Brian Bevan / Pair of Reed warblers (Acrocephalus scirpaceus) feeding young at nest, Bedfordshire, England, UK, July.

Ingo Arndt / Reed Warbler (Acrocephalus scirpaceus) nest in Senckenberg Natural Hystory Collection Dresden, Germany.

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

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

Chris Gomersall / 2020VISION / Reed warbler (Acrocephalus scirpaceus) adult perched in reedbed, Titchwell RSPB reserve, Norfolk, UK, April.

David Tipling / 2020VISION / Reed warbler (Acrocephalus scirpaceus) feeding 12 day chick of European cuckoo (Cuculus canorus) in its nest, East Anglian Fens, Norfolk, May. 2020VISION Book Plate.

David Tipling / 2020VISION / 12 day chick of European cuckoo (Cuculus canorus) in Reed warbler's (Acrocephalus scirpaceus) nest, East Anglian Fens, Norfolk, May

David Kjaer / Reed warbler (Acrocephalus scirpaceus) with large fledgling Cuckoo (Cuculus canorus) in it's nest, Essex, UK

David Kjaer / Juvenile European cuckoo {Cuculus canorus} fed by Reed warbler {Acrocephalus scirpaceus}. Bucks, UK. Cuckoos lay their eggs in the nests of reed warblers and when they hatch, the warbler mother will a...

Jim Hallett / Reedwarbler (Acrocephalus scirpaceus) feeding chicks. Somerset levels, England, UK

David Kjaer / Juvenile European cuckoo {Cuculus canorus} begging for food from 'parent' Reed warbler {Acrocephalus scirpaceus} UK