The Nesting Activities of the Swallow.

Abstract

Summary. Five nests of Hirundo r. rustica were watched for a total of 639 hours in a prisoner‐of‐war camp in Bavaria. A short list of calls or notes was made. Male and female worked equally hard in building the nest except for the lining which was principally made by the female. Incubation was by the female only. It began with the laying of the first egg. A method of recording the average percentage of daytime incubation day by day was devised. The average daytime percentage incubation at the one nest observed at this stage was found to vary in accordance with a mathematical formula Y=a‐|‐bx|cx2|dx3 where Y is the percentage of daytime incubation on any given day and x is the interval in days since the laying of the first egg. This formula was adopted as the most convenient means of describing the data observed. Brooding of the chicks was by the female only. It lasted for six to nine days and decreased regularly from day to day. Both sexes fed the chicks in the nest, the work being shared unequally at one nest (principally by the male) and equally at the other two nests observed at this stage. In fine weather the feeding rate tended to increase arithmetically day by day. Bad weather exerted a limiting effect on the feeding rate. In many details striking discrepancies were found between our records and those of other observers. The behaviour of the swallow during the nesting season appears to be widely variable. Further work, on swallows marked by means of coloured rings, would doubtless elucidate many points of uncertainty.