▁ 2 0 1 2 ▁have ▁placed ▁the ▁number ▁at ▁around ▁ 3 2 , 0 0 0 ▁birds . ▁ ▁E colog ical ▁impact ▁Conc ern s ▁have ▁been ▁raised ▁over ▁the ▁impact ▁of ▁the ▁growing ▁numbers ▁of ▁par ake ets ▁in ▁south - east ▁England . ▁Scient ific ▁research ▁program mes ▁have ▁anal ys ed ▁the ▁behaviour ▁of ▁par ake ets ▁and ▁found ▁that ▁they ▁comp ete ▁with ▁native ▁bird ▁species ▁and ▁b ats ▁for ▁food ▁and ▁nest ing ▁sites . ▁Although ▁not ▁ag gress ive , ▁par ake ets ▁d eter ▁smaller ▁birds ▁with ▁no isy ▁gre g ari ous ▁behaviour , ▁and ▁their ▁large ▁size ▁means ▁that ▁they ▁often ▁crowd ▁small ▁bird ▁feed ers . ▁The ▁det r iment al ▁effect ▁of ▁compet itive ▁ex clusion ▁has ▁been ▁li ken ed ▁to ▁the ▁impact ▁of ▁the ▁introduction ▁of ▁grey ▁squ ir rel ▁on ▁the ▁red ▁squ ir rel . ▁However , ▁British ▁par ake ets ▁are ▁not ▁without ▁natural ▁pred ators ; ▁orn ith olog ists ▁have ▁observed ▁an ▁increase ▁in ▁the ▁population ▁of ▁birds ▁of ▁pre y ▁in ▁London , ▁and ▁have ▁reported ▁sp arrow h aw ks , ▁per egr ine ▁fal cons ▁and ▁h obb ies ▁pre ying ▁on ▁par ake ets . ▁ ▁Par ake ets ▁are ▁considered ▁a ▁p est ▁in ▁many ▁countries ▁such ▁as ▁Israel , ▁where ▁large ▁sw ar ms ▁of ▁par ake ets ▁can ▁have ▁a ▁dev ast ating ▁effect ▁on ▁certain ▁cro ps , ▁and ▁there ▁is ▁concern ▁that ▁the