There's an old saying that says "From January to June, the bittern will boom."
......Well it isn't quite as reliable as that, but this week we've had the first booming of the season! A bittern has been heard on Barrow Scout Field which is of course absolutely fantastic! Due to this momentous sign of spring I thought I would look at bitterns in my history blog this week as part of our 50th anniversary celebrations.
So what is booming and why do bitterns do it?
Booming sounds like the noise you would create if you blew over the top of an empty glass bottle. It is the sound made by male bitterns in spring to attract the ladies and to establish their territory. Bitterns are an incredibly shy bird, that skulks in the reedbeds often unseen. Booming is a way of telling how many males you have in a given reedbed, and is used to approximate populations.
So aside from a strange noise, what is so special about these birds?
There were once lots of bitterns throughout Britain, as their preferred home is reedbed, which was also common around the country. Bitterns were so numerous in fact that they appear on the feast menus of medieval banquets. They were often called 'butterbump' as they have a thick layer of fat which means they are self-basting when cooked!
However, over the centuries, reedbed has largely been lost through drainage for agriculture and development. With the decline of reedbeds, came the demise of bitterns. The low point came in 1997, when there were only 11 booming males left in the entire country. They were almost wiped out.
Thankfully, the RSPB is supported by 1.1 million marvellous members. With these funds we have been able to restore and create new reedbeds around the country, in places like our Ham Wall nature reserve in Somerset. Other conservation organisations have done this too. Together we have been able to bring the bittern back from the brink and there are now over 100 booming males around the country.
Bittern by Andy Hay (rspb-images.com)
So what's the story at Leighton Moss
Well ironically, when there were only 11 booming males in the country, five of them were here. However, we now have just the one. There are likely to be several factors affecting the fall in numbers.
Whilst Leighton Moss is the largest reedbed in the north west of England, we are pretty far from the next nearest breeding populations of bitterns. When bitterns fledge the nest and become independent of their mother (the father has nothing to do with their upbringing), they leave the reedbed they were born in to find their own territories. Because of the distance between us and the next populations (places like our Old Moor reserve in south Yorkshire and our Blacktoft Sands reserve on the Humber) we simply aren't getting the new young birds in. We do get an influx of bitterns from Europe every year, as they come across to spend the winter here. There are sometimes up to 10 (I have been lucky enough to have seen five at once from Public hide on a frozen January day). However, these birds have their own territories back home and so fly away in early spring and so don't add to our breeding population.
Another factor affecting the reduced bittern numbers at Leighton Moss is the overall age of the reedbed. Bitterns like younger reedbed to fish in. Despite the huge amount of work carried out by the Leighton Moss Wardens and volunteers every year to artificially hold back the aging process by cutting areas of reed to re-grow, the overall age of the site is still very old. In order to combat this, back in 2000, thanks to some funding, we purchased Barrow Scout Field and the following year, Silverdale Moss. Both these sites were agricultural fields at the time, but the last decade has been spent turning them into reedbeds. They of course needed time to bed in and flourish, but are now looking fantastic and for the first time last year, a bittern was heard booming on Barrow Scout Field, with one having been heard again this week, so we are hopeful that these two satellite sites will appeal to them for breeding soon.
If you've never seen one of these rare birds, then don't worry, you are not alone. Because of their well camouflaged feathers, they blend in incredibly well with the reeds, and don't often come out. However, a cold, frozen winter is probably the best time to spot them here for two reasons. The first is of course because there are physically more birds on site due to the influx from Europe. The second is because when it freezes, they come out onto the ice looking for places to feed. That doesn't mean that at this time of year you should give up looking though. With the male booming, the females become more active, so keep your eyes peeled for the flights of this elusive cousin of the heron around the reedbed. Good luck.