Sentence:  Most species seem to prefer a ready-made hollow such as a deserted mouse nest , a bird house , or the hole made by a <WSD>woodpecker</WSD> ; some show a definite liking for making their nest in moss . 
Meaning of the word marked with <WSD> tags:  bird with strong claws and a stiff tail adapted for climbing and a hard chisel-like bill for boring into wood for insects