As we are at the beginning of March, it is only a couple of weeks before we begin our surveys here at Lakenheath Fen to try and count ‘booming’ bitterns (through late March and into April) and then bittern nests (during May and June). The results from these surveys really help us to assess, at the end of the breeding season, how well we have done as a reserve in creating a home for bitterns- the priority species the reserve was initially designed for. In 1995, when the RSPB bought the land to turn into Lakenheath Fen, there were only eleven booming males left in the whole of the UK.
Last year at Lakenheath Fen alone we had eleven boomers, with nine as our target for each year. Booming surveys involve an early start- at 5am- when bitterns are most active and can be heard most easily. It’s also a lovely time of day to listen and look out for other special wildlife such as bearded tits, marsh harriers and our cranes too.
Photo credit: One of our bitterns from last year on the reserve, taken by Ken Clegg
On the day one of our wardens or our Site Manager will go out with several of our lovely volunteers and station themselves strategically around the reedbeds, often at elevated points- such as our custom-built high seat in Joist Fen- to keep an ear out for the bitterns, connected by walkie talkies so that the team can get an idea of when they are hearing a separate bird or the same bird. The reason we count the ‘booming’ males is because they each represent a potential breeding site for the weeks ahead- an area a male has decided could be suitable for a nest, and to which he will attempt to attract a female by ‘booming’. It is these sites that will get marked out on a map and looked at again when the reserve team carry out the next phase of the surveys in May- the nest counts.
Once the months of March and April have passed and the birds have settled down to their nests and young, the females (who do all of the rearing of the chicks alone) become conspicuous during ‘feeding flights’ -where they are forced to search a little further afield from the nest for food for the chicks. This is usually because they have exhausted the supply of fish, frogs and invertebrates in the immediate area around the nest as the chicks grow older, bigger and hungrier! It is these feeding flights which our reserve team monitor during the nest watch surveys in May, as they give us the best idea of where the active nests are. Last Spring we had five nests, and our target for the reserve is eight. Though last year this low figure is thought to be because, in common with other bittern reserves across the UK, the fish supply was thought be unusually high and there was less need for feeding flights to look further afield for food. We may well have had several more nests than five but we just couldn’t tell where they all were!During these surveys, we offer visitors (who don’t mind an early start!) the opportunity to join the reserve team for the survey. On each event we only take a maximum of four guests along with us, primarily to give guests plenty of opportunity to ask questions and find out more about how we do the surveys if they wish to. As well as learning more, there is also a very high chance that attendees will get good, close-up views of bitterns, harriers and other special birds such as bearded tits. It’s a lovely time of day to be out- very peaceful and with bright, clear light unique to the early mornings! Many of our summer migrants such as reed warbler, sedge warbler, swallow and cuckoo will be arriving back on site by then and visible out in the reedbed setting too.
Photo credit: A beautiful sedge warbler (which you may see on the later survey dates!) taken by Tim James here at Lakenheath
If you are thinking about attending any of these events, here are the dates and details:Bittern booming surveys- 25th March (1 place left) ; 7th April, 21th April (all on Tuesdays).
We will meet at the Visitor Centre at 05:30 and will be out until 09:30
Cost- £32 for RSPB members and £40 for non-members
Nest watch surveys (for bitterns and marsh harriers)- 5th May, 19th May, 2nd June, 16th June and 30th June (all Tuesdays).
Cost: £40 for RSPB members and £50 for non-RSPB members
We will meet at the Visitor Centre at 07:30 and stay out until about 12:30
For all of the surveys, transport from the Visitor Centre out to the survey site will be provided in one of our work vehicles, as well as a breakfast out on the reserve of hot drinks and pastries. You’ll be guaranteed a high seat, giving you a vantage point over the fen from where to enjoy the wildlife.If you plan to come, do wrap up warm though- sitting around for a few hours early in the morning can be quite and lots of layers of clothes are a good idea! If you want to ask any more questions or book a place, you can phone the Visitor Centre on 01842 863400, e-mail us on lakenheath@rspb.org.uk or pop in to see us. For all events you can pay on the day or in advance if you prefer- either at the Visitor Centre or by postal cheque if you want to pay in advance but save the journey.I hope this blog has given you a bit more of an insight into the survey work that we do in the Spring for some of our star species, and if you’d like to come along and join us for the experience we’d love it.Best wishes,Heidi