Largest Swift colonies on a single building?

[Graham Knight]

Dear all

I am looking for examples of the largest Swift colonies on a single building. I am aware of the Oxford NHM tower (53 breeding attempts in 2025) but am interested in other similar or larger colonies

In East Hertfordshire, we have been surveying the wonderful Swift colony at Redwood Court in Bishop's Stortford, where the Swifts nest in the many slots in the brickwork under the eaves - photos attached. This is an old Victorian Hospital building which was converted to flats in the 1990's. The Swifts have probably nested here for many years, but it was only "discovered" as a significant colony in 2023.

Since then, Gavin Vicary (NE Herts Swift Group) and I have carried out a great deal of survey work to establish the size of the colony. In 2025 we observed Swifts using 47 of the slots, and in the last 3 summers, we have seen them using a total of 70 different slots.

It is not the easiest building to survey, but we think it has 60-70 nesting pairs.

Unfortunately the management company wants to carry out redecorating works this summer. We are trying our best to engage with them and try to defer any scaffolding until the Swifts have gone. 

Any details of other large single-building colonies would help us to put the importance of the site into context

Best wishes

Graham Knight

Sawbridgeworth Swifts

Facebook - Sawbridgeworth Swifts

[Dick Newell]

Hi Graham,

The last time we checked, St Mary's Ely had 58 pairs in 96 nest boxes.

I think St John's Bury St Edmunds has a similar number in 60 nest boxes.

My own church, All Saints' Landbeach has 22 pairs in 60 nest boxes

At one point, St Mary's St Neot's had 48 pairs in 60 nest boxes - down to 4 pairs last year thanks to a Kestrel.

I don't know of any large single building colones near here.

Dick

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[Simon Evans]

Hi Graham,

St John’s in Bury St. Edmunds currently has 60 boxes with 59 breeding attempts and 112 fledged young in 2025. 

20 more boxes being installed ahead of this season.

Best wishes,

Simon

Bury St. Edmunds Swifts

On 22 Mar 2026, at 14:04, Dick Newell <dick....@gmail.com> wrote:



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[Swifts (SOS)]

Hi all, Suffolk

Peasenhall’s small Village Hall (below) has 9 natural nests under the front elevation, we’ve added 7 nest boxes to both front and rear elevations to help.

One building in Wickham Mkt has 23 nests under its tiles, it took for of us 2 evenings to work that one out.

Outside the county in Cambs, the Riverside Mill building in Godmanchester (W3W spruced.dispenser.lives) was completely bonkers with Swifts, I logged 10 Swift nests there on a walk along the river but there could quite easily be many multiples of that on the other elevations. One of the busiest Swift locations I’ve seen.

Very best wishes

Eddie Bathgate

@SoSSwifts

SuffolkBirdGroup.org/sos-swifts

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[Neil Whitaker]

A friend of mine who unfortunately passed a month ago has a property in Bluntisham, Cambridgeshire. I believe he had 13 Swift boxes around the 3 aspects of his semi detached house and over the last few years, with nest cams on each box, had recorded over 100 fledglings. I hope the boxes are maintained somehow in the wake of his passing.

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[nicki.baker]

We don't know of any colonies as large as the largest ones you cite, but a building in Blencathra Street, Keswick, that is rented out in flats, records up to 30 different natural nest sites in two of the walls, 

                                 Rear wall 2025                                                                         Front wall 2025

                                                                            

 and the Staff Quarters at Castle Inn, a hotel spa complex a few miles from Keswick and Cockermouth, has ~17 natural nest sites under the eaves.

     Staff Quarters, Castle Inn

Nicki

Keswick Swifts

[Tanya Hoare]

hi graham

I don't know if this 'counts' as a large colony in a single building, but we have 35 pairs breeding in our own cottage in Cumbria. Over a third are in natural nests in the eaves, the rest are in Cambridge system bricks or S bricks and 4 pairs in boxes.

regards

Tanya & Edmund

ta.h...@btinternet.com

(1) Sedbergh Community Swifts | Facebook

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[Tony Croft]

Sadly we've had 7 empty boxes for 2 years now....our last fledglings left 3 years ago and no returns....☹️

End of last season we had 2 pairs visit at the end of the season (attracted by the caller we have installed we think ) so fingers crossed for this year.

We've had swifts with an expanded colony for over 40yrs..  We do miss them.

Best Regards
Tony & Anne

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[Alistair]

Do foreign countries count too?  I think about 2000 pairs in the roman aqueduct in Segovia, 80km NW of Madrid https://www.turismodesegovia.com/en/acueducto/historia-del-acueducto

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[Graham Knight]

Thank you for the various replies to this request. It is interesting that we don't have many examples of large "natural" nest sites, as opposed to where boxes are provided, although the latter might be easier to monitor. Perhaps the days of 100 or more nests on a building are a thing of the past?

Alistair - the Segovia viaduct must be a wonderful site to visit in summer - I won't use it as a comparison for Bishop's Stortford however!

Best wishes

Graham Knight

Sawbridgeworth Swifts

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[Nick Bentham-Green]

Graham,

There is a significant swift roost site (circa 40 + nests) on the eastern side of Plymouth Sound. It is now called Bovisand Wall, and is a huge piece of stonework about 100m long and about 30m tall. In its former life it was the 'stop-butts' for a Royal Marines rifle range. It used to be an MOD site, but I'm not sure if it is now.

I have attempted to id where all the nests are, with a few others ( inc Stephen Fitt), but with approx 80 swifts hurtling around it proved challenging!

Nick

SE Cornwall 

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