Page:The Zoologist, 4th series, vol 1 (1897).djvu/137

Rh she will lay her full complement. The hen generally begins the sitting; she will occasionally sit for one or two days and nights before the cock takes his turn. Now and then, however, the cock will be first to sit; but, in such a case, he will probably leave the nest for some hours during the day.

When sitting assumes its regular course, the hen sits from 8 or 9 a.m. to about 4 p.m., and the cock from 4 p.m. to about 8 or 9 a.m. The bird whose turn it is to be on the nest keeps its seat until the other arrives to relieve it, when they at once change places. Soon after beginning to sit, the cock loses his sexual vigour and inclinations, and ceases his attentions to the hen.

It is quite incorrect to say that the cock alone sits, or that during the day the eggs are left to the heat of the sun. The cock and hen sit alternately, regularly and steadily, night and day, during the whole period of incubation. Apart from incubation, it is necessary that the eggs should be covered during the day as a protection, in many parts, against small carnivora and monkeys; against the inclemencies of the weather, such as the frequent and violent hail and rain storms which sweep over the country; and against the great heat, which in the summer is almost tropical. The heat from the direct rays of the sun striking upon unprotected eggs, when, after incubation, development has once set in, is so great that it would kill them. Sand thus exposed becomes so hot that even a hardened hand can scarcely endure it. On an average summer's day I tested the heat of the sand, keeping the thermometer in the shade, and found it to be 150° Fahr. The maximum temperature allowed to eggs in an incubator is 104° Fahr., though a few degrees more, if not maintained too long, are not greatly injurious; but if the thermometer stands at 150° Fahr. for some hours daily, chicks will not incubate. However, argument is quite unnecessary; the hen sits on the eggs every day—of this there is no doubt whatever; they are not left to the heat of the sun; if they were, no chicks would ever result; they are covered by the birds during the whole period of incubation.

There are several interesting points connected with the process of sitting. For instance, the time is admirably arranged