Richard Collins: Why do some urban birds have paler feathers than ones in the country?
Birds Than Found To That Coloured New Plumage May Counterparts Has Research More Their Be Great With Others, Revealed Have Countryside Paler Tits Brightly Some That Urban
Researchers from Lund University collected great tit feathers from urban and rural locations in Europe. The colours of feathers from city birds, they found, tended to be duller than those of forest-dwelling ones.
The choice of the great it for the study isn’t surprising; it is said to be the world’s most researched bird. The largest member of the tit family, it has a distinctive black crown, conspicuous white cheek patches, and a black bib. The breast and belly are yellow and the rhythmic ‘chee-u chee-u’ song is distinctive. Found throughout Europe and Asia, from Ireland to Japan, the great tit is highly adaptive; up to three dozen potential sub-species have been described.
2/2 The @AnimalEcology study, led by @lunduniversity and @UofGlasgow, analysed feather samples from great tits in cities and forests around Europe, and found that urban great tits are often noticeably paler than their countryside relatives.
— UofG MVLS (@UofGMVLS) August 14, 2023
Full study⬇️ https://t.co/MO8oW4BgKI
Further analyses showed that differences in diet were most likely responsible for the colour variation. The yellow pigment in a great tit’s feathers comes from carotenoids, which the mother bird obtains from eating insects during egg formation. That urban birds may eat fewer insects than their rural cousins isn’t surprising; insect populations have been decimated and garden birds receive handouts of other foods. But are city great tits less healthy than country ones?
There may be an echo here of what happened to our ancestors, when they began cultivating crops and keeping livestock around 12,000 years ago. The long-established hunter-gatherer lifestyle gradually gave way to a settled one. ‘All property is theft’ declared Pierre-Joseph Proudhon; conflict and violence over property may have been common in early farming communities, but settled people were less vulnerable to environmental disasters, and lean times, than were hunter-gatherers.
Paradoxically, the first farmers seem to have been less healthy than their free-ranging cousins; remains from that time show that they were physically smaller and weaker. Perhaps the settled diet was inadequate. Whereas hunter-gatherers sampled a wide variety of meat fish fruit and wild vegetables, the settlers’ fare tended to be limited to what they could cultivate, resulting in scarcity of some important nutrients.
The farming revolution sparked the most far-reaching changes in human history. It also had a profound impact on wild creatures; some species changed their ways fairly radically. Swifts and swallows, for example, ceased using cliff faces and caves for nesting. Buildings became their locations of choice. Songbirds spread from their traditional woodland and scrub haunts towards human settlements.
Like the early farmers, urban birds enjoy enhanced food security. Handouts from the public help ensure their survival, particularly in winter. There’s also a heat-island effect; birds converge on dwellings for support during cold spells. Bird feeding has become ‘big business’; garden-tables nesting-boxes and hanging-feeders are sold in supermarkets. But it’s not all plain-sailing for the avian city dweller. Domestic cats are on the prowl, being struck by vehicles is a constant fear, brightly lit high-rise buildings take their toll on night migrants and obtaining enough protein-rich food for nestlings is challenging.
But ‘urban dullness’ varies between cities, the Lund research showed. In Malmo, city birds had duller feather colour, but those living in Lisbon were more brightly coloured than their country cousins.