|American Goldfinch in the winter plumage|
I think that is quite funny because even though they lose their bright yellow feathers in the fall, I find their song especially warm and sunny in the winter.
They sing a series of musical warbles and twitters. A tsee-tsi-tsi-tsit call is often given in flight and at the feeders I often hear them end their sentence with a honey-bee? You can listen to a clip HERE. Or go to Cornell's website at: http://www.allaboutbirds.org/guide/american_goldfinch/sounds