ECOS 45 (2.2): Undergraduate Award 2023

The Decline of Swifts in the UK:

Causes and solutions


This article considers the likely reasons for the decline of swifts in the UK. It examines how to combat these causes and looks at potential individual and corporate actions that could help swifts.

The wonder of swifts

The breeding population of UK swifts declined by 60% between 1995 and 2020 and they have now been red listed on the UK birds of conservation concern since 2021.1 There are many reasons why over half of UK swifts have disappeared, including loss and lack of nesting sites, disruptions in insect populations and changes in weather. swifts are one of my favourite species of birds. I love watching them throughout the summer, ascending high before diving, swooping and screeching over my head. You may know the phrase “one swallow doesn’t make a summer” but I definitely think that one swift puts a smile on my face and reminds me that summer is on its way.

Swift nesting and breeding

Swifts make their nests in buildings, under eaves, in small gaps and in the corner of barns. However, improvements to the insulation of old buildings can close up holes which would previously have made perfect nests for swifts. Similarly, demolishing old barns and houses destroys even more potential nesting sites. Changes to our buildings over the last two decades, resulting in less nooks and crannies for swifts to exploit, may have been a contributing factor in the decline of swifts.

A swift nestling in a nest in the corner of a building.
Photo: Klaus Stiefel, Flickr

The RSPB says that as “swifts pair for life, and are ‘site-faithful’, if a building has been demolished, renovated, or the gap obstructed or repaired, they must find somewhere new, quickly. If an alternative site can’t be found fast, a whole breeding season must be skipped” and it is this that causes their population to decline dramatically.2

I still remember a family holiday from my childhood, where I sat watching a pair of breeding swifts diligently and continually flying out to hunt on the wing before darting back to feed the young. I was enthralled by this tiny animal. The idea that this species is in decline and that future generations may miss out on the experience of watching swifts breaks my heart.

This summer, 2023, I was thrilled when we discovered that a pair swifts was nesting under the eaves of one of our neighbours’ houses. As the months went by we watched a pair of swifts become five, then six, then seven, until there was well over ten flying above us every day. I am not sure whether they all came from the same nest, or whether other swifts in the area congregated in the sky above our house, but it was amazing to watch. Seeing the number of swifts we did this summer was so uplifting and gave me hope for this incredible species. Sadly this is not the case for everywhere in the UK.  

The decline of insects

Another factor thought to have been affecting this species is a decline in insects. Swifts feed on flying insects and small spiders. However changes in agriculture have caused natural habitat to be removed, increased pesticides are being used, and thermal and light pollutants are increasing. The quantity of pesticides being used has doubled over the last 25 years.3 These factors are causing insect populations to drop, consequently leaving less food available for many species of birds, including the swift.

The distribution of insect biomass (in grams per day) pooled over all traps and catches in each year between 1990-2015.  
Source: Hallmann et al., 2017

There has been a dramatic decline in insects, with biomass dropping by around 76% since 1990. This will have had a huge impact, not just on birds but a decline in insects will have had negative consequences for species such as bats, spiders, frogs and reptiles. Therefore efforts to increase the number of insects in the UK is necessary if we want to prevent these species from disappearing. The food web is an incredibly complex system, and removing many of the primary and secondary consumers causes detrimental impacts to entire ecosystems, and impacting the likes of otters, foxes, badgers and birds of prey.  

Changes in weather

One of the many impacts of a changing climate that has been found to affect bird populations is an increase in precipitation. Tom Finch et al. (2022) found that greater precipitation was “associated with smaller brood size, a higher nest failure rate and a lower first-year survival”.4 Possible reasons for this link between precipitation and breeding patterns may be due to decreased successful foraging during wet weather. This determines the amount of food that nestlings will receive and may cause more to die prematurely. It may be then that an increase in juvenile bird mortality could be a large factor driving the decline, rather than something impacting the adult swifts directly.

Helping swifts

It is incredibly important that we act on the decline in swifts before it is too late, and they vanish from our skies completely. A few suggestions I have are planting more insect friendly gardens: by including lots of flowering plants and reducing the usage of any insect damaging pesticides and fertilisers. Also installing swift nest boxes on your houses; most garden centres will have them and if not then there are plenty of affordable ones online. If you are unsure how to install one properly then this RSPB article has clear steps to follow. I believe that it should be mandatory for all newly built homes to include a swift brick. These are brick or box structures that provides a nesting site for breeding swifts. They have an opening at the front which leads into a nest box situated behind. This is not a new suggestion; Manthorpe Building Products along with the RSPB and Barratt Developments launched a partnership in 2014 looking at how “nature and wildlife could be incorporated into new communities.” Through working with another conservation group, Action For Swifts, an effective nest brick design was created and nearly 200 were installed into new developments in Exeter and Aylesbury over a year.5

Swift brick created by Manthorpe Building Products. The bricks are cut away to show the nest box that would normally be behind the bricks.
Photo: Manthorpe Building Products

This example demonstrates how implementing this kind of strategy is achievable. If this was put into place on a larger scale throughout the UK and enforced legally, this could have a significant benefit for swift numbers.

Some Conservative MPs have backed a proposition that swift bricks should become mandatory in all new homes, which was first suggested by Hannah Bourne-Taylor. Her idea is that a new national policy should be passed, demanding all new building developments to include a swift brick. Currently the Government has resisted this idea and argued that “local authorities can make their own planning conditions to require them.” However local authorities say that it is difficult to implement new environmental strategies as plans are only revised once every 10 years and as well as this they are often overruled by the Planning Inspectorate.6  Therefore we need to increase the pressure on the Government so this policy will be put into place to help swifts.

As well as implementing these strategies individually and pressurising government, it is important to raise awareness about swifts’ decline in the UK. This could encourage more people to provide swift nesting sites in houses, garages, barns, walls and outbuildings, compensating for those previously removed in recent years, and allowing this incredible bird to flourish in the UK once again.


1. Bird Facts, Swift. British Trust for Ornithology.

2. Nicola Chester. Save Our Swifts. RSPB.

3. Professor Dave Goulson. Insect Declines and Why They Matter. The Wildlife Trusts Somerset.

4. Tom Finch, James R. Bell, Robert A. Robinson, Will J. Peach. Demography of Common Swifts (Apus apus) breeding in the UK associated with local weather but not aphid biomass. International Journal of Avian Science. Volume 165, issue 2. 2022.

5. Manthorpe Building Products. New homes for swifts – the Manthorpe swift brick. RSPB.–the-manthorpe-swift-brick/

6. Patrick Barkham. Tory MPs back mandatory Swift bricks in all new homes to help declining birds. The Guardian. 6 July 2023.

Beth Critchley is studying Environmental Science at the University of York. 


Critchley, Beth “ECOS 45 (2.2): Undergraduate Award 2023” ECOS vol. 45 (2.2) ECOS 2024, British Association of Nature Conservationists,

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