242 



EVOLUTION OF BIRD- SONG 



12 



Ni N IS 1^ 



=5=?=!?=i: 



:l5=qsii 



-^_&. 



13 



i^te^^ 



^ 



j^=i5 





a 



16 



W— I— u 



B 



I 



:S==il: 



i-M:4?3^ 



17 



N ! 18 



1^=*: 



-^_ 



iil 



3= te^ 



5=1: 



*=Jt 



21 



^I^i3^! 



T--r^: 



i«r=S 



^ 



r5="= — u 



22 



i^ 



l^ii^^=i^ 



i 



^j 



^^i^^?^^3^iiiii 



23 



a3fe&=*=^4: 



j?=fa=:^=S=d5=S-4is^=fcs 



:S==S=t^^=S;=:S; 



