Swifts are one of the most urban of birds during the breeding season. A few pairs use cliffs on the coast or quarries and even cracks in dead trees, but the vast majority nest under roof tiles, eaves and crevices in the walls of buildings. They have large, narrow and curved crescent-shaped wings and forked tails, and are dark brown, with a paler throat patch. They are very aerial birds, only landing to nest: they sleep, mate and feed on the wing and they are the fastest recorded bird in level flight. Swifts 6000 mile long round trip annual migration has been researched using geolocators attached to their bodies with tiny harnesses. The data revealed a long-distance
migration pattern to sub-saharan Africa with the birds almost always on the move across several regions to take advantage of the rains and food availability. In the autumn migration they move across to France, Spain and then along the north African coasts. The winter is spent over the Congo and Mozambique rainforests. On the way back to their breeding quarters in early spring the birds stop-over in Liberia for a week or so, presumably fattening up on seasonally plentiful resources.
Swift pair. Pairs often fly together as they feed.
A Swift chase. Parties of Swifts chase screaming around their breeding colonies. The trilling calls of the chasing birds are a feature of summer.
Status and distribution in Hull
In Hull, Swifts are summer visitors and passage migrants. I look forward to the first Swifts returning to Hull on the first or second week of May. The yearlings and two-year old birds won't breed, but they still migrate to pair up and find potential nest sites (top shot). The non-breeders arrive a bit later and migrate back earlier, in the first or second week of July. Then, there is often a peak of Swifts in the air, Swifts are more vocal and the chases are more spectacular. Numbers then decline markedly during August, as the young are reared and they start their migration season. They are with us barely for three months of the year! Swifts are widespread in Hull. Lakes and rivers and wetlands not only in the city but in the surrounding area support dense insect populations and attract feeding swifts. Several thousand gather over the reservoirs at Tophill Low in June, swirling over the water as they feed, coinciding with the mass emergence of non-biting midges.
Clouds of Swifts feeding over the Tophill D-reservoir. 10th June 2019. It was a marvel to behold!
A survey in May 2006 revealed that Swifts were found in 12 of the 90 1x1 km squares in Hull (
Tophill Low 2006 report, RL et al). A repeat survey using the same technique would be welcome to assess the size of the population in Hull.
Conservation and management
Swifts have suffered strong declines in recent decades. Since 1994 we have lost population
60% of the Swifts in the Yorkshire and the Humber area as estimated by the BTO/JNCC/RSPB Breeding Bird Survey. The Swift has recently been moved from the Amber to the Red Listed in the Birds of Conservation Concern 5.
BBS population trends for Swift.
The decline has been attributed to a loss of nest sites due to insulation and renovation or demolition of old buildings and modern building designs which lack suitable nest sites. In addition, stark insect declines in recent decades due to pesticide use might have contributed to Swift declines. Management is three pronged: installation of swift bricks in new buildings, being mindful of swifts during house renovations and monitoring of populations. Swifts are very mobile and fly away from storms and poor weather. They can also take long, 50 mile round trips in search of food for their chicks, so the usual monitoring methods might not be very accurate to estimate local populations. An app which takes into account Swift behaviour, Swift Mapper has been developed by several conservation organisations in order to locate and monitor local colonies.
Åkesson, S., Klaassen, R., Holmgren, J., Fox, J. W. & Hedenström, A.
Migration routes and strategies in a highly aerial migrant, the common swift Apus apus, revealed by light-level geolocators.
PLoS One 7, e41195 (2012).
Lack, David. 1973. Swifts in a tower. Chapman and Hall.
Stanbury, A., Eaton, M., Aebischer, N., Balmer, D. & Win, I. (2021) The status of our bird populations: the fifth Birds of Conservation Concern in the United Kingdom, Channel Islands and Isle of Man and second IUCN Red List assessment of extinction risk for Great Britain. British Birds 114, 723–747.
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