of Swedish controls was shifted +0.5 on the y-axis.