Jan Wegener/ BIA / Horsfield's Bronze-Cuckoo (Chrysococcyx basalis) balancing, Victoria, Australia

Bence Mate / Great reed warbler (Acrocephalus arundinaceus) feeding Cuckoo chick (Cuculus canorus) Pusztaszer, Kiskunsagi National Park, Hungary, June.

Bence Mate / DUPLICATE Cuckoos (Cuculus canorus) squabbling, Kiskunsagi National Park, Pusztaszer, Hungary. February.

Claudio Contreras / Greater roadrunner (Geococcyx californianus) with nuptial gift calling mate, Laredo Borderlands, Texas, USA. April

Alex Hyde / Orange tip butterfly egg (Anthocharis cardamines) on Cuckoo flower / Lady's smock (Cardamine pratensis). Peak DIstrict National Park, Derbyshire, UK. May.

Ole Jorgen Liodden / Meadow pipit (Anthus pratensis) feeding young Eurasian cuckoo (Cuculus canorus), Valdres, Norway, July.

Alan Murphy / Yellow-billed Cuckoo (Coccyzus americanus) male, Texas

Alan Murphy / Black-billed Cuckoo (Coccyzus erythropthalmus) male, Texas

David Tipling / 2020VISION / Reed warbler (Acrocephalus scirpaceus) with twelve day old Cuckoo (Cuculus canorus) chick at nest, Norfolk, England, UK, May

Andy Jackson / 2020VISION / Male Cuckoo wrasse (Labrus mixtus) swimming and looking at camera, with a diver in the background, Lochgary Wreck, Kirkwall, Orkney, Scotland, UK, June.

Andy Jackson / 2020VISION / Male Cuckoo wrasse (Labrus mixtus) feeding on a Sea urchin (Echinoidea), Lochgary Wreck, Kirkwall, Orkney, Scotland, UK, June.

Markus Varesvuo / European Cuckoo (Cuculus canorus) male in flight, Kuusamo Finland June