Sentence:  Given that a combination of factors have "released" males from attending nests, why have some species organized their courtship bouts in <WSD>leks</WSD>, especially the tightly clumped <WSD>leks</WSD> that are typical of manakins and cocks-of-the-rock? 
Meaning of the word marked with <WSD> tags:  an aggregation of male animals for the purposes of courtship and display