Sample sizes of the field experiment to study the effect of photostimulation on laying dates in wild living great tits (Parus major).

We created 3 experimental groups: (i) photostimulated females (ii) females which experienced natural day length in captivity and (iii) females which experienced natural day length in the field. Females from group (i) and (ii) were kept indoors for one day and two nights after which they were released in the field at the location where they were caught.