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<< {Woodhoopoes are perfectly good endothermic homeotherms, they simply 
practice a slightly exagerrated version of the shallow nocturnal 
hypothermia seen in most small birds, presumably as an energy-conserving 
strategy not quite as extreme as true torpor. >>


<< And insulation per se is not of any use to a true ectotherm  _unless_ 
(hypothetically, because no extant etotherms do this) it can be "turned 
off and on", that is, if it could be bypassed completely to allow heat 
gain from the environment and in other circumstances activated to retard 
heat loss. Downy feathers seem to me the least likely form of known 
insulation to be able to accomplish this.>>

My point was that regardless of its "thermocoel of feathers" (sensu 
Houck et al.) it still cannot maintain its body temperature.  I too 
believe that down feathers cannot be sufficient single insulation 
because they bog down in wet conditions and cause hypothermia.  Down 
feathers as single insulators are not advantageous. They were probably 
evolved for some other reason (such as keratin excertion and 
aerodynamics) and then inherited and turned to advantage in an ectotherm 
such as Sinosauropteryx probably was.  What advantage would this be?  
The promise of a more homeothermic body temperature is one.  Many birds 
such as cuckoos, kingfishers, vultures, etc bask and raise their 
temperature regardless of their feathers.  

Feathers can be reasonably seen in an ectotherm.

Matt Troutman

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