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Bird Feed: Seeding Evolution

In September 1835, a ship arrived at the Galápagos Islands off the coast of Ecuador, making just one stop in many on its five-year expedition of discovery around the world. On board was a young naturalist who would spend the next five weeks surveying the geology and biology of the islands. In that short time the discoveries he made would help change the world. That naturalist was, of course, Charles Darwin, and the birds he found there would eventually become known as ‘Darwin’s finches’. At the time Darwin didn’t assign too much importance to the birds. In fact, he barely paid them any heed at all, other than to make some standard observational notes. After all, geology was where his main interest lay, and the volcanic nature of the islands was more than enough to leave him in awe. It wasn’t until two years later, after he'd returned to England, that the birds were seen as a new species, and the shape of their bills in turn shaped Darwin’s famous theory of evolution. Nearly 200 years later, it's a different world. Here in Sheffield, winter has set in once again and we find ourselves gathering together in our homes, warming ourselves with food, drink and friends. And as you do so, spare a thought for the birds, because they do much the same. Great tits, for example, gather in the winter to scour the land for food, more pairs of eyes helping improve their odds. But they aren’t alone in their struggle. For all our destructive tendencies, we hold onto our connection to nature and make offerings to maintain it. We hang bird feeders in our gardens and yards with such passion that in the UK we buy more bird seed than the rest of Europe put together. And this fondness for feeding is doing more than just filling birds’ bellies – it’s altering their genes. Genes tell each part of us what to be. They are like letters in a sentence, and the sentence is the DNA that in turn makes up the individual story of every organism on the planet. Sometimes though, a typo will occur, and whilst the word remains understandable, it is slightly different. Eventually, as the story is copied over and over, an entirely new word can take shape. These changes can manifest themselves in how an organism appears and, in the case of Darwin’s finches, it’s in beak shapes that are better suited to whatever food each type of finch prefers. This may also be true of our friend the great tit, as work done by the University of Sheffield, in collaboration with several other institutions, has discovered that our fondness for feeding could be driving a natural response – increasing the sizes of their beaks, which makes using the feeders easier. What’s more, the birds with bigger bills are the ones that are favoured when it comes to mating. For most of modern history, we have strived to separate ourselves from the rest of nature, adapting our environment to us, rather than ourselves to our environment. But we are still organisms, locked into the natural world as much as to our own newly-created one. Our interactions have an impact and all too often they are to the detriment of other species. Evolution as a natural response to human activity has been seen before: intensive fishing has led to fish becoming smaller in size; the peppered moth changed its camouflaging colour due to industrial pollution; and the warming of the oceans is bleaching huge swathes of coral reefs. But if this one small act is having a positive effect on the great tits, perhaps there are other things we’re doing which might be helping our fellow creatures survive, and offsetting at least some of the damage we cause. 'Evolution in your back garden - great tits may be adapting their beaks to birdfeeders' Background image: Daniel Danger (Now Then #110) )

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