Andy Sands / Small emperor moth (Saturnia pavonia) male below female both displaying eyespots on Gorse, Captive, UK, April

Gerrit Vyn / Two pairs of Harlequin Ducks (Histrionicus histrionicus) in flight. Ocean County, New Jersey, USA, January.

Anup Shah / Lesser Flamingo {Phoeniconaias minor} bill-fencing as part of courtship, Lake Nakuru, Kenya.

Paul Hobson / Avocet (Recurvirostra avosetta) two pairs fighting over territory, Texel, Holland May

Paul Hobson / Avocet (Recurvirostra avosetta), two pairs disputing territory, Texel, Holland May

Bert Willaert / Three pairs of Common european toads (Bufo bufo) and one pair of Common frogs (Rana temporaria) resting during their spring migration, Belgium, March.

Yukihiro Fukuda / White terns (Gygis alba) pair flying over shoreline of Christmas Island, Indian Ocean, July

Alex Mustard / 2020VISION / Two pairs of mating Common cuttlefish (Sepia officinalis) the two large males show off their stripy colouration as they protect their females during the mating season, Babbacombe, Devon, UK, English C...

Nick Upton / 2020VISION / Common teal (Anas crecca) pair on partially frozen flooded marshland on a cold winter day, Greylake RSPB reserve, Somerset Levels, UK, January.

Roy Mangersnes / Two Black-legged kittiwake (Rissa tridactyla) pairs trying to nest on ice near breeding cliff, Finnmark, Norway, April

Stephen Dalton / Azure damselfly (Coenagrion puella) mating pairs laying eggs, UK

Roger Powell / Displaying male Ruff (Philomachus pugnax) flanked by two admiring females ('Reeves'). Varanger, Norway, June.

Juan Carlos Munoz / Two nesting pairs of Red-legged cormorants (Phalacrocorax gaimadi). Puerto Deseado, Patagonia, Argentina, Nov 2008

Yva Momatiuk & John Eastcott / Galah (Eolophus roseicapilla) pairs, Western Australia, Australia

Nick Upton / Male Yellow Dung Fly (Scathophaga stercoraria) approaching two mating pairs on a cow dung before attempting to dislodge a rival male. Wiltshire, UK, April.

Pete Oxford / Two pairs of Galapagos Giant tortoises (Geochelone elephantophus vandenburghi) mating Alcedo Volcano crater floor, Isabela Island Galapagos islands, Ecuador, South America

Tui De Roy / Volcan Alcedo Giant Tortoise (Chelonoidis nigra vandenburghi) pairs mating, Isabella Island, Galapagos Islands, Ecuador

GEORGETTE DOUWMA / Rockmover or Dragon wrasse (Novaculichthys taeniourus) often working in pairs, moving coral rubble to find benthic invertebrates to feed on. Misool, Raja Ampat, West Papua, Indonesia.

Michael Hutchinson / Large red damselfly (Pyrrhosoma nymphula), two mated pairs with females laying eggs in pond, one male holds on to male in the other pair Bristol, UK

Donald M. Jones / Black-legged Kittiwake (Rissa tridactyla) nesting pairs, Prince William Sound, Alaska

Andy Rouse / Wandering albatross (Diomedea exulans) pairs at nest sites, South Georgia

Hanne & Jens Eriksen / Painted stork {Mycteria leucocephala} breeding colony, two pairs in tree, Tamil Nadu, India

Hanne & Jens Eriksen / Painted stork {Mycteria leucocephala} breeding colony, six pairs, Tamil Nadu, India

Inaki Relanzon / Pairs of White storks (Ciconia ciconia) on their nests (artificial), Aiguamolls de l'Emporda Natural Park, Girona, North Spain

Michel Poinsignon / Little grebe (Tachybaptus ruficollis) pair at nest, Lorraine, France

Kerstin Hinze / Black-browed Albatross (Thalassarche melanophrys) pair at nest with egg, Saunders Island, Falkland Islands, South Atlantic Ocean

Doug Wechsler / Common cuban toad mating pairs {Peltophryne peltocephala} Zapata swamp, Cuba

Kim Taylor / Common Blue Butterflies (Polyommatus icarus) roosting in pairs, Europe

Tui De Roy / Campbell Albatross (Thalassarche impavida) pair courtship dance, Bull Rock, North Cape Colony, only breeding area, estimated at 26,000 pairs, Campbell Island, New Zealand

Tui De Roy / Campbell Albatross (Thalassarche impavida) pair courtship dance, Bull Rock, North Cape Colony, only breeding area, estimated at 26,000 pairs, Campbell Island, New Zealand

Dave Watts / Pair of Budgerigars {Melopsittacus undulatus} on branch, Arid woodlands, Australia

Premaphotos / Common soldier beetle (Rhagonycha fulva) mating pairs on Creeping thistle flower, UK

Pete Oxford / Nest site dispute for Royal penguins {Eudyptes schlegeli} Macquarie Island, Tasmania,