THE BUILDERS 51 



and other green things suddenly make a great rush forward, 

 and the summer birds flood in from the south. But occasion- 

 ally a pair of great, or blue, or cole tits is reported building 

 even as early as February, especially in town gardens ; like 

 sparrows and starlings and wood-pigeons they are among 

 the birds which thrive remarkably in modern civilised con- 

 ditions, and tend to change their habits in many respects. 

 House-sparrows do not begin to build until the second half 

 of April in secluded country places where their numbers 

 remain within reasonable bounds. They join in the second 

 great wave of building, which comes distinctly later than the 

 nests of such early species as the robin or thrush or black- 

 bird. But among the gardens of growing towns, and over 

 wide tracts near London and other great cities which are 

 strongholds of their kind, sparrows seem to observe no such 

 rules, and begin nesting in a straggling way from Christ- 

 mas onwards, if the weather is fairly mild. Exactly the 

 same relaxation of habit is seen in the case of the starling, 

 which is another fast multiplying species. Twenty years ago 

 starlings' eggs were not to be expected until the middle or 

 latter part of April, when all the starlings attached to a 

 house and garden used to set to work simultaneously. Since 

 the westward immigration of hordes of starlings from 

 abroad upset the old distribution and feeding habits of the 

 species, they nest almost as early and indiscriminately as the 

 sparrows. The main body begin to build about a fortnight 

 earlier than formerly ; it is hard to say when one may not 

 expect premature sets of the pale blue eggs. 



So even within the cycle of a score of seasons we can see 

 change plainly at work in nature, under the stimulus of the 

 artificial conditions introduced by man. The civilisation of 

 the tramcar and picture palace infects certain birds and 

 animals as well as humanity. The swallow, which was 



