In the past 4 years Hampshire Swifts has installed over 1000 Swift nest boxes on households, churches and public buildings.
With a few notable exceptions, we have no idea how many have been used by Swifts (or indeed, by other species). A lot of time, energy and money goes into this project yet we have no idea how successful it is. Surely it's time we started to accumulate some occupancy figures for Hampshire?
One reason for this lack of data is because determining whether Swifts are breeding is not straightforward (unless you have cameras installed in your boxes) and relies on birds being seen to enter or leave the nest box. Swifts visit their nest sites relatively infrequently so this is a time-consuming business. Another reason is that under normal circumstances people tend to be out and about or go away on holiday during the summer months.
The RSPB Oxford City Swift project has been running for some years and relies on volunteers surveying parts of the city, mapping where Swifts are nesting. They have just released an excellent video explaining why they run this project and the methodology they use. This is well worth watching and can be seen at https://www.youtube.com/watch?v=PFvFJCX7MeU.
The RSPB survey is necessarily quite involved as they are attempting to answer a number of different questions. All we want to know is whether our nest boxes are being used and by what. So what is the most efficient way to monitor a Swift box to see if it is being used? Luckily a group in Germany has recently published some research on this.....
Using light level geolocators attached to Swifts they could detect when, and for how long, birds entered nest sites. Over 2 breeding seasons they assessed the site visits of 11 Swifts and this allowed calculation of the visit duration and number of visits with respect to the stage of the breeding season and different weather conditions. The average visit frequency across the whole breeding season was 5.6 visits per day or 0.32 visits per hour of daylight. The highest daily number of visits was highest at the beginning of July (0.4 visits per hour), increased in warm weather and decreased when it was cold, raining or windy. Within each day there was also a pattern, with a peak around sunset (up to 1 visit per hour), after sunrise and around noon (both up to around 0.5 visits per hour).
Their recommendations are that the best chance of seeing Swifts departing from or returning to boxes is from the end of June until mid-July from 0.5 to 7.75 hours after sunrise or from 3 hours before sunset to sunset in good weather. If viewing during those periods then a viewing period of 0.5 - 2 hours gives over 90% chance of encountering a Swift returning to the nest site. If time really is at a premium, then the 2 hours before sunset in warm, dry and still weather is probably optimum.
For more details see Schaub et al (2020) Bird Study https://doi.org/10.1080/00063657.2020.1732862
So, if you have Swift boxes, how about devoting 1 early morning or an evening in good weather to watch your Swift boxes in late June or the first half of July this year? All we need to know is how many boxes you have, how many have Swifts nesting, how many are unused and, of the others, what else is using them?