GREAT CRESTED GREBE. 24.7 
always in different stages of incubation. It is well 
known that Grebes cover their eggs with nesting 
material during incubation, but the reason of their so 
doing is not clear. Single unstained, and consequently 
conspicuous, eggs are never covered; whereas when in- 
cubation commences, and the need for concealment is 
less, the eggs are always covered by the sitting bird on 
leaving the nest, and uncovered on its return. The 
rotting and fermenting mass generates considerable heat, 
as may be easily proved by thrusting the hand deep 
into the nest, and it is possible that the object in cover- 
ing the eggs is actually to assist in incubation during 
the bird’s absence.1 The porous chalky surface of the 
eggs readily absorbs the juices exuding from the rotting 
vegetation, and they become increasingly discoloured 
as incubation advances. Both sexes participate in 
incubation; and additions to the structure are con- 
tinually made by the bird which is not sitting, until 
the eggs are hatched. 
The old Grebes are assiduous in their attention to 
their offspring for several weeks after birth. When first 
hatched, the young are carried on the back of one of 
the parents, whilst the other adult is engaged in fishing, 
and during the first few days of their existence they 
are never in the water for more than a few seconds 
at atime. The old bird, when carrying the young, sits 
higher in the water than usual, and by slightly raising 
the wings provides a safe cradle for the nestlings. The 
young at first are invisible from the shore, and their 
presence is only indicated by the pose of the old bird. 
We have never known this species to dive with the 
young on its back, as some Grebes are said to do.? 
1 Cf. Seebohm, op. cit. vol. iii. p. 457. 
2 Ibid. p. 471; and Saunders, op. cit. p. 722. 
