Construction employment declined for the third time in the past four months in May as nonresidential contractors coped with lengthening and unpredictable delivery times that limited their ability to start or complete projects, according to an analysis by the Associated General Contractors of America of government data released today. Association officials added that many contractors report they are having a hard time finding qualified workers to hire as some people remain reluctant to return to work while their children are learning from home, or they are collecting elevated unemployment supplements.