Article about Swift nest box siting in British Birds magazine for May

[Edward Mayer]

I have only just got this, it is very detailed, but I haven't managed to
read it yet!

[Tim Collins]

Hi Edward

I’d read the paper very cautiously; I’ve read it and looked up and read the two key references. In my view it uses not especially relevant evidence to extrapolate to a conclusion that nesting swifts will die if temperatures in a nest box reach 40c. It does NOT present evidence about the temperatures that actually cause problems for swifts.

The paper uses 40c as its critical temperature threshold based on a study of chickens published in 1951 and a review of the thermal tolerance of avian embryos from 1987; ‘Apus’ swifts were not part of the latter study. Also in the latter study, where over heating reduced the hatching rate of eggs, it appears that this was normally with exposure to artificially induced high temperatures for periods of 8-24 hours. Clearly swifts nesting in built in swift bricks are only subject to the risk of prolonged over-heating if the bricks are in exposed south facing location (and then for only part of any day).

The paper would have been more convincing if it had studied the actual temperatures at which swift eggs fail to hatch and looked at the temperatures at which swift nestlings jump out of boxes before they are ready to fledge (I realise this would be a challenging study).

Clearly we know that extreme high temperatures can cause problems for swift chicks however the evidence presented in this paper doesn’t convince me that 40c is a lethal threshold, especially if such temperatures are only for a limited duration. To then conclude (as the paper does) that swift bricks shouldn’t be used in exposed east and west facing walls feels to me to be wrong. In my view nest site availability is such a key limiting factor for swift recovery in the UK (and, in Northern Europe at least, overheating of swift bricks in east and west facing walls is many years away from becoming a serious issue) that we need to avail ourselves of all sensible locations for swift brick installation. 

The full paper in British Birds is currently only available to subscribers, though an abstract can be viewed here: https://britishbirds.co.uk/journal/article/positioning-built-nestboxes-common-swifts

The two references discussed above are available online via Google Scholar, search for:

Thermal Tolerance of Avian Embryos: a Review
D. R. Webb

and

Lethal Internal Temperature for the Chicken, from Fertile Embryo to Mature Bird

R.Moreng & C.Shaffner

More work is clearly needed on this issue

Tim 

Author links open overlay panel

[Graham Knight]

Hi Tim 

Very good points made.

In addition, they tested only one type of concrete integrated box. There are now dozens of models of Swift bricks, many of which are masonry-fronted, and hopefully cooler

Tests would be needed on a variety of models but I would expect variations in internal temperature depending on the materials used for both the exterior and interior. 

I wonder if anyone has carried these out already?

Best wishes 

Graham Knight

Sawbridgeworth Swifts 

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[Tanya Hoare]

hi Tim

Excellent review Tim, thank you, very helpful. It's all too common sadly that papers are published where the conclusions extrapolate beyond what the study actually measured or was designed for. And using old and outdated studies in justification as 'evidence'. This gets even worse when the conclusions are then quoted in further papers and they  gradually eventually get accepted as 'fact'.  

Another thing that happens is the use of clever statistics, that very few people would understand, applied to a poorly designed study that is based on too many unwarrented assumptions; the truth is that no amount of sophisticated statistics (that most readers gloss over and do not even read) can rescue a poor design. I've come across this even recently in other papers relevant to swifts.

So that’s great that you read all the methodology and pointed out the flaws. Thank you.

regards

Tanya & Edmund

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[Cally Smith Huntly & District Swift Group]

Hi sorry is it possible to reattach this article please?  I cannot find Edwards original message and attachment.

Thank you

Cally

[Tony Croft]

Hi,

I wondered if anyone has any ideas why in Hathern, Leicestershire (LE Postcode) we have seen such a huge decline in swift numbers. ..

Up to 3 years ago our 5 Schwegler boxes were fully occupied as they have been for over 45yrs when we first moved into our house.  We also had "screaming" parties of 30 to 40 birds regularly around the village and other houses with boxes which were similarly full.

Suddenly 3 years ago we had only 2 pairs return to our boxes and then the last 2 years no returns.. in fact I have only seen 3 swifts this year over the village!

As others seem to be reporting reasonable numbers this year I wonder if on return to Africa  they migrate as a group and go back to a particular site there?

Could some cataclysmic event in Africa where Hathern's swifts return to, be the cause of such massive reduction in numbers returning to our village sites over the last 3 years..?

Just wondering...

We had 2 pairs of youngsters look at our boxes at the end of last season so we were hopeful for this season but despite a caller system and 2 additional new boxes no returns at all.....very sad as we've loved our little colony over the years.

Any thoughts ?

Best Regards
Tony & Anne

Hathern Swifts
   

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[Swifts (SOS)]

Might the interiors of the nest boxes deteriorated over time, if up 45yrs+. 

I know of locations where birds of prey have learnt to target parents returning at the nest box; seen both Kestrels and Sparrowhawks doing this successfully. Is this a possibility there?

Is the decline there replicated elsewhere locally?

We are still waiting for Swifts to return to monitored nest sites here, plenty of time, always fingers-crossed in May

Eddie 

SuffolkBirdGroup.org

On 22 May 2025, at 10:22, Tony Croft <the.cro...@gmail.com> wrote:



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[Dick Newell]

The only cases I know of rapid disappearance of Swifts from established sites is predation by Kestrels or Sparrowhawks.

Typically this has been in larger colonies.

Dick

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[Tony Croft]

This started 3 years ago from 5 full boxes down to one box of a pair of  "returners" 2 years ago to none last year and this year!

After 40+ years of "nest wars", as we only had limited wall space, to silence now..we are just do sad and wondering what could have happened to "our" birds...

Now 7 boxes all empty....our neighbours are doing their bit and have put up swift and bat boxes this spring is as we have a number of bats round the gardens.

 Families of foxes and badgers also go through the top of our garden...

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[Jean Stafford-Baker]

This is so sad to hear. Heartbreaking for you. It doesn't seem feasible for them to have all come to the natural end of their lifespan simultaneously, does it. It must leave you wondering with a giant Swift shaped whole in your life. So sorry. I hope your fortune changes.

Jean (Norwich)

Yahoo Mail: Search, organise, conquer

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[Louise at Bolton and Bury Swifts]

Hi Tony,

I also have missing birds, quite a few of us do. I'm really hoping more breeders will come. There were quite good numbers passing through France yesterday. I really hope you will get some back. Non breeders from last year still have plenty of time too.

Keep us posted.

Louise

Bolton and Bury Swifts 

https://www.facebook.com/BoltonAndBurySwifts

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From: swiftsloc...@googlegroups.com <swiftsloc...@googlegroups.com> on behalf of Tony Croft <the.cro...@gmail.com>
Sent: Thursday, May 22, 2025 3:47:41 PM
To: swiftslocalnetwork <swiftsloc...@googlegroups.com>
Subject: Re: [SLN] Lack of returning Swifts

 

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[Tony Croft]

Thanks for the positive comments and concern...fingers crossed crossed we might get late returns yet!

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[alofanglia]

It’s interesting swifts in colonies and lone nests….A colony once a bird of prey has found it offers a smorgasbord while single discrete nests give less reward for finding it.  My single pair enter and exit silently with my neighbours hardly aware of there presence.

Due to this trying to get more single boxes in buildings over a wider area maybe will offer long term security then high density nest sites in towers although I like the idea of church towers offering  sanctuary to swifts from which they can recolonise new nest sites in new builds or enthusiasts boxes….

All the best and hopefully swifts will return….

Alistair 

Sent from my iPhone

On 22 May 2025, at 18:04, Tony Croft <the.cro...@gmail.com> wrote:



Thanks for the positive comments and concern...fingers crossed crossed we might get late returns yet!

Best Regards
Tony & Anne
   

On Thu, 22 May 2025, 17:43 Louise at Bolton and Bury Swifts, <super...@outlook.com> wrote:

Hi Tony,

I also have missing birds, quite a few of us do. I'm really hoping more breeders will come. There were quite good numbers passing through France yesterday. I really hope you will get some back. Non breeders from last year still have plenty of time too.

Keep us posted.

Louise

Bolton and Bury Swifts 

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[Louise at Bolton and Bury Swifts]

Hi Tony,

Did any Swifts return to your place? Hope so!

Louise 

Bolton and Bury Swifts 

https://www.facebook.com/BoltonAndBurySwifts

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From: swiftsloc...@googlegroups.com <swiftsloc...@googlegroups.com> on behalf of Tony Croft <the.cro...@gmail.com>

Sent: Thursday, May 22, 2025 6:03:51 PM

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[Tony Croft]

Hi Louise

No "returners" but we've had a "gang" of 10 mobbing us this afternoon in the sunshine and now our caller is on we've got some very interested birds !

I assume these must be juvenile 1st year returners (can someone confirm this could be the case please?) who are looking to pair up for next year?

Whatever it's fantastic to see an increase and some interest in our 7 empty boxes!

Our neighbours have also put up some new boxes so fingers crossed they may some activity too.

We've had about 10 to 12 birds in a screaming party most of the day since the sun came out!

Feeling more optimistic now....

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[Louise at Bolton and Bury Swifts]

Hi Tony,

That sounds encouraging! I think they are more likely to be 2+ yr old birds. 1 year old birds may still be winging their way towards us 🤞🏼

Louise 

Bolton and Bury Swifts 

https://www.facebook.com/BoltonAndBurySwifts

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From: swiftsloc...@googlegroups.com <swiftsloc...@googlegroups.com> on behalf of Tony Croft <the.cro...@gmail.com>

Sent: Tuesday, June 10, 2025 5:56:46 PM

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[Tony Croft]

Definitely got one pair looking closely at our empty boxes.  The caller does seem to have attracted them to the boxes....

It's been very sad to be without our birds!

I wonder if all our birds (by that I mean from our boxes on our house not the village population) go back to a single area in Africa and something catastrophic has happened to them there? We'll probably never know!  It's still lovely to have screaming parties back!

Best Regards
Tony


   

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[Nick Bentham-Green]

Dear Tony,

I wonder if the decline in your returning swifts might be because of a lack of decent foraging nearby?

The reason I ask is that here in Cornwall, the number of swifts returning year on year is steadily increasing. Every year when we put up more boxes they are occupied almost immediately.  I put this down to the fact that there is exceptionally good foraging for the birds right on their doorstep, with trees, hedgerows,  meadows, and cattle pasture.

I wonder, if your birds do not have good foraging nearby, and have had to travel long distances to get food, then perhaps, it has become too difficult to rear young, so the adults have gone elsewhere.

Very Best of Luck

Nick

SE Cornwall

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From: swiftsloc...@googlegroups.com <swiftsloc...@googlegroups.com> on behalf of Tony Croft <the.cro...@gmail.com>

Sent: 11 June 2025 09:37

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[Chris Mason]

Hi Tony

Here's another reason not to give up hope.

My sister lives in Otley, West Yorkshire. She moved house in 2019.  No Swifts that year or since, until now when she has a pair roosting regularly. She hasn't been playing the calls. Her neighbour has told her that Swifts nested there regularly until about 15 years ago. These traditional sites remain in the memory for a long time!

Chris Mason

Cherwell Swifts

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[Tony Croft]

Thank you......we've got hopes as we've had small groups approaching the boxes at speed so hopeful for nesters next year.....but so lovely to see than again ...

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