No. Switezianka is correct. They couldn`t be ravens. Neither were they crows. So what?
They were rooks.
I saw rooks as well - beautiful birds, but the ones near my home are definitely ravens pl.wikipedia.org/wiki/
Rooks (and there are plenty round Warsaw) have a very distinctive sound, and also appear this time of year. The part of Warsaw I live in is very green, a lot of wild birds, hedgehogs etc. Not long ago, I saw some sort of mammal at night. Definitely larger than a rat, but nothing I recognised. It could have been a polecat or weasel but was moving too fast (my dog was chasing it) for me to get a good look. Amazing to see something like that so close to the city centre. And counting birds is a fun superstition - One for sorrow, two for joy etc...