In Croatia, Širko families are mainly Serbs, equally Croats (from Sibenik ). In the past century, relatively most of Croatian residents bearing this family name were born in Sibenik and Knin.
Prevalence
About 40 people with faimily name Širko live in Croatia today, in 15 households. There were 20 of them in the middle of the past century, and their number doubled. They are located in threee Croatian counties and threee other places, mostly in Golubic (<10), Sibenik (<5), Radonic (<5), Knin (<5), and in Opatija (<5).