144 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
their adaptation to circumstances, whether it be for concealment or 
deception. All seems to have been fully considered, and the nest is so 
cunningly disguised that it seems a part of the tree trunk or mass of 
rock on which it is placed, and thus deceives the passer-by. We 
have only to examine the nest of the Chaffinch or that of the Golden- 
crested Wren to see how beautifully they are constructed of moss, 
wool, and various other materials, all interwoven and felted together 
with cobwebs, and interspersed with lichens. Take again the nest of 
the Long-tailed Tit, or that of the Willow Wren—both of which are 
domed, and equally beautifully made,—and see how artfully the 
entrance is concealed by a feather or a stray leaf. 
Turning now to nests of a different type of construction, let us 
examine the nests of these veritable house masons, the Swallow and 
House-Martin. See how cleverly and artistically they attach their 
buildings to ours, seizing on some slight projection of the wall or 
beam for a foundation; and as the plasterer works up his plaster with 
hair, so do the Martin and Swallow mix the mud for their nest with 
fine grass and other material. The whole is then firmly cemented 
together with a glutinous secretion which the bird emits, care being 
taken that each layer is sufficiently dry before the next is added. 
Look again at that prince of miners, the little Sand-Martin, with what 
marvellous skill and dexterity it excavates the perpendicular face of a 
sand or gravel bank in which its future nest is to be. Mining opera¬ 
tions are commenced by first forming a small hole, the bird clinging 
to the steep face, sometimes head downwards, and pegging away at 
the opening with closed bill, which its muscular neck enables it to do 
with great effect. In this way it loosens the material much in the 
same way as the collier does with his pick, and the loosened sand 
and gravel fall down belov/. The excavation proceeds at a slightly 
upward incline, which facilitates both digging operations and drainage. 
Should a stone or other hard substance intervene in the course of the 
tunnel, the passage is diverted to right or left, and thus the tunnels 
are not always in straight lines. Sometimes a large boulder is met 
with, and the work has to be begun afresh. When a sufficient depth 
has been attained, the hole is widened to a diameter of five or six 
inches. The flooring on which the scanty nest of grass and feathers 
is placed is kept flat, and on this six white eggs are placed. 
Some birds make no nest at all, but a mere depression in the sand 
in which the eggs are laid, as in the case of the Ring Plover and 
others. Some lay in the hollow of a tree, the decomposed wood 
forming the nest. Others, again, such as the Horned Owl, and some 
of the Hawks, use a deserted nest, such as that of the Raven or 
Hooded Crow. The Peregrine Falcon also frequently does the same, 
while others of the same family, such as the Kite, Osprey, Eagle, 
