114 THE STORY OF THE BIRDS. 
and perhaps part of the same material over again. 
Such are bluebirds, chickadees, wrens, crested flycatch- 
ers, and some swallows. Of course with the wood- 
peckers, house cleaning in the spring is simply the 

Sand martins. 
result of the year’s disinfection. Sand martins or 
bank swallows and some woodpeckers make new 
holes each year. But where a bluebird takes an- 
other bird’s nest, she is often quite particular about 
