PAIRING. 71 



the female alone to procure the requisite supply. 

 Rooks, for example, which feed their young upon 

 the grubs of chafers and similar insects, have often 

 to make long excursions from their nest-trees be- 

 fore they can find the required prey; and if this 

 task were assigned to the female alone she could not 

 obtain enough to sustain her own wants and the in- 

 cessant cravings of five young ones, which will readily 

 devour their own weight of food in the course of a 

 single day. Accordingly, when rooks, as they some- 

 times do, build a second nest late in the season, in 

 consequence of the first being destroyed, they find it 

 scarcely possible to rear their young ; the warmth of 

 the advancing summer drying up the ground and 

 forcing the grubs and worms so deep into it as to 

 be out of reach, while, the operations of plough- 

 ing and digging having almost ceased, they have 

 little aid from the labours of man. In such cases it 

 has been remarked, that " the constant clamour of the 

 young for food, so unusual in nestling birds, renders 

 it manifest that the labour and exertion of the parents 

 cannot supply a sufficiency for their requirements*." 

 If then the difficulty is so considerable when both 

 parents conjoin their labours, it may be inferred that 

 it would even in ordinary circumstances be too much 

 for the female alone, more particularly as her energies 

 must be somewhat impaired by the previous fatigue 

 undergone in the process of hatching. During this 

 process the aid of the male is no less indispensable 

 than in feeding the young. 



It is obvious, that while the hen has to sit for a 

 number of days in order to hatch her eggs, and can- 

 not, as we shall afterwards see, leave them for many 

 minutes, without incurring the risk of destroying 

 the embryo chicks, she must either run this hazard 

 or perish of hunger, unless she had food brought to 

 * Journal of a Naturalist, p. 257, 3d edit, 



