Robin Chittenden / Common swift (Apus apus) flying low to water while hunting, Norfolk, England, UK, July. Winner of Animal Behaviour Category of the British Wildlife Photography Awards 2019.

Dave Bevan / Slow motion clip of a pair of Common swifts (Apus apus) approaching and entering a nest hole in limestone cliff, Norfolk, England, UK, May.

Nick Upton / Common swifts (Apus apus) flying overhead, Wiltshire, UK, June. Digital composite image.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire Wales, UK, July.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire, Wales, UK, July.

Phil Savoie / Swift (Apus apus) flock screaming in flight against blue sky and clouds, Monmouthshire, Wales, UK, July.

Nick Upton / Common swift (Apus apus) feeding chick in a nest box, filmed using infrared light, Cambridge, England, UK, August.

Markus Varesvuo / Swift (Apus apus) in flight. Helsinki, Finland. July

Roland Seitre / Swift Fox (Vulpes velox) emerging from den, native to North America

Ben Lascelles / Great Dusky Swift (Cypseloides senex) Birds flying past rainbow created by waterfalls, Iguazu National Park, Argentina, October 2008

Markus Varesvuo / Common Swift (Apus apus) in flight, Helsinki Finland July

Shattil & Rozinski / Juvenile Swift fox (Vulpes velox) stalking prey on the shortgrass prairie of Southern Wyoming, Wyoming, USA

Shattil & Rozinski / Swift fox (Vulpes velox) running, backlit, Wyoming, USA

Shattil & Rozinski / Swift fox (Vulpes velox) cubs near den, Wyoming, USA

Pete Oxford / Great dusky swifts {Cypseloides senex} flying to roost behind waterfall, Noel Kempff, Bolivia, South America

Kim Taylor / Common swift {Apus apus} nestling. Captive, UK

Tim Fitzharris / Autumn along Swift River, White Mountains National Forest, New Hampshire

Pete Oxford / Great dusky swifts {Cypseloides senex} flock in flight, morning exit from Ahlfeld waterfall, Noel Kempff NP, Bolivia, South America

Ann & Steve Toon / Merlin (Falco columbarius) with Swift (Apus apus) prey , Cumbria, UK, captive. July

Phil Savoie / Swift (Apus apus) in flight with blue cloudy sky, Monmouthshire, Wales, UK. April

Phil Savoie / Swift (Apus apus) in flight with blue cloudy sky, Monmouthshire, Wales, UK. July

Tony Wu / Greater crested tern (Thalasseus bergii) feeding on Sardine, Tonga.

Suzi Eszterhas / Glossy swiftlets (Collocalia esculenta) in cave, Sabah, Malaysia

Suzi Eszterhas / Glossy swiftlets (Collocalia esculenta) in cave, Sabah, Malaysia

Duncan Murrell / Palawan swiftlets (Aerodramus palawanensis) returning to the subterranean river cave, Puerto Princesa Subterranean River National Park UNESCO World Heritage Site, Palawan, the Philippines. Endemic to...

Nick Upton / Common swift (Apus apus) flying overhead, Lacock, Wiltshire, UK, June.

Steven David Miller / Australian sea lion (Neophoca cinerea) male basking on beach with Great crested terns (Thalasseus bergii) in foreground. Seal Bay Conservation Park, Kangaroo Island, South Australia.

Robin Chittenden / Orange swift moth (Triodia sylvina) Norfolk, England, UK. August

Robin Chittenden / Common Swift (Apus apus) in flight reflected in water, Norfolk, England, UK. July.

Robin Chittenden / Common Swift (Apus apus) in flight reflected in water, Norfolk, England, UK. July.

Robin Chittenden / Common swift (Apus apus) hunting over water, Norfolk, England, UK, July.

Robin Chittenden / Common swift (Apus apus) hunting over water, Norfolk, England, UK, July.

Robin Chittenden / Common swift (Apus apus) hunting over water, Norfolk, England, UK, July.

Robin Chittenden / Common swift (Apus apus) Norfolk, England, UK. July.

Martin Grimm/ BIA / Pallid Swift (Apus pallidus) flying, Zadar, Croatia

Dave Bevan / Slow motion clip of a Common swift (Apus apus) flying and landing on a rockface before entering nest crevice, Norfolk, England, UK, July.

Dave Bevan / Slow motion clip of a Common swift (Apus apus) flying from nest crevice in a rock face Norfolk, England, UK, July.

Luke Massey / Great dusky swifts (Cypseloides senex) roosting behind one of the falls at Iguassu Falls, Brazil

Luke Massey / Great dusky swifts (Cypseloides senex) roosting behind one of the falls at Iguassu Falls, Brazil

Ann & Steve Toon / Swift terns (Thalasseus bergii) Luderitz, Namibia.

Jiri Lochman / Crested tern (Sterna bergii) juvenile entangled in a fishing line, likely cut off by a fisherman after the bird swallowed the hooked bait. Australia.

Jiri Lochman / Crested tern (Sterna bergii) juvenile, entangled in a fishing line, likely cut off by a fisherman after the bird swallowed the hooked bait Australia.

Charlie Summers / Greenback cutthroat trout (Oncorhynchus clarkii stomias) under branches of a tree root eroded away by the swift current of their annual spawning stream. Neota Wilderness Area, Colorado, USA, July.

Charlie Summers / Arctic grayling (Thymallus arcticus) together in the swift current of a spawning stream. They will feed when the current brings food to them. The male on the right has a deformed mouth from a fisher...

MYN / Lily Kumpe / Karri moth (Aenetus dulcis) William Bay National Park, Western Australia. Meetyourneighbours.net project.

Nick Upton / Four Common swifts (Apus apus) silhouetted against the sky as they fly in formation over the chimney of a cottage at dusk, Lacock, Wiltshire, UK, June 2018.

Nick Upton / Common swift (Apus apus) flying overhead with its tail feathers spread out, Lacock, Wiltshire, UK, June 2018.

Nick Upton / Common swift (Apus apus) screaming as they fly in formation over cottage roofs at dusk, Lacock, Wiltshire, UK, June 2018.

Nick Upton / Common swift (Apus apus) screaming as they fly in formation over cottage roofs at dusk, Lacock, Wiltshire, UK, June 2018.

Nick Upton / Nick Upton setting up a remote camera on an extension roof to photograph Common swifts (Apus apus) coming and going from a nest box under the eaves of a cottage, Hilperton, Wiltshire, UK, June 2016. M...

Nick Upton / Common swift (Apus apus) flying to a nest box attached to the eaves of a cottage with a feather and straw in its beak to build its nest with, Hilperton, Wiltshire, UK, May 2018.

Nick Upton / Remote camera set up on an extension roof to photograph Common swifts (Apus apus) coming and going from a nest box under the eaves of a cottage, Hilperton, Wiltshire, UK, June 2016.

Nick Upton / Common swift (Apus apus) two flying overhead, Lacock, Wiltshire, UK, May 2018.

Nick Upton / Common swift (Apus apus) flying overhead, Lacock, Wiltshire, UK, May 2018.

Nick Upton / Common swift (Apus apus) flying to its nest site under roof tiles on an old cottage, Lacock, Wiltshire, UK, May 2018.

Nick Upton / Common swift (Apus apus) flying overhead, having just arrived after migration from African wintering grounds, Lacock, Wiltshire, UK, May.

Nick Upton / Common swifts (Apus apus) flying over rooftops, having just arrived after migration from African wintering grounds, Lacock, Wiltshire, UK, May.

Martin Grimm/ BIA / Common Swift (Apus apus) flying, Baden-Wurttemberg, Germany

Nick Upton / People watching Swifts (Apus apus) flying around an old cottage they are nesting in during a swift walk organised by the local swift group, Bradford-on-Avon, Wiltshire, UK, June. Model released.

Nick Upton / Four orphaned Common swift chicks (Apus apus), almost grown to full size, held in a keeping cage and about to be fed by Judith Wakelam, Worlington, Suffolk, UK, July.

Nick Upton / Two orphaned Common swift chicks (Apus apus), almost grown to full size, held in a keeping cage and about to be fed by Judith Wakelam, Worlington, Suffolk, UK, July.

Nick Upton / People watching Swifts (Apus apus) flying around Holy Trinity church during a swift walk organised by the local swift group, Bradford-on-Avon, Wiltshire, UK, June. Digital composite. Model released.

Nick Upton / Common swift (Apus apus) flying to its nest in a Swift nest box in the belfry of All Saints Church, Worlington, Suffolk, UK, July.

Nick Upton / Common swift (Apus apus) flying from a nest box after feeding its chicks, Hilperton, Wiltshire, UK, June.

Nick Upton / Monitor linked to an infra red camera in a Common swift (Apus apus) nestbox with an adult sitting beside two well developed chicks in a nest cup, Worlington, UK, Suffolk.

Nick Upton / Two Common swift eggs (Apus apus) in a nest box in a church belfry, inspected during a ringing study, Worlington, Suffolk, UK, July.

Nick Upton / Two compartment nest box for Common swifts (Apus apus) attached under the eaves of a house, Landbeach, Cambridgeshire, UK, July.

Nick Upton / Common swift chick (Apus apus) reared to full size by Judith Wakelam, climbing up the side of a child's play pen and almost ready to be released, Worlington, Suffolk, UK, July.

Nick Upton / Judith Wakelam returns an orphan Common swift chick (Apus apus) to a child's play pen used to house several chicks after feeding it, Worlington, Suffolk, UK, July. Model released.

Nick Upton / House sparrow (Passer domesticus) using a nestbox intended for Common swifts (Apus apus) made from plastic piping, attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / All Saints Church which has over 40 swift nestboxes in the belfry and a thriving colony of breeding Common swifts (Apus apus), Worlington, Suffolk, UK, July.

Nick Upton / Common swift (Apus apus) two flying over the weathercock on the spire of Holy Trinity Church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Screaming party of Common swifts (Apus apus) flying around a church bell tower at dusk, where a large colony breeds in nestboxes behind the window louvres, All Saints Church, Worlington, Suffolk, UK,...

Nick Upton / Screaming party of Common swifts (Apus apus) flying around a church bell tower at dusk, where a large colony breeds in nestboxes behind the window louvres, All Saints Church, Worlington, Suffolk, UK,...

Nick Upton / Two nestboxes for Common swifts (Apus apus) made from plastic piping, attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Five nestboxes for Common swifts (Apus apus) made from plastic piping, attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Five nestboxes for Common swifts (Apus apus) made from plastic piping, attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Nestbox for Common swifts (Apus apus) made from plastic piping, attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Hollow swift nest box with a feather filled nest cup held by a member of the local swift group, Bradford-on-Avon, Wiltshire, UK, June. Model released.

Nick Upton / Swift nest boxes atached to the eaves of a cottage, Hilperton, Wiltshire, UK, June.

Nick Upton / Swift nest boxes atached to the eaves of a cottage, Hilperton, Wiltshire, UK, June.

Nick Upton / Five nest boxes for Common swifts (Apus apus) attached under the eaves of a house, Milton, Cambridge, UK, July.

Nick Upton / Two nest boxes for Common swifts (Apus apus) attached under the eaves of a block of flats, with a nesting Swift peering from one, Edgecombe, Cambridge, UK, July.

Nick Upton / Roger Beckett building a nestbox for Common swifts (Apus apus) with nest cups, access ports for nest inspection and CCTV cameras, to be fitted in a church tower, Hilperton, Wiltshire, UK, June. Model...

Nick Upton / Nestbox being built for Common swifts (Apus apus) with nest cups, access ports for nest inspection and CCTV cameras, to be fitted in a church tower, Hilperton, Wiltshire, UK, June. Model released.

Nick Upton / Roger Beckett building a nestbox for Common swifts (Apus apus) with nest cups, access ports for nest inspection and CCTV cameras, to be fitted in a church tower, Hilperton, Wiltshire, UK, June. Model...

Nick Upton / Six nest boxes for Common swifts (Apus apus) in a roof space with swift brick entrance holes and perspex backs so nesting birds can be monitored by a cctv camera and a call playback system, with one n...

Nick Upton / Swift nestbox on a house wall alongside hollow "swift brick" entrances to nest boxes in a roof space, Worlington, Suffolk, UK, July.

Nick Upton / Two multiple nestboxes for Common swifts (Apus apus) made from attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Two multiple nestboxes for Common swifts (Apus apus) attached to the wall of a block of flats, Edgecombe, Cambridge, UK, July.

Nick Upton / Swift lousefly (Craeterina pallida), a blood sucking parasite unique to swift nests, found on a Swift chick (Apus apus) and held in the hands of a bird ringer, Worlington, Suffolk, UK, July. Model rel...

Nick Upton / Common swift (Apus apus) flying back to its nest under the roof of an old half-timbered house with several swift nests under it, Lacock, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) flying overhead, Lacock, Wiltshire, UK, May.

Nick Upton / Common swift (Apus apus) flying to a nest box with its throat pouch bulging with insects it has caught to feed its chicks, Hilperton, Wiltshire, UK, June.

Nick Upton / Two recently hatched Common swift chicks (Apus apus) in a nest box in a church belfry, inspected during a ringing study, Worlington, Suffolk, UK, July.

Nick Upton / Two recently hatched Common swift chicks (Apus apus) in a nest box in a church belfry, inspected during a ringing study, Worlington, Suffolk, UK, July.