This is part of a series of notes and observations on Swifts and our attempt to persuade a pair to adopt one of our nest boxes. It is also the context for describing the amazing and complex behaviour of these wonderful birds. The more we learn about them the more fascinating they become.
Although they are sometimes referred to as the European Swift (Apus apus) they spend relatively little time in Europe. They arrive here between the end of April and beginning of June to nest, and depart as early as the beginning of August, heading for their wintering grounds across Central Africa.
And when they are here we don’t necessarily see that much of them. They fly high and fast, and when weather conditions are poor they can easily depart to feed up to a 100km away from where they are nesting.
They are at their most prominent when the juveniles arrive in early June, and form noisy groups that scream with excitement as they fly at speed, especially during evening time. These groups of juveniles contain birds from one to four years old. The older juveniles will be on the lookout for a suitable nesting site for the following year.
They nest in small colonies and will be attracted to existing nesting sites with breeding adults – hence the importance of using a swift caller when trying to encourage the first pair to adopt a box.
The Story So Far – 2023 to 2025
Three boxes went up in 2023. A camera went into each in the hope of seeing something of the nesting behaviour of these extraordinary birds. To attract them to the boxes we set up a small directional speaker on an adjacent window sill to project a recording of the territorial / defensive call of the Swift towards the box – see Part 2: Nest Boxes and the Attraction of Swifts:
The result was plenty of Swifts, but all ignored the boxes. One possibility was that the call wasn’t sufficiently directed to a box, and so in 2025 we fitted a camera and small speaker inside a new box and added this to the row of three.
We started the internal caller in mid-April 2025 and continued to use the directional speaker on the windowsill. Although we saw less Swift activity during the summer than in previous years we finally got the result we were after, a number of juvenile Swifts entered the box, including a pair that returned regularly for several days.
The layout of the new box and the behaviour of the Swifts in relation to the internal caller is described and explained (as far as we are able!) in The Common Swift and Nest Boxes – 2025 update:
May 2026 to date – a diary:
A cold dry April and early May, and no views of Swifts until the 20th when we began to have regular views of ones and twos flying high and feeding.
On the 20th we saw the start of an exceptionally warm dry spell, with temperatures well into the twenties.
On the 25th we had our first view of a pair of Swifts flying low in the proximity of the boxes. On the same day at 4.00pm two entered the box and stayed until after 4.00am … a 12 hour stint.
For the next five days they maintained this schedule of about 12 hours in the box and 12 hours out, although on the 26th and 29th they also returned during the day for an hour a half.
Our assumption is that these birds are the pair that explored the box in 2025. They entered the box quickly. There was nothing tentative and exploratory about their behaviour, as we saw from them last year. Also, as yet we haven’t seen or heard the screaming parties of unmated birds that usually arrive in the UK in early June.These come well after the established pairs have returned to claim their nesting sites from the previous year – they are nest-site faithful year on year, and will defend their site against prospecting youngsters.
It is wonderful see their intimately entwined bodies on the nesting pad. Rarely still for more than a few minutes, they are constantly preening themselves and each other. Sleep as we understand is fleeting, but of course this is for birds that sleep on the wing when they are not at the nest. There is still so much to learn and understand about these birds.
An On-going Diary
The Swifts have been established in the box for six days. They have settled into a clear routine of leaving the box at around 7.00am and returning 12 hours later to spend the night there.
We would expect the pair to start building a rudimentary nest as their next step. They have made a start with this. One evening, one of the birds returned with material gathered on the wing and proceeded to stick small bits around the edge of the nesting pad – but nothing more since then.
To be continued …..
