I've looked hard, very hard, but I've never seen a bittern, which is why I'm desperately trying to find time to get to our Rye Meads nature reserve just north of east London.
I'm not one of those who'll bear discomfort to see a particular bird, but for a bittern, I might defy the cold snap. Especially as it's the cold weather that's forcing these shy and well camoflaged birds out into the open where they can be seen.
They were once declared extinct in Britain and Ireland, but we now have some 75 breeding male bitterns. We know this not because we can see them, but because we can hear them. In the mating season the males make a distinctive and spooky booming noise, and that's how we keep track of them.
So, Rye Meads volunteers and staff have been toiling to create a reedbed rich area, full of fish, that will act as a magnet for bittern... and guess what. It may have paid off, as two have been spotted on site. Much of the wetland habitat is frozen, so the bittern have to venture to the edges of the dense reedbeds to seek food, where there is free flowing water.
I was there recently, before the bittern were spotted. I'm unlikely to have another excuse to visit for a while. Instead, I'm staying in the warmth, presenting prizes for our Life Between the Lines competition winners. This is the second year London Underground have worked with us to highlight the great wildlife found in the Capital. I'll also be practicising my moves to celebrate Bird is the Word getting to the coveted Christmas number 1 spot, watch the video for top dance tips from my fellow RSPB staff... less 'strictly come dancing', more 'night out with your mates'!