Photo by Hamish Smith
By Brandon Mak, Edward Drewitt, Robert Francis, and Michael Chadwick.
Read the full paper here.
Urban raptors may be indirectly reliant on human activity in cities which provide them, through their prey, a stable supply of food. It is not hard to find pigeons, the favorite prey of several urban raptor species, begging for food from sympathetic bird feeders or loitering around litter bins in large numbers! But when lockdown happened, human activity was greatly reduced, which likely affected the behaviour of these dependent birds when their feeding opportunities dried up. Did this have an effect on their predators, the peregrine falcon?
To find out, we recruited community scientists to watch online nest cameras and record what urban peregrine falcons ate over 3 breeding seasons in 27 cities across the UK to understand how their diets changed during and after lockdown. We also studied their breeding parameters – the number of eggs laid, hatched and young fledged – to see if these were affected. As we know pigeons are an important prey item, and they are very dependent on human food, we expected peregrines to experience food shortages as their prey supplies shrank, which would lead the predators to produce fewer eggs and young that year.
We found peregrine diets changed during lockdown, but this was different in London compared to other UK cities. As expected in London, there was a much lower proportion of pigeons eaten, which was compensated for by taking more parakeets and starlings. But in other cities, pigeons did not change, while more starlings and other birds were taken instead. The differences between London and other cities may be due to the size of the cities – compared to the other birds, pigeons likely had a more difficult time finding alternative food in the capital, resulting in there being fewer of them. In smaller cities residential areas (and food therein) were more accessible; visiting pigeons then outcompeted the smaller birds, which reflected in what the peregrines could choose from. Despite these changes, we found no evidence to suggest food shortages occurred, as
peregrines did not produce significantly fewer eggs or young.
Our research indicates that cities have high baseline levels of prey available for urban peregrines, which changes in human activities can impact, but this is unlikely to be more influential than other factors like habitat availability.
Relational Thinking 