Birt families are Croats and they are mostly from Bjelovar area. In the past century, relatively most of Croatian residents bearing this family name were born in Bjelovar and in Bjelovar area.
Prevalence
About 100 people with faimily name Birt live in Croatia today, in 40 households. There were 90 of them in the middle of the past century, and their number increased by 10 percent. They are located in 7 Croatian counties, in 11 cities and 14 other places, mostly in Cazma (15), Lukarisce (10), Miholec in Krizevci area (<10), Bjelovar (<10), and in Gradec in Vrbovec area (<10).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.