Earlier this month I watched a flock of robins and starlings feast on the Bradford pears near Heinz Chapel. Birds usually don't sing in the fall but this flock was muttering and whisper-singing. Three birds in particular caught my ear.
A robin sang softly.
A starling mimicked the robin.
A mockingbird mimicked the starling mimicking the robin.
By the time the robin's song came out of the mockingbird's mouth it was nearly unrecognizable. (Click here for the robin's song.)
European starlings, on the left above, are considered mimics but they have wiry voices that distort whatever they say. Here's a typical starling song. At the 00:32 mark he does a good imitation of a house sparrow. I couldn't find an audio clip of a starling mimicking a robin.
Northern mockingbirds, on the right, are much better mimics than starlings. They can follow a robin's tune and cadence but miss the melodious thrush harmony. They brazenly mask this deficiency: "I meant to sing the tune without the harmony." Click here to hear a mockingbird mimicking many birds, including robins.
The mockingbird at Heinz Chapel clearly copied the starling's wiry song including his poor imitation of the robin.
It was like a game of telephone. There were two levels of distortion.