Terry Whittaker / 2020VISION / Avocet (Recurvirostra avosetta) in mist on grazing marsh at dawn with cattle grazing in the background, Thames Estuary, Elmley Marshes RSPB reserve, North Kent, UK,, April 2011. Photographer quote: 'G...

Tui De Roy / Waved albatross (Phoebastria irrorata) performing display, courting partner with colony in background. Punta Cevallos, Espanola (Hood) Island, Galapagos, Ecuador, May. Sequence 1 of 3.

Tui De Roy / Waved albatross (Phoebastria irrorata) performing display, courting partner with colony in background. Punta Cevallos, Espanola (Hood) Island, Galapagos, Ecuador, May. Sequence 3 of 3.

Tui De Roy / Waved albatross (Phoebastria irrorata) performing display, courting partner with colony in background. Punta Cevallos, Espanola (Hood) Island, Galapagos, Ecuador, May. Sequence 2 of 3.

Philip Stephen / MFV coming alongside partner vessel to start pair trawling operations. North Sea, 2008. Property released.

Philip Stephen / MFV coming alongside partner vessel to start pair trawling operations. North Sea, 2009. Property released.

Philip Stephen / Crewmen shakle trawl warp to the net, with partner vessel coming alongside in the background, for pair trawling. North Sea, September 2008. Model released.

Nick Upton / Male Coot (Fulica atra) fighting a rival in a territorial dispute, as its partner swims towards them, Wiltshire, UK, October

Philip Stephen / MFV "Harvester" coming alongside partner vessel to start pair trawling operations. North Sea, September 2008. Property Released.

Philip Stephen / MFV coming alongside partner vessel to start pair trawling operations. North Sea, 2009. Property released.

Andrew Parkinson / 2020VISION / Great crested grebe (Podiceps cristatus) adult in profile calling to its partner, Derbyshire, UK, March

Adrian Davies / Great Blue Heron (Ardea herodias) displaying to its partner on their nest Venice Rookery, Florida, USA, January.

Juergen Freund / Banded shrimp goby (Cryptocentrus cinctus) yellow morph with snapping shrimp partner (Alpheus sp.) Papua New Guinea.

Edwin Giesbers / White Stork (Ciconia ciconia) coming in to land while its partner sits on nest. The Netherlands, April.

Philip Stephen / Crewman throwing heaving line across to partner vessel during pair trawl operations, North Sea, January 2010.

Fred Bavendam / Metallic Shrimp-goby (Amblyeleotris latifasciata) keeps watch while its Snapping Shrimp (Alpheus sp) partner works on their burrow, Bali, Indonesia

Juergen Freund / Egg / Allied partner cowrie {Dentiovula dorsuosa} camouflaged on soft coral, Indo-pacific

Juergen Freund / Egg / Allied partner cowrie {Dentiovula dorsuosa} camouflaged on soft coral, Indo-pacific

Philip Stephen / MFV coming alongside partner vessel to start pair trawling operations. North Sea, 2009. Property released.

Philip Stephen / MFV coming alongside partner vessel to start pair trawling operations. North Sea, 2008. Property released.

Paul Hobson / Cape Barren / Cereopsis Goose (Cereopsis novaehollandiae) one bird biting its partner, Kangaroo Island, South Australia

Scott Leslie / Tree Swallow (Tachycineta bicolor) landing near nest cavity with partner calling, Tobeatic Wilderness Area, Nova Scotia, Canada

Pete Oxford / Red-footed Booby (Sula sula) pair sitting on nest in mangroves, Genovesa Island, Galapagos Islands, Ecuador

Tui De Roy / Chatham Albatross (Thalassarche eremita) courting pair, critically endangered, The Pyramid, Chatham Islands

Tui De Roy / Chatham Albatross (Thalassarche eremita) affectionate pair, critically endangered, The Pyramid, Chatham Islands

Tui De Roy / Chatham Albatross (Thalassarche eremita) portrait of two, critically endangered, The Pyramid, Chatham Islands

David Pike / Japanese crane courtship display {Grus japonensis} Hokkaido, Japan, annual mating season between February / March. Cranes are generally monogamous, mating with same partner for life - these dancing r...

Gary Smith / Sandwich Tern {Sterna sandvichensis} chick with adult calling to partner bird for food, Blakeney Point, Norfolk, UK.

Hiroya Minakuchi / Whip Coral Partner Shrimp (Dasycaris zanzibarica), Sulu Sea, Borneo, Malaysia

Michael Quinton / Common Raven (Corvus corax) male mates with a female in her nest while her partner is away, North America

Michael Quinton / Common Raven (Corvus corax) male mates with a female in her nest while her partner is away, North America

Philip Stephen / Crewmen onboard trawler "Carisanne" passing the trawl wire to their partner vessel at the commencement of their trawl operations in the North Sea. June 2007.

Roberto Rinaldi / Two nudibranchs / sea slugs (dorids), New South Wales, Australia. ^^^Dorids are the largest group of nudibranchs, typically they have a pair of rhinopores at the front of the head used to locate food...