curiously, current usage in British English is always plural

“he conducted his research under the auspices of the Spartan Soldiers Society” 

“perusing that tightly muscled body he knew the auspices were favourable”  

6 minutes ago, drpaladin said:

This is the usage I see most often.

with Spartan soldiers & tightly muscled bodies?  

54 minutes ago, Zombie said:

with Spartan soldiers & tightly muscled bodies?  

Yes, I see that as being very auspicious as well.