John Chan / Male California least tern (Sternula antillarum browni) presenting fish offering to female during mating, Huntington Beach, California, USA, May.

John Chan / Male California Least Tern (Sternula antillarum browni) courting a female, presenting a fish before chasing off another male, Huntington Beach, California, USA, May.

Frederique Olivier / Pair of Blue footed boobies (Sula nebouxii) courting, with the male picking up and offering grass, Isla Lobos de Terra, Peru.

Danny Green / Atlantic Puffin (Fratercula arctica) coming out of its burrow with a gift, Skomer Island, Wales, UK, May

Anup Shah / Southern plains grey langur / Hanuman langurs (Semnopithecus dussumieri) group of females feeding on potatoes left as an offering at a temple. Jodhpur, Rajasthan, India. March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) pair in 'weed dance' courtship display, The Netherlands, March.

David Pattyn / Great crested grebe (Podiceps cristatus) pair performing their 'weed dance' in which they take a vertical position in front of each other and offer plant material to each other. The Netherlands. March...

David Pattyn / Great crested grebe (Podiceps cristatus) pair performing their courtship dance in which they mimic each other's movements. Here the male is offering the female plant material. The Netherlands. April.

Ramon Navarro / Male European bee eater (Merops apiaster) offering insect to female as part of a courtship display, before mating, Seville, Spain, May.

Staffan Widstrand,Staffan Widstrand / Mangrove planting team from CRINEO planting Rhzophora mangrove trees, Pulicat Lake, Tamil Nadu, India, February 2013.

Laurent Geslin / Offering milk to 'holy' Black rats {Rattus rattus} temple Deshnoke, Rajasthan, India

Bence Mate / Male Red-footed falcon (Falco vespertinus) offering small mammal prey to female, Hortobagyi National Park, Hungary