4 
Is your problem with the long ''song" phrases in Callicebus the 
same song problem as in birds - why the seemingly unnecessary 
complexity? Are these displays functionally equivalent? I 
have 2 net necessarily exclusive thoughts based on the tyrannids. 
1) Complexity is being favoured for 2 ends (species and individual 
recognition) and there is no (?) countering selection pressure - 
hence the process carries on under its own momentum; 
2) The "dawn song” of T. tyrannus contains units which, in a way, 
represent the entire vocabulary of the species, arranged in a highly 
fixed order. This may be illusionary. It may be that a kingbird when 
"singing” has highly mixed emotions - to seme degree all of his buttons 
are pushed, but he can’t do anything about it (as he’s usually singing 
in predawn darkness, or when extremely frustrated). It may be a 
sure-fire way of identifying the s re cies - other individuals are 
supplied with a completed vocabulary organized into a p&ttern, with 
variatiens in the pattern giving xpscxBX identity. The redundancy 
individual 
would be tremendous, but would permit absolute identification in any 
sonic environment. 
I don’t find any of these explanations really 
satisfying. Are we asking the equivalent question to "why does this 
beetle have 60 spots of white on his elytra and net 59, 61, or 30?" 
£>est regards to all. Susan sends her greetings to you, 
the Rs, and Stan, if he’s arrived. 
