In St Davids I noted ‘the swifts continue swooping and circling in the late western twilight’ on the 14th July. Back home I watched them in Cambridge and Cottenham. Friends alerted me to two breeding successes: in the Swift Tower on Logan’s Meadow; and in a new box on a bungalow at Waterbeach. I kept a note of the last sightings from our back gardens: 31st July at Cottenham and 2nd August at Cambridge. Swifts are one of the last migrants to arrive (mid-late April) and the first to leave. Naturescalendar.woodlandtrust.org.uk has them still present across the country on 18th August. The Trust notes: ‘Their departure date depends on the success of breeding. If there are lots of insects and the chicks have fattened up quickly they leave earlier. They also leave early if their breeding attempt is unsuccessful. If the summer is damp and cool there are fewer insects and it takes longer to feed up the chicks to the ideal weight for fledging and they leave later.’
Gilbert White notes that ‘Our swifts, in general, withdrew this year about the first day of August’, in The Natural History of Selborne, Letter XCVI, 9th September 1781. One bird remained until the end of the month, apparently due to a late second brood, however.