Ringing is an incredible practice. You'll hold a multitude of magnificent birds – and crucially obtain vital data that allows us to discover the distribution of species, where they might migrate, population sizes and so on.
I started ringing in 2022 at Knepp Castle Estate, West Sussex. My time at Knepp led to three months at the Wytham Tit Project, a decades-long study run by Oxford University, which focuses on the nesting habitats of Great Tits at Wytham Woods, west of Oxford. The project started in 1947 and is the longest, continuous study of a bird population anywhere in the world. It set out to understand how birds behave and how climate change affects their nesting habits and success rates.
The 1,000 or more nestboxes in the woodland are checked at the start of each season, to see what, if anything, is beginning to nest. Other species also head for the boxes, especially Blue and Coal Tits and, sometimes, Marsh Tits.
If any birds are nesting, the boxes keep getting checked to log nest-building progress, including the start of egg laying, incubation and when the eggs hatch. The latter means you can work out when the chicks need ringing (usually on day 15). The final act is to check the nests about a week later to ensure the chicks have successfully fledged. Why does the project focus on Great Tits? Partly because they more readily nest in boxes, unlike Blue Tits, which favour natural cavities.
Ringing Blue and Great Tit chicks is superbly impersonal. These feathered jellybeans are sun-dazzled and blinded on suddenly being exposed to the light when you whip off the face of the box. You then gently jiggle the birds into a cloth bag to calm them, ensuring they don't get injured.
A brood of young Great Tits in the nest (Alex Rosenfield).
Youngsters often try to leg it, waddling off to freedom, so you have to catch them and put them back in the bag! They yell, squawk, shriek for reinforcements and then the parents start dive-bombing. Even the old hands get anxious.
When ringing the chicks, we take one out at a time – using a special grip, which ensures their safety. Blue Tits are fitted with a snazzy, shiny ring, while Great Tits also get an electronic tag. These PIT tags (passive integrated transponders) help track individual bird movements, for which you'll also need electronic tag readers. PIT tags are generally used on Great Tit chicks only. This is because when you're tagging hundreds it gets expensive, and because Great Tits have a better chance of fledging and surviving.
Once the chicks are ringed, they are weighed, being popped upside-down in a small pot to stop them wriggling. Then they're posted back into their nest through the small opening in the front of the box.
And it's not just the chicks we ringed. The adults can be a much trickier prospect as they are savvy and will not go near the boxes unless the coast is clear. When they do fly in, it helps if a trap has been set. It's a spring-loaded door fitted inside the box, trapping the adult. Traps are never left for more than 30 minutes to ensure the chicks don’t go hungry.
Another option is 'rushing the box'. This means we'd hide in the undergrowth, waiting for the adult to enter, jump out, sprint to the box and jam a cloth bag over the entrance hole, trapping the adult inside. That's the theory. And does it actually work? Of course not!
I went to Wytham Woods in mid-March and was greeted by snow, fog and enough mud to sink a tank. But when the weather warmed and the sun shone, these woods (from which people are more or less excluded) are magic. Bluebells by the zillion, orange-eyed Eurasian Sparrowhawks, Wild Garlic and wet meadows beside the Thames. The after-work aim was to get lost and get back before dark.
The workdays often hit 14 hours, starting at 4 am. Hacking and thwacking through the wood was a never-ending battle, an onslaught of brambles, a horde of ticks up your trousers ... but on the good days, it was worth every scratch and every bite – watching a nest being crafted from horse hair, badger fur and moss is a special thing, as is watching the first egg hatching and the never-ending frenzy of feeding.
Some of the adult birds were so efficient, driven and punctilious. They'd fly to a box every three minutes with a 1-cm lepidopteran, a plump Winter Moth caterpillar. Great Tits lay one egg per day and wait to incubate when they please, when food availability is reliable and the weather is stable. They do not gamble.
An adult Great Tit brings food to the nest (Alex Rosenfield).
The Wytham Tit Project also involves logging bud burst dates for trees. This is important because the Winter Moth caterpillars, the favourite food of Great Tits, feed on oak-leaf buds. Understanding when trees are going to come into leaf helps us predict how nesting habits will change. Over the past 60 years, average nesting dates in the woods have moved forward by around two weeks.
Birds in parts of the woodland with healthier trees appear to nest earlier, as the trees adapt to conditions faster and provide caterpillars earlier, while the unhealthy, less adaptable woodland trees provide food later. So, the birds here nest later to ensure they get food for their young.
The best job at Wytham was mistnetting. Never had a go? The specially trained and accredited ringers erect two vertical poles, 2.5 m high, some 20 m apart. Attach a net between the two, have a coffee, four chocolate croissants and wait. The nets can catch anything from eagles to hummingbirds (with the correct netting). Once extracted, caught birds go straight in a cloth bag to calm them. Then back to the ringing area – identify and ring them, log the age, the sex, wing length and weight, and release. Bingo.
The mini metal rings are about 3% of the bird's body weight – the equivalent of a dainty wristwatch for an adult. Each tiny metal ring has a unique code so if the bird is caught again, we know exactly where it has come from.
Find out more about the Wytham Tit Project at wythamtits.com.
