Jan M. Swart and Vít Zavadil A Corn Bunting (Emberiza calandra) imitating Yellowhammer (Emberiza citrinella) song Article published in Sylvia, 2015. Recordings of this bird are on Xeno-canto: XC246734, XC246735, XC246736, XC246737, XC246738. Here is an aberrant yellowhammer also mentioned in the article: XC246739. The corn bunting is also on Youtube. (The sound quality of the video is unfortunately very bad.)

A Similar case I was informed by Ivan Zídek from Žďár nad Sázavou about a case similar to the one described in the article above. On July 3, 12 and 16, 2014, at the fishpond Homolů near Nové Veselí, a Corn Bunting was observed. On July 12, in a break between songs, the bird made sounds "tsrt tsrt" similar to Yellowhammer. At one moment, it sang like a Yellowhammer "dza dza dza dza dza dza tá · · · · · ·_", then at one place it changed back to the song of Corn Bunting. According to the observer, Corn Buntings are unusual in this area but Yellowhammers are common. At least two Yellowhammers sang near the Corn Bunting.