At first I thought "What the hell?" because it looked like a red-bellied woodpecker with a fluffy gray head rather than the usual red-tan. It had the same tweed back as the adult with it. I was trying to figure out what it was--it was nearly as big as the adult, and I was thinking maybe it was a different species--when the adult plucked a chunk out of the suet feeder and the juvenile scooted over and shoved its head practically down the adult's throat. The adult continued feeding it for a minute, pulling suet out of the feeder and then holding it for the baby to get at, and then they both flew off.
I feel terribly privileged. I have no idea when most birds nest, so it didn't even occur to me that there'd be babies in the yard.