Over the last couple of weeks we have begun to see signs of spring. We have had male marsh harriers sky dancing, the cranes have been dancing and many other birds are starting to sing to mark out their territories. As I’m sure you know male bitterns are the Barry White’s of the bird world and produce a wondrous low booming sound to mark out their territories. At this time of the year the male bitterns have not quite tuned up their vocal cords so we describe them as ‘grunters’ rather than ‘boomers’. Recently we have had a couple of reports of bitterns starting to call so to see how the boys were progressing Katherine organised a little early morning session for a few of us to see how many bitterns we had grunting around the reserve. We assembled at the visitor centre for 7AM for an hour and half of listening before we had to get back to open the Centre.
I was lucky and heard two different birds grunting in Norfolk Fen. I don’t have the best hearing but even I could tell there were two distinct voices producing the sounds and the sounds were clearly coming from different parts of the reedbed. I'm sure the two bitterns could hear each other and thus there was some competition going on. Suzanne heard another bird from Joist Fen viewpoint and we have had reports of a bird calling in New Fen North so it definitely worth listening out if you visit us.
Bittern image credit: Dave Rogers
So why do the males boom? Well they are telling other males that this is their patch of reedbed so clear off. They are also trying to attract female bitterns in to breed. The males put a huge amount of effort into producing a full on boom. I have heard figure that they add an additional 30% body mass to develop the throat muscles to make that amazing sound. So a male that can produce a full deep Barry White style boom is saying to the female bitterns ‘look ladies I have great genes, I have got through the winter in great condition I am the one you want to mate with….’ If it is a hard winter only the best males will boom and some will stay as grunters, not able to produce a full on boom that can carry for miles.
We are in the process of finishing off our winter work programme. Katherine and Emma have been adjusting water control sluices to buildup the water levels in the reedbeds to get them at the optimal height for the breeding season ahead. Most areas are nearly where we need them to be, with Joist Fen North being the only one we still have to add significant water too. We want to cut a little more reed in front of the viewpoint which we hope to use to re-thatch the roof of the shelter. Weather permitting our volunteers will be helping us with that this week. Once that is done then we will raise the water level in there too.
Both cranes pairs in the area of reed cutting after raising water levels. Video credit: Dave Rogers
Most of the tree felling is now completed in the West Wood and you can now clearly see the alder trees that were being suppressed by the taller poplars.
So our wildlife knows that spring is not far away and things are hotting up so do pay us a visit and see and hear some of the action for yourself.
David Rogers Senior Site Manager - Lakenheath Fen