The study, carried out by scientists at the University of Bristol and King’s College London, has been published in the British Ecological Society journal, People and Nature.
The researchers discovered that during lockdown, peregrine falcons in London were forced to change their diet away from pigeons, with fewer of these birds being drawn in by human food supplies such as discarded food waste or direct feeding.
Citizen scientists used online live streams to monitor 31 peregrine falcon nests in 27 UK cities over the course of three breeding seasons, the first of which took place during pandemic restrictions.
In London, peregrines took a lower proportion of pigeons as prey (-15%) and replaced them with starlings (+7%) and parakeets (+3%). However, in other cities, pigeons remained the dominant prey.
The study was written by Brandon Mak – a King’s College London PhD alongside Ed Drewitt from Bristol's School of Biological Sciences.
Ed Drewitt said: "This is a really exciting discovery - web cameras are offering a world into peregrines that we've not seen before and revealing the meal-by-meal detail of what urban-dwelling peregrines eat. This detail means we can really show how their diet changed during lockdown. Peregrines are very opportunistic and as soon as pigeons became less available, they switched to eating other birds such as parakeets, which are obvious and probably easier to catch!"
Brandon Mak added: “Our results indicate that peregrines in larger, highly urbanised cities like London may be more dependent on, and hence more vulnerable to changes in, human activities which support their prey populations, particularly feral pigeons.”
The changes to peregrine diets during the study raises questions surrounding how pest control may affect falcons and other predators that depend on ‘pest’ species. For example, northern goshawk populations in Poland almost halved when farmers stopped rearing domestic pigeons and other poultry that would otherwise have been prey for them.
The management of pest species and their food sources are usually human driven. Therefore reductions in pest species, like pigeons, can force raptors to switch prey or forage further away from their nests, which can result in poorer nutrition from less ideal prey, or a decrease in energy for fitness or reproduction due to the effort spent on hunting.
Brandon explained: “The world is still learning about the consequences of lockdowns on wildlife, which promises to shed light on how human and animal lives are linked in our shared environments.”
In the future, the authors of the study hope to contribute towards the Global Anthropause Raptor Research Network (GARRN) which brings together similarly conducted research from the pandemic.
“How did UK peregrines fare compared to elsewhere, and how did other raptors experience the lockdowns? We hope these questions will be answered in the coming years,” continued Brandon.
Paper
'The raptor lockdown menu—Shifts in prey composition suggest urban peregrine diets are linked to human activities' by Brandon Mak, Edward J. A. Drewitt, Robert A. Francis, Michael A. Chadwick in People and Nature [open access]