h anging ▁branch , ▁though ▁apple ▁and ▁al der ▁trees ▁have ▁also ▁been ▁used . ▁The ▁nest ▁is ▁often ▁built ▁on ▁the ▁base ▁of ▁large ▁p ine ▁con es ▁and ▁somewhat ▁res emb les ▁a ▁p ine ▁cone ▁itself . ▁A ▁nest ▁may ▁be ▁used ▁repeatedly ▁over ▁the ▁course ▁of ▁several ▁years . ▁Two ▁eggs ▁are ▁laid ▁from ▁late ▁May ▁to ▁early ▁July ▁and ▁are ▁inc ub ated ▁for ▁ 1 5 ▁to ▁ 1 6 ▁days . ▁The ▁young ▁are ▁capable ▁of ▁flight ▁about ▁ 2 0 ▁days ▁after ▁h atch ing . ▁ ▁Court ship ▁display ▁and ▁son ation ▁During ▁court ship , ▁a ▁male ▁cal li ope ▁hum ming bird ▁ho vers ▁at ▁acceler ated ▁wing be at ▁frequency ▁up ▁to ▁ 9 5 ▁f laps ▁per ▁second ▁( 4 2 % ▁higher ▁than ▁normal ▁hover ing ), ▁ ▁creating ▁a ▁loud ▁bu zz ing ▁sound , ▁with ▁thro at ▁fe athers ▁pro tr ud ing ▁and ▁facing ▁a ▁female . ▁The ▁male ▁then ▁asc ends ▁tempor arily ▁to ▁ 2 0 ▁meters ▁and ▁div es ▁at ▁high ▁speed , ▁with ▁the ▁rapid ▁descent ▁causing ▁son ation ▁of ▁wing ▁and ▁tail ▁fe athers ▁combined ▁with ▁vocal ization , ▁int ending ▁to ▁attract ▁attention ▁of ▁the ▁female . ▁Research ▁in ▁a ▁wind ▁tunnel ▁demonstrated ▁that ▁the ▁male ▁court ship ▁display ▁includes ▁sounds ▁produced ▁by ▁three ▁independent ▁fe ather ▁or ▁vocal ▁components , ▁each ▁with ▁different ▁ac oust ic ▁characteristics , ▁thus ▁potentially ▁containing ▁different ▁messages ▁appe aling ▁to ▁the ▁female .