Sentence:  Two studies of British civil servants, for example, suggest that those at the top of the heap are less stressed than those near the bottom. Work on other species, too, indicates that when it comes to pecking orders, the peckees are more stressed than the <WSD>peckers</WSD>. 
Meaning of the word marked with <WSD> tags:  Someone who or something that pecks, striking or piercing in the manner of a bird's beak or bill, particularly: