It’s before dawn on a summer’s morning. The sky has only the faintest hint of red in the east, and it’s still crisply cold. I cycle from my home village in Hertfordshire down into the Gade Valley along deserted roads.

My destination is a small nature reserve called Gadespring and it is here that my trainer and I will set up a fine-mesh net (known as a mist-net) to catch birds as they start to become active.

Although this might sound macabre, our intentions are anything but: we are bird-ringers, gathering crucial data to inform conservation and ecological studies.

The first bird-ringers

The British Trust for Ornithology (BTO) ringing scheme is one of the world’s longest-running ecological surveys, having existed for over a century.

It was initially set up to help us understand the behaviour of migratory birds. For example, the same swallows ringed in Britain during the summer were picked up spending the winter in South Africa, revealing a remarkable long-distance migration route.

It might seem obvious to us now that such migrations occur, but back then, it was a major breakthrough in understanding. Bird-ringing was the first way of being able to confirm the movements of birds, and refute opposing theories such as the bizarre idea that swallows overwintered in Britain at the bottom of ponds!

How does it work?

Bird-ringing involves catching birds, securing a small metal ring around one of their legs, and ideally recording the bird’s species, age, sex, wing length and weight. Rings have a reference code inscribed on them that allows that particular bird to be uniquely identified if it is caught again in the future.

Rings are lightweight and harmless, akin to a human wearing a watch.

Bird-ringing techniques have been carefully designed to minimise harm, although trapping and handling birds inevitably causes a small amount of stress to the birds. Many studies have shown that ringed and handled birds very quickly return to what they were doing previously, whether that’s sitting on eggs, feeding chicks or migrating.

Bird-ringers must train alongside experienced professionals for hundreds of hours in order to ensure they are trapping and handling birds with the utmost care and minimal disturbance.

The disturbance to the birds is justified in the huge wealth of data gathered as a result. This data is absolutely invaluable in helping us to protect our bird populations.

The importance of data

The main focus of bird-ringing is to gather ‘demographic’ data. Our bird populations are influenced by a complex interplay of causes, including:

• the number of offspring produced per brood
• number of broods per year
• fledging rate
• survival rate of juveniles
• survival rate of adults

Bird-ringing, alongside other surveys and data, helps us to build up a picture of each population and whether they're struggling or thriving.

Data collected over the last few decades indicates a severe population decline of many UK bird species. Understanding which threatened species we need to support and protect, as well as the underlying causes behind their decline, has never been more important.

We use this data in our practical conservation work, helping to create the habitats and circumstances that will help these bird populations recover, and hopefully thrive once again.

Understanding changes

Bird-ringing can also reveal how bird behaviours are changing because of shifts in the world around them.

For example, we know through ringing that bird nesting dates are shifting with climate change. Certain physical features of the bird, such as the presence of a ‘brood patch’ in females, or the stage of feather moult, can tell us whether the bird is nesting or not. We compare our current data with past records to see if the nesting dates matches up. 

We're seeing a 'phenological mismatch' in bird nesting times - they're not keeping up with shifts in the emergence of food supplies (such as caterpillars) due to our changing climate. If food doesn't appear when expected, their chicks are put at risk, causing a threat to the bird population as a whole.

Getting to know our birds

Bird-ringing reveals many other aspects of bird ecology. For instance, it can reveal how long different bird species can live. The oldest bird on record to be ringed was a 51-year-old Manx shearwater!

It can, of course, still tell us about migrations. Perhaps surprisingly, we still know little about where some of our summer migrants, such as house martins, swifts and pied flycatchers, spend their winter.

Become a bird-ringer

I would strongly encourage anyone with an interest in birds to consider learning to ring birds under the guidance of a BTO trainer, and join over 2600 volunteers ringing over 900,000 birds every year in Britain. The BTO website provides information on how to start training.

It is an amazing privilege to witness birds so close-up, learn about their fascinating lives, and to be at the forefront of the science informing bird conservation.