Apart from being one of Britains rarest birds, the fascination of the Bittern is the challenge of finding it. The brown mottled, streaky plumage blends in with the reedbeds especially when they freeze, often sky pointing. You can give yourself a better than average chance by visiting Tring Reservoirs in the winter.
Ringing records have shown that there is some movement of Bitterns within the UK but extra numbers of overwintering birds arrive from Northern and Eastern Europe, usually around the end of November and leave in early March.
Each breeding male holds a large territory, at least 20,000 sq.metres if the conditions are very favourable. The males, which are polygamous, can have 1-5 mates within his territory and these can nest quite closely together. After mating the male doesn't have anything much else to do with rearing the young except in holding territory against other males, which he can do extremely aggressively. The female tends the young until shortly after fledging.
They need a reasonably constant water level.
Bitterns regularly overwinter at Marsworth Reservoir, with occasional sightings at Wilstone Reservoir and the Tring Water Treatment Works.
A good place to try and see one is to stand on the causeway between Marsworth and Startops Reservoirs looking over the Marsworth reedbed, where you might see one flying, usually only a short distance, over the reeds. If you stand where the reedbed almost comes up to the causeway and peer into the reedbed you might get a good close-up view like this photo taken by Mike Collard on 10th January 2003 at Marsworth Reservoir. The best time is between December and February late afternoon and at dusk.
Normally Tring's bitterns leave in early March and there is no booming by the males, however a Bittern was booming at Marsworth Reservoir in 1999 from 1st March to 3rd April. Mostly this was heard in the evening during and after dusk and overnight fishermen have told us it kept them awake at night. A Bittern was also booming at Wilstone Reservoir on 4th March, possibly the same bird.
Since 1999 we have only two more records of a Bittern booming, albeit briefly, in early 2002 and 2008. Interestingly, the last sighting in subsequent years is around the second week of March. Perhaps the booming male in 1999 had some intention of breeding instead of just overwintering here. If so, he must have given up and gone to try his luck elsewhere because the last sighting that winter was on the 23rd April; there is more on the 1999 bird on the Bittern Sightings page (link below). The 2002 bird boomed only once, in February; the 2008 bird gave up without really trying and was last seen on 13th March.
In the early winter of 2008/09 British Waterways funded the use of a specialist reed cutting machine, which was used to cut several channels deep into the reedbed to encourage bitterns, by increasing the reed-to-water margins making it easier for small fish to penetrate the reedbed. This work also had the added benefit of giving us a better view into the reedbed, potentially increasing our chances of spotting a bittern. This reed cutting was repeated and extended during the early 2009/10 winter, but a prolonged cold spell left the reservoir frozen for much of January 2010.
So, look out for Bitterns anytime between November and March (December to February is best) and listen out for booming from end of February and through March, mainly during and after dusk. Good luck, and please let us know via the Sightings links on this web site if you see, or hear, anything.
For further background information on Tring's Bitterns click here
For a summary of Bittern sightings at Tring since 1998 click here
(Last updated 16/01/2009)