THE DEVELOPMENT OF BIRDS, 231 
some carefully formed open ones, some very rough open ones, 
and some make none at all. Thus the Guillemots are content 
to lay their single egg, without shelter or protection, on the 
naked surface of a ledge of rock, where its conical shape, how- 
ever, affords it a certain help in retaining its place. 
The Penguin is said to carry its one egg about with it in a 
sort of pouch of the skin of the belly; reminding us of the 
Kangaroo amongst beasts. 
The Goatsucker and the Stone-curlew lay their eggs on 
the ground without any previous arrangement for their pro- 
tection, though they are efficiently protected by careful selec- 
tion as to their surroundings. Many Gulls and Plovers lay 
their eggs in a shallow pit. Pigeons only make a nest of a few 
sticks loosely put together. Grebes collect vegetable refuse and 
pile it on some growing water-weed and lay on it. The mounds 
built and supplied with refuse by the Megapodius have been 
already described. The Magpie makes a domed nest which 
bristles with thorns. Some birds make use of burrows, as does 
the Burrowing-owl (Speotyto cwnicularia) and the Sand-martin; 
while our Kingfisher generally makes a so-called nest with fish- 
bones ejected from its stomach, thus differing widely from the 
Sand-martin, which makes a ‘feather bed” in the bottom of the 
burrow it breeds in. The Woodpecker makes use of a hole in 
a tree-trunk, which it perforates. Many small Birds seem to 
moisten and glue together the twigs and straws of their nest 
with their saliva, but the adhesive nests of the House-martin 
are known to all. Some Swifts, however, secrete a saliva 
which rapidly hardens, and so construct a sort of isinglass nest, 
which is the material whereof “ birds’-nest soup” is made. 
The Chaftinch and Goldfinch make admirable open nests, 
but the Wren makes a domed one. Some domed and covered 
nests have a pendent, cylindrical tube, which has to be traversed 
to reach the nest’s interior. 
The Indian Tailor-bird (Orthotomus longicauda) selects a 
broad leaf, and sews the edges together with thread-like fibre. 
The hollow interior it lines with fine grass and vegetable down. 
The female Hornbill retires into the hollow of a tree, the 
opening of which is closed in by her mate with a partition of 
mud, which drying, forms a solid wall, through an aperture left 
in which he assiduously feeds her and her young. 
As arule, only those birds in which the female is dull coloured 
make open nests, Certain Birds in which both the sexes are 
