Attracting swifts to nest- some personal observations
I should stress that these are personal observations. They arise from three colonies started on houses we have moved to in Westwood, Wiltshire and Ampleforth and Gilling East in North Yorkshire. We have managed to attract swifts at all three houses, all within two years of moving in. I am often contacted by people worrying that they are not playing calls frequently enough or loud enough and my experience shows that you can attract swifts by playing calls for very limited periods at relatively low volume. This is important when considering neighbours, but frankly I really dislike repetitive swift call recordings! There is plenty of room still for experimentation with calls and with different nest site designs- we are all still learning!
A brief history of attracting swifts in Gilling East
From first playing calls here in Gilling East in 2018 we had three pairs of swifts in occupation of nest sites at the end of the 2021 season.
A brief summary of success 2018-2021
2018- calls first played around boxes on our house in Gilling East. A pair enter a box for a few days in the last week of July but do not roost.
2019- a pair occupy a nest box 3rd June breed late and fledge young in late August
2020- the same pair returns and breeds fledging young on 31st July. Plenty of prospecting but no second pair this year.
2021- the original breeding pair returns. They are joined by another pair on 9th June which fledge young in late August. In addition a third pair occupies another box 8th July and they build a nest so we are hopeful that this year we will have three breeding pairs from none in 2018.
2022- all three pairs return between 9th-16th May. Already another pair are prospecting.
I have attracted swifts to nest at three different houses now as work has meant we have moved several times in the last twenty years. In each case calls were almost certainly essential in attracting the first pair. I usually stop playing calls when the first pair breeds. This is a personal choice because I love to hear only the natural calls of swifts. Be warned though, descended sky roosting non-breeders can scream loudly as they first pass at dawn! It is though a wonderful way to be woken up.
At each new house, after the first pair has been attracted we have gained on average about one additional pair each year. It is clear that other swifts learn to recognise a type of nest site based on observing the first nest box pair. Once this happens boxes on nearby houses can be recognised by swifts and occupied even if calls are not played. This happened back in 2003 when a friend put up boxes about 300m away from our house and didn’t play calls; he had swifts entering within days of putting the boxes up. Here, last year swifts checked similar boxes to ours about 100m away with no calls played- hopefully they will occupy this year. Already at Helmsley Swifts we are seeing nest boxes taken where calls are not played- we play calls at several nest boxes at chosen sites across the town as it is impractical to play them at each site. We are sure this is because swifts prospecting learn to recognise nest boxes as potential nesting sites. Having boxes on different houses makes a lot of sense. For example when we move house all the ‘eggs are not in one basket’. One always hopes that the next owners of the house will keep the swifts but there is no guarantee so it is wise to encourage neighbours to put up boxes too.
I always block entrance holes up until mid April to prevent tree sparrows from ramming them full of nest material, but keep a keen look out from mid April. We once had a swift back in a nest site in Ampleforth on 16th April! I have many tree sparrow boxes but they do show a preference for swift boxes, often moving to them for their second or third broods.
I have always used front entrance ‘shoe box’ sized swift boxes and uptake has always been quick- within two seasons. Where eaves are on the lower side I think a front entrance enables departing swifts to keep more height than bottom entrance boxes. Bottom entrance boxes are a well proven design but as an artist front entrance boxes give me a better view of the adult swifts as they emerge and enable me to more easily sketch the young as they peer from the entrance in the days before they fledge. Each year I sketch the face markings of adult swifts which enables me to identify some individuals and front opening boxes make this much easier. I don’t think a different design of nest box could have attracted swifts any quicker.
The first box to be occupied here had the most difficult(to our eyes) flightpath, particularly when my son’s bedroom window was wide open(see photo above)- again I have watched several successful fledgings from this box so can feel completely satisfied that it is well positioned.
Of the eight swift boxes on this house all three occupied boxes are next to each other, the second pair nested next door to the first and the third pair nested next door to the second. However this is only one site so I am careful not to draw too many conclusions from this. When our first pair started breeding I did play calls on the other side of the house, but it seems new pairs were more attracted to the sight and sound of a real pair than calls.
Nest site prospecting (‘bangers’)
I used to get frustrated watching ‘banging’- “why aren’t they going in”?! But I have come to learn that these near misses are an essential part of the process. Remember a few weeks or even days before you had no swifts visiting your house at all! With each new colony I have observed periods of birds flying up to the eaves but not going in to boxes. I have long thought that ‘bangers’ as a description of swift behaviour should be more specific. After countless observations I see two distinct types of ‘banging’.
The first type is most noticeable earlier in the season (from end of May) when the younger ‘bangers’ are not here. Some of these early ‘bangers’ will breed by mid June and might fledge young as late as September. They are older non breeders, more experienced at approach and landing(perhaps last year’s July bangers). They aim at a breeders’ box and perch first time. My second breeding pair did this to the breeders a couple of days before they moved in to a box next door and started to breed. They could clearly land on any box but choose the breeders’ box. Why, curiosity, or perhaps they are already fellow members of the colony so perhaps this banging is an extension of social aerial activity??
The behaviour most often referred to as ‘banging’ is more random and involves touching or landing on multiple boxes or below them, under gutters etc. This behaviour is more commonly seen towards the end of June and throughout July. In my view many of these birds will not be persuaded to enter that year because they are simply not mature enough. They appear to be practicing approach and landing as well as scanning potential cavities. Swifts although amazing fliers have to learn manoeuvres in tight spaces. If you watch them you can see they try different approach angles. Eventually more experienced birds learn the most efficient flight path and tend to stick to it.
Much of the swift behaviour we watch (and many get frustrated by) will not lead to finding a nest site that season because they are not sexually mature enough to feel the urge to do so. Can we even prove that this behaviour is prospecting for nest sites or could it be something else? Perhaps it is largely a social activity where younger birds are joining a colony for the first time?
When swifts do become sexually mature the ‘switch’ is flicked and they may suddenly enter nest boxes confidently and rapidly. No amount of call playing will persuade them to do so until that ‘maturity switch’ is flicked, however the calls have attracted them to a new potential nesting area which they will probably return to the next year. I have no doubt they see the nest box entrances, how couldn’t they when in flight they can catch tiny insects, but they have to be old enough to take it further?
My advice is to relax and enjoy watching ‘banging’ behaviour- it is spectacular behaviour to watch and is very often the beginning of a new colony. It is easy to be frustrated that they are not entering boxes, but if they are not mature enough the likelihood is that nothing will persuade them that year. Often bangers will visit and display intense activity for twenty minutes or so then move on- sometimes you can see them move to another location to do the same, here they ‘banged’ at our house then repeated the performance 150m away at the village hall where two pairs nest. This indicates they have not yet chosen a colony to join, let alone a nest site. It is a stage I have observed with every new colony I’ve started and in each case the following year a box was entered. So these days I sit and enjoy watching the ‘bangers’, sketchbook to hand- the ‘bangers’ offer some of the best views of swifts, especially when they linger on a wall in the open then fall away to fly inches from my face!
One more thought on nest site selection, in my opinion a very important one. Consistently the birds to watch have been the solo prospectors(male swifts?). There is no doubt they select quiet times to prospect for nest sites, when groups of ‘bangers’ are not around. They make no calls at all. At our colony in Ampleforth one such bird was an aberrant male which silently and alone entered a nest box three short times in a season. It never roosted and didn’t attract a mate but it came straight back to breed in the same box the following spring.
Once the site is entered and selected the swift will return with a mate, sometimes in the following year. The pair will circuit fast with the lead bird showing its mate the nest site often screaming when close to the entrance. After a few fast circuits the lead bird will enter the site hoping the mate will follow. This can happen quickly or the mate can take many attempts to get the approach and landing right. Sometimes the lead bird(male?) in the box will leave, join up with its mate in the air again and repeat the process until she(?) enters the nest site.
It is possible that all these silent prospectors (as with many other species) are males who select the site then attract a female, but we cannot identify their sex in flight. The aberrant male in Ampleforth presented me with a rare opportunity to identify the sex of the solo prospector, but I could only do this a year later when I saw it mate in the box!
Non breeding occupants to breeding pair
I have seen two main scenarios where birds enter nest boxes then breed.
- A pair enter from June onwards and start a nest to be used the following year. They can enter for the first time a few days before most swifts leave and breed the following spring. I put a new nest box up on 20th July 2018, a pair was in on 23rd July 2018 and it was used for breeding in 2019.
- A single bird (male?) enters a box several times in a season but doesn’t roost or attract a mate in. It returns to the box the following spring, attracts a mate and breeds that year.
Swifts have an aerial territory around a nesting site. With frequent observation you can observe this as birds tend to circle, especially in the evenings around their aerial territory. In the early stages of colony formation birds may circle frequently over your house. Increasingly you may see high speed, low level flypasts with very loud ‘screaming’. We can only speculate as to the reason but these flypasts probably consist of colony members perhaps with prospective colony members as summer progresses. With a new colony you might experience many flypasts before birds have even entered nest sites. In my experience frequent screaming flypasts, especially if they continue with your calls off are a very good sign for future colony development.
Playing swift calls
Most swifts arriving in May are already tied to a nest site. It is very unlikely that these birds will prospect your nest boxes. You can play calls at high volume with birds nearby and they are usually completely ignored. There is however a chance that birds whose nest sites have been destroyed over the winter will prospect so it is worth a try. But don’t be despondent if your calls have no reaction even from swifts overhead in May, hopefully towards the end of the month, given warmer weather the first prospecting swifts will be here; this is the time playing calls can really work its magic.
From my observations starting colonies, 6-11am is the peak time for prospecting or ‘banging’, perhaps especially 7-10am. There is sometimes a session at lunchtime or at the end of the afternoon on really warm or humid days. Evenings in my experience are best for watching high speed low level fly-pasts- I have seen very few evening ‘banging’ or prospecting sessions at any of our colonies. I have noticed that if you are playing calls and have prospecting swifts in the morning they almost always return to perform low level flypasts in the evenings with calls off. The evenings seem to be social time for swifts and I usually turn the calls off and enjoy the show. If haven’t got a nesting pair but they keep returning time after time without calls playing the main attraction work might already be done.
I have a strong feeling that in many cases once swifts have been attracted to calls a few times that could be all that is needed, but it is perfectly understandable that people keep playing them to be sure. Every situation is different- you may be wary of upsetting neighbours or you may live in the middle of nowhere where nobody is affected. It is very important though to be sensitive to people living around you.
Try turning calls off once the bangers arrive, then give them a burst every so often- this is much more likely a natural colony situation. There is so much experimentation to be done still. Once I have attracted a first pair I stop playing completely and enjoy watching the swifts attract more swifts. It is easy to see swifts join swifts in the air before they descend to eaves level. The presence of house martins as they come and go also frequently attracts the attention of ‘bangers’
I made a lot of notes on prospecting times in 2021 and the morning period still proved to be by far the most productive for prospecting. If you are playing calls and don’t want to disturb neighbours too much it may help to concentrate calls only to the most effective times- if I was choosing 2 hours playing I would go for 7.30-9.30am. Also once activity is sustained and birds come back when calls are not being played I found that reducing the volume even to well below natural levels was still effective, possibly more effective, perhaps imitating the sound of birds calling from within a loft? In some cases just a few doses of calls may be enough to sustain interest. So don’t feel you have to pump up the volume all the time- once prospecting is sustained and screaming flypasts are frequent without calls, you are probably already there. Good luck!
Positioning a swift nest box- height
Many people are concerned about positioning a swift box too low. I know of several nest sites in eaves of 2 metres height. These are unusually low but nevertheless the swifts choose to use them. Agile cats could be an issue for the swifts on low approach or departure(Gilbert White wrote about this problem in 18th century!) and at another colony I watched in Hungerford High Street some swifts were killed by cars when they swooped low over the road to access nests 3 metres above the ground. Sometimes swifts are downed by corvids or sparrowhawks as they access nest sites, but this could occur at any height.
A question I am often asked is, will the nest box be too low for a swift to fledge successfully? I have seen many swifts fledge and in each case the fledgling lost less height than a typical adult leaving the nest. Basically the fledglings flap hard from the outset and take a far more level course before rapidly gaining height. So from my own observations I would not be particularly concerned about fledglings losing height, the adult birds lose more height. I have seen fledglings leave at dusk through tree ‘cluttered’ flight paths where we would not recommend siting boxes and all were successful. To me it is clear they have great spatial awareness from the outset even in near darkness.
Even at recommended minimum heights of 4-5 metres and more, adult swifts often take a trajectory that takes them very close to the ground- frequently 1 metre or even less over our lawn when they leave the box. This is clearly a choice as they have the ability to stay higher. The ‘drop’ from the nest, aided by gravity gives the swift quick acceleration which gives it a better chance of evading predators before climbing to a relatively safe altitude. Almost any situation will have its dangers as would a ‘natural’ nest site eg. weaving in and out of trees or cliff face situations. Each potential site should be judged on its own merit.
I am an area adviser for Swift Conservation in Yorkshire and with Ian Kibble and Paula Sidebottom started Helmsley Swifts https://twitter.com/helmsleyswifts?lang=enI do follow us on Twitter
Swift Conservation and Action for Swifts have websites packed with advice on attracting swifts. Swift Conservation even has a shopping page with many links to nest box suppliers etc.
There are too many swift conservation groups to mention individually. Twitter is very useful for finding your local group.
Bristol Swifts run by my friends Mark and Jane Glanville is a superbly informative site about swifts, especially on news from their own Bristol colony. Mark keeps a superb blog through the swift season.
Leeds Swifts, fellow Yorkshire swift fans have lots of information about swifts and swift rescue. They keep a superb blog on Facebook throughout the swift nesting season https://www.facebook.com/search/top?q=leeds%20swifts
Bolton and Bury Swifts carry out extensive swift(and house martin) conservation work in Lancashire
Sketches of swifts in 2021
These sketches were all made from observations of common swifts last year. The are presented in chronological order. We had a single pair of swifts nesting on our house in a Gilling East, North Yorkshire. I have sketched them in the air and in the nest box. The common swift has captured my imagination since childhood. Don’t waste any opportunity to watch and listen to these incredible animals this summer. Hold the memories firm in your mind and you will be able to recapture your swift experiences in the darkest days of winter.