FINCHforum

When I raised chickens eventually I began feeding them sardine cat food as a protein suppliment, and they started to shine beautifully. It seems like it was the oil in the sardines that really got them there. Birds produce their own oil from glands beneath their tail, but could it help them to get fish oil in their diet? They get oil from seeds I guess, but I haven't seen any finches that look real shiny like that. I feed them meal worms. What else is good for protein? Do any of you feed flightless fruit flies, and if so, how do you get them from the container and present them to the birds?

For protein I just feed hard boiled eggs, has everything they need.

Supplying a good quality varied diet will go a long way to getting finches in good feather. Bear in mind they don’t often display that same lustre you may see in chickens, possibly the actual feather structure has something to do with it too.
You can overdo it with proteins and oils and it will be detrimental to their body function & breeding. It's our nature to give them everything we think we need to give them and then just a bit more in case! We must moderate ourselves too.