HI

There is enough information to answer this question . Let H , T , B denote head , tail and body respectively .

H = 12

T = H + 1/2 B , multiply the whole thing by 2

2T=2H+B

B=2T-2H ---1

B=H+T --- 2

1=2 , 2T-2H=H+T

T=3H=3(12)=36

B=H+T=12+36=48

So the length of the bird would be its head + tail + body = 12+36+48