Birek families are Croats and they are mostly from Petrinja area. In the past century, relatively most of Croatian residents bearing this family name were born in Velika Gorica and Zagreb.
Prevalence
About 80 people with faimily name Birek live in Croatia today, in 40 households. There were 90 of them in the middle of the past century, and their number decreased by 10 percent. They are located in four Croatian counties, in 6 cities and 11 other places, mostly in Donji Vukojevac in Petrinja area (15), Velika Gorica (15), Zagreb (<10), Kljucic Brdo (<10), and in Petrinja (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.