Boxes under sloping eaves

Pictures by Kerry Vaughan

[UPDATE July 2017: Swifts have occupied 2 boxes on the west side]

Sloping eaves can be a bit awkward, because, in general no standard box will fit nicely. We had a similar situation at Milton Road Primary School a couple of years ago, and the design used here at Suffolk Wildlife Trust, Lackford Lakes is essentially the same.

The box is installed by removing the sloping front, 2 screws through the back into the wall, then replace the front.

The end result looks rather good and in keeping with the building. The Suffolk Wildlife Trust has done a great job. AND Swifts have already been seen over the lake - on 5th April!

More pictures and design drawings:

click for larger pictures

Actual dimensions will depend on the angle of the roof slope

Swifts nesting in an open church loft

This is another situation where Swifts have access to each other's nests. 
Contributed by Lyndon Kearsley

"Onze-Lieve-Vrouw" (Our Dear Lady)

Last year, on 5th July, I was invited by Jaak Brosens to visit a church in Kalmthout to the north of Antwerp. The brick and stone church has a number of nest bricks inserted into the main roof. In the church tower the wooden steeple construction forms an open loft above the level of the belfry (just above the clocks).

The last row of stone has a lot of mortar missing between the blocks where the wooden steeple takes over and swifts are able to get into the open loft through these cracks. They nest next to an entrance hole and the loft is 15 x 15 meters. There are more than 20 nests and some quite close to each other.

We found that well grown young were visiting neighboring nests and very inquisitive. We also controlled a couple of ringed adults; one ringed as a chick in the same tower 10 years before to the day 5th July 2001, another was ringed as an adult bird (age unknown) on 2nd July 2004.

I hope to visit again this season.

Swifts nesting in an open roof space

Written by Dick


This is an interesting story which could have some implications for colony nest-box design. [Photos by Colin Smale (www.fotolincs.com), click any image to see them at a larger size. ]

The first three doors this end of the cottages
were empty dwellings © Colin Smale

Back in 1982, Colin Smale was studying a Swift colony in an old house in Lincolnshire. He estimated that some 30 pairs of Swifts nested there, but, as so often happens, the colony has long since been destroyed by roof renovations.

Eggs in adjacent nests © Colin Smale

There was a long row of nests, all on one level under the eaves, with little or no barrier between adjacent nests. Colin noticed that the numbers of eggs in the nests fluctuated up and down, as if the birds were moving eggs between nests, though he never actually observed birds carrying eggs.

Young Swifts in adjacent nests © Colin Smale

On 13th July 1982, he found that young Swifts were moving from one nest to another, some of which contained an infertile egg, so such nests would appear to not have failed. Also he often saw young Swifts doing push up exercises in preparation for fledging.

A fledgling Swift exercises © Colin Smale

The life of colonial Swifts is perhaps more complicated than we thought, and these observations may have implications for the internal design of colony nest-boxes.

In Colin's colony, it seems as though breeding adults could see each other, but the distance between the nests was approximately 2 feet (600mm).  Possibly the roof joists are just sufficient to keep them visually separated.

In a colony box, normally the nesting compartments are completely separated from one another, but is this necessarily the best thing to do? Should one separate nesting places by partitions, which stop short of the top of the box? So the birds would not be able to see each other, but any Swift screaming in one box would certainly cause sound to emerge from the entrance of an adjacent box, which could attract birds into that box.
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Swift boxes at Belfast Zoo

Here is a novel idea to attract Swifts - make them feel as if they are in Africa!

Contributed by Gayle Turley

Over the past ten years, Belfast Zoo has played an active role in native species conservation in Northern Ireland. Although swifts are regularly seen within the grounds of the zoo, there have never been any known nesting sites.

Schwegler 16s nest-boxes in the Giraffe enclosure

We are keen to change this and, after taking advice from a local enthusiast, we decided to go forward with a plan to attract the swifts to nest in the zoo for the first time. We ordered Schwegler No.16s boxes, 5 in total, and set about finding a suitable position to place them. We found that the side of our giraffe house was an ideal height and a perfect location to place the boxes. As the boxes are in the giraffe enclosure, extra care was taken to ensure they were high enough to be out of the giraffe’s reach! We plan to start playing a swift attraction CD from the end of April to increase our chances of attracting swifts to nest in the zoo.

We will also be placing educational signs in that area of the zoo, explaining to visitors what the nest boxes are for, why they are needed and hopefully raising awareness for the plight of the swift and encouraging others to put up nesting boxes.

For more information:

www.belfastzoo.co.uk

www.facebook.com/belfastzoo

www.twitter.com/belfastzoo

Wailing Wall welcome ceremony for returning Swifts

When this hit the news, we thought it worth highlighting and summarising here. As Jerusalem, is much further south and east, Swifts arrive in March, 2 months earlier than our birds, so they have already welcomed their birds back.  


Contributed by Jake

We all know that moment of joy when we welcome our returning Swifts, but in Jerusalem the welcome is huge, formal and very well organised. Every year, a ceremony takes place at the Western Wall in Jerusalem, where there is a breeding colony of Swifts.

Announcing the welcoming event

The proceedings are led by the Mayor and other local dignatories, together with Swift specialists like Dr. Yossi Leshem, from the Tel-Aviv University and Society for the Protection of Nature and Amnonn Hahn, General Manager of “FRIENDS OF THE SWIFTS” Association.
The Western Wall in Jerusalem is of great historical and religious significance.

American Black Swift wintering grounds discovered

We thought that this story of the American Black Swift Cypseloides niger is so amazing, that we are putting a link to it here. 

To quote from the article:


"It was one of the last North American bird species to be described to science, in 1857.  Its nest was not found until 1901.  The first audio recording of its voice was not made until 1993.  And every summer, across most of its breeding range, it is the last species to arrive from the south, often not appearing until the end of June. But most remarkably of all, it was the only North American migratory bird to enter the 21st century with the location of its wintering grounds still a complete mystery."


Here on the left are the maps produced of the wintering range of 3 birds and their return spring migration route.


We look forward to seeing equivalent results from geolocator tracking of European Swifts.


Read more here

An interview with John Stimpson

Contributed by Jake

The other day, I went to interview John Stimpson. John makes a range of nestboxes as well as other wildlife products such as bird tables and hedgehog shelters. For many years he had a garden nursery and just made a few nestboxes as a sideline, initially to provide boxes for his brother's garden to prevent his brother from paying "silly prices" for commercially-produced boxes. When John decided to give up the nursery business, he also decided to spend more time on nestboxing, or what he calls his "glorified hobby".

John Stimpson in his workshop (click to enlarge)

At first, John tells me, all his customers were locals, attracted both by the quality of his boxes, and by the reasonable prices he charges. In response to requests, he found himself extending his initial repertoire from boxes for small hole-nesters like Blue Tit and Great Tit and open-fronted boxes suitable for Robins, and Spotted Flycatchers to woodpecker boxes, getting his designs from published sources.

Today, John also produces more specialist boxes, notably for Barn Owls, Kestrels and Swifts. For the design of these, he took advice from specialists in the field. In the case of his Swift box - he only produces one type - he was advised by Dick, who based the design on the Dutch Zeist box.

The original computer model used by John

 It is a compact box, about 440mm overall length, 200mm at the widest point and about 190mm high. Particular attention was paid to the dimensions of the access hole, typically an oblong shape measuring 30mm x 70mm to discourage access by Starlings. It was also important to make the box easy to put up by having a removable roof, held by a single screw, in order to give access to the back for fixing. John points out that he does not pre-drill holes in the back, as each mounting situation is different.

John uses 12mm ply, which is described as "Far Eastern hardwood exterior quality ply". As a precaution, he gives his boxes a coat of preservative, and estimates that in normal conditions, ie not exposed to excessive sunlight or precipitation, they have an indefinite life. I asked him if the ply was from a sustainable source such as wood that bears the FSC stamp, and he assured me that his suppliers said it was.

Swift nest boxes ready for the new season (click to enlarge)

There is no doubt about the success of John's Swift box. In the last two and half years, he has sold just over 1700. Customers, mostly private individuals (though he has sold in quantity to two city councils, and to some local agribusinesses), usually ask John questions like where to mount the box and what they can do to attract the Swifts. For the former, he offers common sense and a leaflet, for the latter the CD lure.

Although John supplies only the one-size-fits-all Zeist-style box, he has on occasion undertaken to provide tailor-made boxes, as happened at the Maltings in Ely, where the spaces between the protruding rafters were all different. It is a costly and time-consuming business, though, so not something that John will undertake lightly. And, in a way, he doesn't need to. His reputation for quality and price has spread by word-of-mouth, underpinned by his frequent exhibitions at agricultural shows, village fetes and fairs and the like, thereby bringing in a steady flow of orders. He agrees that he received an enormous boost when the profile of the Swift was raised following its admission to the Amber list of Conservation Concern

I asked him about feedback. Although he asks every customer to let him know what happens, the feedback is disappontingly, but not surprisingly, no more than 15%, and that is usually from people who either want to communicate their joy at having breeding Swifts in their box, or from people who express indignation that they haven't. He recounted one striking success story of an order for six boxes from a woman who was having work done on her house, which necessitated scaffolding and other disturbance to her colony. The boxes were all immediately occupied, so she ordered another four, and these were immediately occupied too.

Before I left John, I asked him for a tour of his workshop. I make a few nestboxes myself, using some very basic equipment - a rickety old Bosch drill, my father's old tenon saw, a ratchet screwdriver, and an assortment of mostly recycled screws. John's equipment is mouth-watering: a state-of-the-art Bench Saw, a shiny new Band Saw and two Chop Saws. As to screws, he says with a grin that his suppliers, Screwfix, describe him as their "best customer" - he gets through thousands of screws every year.
The impression that John makes on his visitors is that of a happy man, doing what he enjoys most, getting satisfaction from knowing that he produces a good box at a fair price, and knowing, too, that he is making a contribution to the conservation of wildlife.

Lang may your lum reek, John Stimpson!

Contact details for John: j.stimpson1@btopenworld.com 01353 740451

Keeping Starlings out of the Schwegler 1 MF

Update 23rd May - see how this modification was implemented here

Contributed by Dick

Schwegler 1MF

In the first phase of the Fulbourn project, a number of the Schwegler 1MF boxes were occupied by Swifts, but also several were occupied by Starlings. This is because the entrance is too large.

On the inside of the louvres of this box, where the entrance is, there is a recess about 10mm deep . We have recommended to South Cambridgeshire District Council that they fill this recess with Polyfilla in order to reduce the entrance to 30mm.

If Starlings are occupying your Swift boxes, then reduce the entrance sizes and put up Starling boxes some distance away from the Swift boxes.

You can read more about entrance sizes in this post

Why are our African migrants declining?

Contributed by Dick

A recent paper in Bird Study (see reference at the end) has looked at correlations between population trends of migrants in Britain and a number of 'bioclimatic' factors in Africa. Of course, Swift is included in the 26 species they looked at.

Click for larger image

Some African migrants are increasing, including those which might have similar pressures to Swift, e.g. Swallow, House Martin and Sand Martin, but many are decreasing, especially Turtle Dove, Cuckoo and Spotted Flycatcher.

Two of the factors analysed are 'bioclimatic zone' with categories 'southern', 'humid', 'arid' and 'north', and 'winter habitat' with categories 'general', 'wetland', 'open' and 'wood'.

Swift is categorised as bioclimatic zone 'southern'  and winter habitat 'general'.

AfS Church Porch Poster

If you would like to promote awareness of Swifts in your local church, then why not download and print the AfS Church Porch Poster to place on your church notice board?

Click for larger image

First click on the image to see it a bit larger, then go here and hit 'File>download'.

The wonderful picture of a Swift is courtesy of Tom Lindroos.
The picture of the church is by Helen.

New light-weight geolocator for Swifts from Migrate Technology

Although we still wait to see published results, geolocators have already proved their effectiveness in tracking Swifts all the way from Europe to Africa and back. Particularly pleasing is that return rates are no worse than from ringed birds, showing that they have negligible impact on survival.

Now, Migrate Technology Ltd has announced a new range of devices, the Intigeo-W65 and Intigeo-W55, weighing 0.65gm and 0.55gm respectively. Especially attractive is the low price of these devices at £95 ex VAT.

Swift with Integeo-W55B1J geolocator
© Lyndon Kearsley

Novel in many ways, the manufacturer claims that this extremely energy efficient yet powerful miniature device will be the smallest geolocator available in the world to record near full range light level for an entire annual cycle. The device may be particularly useful for wader (shorebird) researchers or those studying highly aerial birds such as swifts, martins and swallows.

These new devices record, not only light levels for the determination of dawn and dusk for location, but also temperature and conductivity. Could temperature give an indication of the altitude that Swifts fly, given that temperature drops about 6.5°C for every 1km increase in altitude? Conductivity is unlikely to be useful with Swifts, but it could tell what kind of wet habitat a shorebird or waterbird is occupying.

This technology is in the process of causing a revolution in our knowledge of where Swifts and other small migrants spend their time in Africa.

Great Shelford Swift Belfry

This is another triumph for Rob Mungovan, ecology officer with South Cambridgeshire District Council. 

He has this to say: "Here is the recently restored school building in Great Shelford.  There were swifts nesting under part of the end wall. That aspect of the building could not be entirely retained but Hill Residential were happy to adapt the bell tower to provide for swifts and bats (as well as putting up other swift boxes).

The historic building people are happy with the look and the fact that we now have a restored landmark building, and I'm happy that we've provided for swifts and bats. This is a great outcome. We'll have to wait for next summer to see if it works."

There is a total of 20 nest-boxes for Swifts in the belfry, 12 in the lower level and 8 in the upper level.

A closer view showing some of the Swift entrances.






















Here are the Swift boxes at the top and bottom of the bell tower.

This is the partially completed bat roost.

A-frame Swift Tower

Contributed by Bob Tonks and Dick Newell

This is an idea borrowed from the Barn Owl A-frame, a very successful, well tried design for owls (Little, Tawny and Barn), Kestrel, Stock Dove, Jackdaw and even squirrels and cats.

It accommodates 6 pairs of Swifts. The whole thing can be assembled on the ground, then hoisted into position on a pole or wall. With the double roof it is well insulated from the sun, the front is easily removed for maintenance purposes.

Click for large picture

The front is an equilateral triangle with side 825mm. The depth of each nesting chamber is 425mm. The supporting strut below is as much there for aesthetic effect as it is to support the A-frame.

It is best not to orientate this box directly south, unless an extra thick front is provided. A smooth metal sleeve around the pole is also a good idea to deter rats and squirrels.



More pictures:

Idea for a Swift Tower

Contributed by Dick

This is an idea for a a swift tower which is intended to be relatively inexpensive and that hopefully can be erected by a group of competent amateurs without the use of cranes or cherry-pickers - but you are responsible for abiding by your local health and safety regulations. It is a modular design for ease of assembly. If you feel inspired to erect something like this, then please get in touch to discuss options.

Click for large picture

This is what it looks like from below. It contains 18 nesting places, 12 in the louvred cabinets and 6 in the roof. Access for maintenance to all nest-boxes can be achieved by removing any of the louvres or the gable ends. The materials are 12mm marine ply, 200mm x 25mm rough-sawn treated timber. 175mm wide feather-boarding, and 4 x 2 inch timbers. The dimensions quoted below are for guidance.


Assembly instructions:

A Swift game from Devon

Here is some fun for kids of any age - thanks to the Devon Wildlife Trust. It is educational and informative too!

Decay of a Swift nest

Contributed by Dick

People often ask whether it is necessary to clear out a Swift nest-box at the end of the season. This video shows that it is not necessary, as a thriving population of invertebrates will do it for you.



Between 14th August, after the 2nd chick fledged, and 6th November, the video shows one second per day. It is remarkable how much the bugs disturb the nest every day, reducing it from a beautiful feathered construction to a pile of detritus.

Swifts in Fulbourn, Cambridgeshire

Contributed by John Willis

Our project began in January 2011 when Rob Mungovan, the South Cambridgeshire District Council Ecology Officer, gave a very interesting talk to Fulbourn Forum on the work that was being undertaken to maintain a swift colony during the redevelopment of the Windmill Estate in Fulbourn. 

St Vigor’s Church: swifts nested above the clerestory windows

This colony is being monitored by professional ecologists during the redevelopment but there was little information available on numbers of swifts elsewhere in the village, so we were inspired to set up a small survey group for the 2011 season.

There was good general awareness about swifts in the village because of the size of the above colony (72 active nests in 2009) and the publicity generated by a feature in the BBC programme Inside Out East, broadcast in October 2009. The new housing development is called The Swifts and the name is also used for the new Parish rooms where the Community Library is based.

Many people were aware that in previous years swifts had frequented the area around St Vigor’s Church and the Old Manor House, which is a few hundred yards away to the east.

Cambridge AfS End of Year Report 2011

This report describes what we in Cambridgeshire have been up to this year. The Cambs team includes Jake Allsop, Guy Belcher, Helen Hodgson, Bill Murrells, Dick Newell and Bob Tonks

To say the least, we have been busy. We have progressed projects started in previous years, we have been involved in new projects, some of them spectacular and we have done a number of innovative things, including this blog.

Nest-box progress

Swift sculpture at Edgecombe

In 2010, we helped Cambridge City Council install 71 nest-boxes on Edgecombe flats. Resident, Peter Glass, used his CD player on his balcony, and succeeded in attracting Swifts to the area. In 2011 we provided “A Box of Swifts” to Peter, with the speaker attached to one of the Zeist boxes, with the result that Swifts were seen entering all 4 boxes next to his flat. Edgecombe flats promises to be a substantial Swift colony. The opening of the project was celebrated with this sculpture.

At Ekin flats, Cambridge, we advised the City Council roofing contractors how to avoid disturbing 3 existing nest sites in summer 2010; all 3 nests were again occupied in 2011. An additional 12 nest sites created by the roofing contractors are yet to be occupied.

At Birdlife International headquarters in Girton, a single pair of Swifts returned to breed in 1 of the 8 boxes installed in 2010. CD playing has been well supervised by Trish Aspinall.

Article in Cambridge News 20/7/2011
click image to enlarge

At Milton Road Primary School, the pair of Swifts that occupied one of the boxes in 2010 returned to breed. Fortunately, we had installed a CCTV camera, so the children could see the nesting Swifts on a TV screen in their library. After more CD playing, Swifts were seen entering all 4 boxes. We ran another workshop where all of the children made Swift mobiles, and we also added 2 more nest-boxes bringing the total to 6. The project featured in the local newspaper, the Cambridge News, in July.

Nest-boxes installed on people's houses in previous years included Bob’s house in Milton, where boxes were first installed in 2008, first occupants in 2009, first breeding in 2010, and probably two more boxes occupied in 2011. Bob has had this success as a result of dedicated CD playing. [we also discovered another house in Milton where Clarke Brunt succeeded in achieving an occupied nest-box for the first time after several years of CD playing].

Bob and Mary Osborne in Histon used “A Box of Swifts” to acquire their first occupants in boxes installed in 2009.

Bob Humphrey in Landbeach had his first occupants in a Pipe Box, in his 3rd summer of CD playing, and Neil Roberts, also of Landbeach, had his first occupants in a 4-Box Cabinet in his second year, with virtually no CD playing!

Dick's colony, also in Landbeach, increased from 6 to 7 breeding pairs. One bird was caught leaving the nest, then fitted with a geolocator by the BTO. The Landbeach Swift population has increased from 2 or 3 pairs to 11 or 12 pairs as a result of new nest-boxes.

After building work disrupted Swifts breeding in the eaves of St Andrews, Oakington, we installed “A Box of Swifts” in the belfry for a whole month. The Swifts responded well, and although we did not attract them into the 8 nest-boxes there, a pair of Swifts did nest in a small space outside of the louvres near the speaker.

At St Mary the Virgin, St Neots, where one pair occupied one of the 12 boxes last year, David Gill installed a new CD player, and he believes there may be two pairs this year.

At All Saints, Worlington in Suffolk, there was an increase from 1 breeding pair in 2010 with a second occupied box in 2011. CD playing has been well organised here by Judith Wakelam and Don Macbean. With 17 boxes in the belfry, the future looks bright.

At St Mary's Church Ely, where Bill inspired the first nest-boxes in 2007, this year, 26 boxes contained substantial nests, 13 of these contained 16 chicks, 2 contained eggs, so, there were at least 15 breeding pairs and 11 other occupied boxes. St Mary's is a great success despite no CD playing there. The evening Swift spectacle is well worth a visit.

Quite a few other projects are still waiting for their first occupants, despite well organised CD playing at some of them

New projects

The Cambridge Swift Tower
inspired by the African setting sun

The most sensational new project of 2011 was the Cambridge City Council Swift Tower, a piece of urban art, accommodating 100 Swift boxes and 10 bat boxes. At the opening event in July, the solar-power charged ‘bird scarer’ inspired a flypast by a squadron of 14 Swifts as the Mayor was starting his speech. Swifts were frequently seen around the tower, so signs are good for the future. Cambridge City Council, under the leadership of Guy Belcher, is doing an excellent job implementing projects for Swifts around the city.

As part of the Swift Tower project we ran a workshop with the children at Shirley Primary School, in which they made nest concaves out of Modroc and assembled Swift mobiles. They all received a copy of “I am a Swift - I am in Trouble”.

Other school projects included Newnham Croft, where we ran a workshop and installed 4 nest-boxes; and Elsworth Primary School, where we joined an eco-day and gave a presentation about Swifts to the whole school as well as running a workshop making a Swift mobile with a group of 12 children.

We worked with Anthony Clay to install 8 nest-boxes in the belfry of St Mary, Longstowe. CD playing was well organised, but there was no evidence of occupancy.

Further afield, we advised Carol Collins and Alan Wilkins in their project to install 10 Swift-boxes in the belfry of St Luke’s, Kinoulton, Nottinghamshire, which resulted in one pair of breeding Swifts in this first year.

Not least in our nest boxing campaign is the success of John Stimpson's sales of Zeist Swift boxes, made to our specification. John has now sold over 2000 Swift boxes. The same design has inspired Filcris to make a robust, waterproof box out of recycled plastic. Bob has now delivered over 40 4-box cabinets, mostly deployed in the Cambridge area.

Other activities included manning a stall at village fetes and a street party to celebrate the royal wedding in April. We responded to a large number of enquiries by people wanting to put up Swift nest-boxes; many more swift-boxes have been installed as a result.

Innovations

Knowing early in the year that we would be involved with children in schools, we set about finding ideas for children. These include the small book, conceived by Helen, titled “I am a Swift - I am in trouble”. We handed out about 300 of these, but we still have a few left for those who want them (price £1.50).

We devised a method of making nesting concaves out of Modroc. Some children stuck feathers onto nest-concaves. This involved autoclaving 10 kilos of pheasant feathers. We chose pheasant feathers so that we could easily recognise feathers that the Swifts might add - typically pigeon feathers.

We came up with a prototype Swift mobile design, which, with the use of some CAD (Computer-aided Design) software, was turned into a production design.

We also produced an attractive AfS polo shirt, using the AfS logo (Available from Jake at £15).

One of the main barriers to success in attracting Swifts is the hassle of installing and playing Swift calls. As a result, John Clamp, of Newnham Croft PTA, developed a small solid state player which drives a “tweeter” speaker. This kit, which we call  “A Box of Swifts”, has been successful in getting Swifts to occupy nest sites in 3 places this year.

An exciting project with which we were involved in 2010 was the deployment of geolocators on Swifts by the BTO, resulting in a massive increase in knowledge of where Swifts spend their time in Africa, where they linger and where they might be getting into trouble.

Our last innovation has been this blog, which started in February 2011 and has now had over 10,000 pageviews, so we hope people are finding it useful. We will continue to accumulate ideas and experiences which can be used by others who wish to help Swifts.

Encouraging Swifts in Oxfordshire

Contributed by Chris Mason


Our Swifts have gone for another year and I’m left to make plans for next summer and to reminisce about the positive things of the last few months. This year it has been not only the Swifts themselves that have inspired me. It had also been the time and trouble people take to look after their Swifts, and the lengths to which they will go to encourage them. Here are a few examples of what I’m talking about.

Two chicks ready to fledge

First of all there’s Richard who lives in Combe. A pair of Swifts took up residence at his home in 2000. They took over a small hole in the gable of his stone cottage which Starlings had just vacated and nested successfully. Encouraged by this, Richard began creating more cavities for Swifts in the gable end of his stone cottage. The numbers increased steadily, and by 2011 he had 10 nesting pairs, and one pair prospecting. He has made the nest spaces so that he can view the nests from his attic and this year an amazing 25 young Swifts have fledged from his home. The last two (pictured opposite in the nest space, just before fledging - perspex backing removed) left on August 20th.

How long do Swifts live?

Contributed by Dick

This question is often asked, and one answer is that the oldest known Swift was 21 years old. We know this, because the bird was ringed as a chick in Switzerland and recovered still alive. Just how many Swifts get to 21 years old? For that we need an estimate of survival rate, which Perrins 1971 gives as 83%. In the chart below, you can see what percentage of Swifts there are in the population at each age. For example, ~8% are 5 years old. Swifts that get to 21 and beyond make up 2.4% of the population.

Swift population structure