HOW DO YOU WEIGH A SMALL BIRD?
For decades, tits and other small passerines were weighed using spring scales. Birds were placed in a cloth bag, which was loosely tied at the top, then suspended from the scale. Today, Wytham fieldworkers carry small electronic scales that give a more precise digital output. “The best way to keep the birds still on the scales is to pop them, head down, in an old 35mm film canister,” says Ella Cole. “This doesn’t look very dignified, but it minimises distress for the birds as it limits their vision. It calms them in a similar way to putting a hood on a bird of prey.” When chicks hatch, they weigh close to 1g. In just two weeks, thanks to industrious parents provisioning around 1,000 caterpillars per chick, the young are ready to fledge and often weigh more than their parents. The personality research represents one of the huge research shifts since Lack’s time. Back then, much was still unknown about fundamental great tit biology, such as how long the birds lived, how many eggs they laid or how far they moved. All that data is still being collected, but the beauty of the Wytham tit research is that this robust foundation of data has made possible finer-grained studies of behaviour, genetics and ecology.