A trained mathematician does a rough, back-of-an-envelope calculation. "About 29,000," he says with a smile. It's a staggering number for what it represents, yet curiously, the man who once juggled figures for a living has never done this sum before. Over 38 years, Maurice Durham has ringed a lot of birds. Twenty-nine thousand of them, give or take a few.
How it started
Maurice describes how he fell into ringing almost by accident. "I knew a bird ringer at my local pub. I'd not had a break for a while so I asked if he'd mind me tagging along on a trip to Steep Holm in the Bristol Channel, to see what was migrating through in September. I didn't handle any birds that time - I acted as scribe for the team. But I was fascinated and asked my friend - a registered trainer - if he'd teach me how to ring. Some people I work with today say they thought I'd never make a ringer, because I was so nervous about harming the birds. Whenever I held one, I would shake." Watching his swift and steady hands at work today, it's scarcely believable.
Building a bigger picture
Eight years after Maurice began ringing birds, he was drawn to a new project at WWT Slimbridge. The British Trust for Ornithology (BTO) was launching a clever, new bird-recording scheme called Constant Effort Sites, and it was seeking a network of different habitats across the UK - from dry scrub to reedbeds and woodlands - where 24 common breeding songbirds could be monitored throughout the summer, year after year.
Slimbridge had just what was needed. Maurice was one of the local volunteer ringers that WWT's former Head of Conservation Action, Baz Hughes, asked to help. "Baz ran the scheme for several years until he was needed on other fieldwork when I took over," explains Maurice. He now leads a dedicated team who get up well before dawn on 12 Saturdays between May and September to put out mist nets to catch birds. They are one of about 140 teams across the country who use identical methods every summer, so that each site provides a single piece to complete a vital national jigsaw.
Collecting data
Speaking in 2019, Richard Hearn, a key member of WWT who worked as Head of Monitoring, was in no doubt about the importance of this study. "For a lot of common bird species, this scheme is the best information we have about their population dynamics," he explained. "The longer a Constant Effort Site has been running, the more valuable the data set it produces. At nearly 30 years, Slimbridge is one of the longest-running sites to exist." There's a key point here; the scheme does not count absolute numbers of birds - an enormous task of estimating totals breeding at every location. Instead it monitors changes from year to year. Combining all the figures from more than 140 sites scattered throughout Britain and Ireland provides an impressive and reliable body of information.
Why ringing?
But why, at a time when there are huge advances in tracking technology, is there still a need for ringing? Why today do nearly 3,000 volunteers ring a million or so birds using a method of recording dating back to Edwardian times?
"The main reason for ringing in the early years was to understand basic facts about birds, such as where they go in winter," explained Richard. "Now it helps us to gain essential information about numbers, changes in populations, breeding success (the number of births) and survival rates. When you have a bird in the hand you can age it, and get an idea of how the breeding season is going. If you ring a bird and it's caught again at a later date, you can find out how long it lives. With this information, we can calculate expected changes in numbers and identify the stage in the life cycle when birds are most affected by environmental change. This helps us to narrow down the possible causes of any declines and target our conservation efforts where they're needed most."
Ninja ringers
When all the world's asleep, a band of volunteers steals noiselessly into Slimbridge and sets up 12 mist nets in Decoy Wood before the sun even peeps over the trees. The nets are then checked at least every half hour, to make sure birds that fly into the micro-fine mesh, do not wait there for too long. Skilled and gentle hands grip the captives and deftly unknit claws and beaks, and ease out tails, from the strands of the net.
The individual characters of different species become apparent during the experience. Most songbirds lie quietly in the mesh awaiting release, but blue tits are "feisty" and seem to take pleasure in pecking their rescuers "and hanging on!" exclaims Maurice. As for birds of prey - "you better watch those talons."
Into action
As soon as a bird is released from the net, the ringer slips it at once into a soft cloth bag, where it lies still, calm in the dark and quiet. They carry it to a 'processing table' for a full-body scan. Each bird is then weighed and fitted with a unique leg ring - the equivalent of a human wearing a watch. Careful fingers fan out and measure the length of the wings, while experienced eyes judge the age, sex and state of moult, noting the fluff of a juvenile. Everyone knows exactly what they're doing - they've spent around two years working as apprentices at least once a fortnight under expert supervision to get the knowledge, dexterity and wisdom to gain even a basic permit to ring by themselves. The most highly trained and qualified ringers then continue to grow their skills for another five years or more. The quality of its ringers is one reason why the British and Irish Ringing Scheme is among the most respected in the world.
Observing trends
Over the years, Slimbridge's Decoy Wood has proved to be a reliable microcosm of a bigger world outside - the trends Maurice and his team observe from year to year are mirrored in the national picture. The migrating nightingales, redstarts and flycatchers that they would catch up until a decade or so ago are no more - a telling indicator of their complete disappearance from some time-honoured sites. The ringing team also observes weather patterns that bring population fluctuations. Last year was a breeding disaster. First, the Beast from the East was bad news for our resident birds, then later, in April, cold northerlies held back migration, while the hot, dry summer scuppered the breeding attempts of ground-feeders such as blackbirds. By contrast, the previous summer was thoroughly average in both temperature and rainfall. Without the extremes that disrupt breeding, it proved to be exceptional, with baby long-tailed tits out of the nest a full fortnight earlier than average, and many pairs fledging second broods by mid August. Annual monitoring in Decoy Wood has demonstrated the robustness of our site management. While pollarding of willows in one area of the wood removes cover for breeding birds, we always carry out such necessary operations on rotation, leaving the rest of the wood intact. So there's always plenty of other suitable habitat nearby.
Going digital
Today, a new urgency has crept into our ringing. Climate change has seen a shift in some wintering duck species to wetlands in eastern countries of Europe that would have been inaccessibly frozen before. Some of these drifts to the east have been truly startling - a halving in goldeneye numbers in the UK over 25 years has been balanced by colossal increases in Finland. But there is evidence that some of the changes in UK winter numbers could also be the result of genuine declines rather than shifts in distribution, most notably in common pochards and possibly wigeons too. More duck ringing could draw out the facts that will help us to address this worrying development.
That's why Maurice is computerising a whole shed of paper duck-ringing records gathered since 1947 from all our centres. This will enable us to share and analyse long-term trends in survival rates and to understand more about the declines in some species that we're now observing. "It's my main mission for the Trust," he laughs. "I've made it to 1980. I suppose I've got a bit of a way to go."
