Sentence:The skies were also filled with a [e1]desert[/e1] of [e2]lapwings[/e2] and a congregation of golden plover, mixed together in a cloud of birds which filled the sky as they escaped a passing (but unseen by me) predator.
 e1: desert. 
 e2 : lapwings.
Answer: Member-Collection(e2,e1)