An unfamiliar whistle-chirp call caught my ear when I was exiting Dunback Meadow in Lexington, Massachusetts, on December 10, 2024. The simple tone was difficult to track down; every time I was certain of the direction, all I saw were American Robins. Eventually, I watched as the closest robin, perched alone just in front of me in the sumac, made the unique call, interspersing it with the more familiar robin kuk.

This spectrogram shows the unfamiliar whistle-chirp call (left) with its lowest tone at roughly 2 kHz and only one overtone, contrasted with a standard kuk call (right) with its lowest tone at roughly 1 kHz and overtones repeating through the highest frequencies. The full spectogram can be found at https://macaulaylibrary.org/asset/627357873. Image credit: Andrew Whitacre and Macaulay Library.