Pressure mounted on beleaguered Hibernian boss Nick Montgomery as his side slipped to ninth in the cinch Premiership following a limp 4-0 defeat at home to resurgent Aberdeen.Leighton Clarkson, Dante Polvara, Bojan Miovski and 16-year-old debutant Fletcher Boyd were all on target as the Dons made it seven league games in a row unbeaten and three victories on the spin since the cinch Premiership split.The victory took Aberdeen above faltering Hibs into seventh place, cranking up the heat on Montgomery whose job was already widely deemed to be under threat after he failed to lead the team into the top six last month.The Easter Road boss surprisingly sent out the same side that started the 2-1 defeat at Ross County the previous weekend, although there was a notable addition to the subs’ bench as Jake Doyle-Hayes returned to the squad after almost nine months out with ankle problems.Aberdeen were also unchanged as they sought to continue their upturn in form since caretaker boss Peter Leven took over from Neil Warnock in March.The Hibees started promisingly and most of the early play was in the Dons half. Nathan Moriah-Welsh had the first notable attempt of the match when he fired just wide from 25 yards out in the 20th minute.Aberdeen keeper Kelle Roos then pulled off a superb double save to deny Myziane Maolida and Martin Boyle.It proved pivotal as the Dons took command of the match thereafter. The visitors signalled their intent in the 26th minute when Polvara saw a low angled shot deflected behind by Chris Cadden after being slipped in by a clever pass from Jamie McGrath.The breakthrough came four minutes later when Clarkson curled home a lovely shot from 25 yards out.Things got worse for Hibs in the 39th when Nicky Devlin dispossessed Jordan Obita and fed Junior Hoilett who cut the ball back for Polvara to fire home a firm angled strike from 15 yards out.The Dons finished the first half firmly in the ascendancy and Miovski headed over at the back post following a corner from Hoilett.Aberdeen’s third came seven minutes after the break when Miovski drilled in a low angled shot from 10 yards out after Clarkson dummied Hoilett’s pass into his path.With thousands of their exasperated supporters long since headed for the exits, Hibs’ misery was compounded with virtually the last kick of the game when teenager Boyd – who had been introduced as an 83rd-minute sub – capped a dream debut by slamming home the Dons’ fourth from close range.