A 15-year study by the RSPB has found that swifts show stronger loyalty to their nesting sites than to their partners. The research, which tracked 190 different swifts across 243 nests, revealed that 94% of the birds reused the same nesting site as the previous year. In contrast, only 59% of nesting attempts were with the same partner.
Study Findings on Nest and Partner Fidelity
Malcom Burgess, RSPB principal conservation scientist, said: “We’ve anecdotally thought for a long time that swifts are loyal, returning to the same nesting sites and partners each spring. But for the first time we’ve documented just how strongly faithful they are to their nest sites, which highlights just how important it is to protect their nesting sites in our neighbourhoods.”
The study underscores the birds' preference for familiar nesting locations over maintaining pair bonds. This fidelity to nesting sites has significant implications for conservation efforts.
Decline in Swift Numbers
The number of swifts in the UK declined by 70% between 1995 and 2024. The species was added to the Red List of Birds of Conservation Concern in the UK in 2021. Increasingly, swifts return from long migrations to find their traditional nest sites blocked or gone, forcing them to expend extra energy and time searching for alternatives.
Nest sites have become harder for swifts to find due to fewer spaces available in modern and renovated buildings. Mr Burgess added: “The decline in swift numbers is a great cause for concern and without increasing the availability of nest sites, and replacing those that are being lost, we will see further declines of this extraordinary bird in our towns and cities.”
Calls for Policy Changes
The RSPB has called for swift boxes to be fitted to new buildings by law. It also urged stronger controls and penalties to prevent the demolition of buildings while swifts are nesting in them. Carl Bunnage, head of nature policy at the RSPB, said: “Recent changes to planning policy made by the Westminster Government to more strongly encourage developers to fit Swift bricks to new buildings are a small step in the right direction. However, they fall far short of what is needed if we are to halt and reverse the decline in our Swifts.”
