Swift bricks debated in the House of Lords

There was a debate in the House of Lords last week to discuss the proposed Amendment 245 to the Planning and Infrastructure Bill. This has been put forward by Lord Zac Goldsmith and proposes that a universal Swift brick be built into all new homes constructed in the UK. This would prove to be a game-changing moment for Swifts (and our other red-listed home-nesting birds) because both the last Tory Government and the current Labour Government have refused to do this to date. On Wednesday Lord Krebs (who is an Oxford academic) claimed that swift bricks don’t work - and objected to the Swift brick amendment - based on stating that swifts only nest in towers (like those in the Oxford University Museum of Natural History). Unfortunately due to his credibility, his claims could be very damaging not just for the proposed legislation and campaign, but on the whole concept of swift bricks. How anyone, not least an eminent scientist and ornithologist like Lord Krebs, can have views on the natural history of Swifts and the causes of their decline, so at odds with the Swift conservation community seems to defy reason. You can read what Lord Krebs said below. And also our reply to Lord Krebs below that.

Lord Krebs said:

“I rise with some trepidation to speak against Amendment 245. In so doing, I emphasise that I have the greatest respect for the noble Lord, Lord Goldsmith, and his superb work as Environment Minister in your Lordships’ House, as well as respect for the other signatories to this amendment. My opposition may be surprising if your Lordships recognise that I am an emeritus professor at the Edward Grey Institute of Field Ornithology at Oxford University—which is arguably the world’s leading ornithological research institute—as well as being a life member of the RSPB. So why am I against swift boxes? I am absolutely in favour of measures to halt the decline in swifts and in other species I will come to in a moment; my objection to this amendment is that it simply will not work. The amendment refers to fitting swift bricks on houses or buildings over five metres tall. Let me describe the basis on which I suggest that this will not work. The Edward Grey Institute is home to the longest-running study of swift populations anywhere in the world: it has been running for 78 years. The first thing to say about this long-running study is that the swifts nest in the tower of the Oxford University Museum of Natural History, which is not five metres tall but 58 metres tall. I will explain why that is important in a moment. I do not want noble Lords to think that this is my opinion alone. I consulted my colleague, Professor Christopher Perrins, who ran the swift study for many years and is a former director of the Edward Grey Institute. What he points out, and I agree, is that swifts are very specialised aerial feeders and flyers. They are superb flyers, and one consequence of their specialisation for flight is that in order to get into their nest, they need a very long, exposed flight path: like a jumbo jet landing at an airport, they need a long entry point. Equally important, when they leave the nest, they need a very large drop space in order to come out of the nest, drop and start flapping their wings to take off. That is why, when nesting in the tower of the university museum at Oxford, which is 58 metres tall, the swifts prefer to nest at the very top. Even boxes that are 15 or 20 metres from the top are not used by the swifts; only the ones at the very top. This is a very well-intentioned idea, and I am all in favour of measures that will help reverse the decline in swift populations, but I do not think this is the right one. So what is the cause of the decline in swift populations in this country? We have to look at the fact that it is not just swifts, but other bird species that are aerial insect feeders: house martins, sand martins and swallows are all in steep decline. They all have very different nesting requirements. The swift is the only one that nests in a hole, as the swift brick amendment would suggest, or under eaves. The real cause of the decline of these bird species is the decline in aerial insect populations. We all know, and it is an oft-repeated fact, that in the good old days when even I was young, if you drove down a country lane at night, your windscreen would be spattered with insect corpses. Now you drive down a country lane at night and your windscreen is completely clear. Yes, we should tackle the problem of declining aerial insectivores—swifts, house martins, sand martins and swallows—and declining insects, but swift boxes are really a bit player in this whole question. Although I support the intention of the amendment, I do not think it would deliver what is claimed and therefore, reluctantly, I do not support it.”

Response letter from Hampshire Swifts to Lord Krebs

Dear Lord Krebs

As trustees of Hampshire Swifts, we were surprised and dismayed to read your stated reasons for opposing Amendment 245 of the Planning & Infrastructure Bill whereby building regulations will make provision for the installation of an average of one swift brick per dwelling or unit greater than 5 metres in height.    While we respect your eminence and expertise in the field of ornithology, we think you are incorrect in your remark that ‘it simply will not work’.

You justify this remark by saying that swifts nesting in the University Museum tower in Oxford prefer to nest as high up as possible, over 50 metres, because they need to drop down a long way on leaving their nest.   Your comment ignores the fact that the vast majority of swifts in this country nest at the level of the eaves of a 2- or 3-storey house, as the many local Swift groups throughout the country can attest, and as records submitted to the RSPB’s Swift Mapper, to the Hampshire Swifts survey, or to county biodiversity recording systems show.     Our survey data includes many instances where swifts - birds with exceptional manoeuvrability in the air - naturally nest at around 5 metres above the ground and/or in sites where the flight path they use to and from their nest entrance appears far from ideal. The lowest Swift nest site that we know of here in Hampshire is in the eaves of the porch of St Hubert’s Church at Idsworth, north of Portsmouth; the nest is at a height of about 1.6m above ground level. The ground does not drop away and the birds fly out between the rails of a post and rail fence. You can read about this and see pictures here https://www.hampshireswifts.co.uk/post/swifts-at-st-hubert-s-church.  It is incorrect to say that ‘they need a very large drop space in order to come out of the nest’. Swifts are perfectly capable of flying out of their nest sites almost horizontally as they do at Idsworth.

You state that the decline in swifts is due to decline in aerial insects, but so far there has been no good scientific evidence in support of that claim. Scientists have been trying to prove this for years and failed to find any evidence.  Anecdotal evidence on swift colonies both here in Hampshire and elsewhere doesn’t suggest that the adults are having difficulty feeding their chicks which one might expect if insect decline was affecting their ability to find food.  The first thing that would happen if that were to be the case would be a decline in fledging rates. Whilst these do vary from year to year, that is caused by prevailing summer weather conditions and there is no evidence of a long-term decline.  By contrast, those, like us, working in swift conservation are all too aware of how building renovations, roof repairs, and particularly uPVC soffit and fascia replacements, has destroyed huge numbers of swift nest sites in the areas we work and live in.   Modern building techniques and regulations requiring better insulation mean that growing numbers of houses offer nowhere for swifts to nest, or indeed for other urban bird species such as starlings and house sparrows.  

The proposed change in building regulations to require the installation of swift bricks in new buildings would make it far easier for swifts to find places to breed and hence recover their numbers.    And we know swift bricks work.    See, for example, the 2023 paper in British Wildlife by Newell & Willis.    Here in Hampshire, large numbers of artificial nest sites, including many swift bricks, were installed on the New Milton Estate in 2011-12 to compensate for loss of natural nest sites.    This year a record 80 pairs of swifts nested there, along with many starlings and house sparrows (see https://www.hampshireswifts.co.uk/post/new-milton-estate-swifts-2025 ).   In Winchester, where we have installed over 500 swift boxes in the last 7 years, our survey data estimates that the number of breeding pairs of swifts has increased by 31% between 2018 and 2024 (see https://www.hampshireswifts.co.uk/post/winchester-s-swifts-in-2018-and-2024 ) and has further increased to 43% this year. This is entirely due to the fact that as natural sites have declined due to roof repairs/enhancements, Swifts have moved into the boxes provided. The vast majority of these boxes are fixed at around 5m in height.

In your speech, you said that you were “all in favour of measures that reverse the decline in the swift population”.   As a scientist and ornithologist, you can surely appreciate the potential benefits at the population-level of providing swift bricks in new buildings.      We very much hope that you will vote in favour of the swift brick amendment on Monday. 

Yours sincerely

Prof Catharine Gale

Tim Norriss

Hampshire Swifts