Alan, I'm not sure. Actually I first thought it was a grey heron, but the picture on the German wikipedia page is different. The page of the (German) Kanadareiher looks much better. And that is the Great Blue Heron in English.
I understand your point Daniel, but the top photo you refer to is an immature bird, if you scroll down you'll see a breeding grey heron like yours.
Actually, it's quite simple; if the bird is in North, Central or South America it's a great blue. But if it's in Europe, Asia or Africa, it's a grey.
But I agree with Stuart, they are wary birds - so this is a good shot!
Thanks Alan for pointing out. I wasn't aware that the top picture of the German Wikipedia article is showing an immature bird (bad, they should at least have written that). I also looked at the English article and yes, I agree, it must be a grey heron, because the GBH "differs in slightly larger size, and chestnut-brown flanks and thighs".