A closer examination revealed thousands of very thin, fine stalks of some type of fungus. Remembering some of the mycological marvels that have been posted recently, I dutifully gathered a sample and put it under the scope. The tiny fruiting bodies (?) were beautiful yellow spheres atop thin white stalks. I have no idea about an ID... perhaps someone can point me in the right direction. The diameter of the yellow sphere was 0.65mm, the stalk diameter was about 0.17mm.
Olympus 4/0.16 S Plan Apo, Canon 350D
Nikon 10/0.30 CFN Plan, Canon 350D
I have never encountered the smaller side of myxos and have only seen them mentioned once or twice but nothing about them in great detail. It would seem that like the larger myxos, up to 10mm, they too are even more so less noticed, except by those who diligently search for them or come across them by chance. Beautiful images Charlie 
, if possible. You are correct in referring to it as a “fruiting body.” I would almost bet this is a very tiny myxo, some plasmodia are microscopic and do produce fruiting bodies that are either microscopic or near microscopic. However you like most of us, should be I the dead of winter and myxos don’t do well in the cold. However, stranger things have happened. Where is your bird feeder located? Would or could it support temperatures above 60°F?