14 BRITISH BIRDS, THEIR EGGS AND NESTS. 
or instinctively use for building their nests, to adopt instead of 
sticks the sea-weed stems which their home does produce. And 
so too of the House-Sparrow, which builds a huge domed or well 
covered-in nest, if it selects a tree or ivy for its site, but only 
lines the bottom of the hole in thatch, or a wall, with abundant 
feathers or hair or straw. The Wren, again, which usually 
builds its nest so that it may easily be removed entire and com- 
pact, may be found to avail itself of such a site for its nest, 
that it may be built on the principle of application—like the 
Martin’s to the wall beneath the eaves—so that, when taken from 
its site, it shall appear to have had a segment completely cut out 
or sliced off from it. 
The adaptation of materials to site also, so as to secure a 
greater degree of concealment by making the intrusive structure 
assimilate in external fabric and hue to the surrounding objects, 
is well worthy of ‘noticing attention, as supplying not only fresh 
sources of seeming unlikeness in nests of the same species of 
birds, but also fresh instances of the lMttle feathered architect’s 
wonderful adaptive intelligence. : 
The question,—Why are Birds’ Eggs, in so many cases, so varl- 
ously and beautifully ornamented? Why are their hues and 
markings made so attractive to look at? has often been asked, 
and two or three different answers or modes of answer have been 
suggested. I have seen the idea started that the design of such 
various colouring and marking is intended to facilitate conceal- 
ment, by the adaptation of the general hue of the egg to that of 
the recipient or supporting substances. The theory is at least 
otginal and amusing; but unfortunately less happy than when 
applied to the plumage of the birds themselves which lay the 
egos. It is no easy thing to detect a Partridge as she sits, 
lifeless-seeming, amid other objects not more still than herself, 
