The swifts returned to the University of Gloucestershire in early May, filling the air with their excited screams and inviting me outside while I was supposed to be revising! It was too hard to resist sticking my head out of the window to watch them speeding past the rooftops: it put a big grin on my face.
I studied the swifts at FCH for my Bioscience dissertation project. I estimate that the population here is between 40-50 pairs, which is a big colony, potentially nationally important, and even larger than the well-studied colony at Oxford University Museum of Natural History.
I spent many hours watching these swifts and managed to follow the progress of individual nests last summer. The best time to see swifts in action is in the evening on a sunny, dry day with low wind. I found that their activity rate increases leading up to sunset.
This year’s breeding season is currently in full swing; most of the eggs are now due to hatch any day now, when the roof space above the library and main biosciences labs at Francis Close Hall will be full of nestling swifts!
I think it’s a real privilege to have swifts nest in our buildings. They are neat and tidy birds, and don’t cause damage or excessive mess in the roof space that they nest within. When they leave for Africa in August, all that remains is a small shallow cup made of grass and feathers (which they find floating in the air and capture in flight). The nest is used year after year by the same pair, they are long-lived (15 years is not unusual) and loyal to their chosen nest site, returning year after year. Many modern developments and renovations remove roof space entry points and nesting places. This could prevent a pair from breeding in that year, as they will struggle to find a suitable alternative site. Low nest site availability appears to be a major limiting factor to breeding and pairs spend a long time prospecting for a nest site, so the large FCH population is really important.
The solution to this is to put up nest boxes with a specific letterbox style 65x30mm entrance hole. In order to preserve the nesting place after renovation work, this hole must line up exactly with the old entrance, otherwise the birds may not adopt the nest box.
Last summer I used a state of the art infra-red thermal imaging camera to locate swift nests, by detecting heat produced by nestlings and brooding adults near to their entrance holes underneath the eaves.
This took place in the cooler parts of the day, at dawn and dusk, when the contrast between ambient and body temperature was greatest. If this difference was greater than 1.6 degrees there was a 32.5% chance that the nest would be occupied. This showed that nests could be detected using thermal imagery by this method, although it was not consistent and reliable enough to be useful for accurate ‘cold’ survey work to find unknown nest sites. Thermal imagery was, however, very useful for pinpointing the exact entry points used by swifts, which is difficult to do in the shadows of the overhanging roof by eye and would be ideal to guide nest box positioning after a renovation.
This project gave me the chance to use state of the art equipment to study a charismatic species that I have subsequently become slightly obsessed with. It also taught me a huge amount about project planning and writing that I will take with me into the future.
Matt Sharp, soon-to-be B.Sc Animal Biology