For a more detailed explanation of the ethnic makeup of Bohemia during/immediately preceding this era and the influx of settlers (called proto-colonization by some historians, but its really kind of not), check out Central Europe in the High Middle Ages: Bohemia, Hungary and Poland, c. 900-c. 1300 by Nora Berend, Przemysław Urbańczyk, Przemysław Wiszewski, Chapter 5: Society and Economy (p. 250), and Chapter 7: New developments of the 13th Century (The Mongol Invasion; p. 244).
Theres also East Central Europe in the Middle Ages, 1000-1500 by Jean W Sedlar, Chapter 13: Ethnicity and Nationalism (p. 401) to read more about the integration of the Turkic-speaking Cumans into the overall identity of the region. Keep in mind, however, that many of these distinctions do not reflect race as we think of it or have it now, but denote religious and/or ethnic affiliations. Which is not the same as race. It does however, show just how diverse and well-traveled the general population was at that time, and how much immigration to the area there was: from Italy, Greece, Germany, Turkey, and Central/South Asia.