Ravens? In Hertfordshire?

I have had a lot of difficulty choosing my photo for today as I had so many good ones, but I had to pick this. These two flew over me while I was trying to hide from a blue tit. I would have thought "blimey those are big crows" if one had not started calling. Ravens are not common in the UK and normally reside in the mountainous regions, so finding one let alone a displaying pair in Hertfordshire made my day. Ravens may be jus big crows but being as large as a buzzard it is a lot more than just a big crow.

http://www.rspb.org.uk/wildlife/birdguide/name/r/raven/index.aspxhttp://www.allaboutbirds.org/guide/Common_Raven/sounds