I have received an email from a man named Engelbart Rolf from a website that has church records from Posen. He was letting me know that the Zierkes actually didn’t live in Posen (Jastrowie is in West Prussia, just over the border from Posen). I have written him back asking about the Schmidts who lived in Gornitz and Wirsitz.
Evangelisches Zentralarchiv in Berlin Kirchenbuchstelle
Bethaniendamm 29, 10997 Berlin
Tel. 030 / 22 50 45 34
Fax 030 / 22 50 45 40