Sentence:  At the very moment he cried out, David realised that what he had run into was only the Christmas tree. Disgusted with himself at such cowardice, he spat a needle from his mouth, stepped back from the tree and listened. There were no sounds of any movement upstairs: no shouts, no <WSD>sleepy</WSD> grumbles, only a gentle tinkle from the decorations as the tree had recovered from the collision. 
Meaning of the word marked with <WSD> tags:  Suggesting tiredness.