Hermann Brehm / Cuckoo (Cuculus canorus) in flight, Germany, April. May

Rolf Nussbaumer / Greater roadrunner (Geococcyx californianus), adult drinking, Rio Grande Valley, South Texas, Texas, USA. June

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.

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

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

Markus Varesvuo / European Cuckoo (Cuculus canorus). Hungary. May

Bence Mate / Common cuckoo chick (Cuculus canorus) begging for food from Great reed warbler (Acrocephalus arundinaceus) foster parent, Pusztaszer, Kiskunsagi National Park, Hungary

Bence Mate / Common cuckoo chick (Cuculus canorus) begging for food from Spotted flycatcher (Muscicapa striata) Pusztaszer, Kiskunsagi National Park, Hungary

David Kjaer / Cuckoo (Cuculus canorus) perched in tree. Buckinghamshire, UK, June.

David Tipling / 2020VISION / Cuckoo (Cuculus canorus) 12 day chick in Reed Warbler nest (Acrocephalus scirpaceus) fed by Reed warbler, Fenland, Norfolk, UK, May

David Tipling / 2020VISION / Reed Warbler (Acrocephalus scirpaceus) at nest feeding 12 day Cuckoo chick (Cuculus canorus), Fenland, Norfolk, UK, May