In July 1983 I sat in the backyard of a friend's home in Laurel Maryland where we listened to a Northern Mockingbird going through his repertoire of voices. Because this bird was so prolific with the number of songs it knew, Danny and I decided to make a checklist of all the species it mimicked. By the end of the day we counted 34 species that this Mockingbird had mimicked almost to perfection. One of them was a Western Kingbird.
At first I was a little baffled by how a Northern Mockingbird living within spitting distance of the Chesapeake Bay in Maryland could know the voice of a decidedly western species like Western Kingbird. Over time it dawned on me that the Mockingbird may have encountered a Western Kingbird (or plural) in the winter in Florida where Western Kingbirds are fairly regularly as a wintering species.
That made sense. However how do you explain the Northern Mockingbird I watched yesterday (June 18, 2009) as it repeatedly uttered the song and call of a Black-billed Magpie!
This range map from the Cornell Laboratory of Ornithology shows the normal range of Black-billed Magpie in North America. While looking at the range map note how incredibly far the west coast of Florida is from the normal range of Black-billed Magpie. How on earth did this Mockingbird in my yard learn a Black-billed Magpie's voice and be able to mimic is so perfectly. Was it innate or did he just randomly sing the Magpie's voice? Baffles the hell out of me!