▁may ▁be ▁pol yg am ous , ▁then ▁having ▁to ▁feed ▁two ▁females ▁and ▁later ▁two ▁bro ods , ▁either ▁simultaneously ▁or ▁consec ut ively . ▁ ▁M igration ▁The ▁Mont agu ' s ▁har rier ▁is ▁a ▁long ▁distance ▁migr ant . ▁Bird s ▁from ▁E uras ia ▁spend ▁the ▁winter ▁in ▁sub - S ah aran ▁Africa , ▁while ▁those ▁from ▁the ▁eastern ▁part ▁of ▁the ▁range ▁migr ate ▁to ▁the ▁Indian ▁sub cont inent . ▁In ▁Europe , ▁the ▁first ▁birds ▁start ▁to ▁move ▁at ▁the ▁beginning ▁of ▁August ▁and ▁most ▁have ▁left ▁by ▁mid - Oct ober . ▁They ▁travel ▁over ▁a ▁broad ▁front , ▁crossing ▁the ▁Mediter rane an ▁at ▁various ▁points , ▁and ▁only ▁a ▁small ▁number ▁are ▁observed ▁at ▁migration ▁cho ke ▁points . ▁Western ▁birds ▁don ' t ▁go ▁further ▁south ▁than ▁the ▁g ulf ▁of ▁Guinea , ▁but ▁some ▁eastern ▁birds ▁travel ▁as ▁far ▁as ▁South ▁Africa . ▁In ▁Africa , ▁their ▁di et ▁is ▁composed ▁mostly ▁of ▁insect s ▁and ▁birds , ▁and ▁it ▁is ▁possible ▁that ▁they ▁follow ▁loc ust ▁sw ar ms . ▁▁ ▁Spring ▁return ▁pe aks ▁in ▁April , ▁and ▁most ▁birds ▁have ▁arrived ▁by ▁May ▁though ▁there ▁is ▁evidence ▁that ▁first - year ▁ju ven iles ▁spend ▁their ▁first ▁summer ▁in ▁the ▁winter ▁qu arters ▁ ▁Conserv ation ▁issues ▁In ▁western ▁Europe , ▁an ▁estimated ▁ 7 0 % ▁of ▁bre eding ▁pairs ▁nest ▁in ▁agricult ural ▁far ml ands , ▁especially ▁c ere al ▁cro ps .