Lockdown forced London's peregrine falcons to eat more parakeets

London’s peregrine falcons switched from eating pigeons to parakeets during the first covid-19 lockdown in 2020, as urban birds felt the impact of humans staying at home.

Peregrine falcons (Falco peregrinus), the world’s fastest birds, arrived in UK cities in the 1990s, attracted by the abundance of their preferred prey, pigeons.

But the covid-19 pandemic prompted a sharp shift in the eating habits of some of them.

Citizen scientists working with researchers from King’s College London used live streams of 42 peregrine falcon nests in 27 cities in England to monitor the birds’ diets during three breeding seasons.

The first – between March and June 2020 – coincided with the initial coronavirus lockdown in England. At this time in London, pigeons made up 35 per cent of the falcon’s prey, starlings 36 per cent and parakeets 18 per cent.

At the same time of year in 2021 and 2022, when covid-19 restrictions were much less stringent, pigeons made up 49 per cent of falcons’ diets in London, starlings 29 per cent and parakeets 15 per cent.

Brandon Mak at King’s College London says the shift in diet was probably due to the effects of lockdown. Without tourists scattering sandwich crusts and crisp crumbs across London’s parks and squares, pigeons scattered to the suburbs during lockdown, leaving peregrines to rely on other prey.

The same dietary shift wasn’t observed in peregrines in other English cities. That is probably because the pigeons there weren’t as reliant on human litter for food, says Mak, and so lockdown didn’t prompt such a dramatic change in behaviour.

Ring-necked parakeets (Psittacus krameri) became established around London in the 1970s. The RSPB, a bird conservation charity, is concerned the rising population in south-east England could be outcompeting native birds for food and nesting sites.

More peregrine falcons could offer a solution. It is thought there are 40 breeding pairs in London, making it one of the densest populations in the world.

Since lockdown ended, their eating habits have returned to a normal, pigeon-heavy diet, says Mak. But their growing numbers could help to keep pigeon and parakeet numbers in check regardless, he says.

“Eventually the numbers of the predators would reflect the number of prey,” says Mak. “Over time, once the peregrines reach saturation, you will start seeing lower numbers of pigeons or parakeets.”

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