Saving the Bittern
The bittern, a British waterbird, does not have a good record as far as survival is concerned. By 1886, habitat destruction and other pressures had pushed it close to extinction. Fortunately, it recovered a few decades later, and in 1950 the numbers of mature male bitterns rose to a peak of about 70. By the 1980s, however, it was clear that the bird was in trouble again. The bittern needs extensive wet reedbeds to survive, and long periods of drainage, pollution, and lack of management had destroyed most of its habitat. By 1997, it again faced imminent extinction. To prevent this, the British government set up a plan for the bittern, aiming to establish a population of 50 males by 2010. However, this target was reached six years early, a rate of recovery faster than anyone had dared hope for. We at the Royal Society for the Protection of Birds (RSPB) now claim the bittern as one of Britain's greatest wildlife success stories since figures reveal that the number of these rare birds has increased fivefold in just seven years.

B
Bitterns have feathers that help them to conceal themselves and a shy nature; they usually remain hidden within the cover of reedbed vegetation. Our first challenge was to develop standard methods to monitor their numbers. The booming call of the male bittern is its most distinctive feature during the breeding season, and we developed a method to count them using the sound patterns unique to each individual. This not only allowed us to be much more certain of the number of booming males in the UK but also enabled us to estimate local survival of males from one year to the next.

C
Our first direct understanding of what breeding bitterns require in their ideal habitat came from comparisons of reedbed sites that had lost their male birds with those that retained them. This research showed that bitterns had been retained in reedbeds where the natural process of drying out had been slowed through management. Based on this work, broad recommendations on how to manage and rehabilitate reedbeds for bitterns were made, and funding was provided through a European Union (EU) wildlife fund to manage 13 sites within the core breeding range.

D
To refine these recommendations and provide fine-scale, quantitative habitat prescriptions on the bitterns' preferred feeding habitat, we started radio-tracking male bitterns on the RSPB's Minsmere and Leighton Moss reserves. This showed clear preferences for feeding in the wetter reedbed areas, particularly within reedbed next to larger open pools. The average home range sizes of the male bitterns we followed (about 20 hectares) provided a good indication of the area of reedbed necessary when managing or creating habitat for this species. Female bitterns undertake all the incubation and care of the young, so it was important to understand their requirements as well. Over the course of our research, we located 87 bittern nests and found that female bitterns preferred to nest in areas of continuous vegetation, well into the reedbed, but where water was still present during the driest part of the breeding season.

E
The success of the habitat prescriptions developed from this research has been spectacular. For instance, at Minsmere, male bittern numbers gradually increased from one to ten following reedbed lowering, a management technique designed to halt the drying out process. After a low point of 11 mature males in 1997, bittern numbers in Britain responded to all the habitat management work and started to increase for the first time since 1950.

F
The final phase of research involved understanding the diet, survival, and dispersal of bittern chicks. To do this, we fitted small radio tags to young bittern chicks in the nest, to determine their fate through to fledging, when they begin to fly, and beyond. Many chicks did not survive to this stage, and starvation was found to be the most likely reason for their demise. The fish prey fed to chicks was mainly those species penetrating into the reed edge. So, an important element of recent studies has been the development of recommendations on habitat and water conditions to promote native fish populations. Once independent, radio-tagged young bitterns were found to seek out new sites during their first winter; a proportion of these would remain on new sites to breed if the conditions were suitable. A second EU-funded project aims to provide these suitable sites in new areas. A network of 19 sites developed through this partnership project will secure a more sustainable UK bittern population with successful breeding outside of the core area, less vulnerable to chance events and sea-level rise.

G
By 2004, the number of booming male bitterns in the UK had increased to 55. Almost all of the increase occurred on those sites undertaking management based on advice derived from our research. While rescuing the bittern, the work has helped a range of other spectacular wetland species such as otters. Although science has been at the core of the bittern story, success has only been achieved through the trust, hard work, and dedication of all the managers, owners, and wardens of sites that have implemented, in some cases very drastic, management to secure the future of this wetland species in the UK.