Wildlife articles
Researching our feathered friends around Hanningfield reservoir
For Chris Hall and Dave Strand, birds are a passion to which they dedicate much of their spare time. They both privately volunteer, assisting in data collection and ongoing research to assess bird populations, with their data being passed on to both Natural England and the British Trust for Ornithology (BTO). This work helps provide valuable information to aid in avian conservation and enhance scientific knowledge, as numerous bird species have suffered from declining numbers over many years.
It all started in 1996 with badger watching at a farm near Downham. Whilst there, the farmer gave Chris and Dave permission to put a kestrel box on the farm. In 1999, after years in which Kestrels and then Barn Owls had successfully raised young in the box, Chris was spurred on to obtain his license for schedule 1 birds*, enabling him to visit and record the offspring of the now resident Barn Owls.
Chris and Dave started working with Essex & Suffolk Water in 2000, building and putting up bird 
boxes then recording chick numbers
around Hanningfield Reservoir and Crowsheath Community Woodland (along with three local farms). The project has grown to include approximately 150 small bird boxes, 30 large owl boxes and 16 large pole boxes. During this time, there have been many successes, with Tawny Owls, Barn Owls, Kestrels, Blue Tits and Great Tits (to name but a few) having all fledged from the boxes.
Chris, Dave and their wives Sue and Sue also walk the sites to check for birds which are nesting in natural locations. At one point in 2004, a single pollarded mature Oak tree was found to have 
Mallards nesting with 13 chicks, Great Tits nesting with six chicks and Little Owls nesting with three chicks - a truly remarkable event, demonstrating the importance of mature trees as habitats (and within habitats). This same year also saw seven Barn Owlets fledge from a single nest, indicating the health of the local ecosystem.
When targeted bird species are found to have produced a brood, Chris and Dave enlist the help of Chris Harris, a licensed BTO bird ringer* (who also helps a great deal at Abberton Reservoir). The ringing of chicks is an important tool in avian research. The main objective of the BTO ringing scheme is to monitor productivity, dispersal and survival rate changes amongst populations of bird species. Ringed birds can be recaptured, to collect data. However, most of the information gained from the birds around Hanningfield has been upon the death of a bird. This was the case with two recent Barn Owl casualties: The first, was found near Braintree, which is not a great distance away, but was six years old, which is roughly double the average life expectancy for Barn Owls; the second was found in Suffolk, and had only fledged 60 days earlier, showing that the owl had migrated a good distance in that time. The majority of (Hanningfield) Barn Owl casualties that are recorded via their rings have travelled North – leading us to wonder why?
*Wildlife & Countryside Act 1981 (as amended); Schedule 1 species require a license to approach during bird breeding season and further licensing to ring (begin Mar - end Aug).
For more information on bird ringing visit: http://www.bto.org/ringing/index.htm
Facts
• Both the Barn Owl and Kestrel are on the BTO population status amber concern list, with both showing a >25% decline over the last 25 years.1
• This year is the 100th birthday of bird ringing in Britain and Ireland – it was started in 1909 by Arthur Landsborough Thomson of Aberdeen University and by Harry Whitherby of British Birds.2
• Some 2300 ringers mark more than 750,000 birds each year!2
• A Brent Goose ringed in Essex was found in Artic Russia, 5,443 kms away.3
• A Tufted Duck ringed in Essex was found 6,153 kms away in Pakistan.3
• An Artic Tern originally rung in the UK was found 18,056 kms away in Australia.3
• An Osprey, originating from Strathclyde, was discovered in the stomach of a crocodile in Gambia.4
• A reed warbler was found dead in a spiders web.4
• The BTO receives around 14,000 reports of birds with rings every year, by far the biggest cause are the 41,900 recorded birds killed by domestic cats.4
1) British Trust for Ornithology, The population status of birds in the UK [online]. Available at: http://www.bto.org/psob/amberlist.htm [Accessed 17th February 2009]
2) Baillie, S., 2009. 100 years of bird ringing. BTO news, January – February 2009. p 5. Issue 280.
3) British Trust for Ornithology, So where do our birds go? [online] (Updated 2nd July 2008). Available at: http://www.bto.org/ringing/ringinfo/recovery-map.htm [Accessed 19th Jan 2009]
4) Balmer, D.E. et al., 2008. Bird Ringing: A concise guide. British Trust for Ornithology.
Picture refs - 1) Little Owls: Copyright Chris Hall – Little Owlets (2004) - 2) Owl ringing 18: Copyright Chris Hall – Chris Hall (far left) Dave Strand (middle) Volunteer (right)…The mighty brood of seven! (2004) - 3) Tawny owl 2: Copyright Chris Hall – Tawny Owlet (2004) - 4) DSCN2451: Copyright Leon DeBell – Chris Hall (left) Dave Strand (right) with Barn Owlets (2008)
Bitterns galore
Abberton Reservoir was home to three passing bitterns for three months this winter. In previous years we have had one bittern that hangs around for a month, but this year he decided to bring two of his mates with him. Visitors were treated to spectacular views down at the western end of the reservoir. Thankfully there were plenty of people looking for the bitterns so you were almost guaranteed that it had been spotted. Even with directions to the exact location, until the bird moved it was almost impossible to see due to their amazing camouflage.
One of the bitterns would frequent a small strip of reed close to the Layer Breton Causeway. It would occasionally move up and down just within the edge of the reed; then without fail at the same location most evenings it would climb up the reed. It’s is amazing how the reed stem is strong enough to hold the bird, but it does. The bittern uses its neck to scoop a group of stems together and then grasping them in its feet it climbs the reed. This is the time when you get the best views as the bittern as it is now right on the edge and in full view. It uses its wings to balance as it traverses up the reed; moving more reeds as it goes until it reaches the height that it desires. Once at the top it is easy to loose sight of the bittern as it blends so well with the seed head. Then without fail it would fly off down the reservoir to a larger clump of reed to overnight there. If you were lucky you would see the other bitterns too.
These bitterns were a real treat for serious birdwatchers and general visitors alike. To see so many different characteristics was a delight. Essex Suffolk Water and Essex Wildlife Trust (EWT) have plans to increase the amount of reed around the reservoir in the hope that we can persuade the bitterns to stay here throughout the summer; who knows in a few years time we may have breeding bitterns walking infront of one of EWT’s new bird hides. Watch this space!
Jo Wray
Senior Warden
Essex Wildlife Trust, Abberton Reservoir Nature Reserve
(Abberton Bittern image copyright Adrian Kettle)
Bittern Facts
• In 1997, there were only 11 male bitterns calling in the UK. Thanks to concerted action by conservationists, numbers are recovering, with 55 booming males recorded in 2004 - up from 43 the year before.
• Recent research shows that bitterns need a varied reedbed habitat with plenty of variation in depths and edge in order to thrive. They mainly feed in the 30m of reed from the edge of open water and reed fringed ditches, because that is where the fish are.
• Although reedbeds are widely distributed, they are by no means common. A programme of intensive drainage and the decline of traditional management, caused by the failing market for thatching products and marsh hay, led to an estimated loss of 10-40pc of the UK’s reedbeds between 1945 and 1990 (Bibby et al 1989). A 1994 survey by the RSPB revealed that there are 926 reedbeds in the UK totaling 6,530ha but that they are mostly fragmented into small blocks of less than one hectare (Painter 1994).
• Bittern numbers are estimated from the number of male bitterns that boom in the breeding season. They do this to attract the females and establish their territory each male has a unique voice.
• Bitterns used to be hunted for food. In Norfolk, they were called butterbump because they have so much fat on them.
• Bitterns look like a small, brown heron with a shorter neck.
• The average booming territory of UK bitterns is about 20 hectares (about 24 football pitches) of wet reedbed and open water.
• Bittern nests are a platform of reed stems among standing reeds.
• When alarmed, bitterns imitate the reeds by sticking their head up straight and swaying in the wind.
• Their favourite food is eels.
• Bitterns can swim.
• Neolithic bitterns are preserved in the peat of many areas of eastern England and Wales indicating the past wide distribution of the species.
• The boom of the male bittern is the lowest-pitched and the most far-carrying song produced by any European bird. It can be heard up to 5 km away in the right weather conditions.