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.

Bence Mate / Little bittern (Ixobrychus minutus) watching Great warbler (Acrocephalus arundinaceus) with prey, Lake Csaj, Kiskunsagi National Park, Hungary.

Bence Mate / Great reed warbler (Acrocephalus arundinaceus) taking fish from water, Hungary, June.

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

Loic Poidevin / Aquatic warbler (Acrocephalus schoenobaenus) Breton Marsh, Vendee, France, May.

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

Bence Mate / Great reed warbler (Arcocephalus arundinaceus) chick begging for food, with bokeh affect from water, Pusztaszer, Hungary, June.

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

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

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

Andy Sands / European Cuckoo chick (Cuculus canorus) being fed by Reed Warbler on post, West Sussex, England, 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...

John Cancalosi / Reed warbler's nest with eggs and European cuckoo chick just hatched, UK

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

Paul Hobson / Sedge warbler (Acrocephalus schoenobaenus) male singing whilst perched on Willow (Salix sp) branch. Sheffield, England, UK. May.

Paul Hobson / Reed warbler (Acrocephalus scirpaceus) vocalising whilst perched amongst reeds in morning light. Sheffield, England, UK. May.

Paul Hobson / Reed warbler (Acrocephalus scirpaceus) perched on stem in morning light. Sheffield, England, UK. May.

David Tipling / Cuckoo (Cuculus canorus) 12 day old chick in Reed Warblers (Acrocephalus scirpaceus) nest, Norfolk, England, UK. May.

David Perpinan / Sedge warbler (Acrocephalus schoenobaenus) singing. Scotland, UK, July.

Matthew Maran / Reed warbler (Acrocephalus scirpaceus) being released after ringing, reedbeds on the Otter Estuary, Devon, England, UK, May.

Matthew Maran / Bird ringer measuring migrant Reed warblers (Acrocephalus scirpaceus) in reedbeds, Otter Estuary, East Devon, England, UK, May.

Matthew Maran / Man ringing migrant reed warblers (Acrocephalus scirpaceus) noting down details, in reedbeds on the Otter Estuary, East Devon, England, UK, May 2017.

Matthew Maran / Ringing migrant reed warblers (Acrocephalus scirpaceus) in reedbeds on the Otter Estuary to improve understanding of their ecology and life cycle. Devon UK

Roger Powell / Sedge warbler (Acrocephalus schoenobaenus) perched in a hawthorn bush. Druridge Bay, Northumberland, England, UK, July.

Roger Powell / Sedge warbler (Acrocephalus schoenobaenus) perched in a hawthorn bush. Druridge Bay, Northumberland, England, UK, July.

David Kjaer / Sedge Warbler (Acrocephalus schoenobaenus) Greylake RSPB Reserve, Somerset Levels, England, UK, August.

David Kjaer / Sedge warbler (Acrocephalus schoenobaenus) singing, Greylake RSPB Reserve, Somerset Levels, England, UK, May.

David Kjaer / Sedge warbler (Acrocephalus schoenobaenus) singing, Greylake RSPB Reserve, Somerset Levels, England, UK, May.

David Kjaer / Reed warbler (Acrocephalus scirpaceus) with insect larvae in beak, Greylake RSPB Reserve, Somerset Levels, England, UK, June.

David Kjaer / Reed warbler (Acrocephalus scirpaceus) Greylake RSPB Reserve, Somerset Levels, England, UK, June.

Michel Poinsignon / Sedge warbler (Acrocephalus schoenobaenus) adult singing in reedbed. Baie de Somme. France. April

Brian Bevan / Close-up of a pair of Reed warblers (Acrocephalus scirpaceus) feeding young at nest, Bedfordshire, England, UK, July.

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

Ingo Arndt / Great reed warbler (Acrocephalus arundinaceus) singing in reedbed, Lake Neusiedl, Austria, May.

Ingo Arndt / Great reed-warbler (Acrocephalus arundinaceus) singing in reed, Lake Neusiedl, Austria , April.

Ingo Arndt / Great reed-warbler (Acrocephalus arundinaceus) singing in reed, Lake Neusiedl, Austria , April.

Ingo Arndt / Great reed-warbler (Acrocephalus arundinaceus) singing in reed, sitting on reed stem, Lake Neusiedl, Austria , April.

Ingo Arndt / Sedge warbler (Acrocephalus schoenobaenus) male singing, sitting on reed stem, Lake Neusiedl, Austria , April.

Ingo Arndt / Sedge warbler (Acrocephalus schoenobaenus) male singing, sitting on reed stem, Lake Neusiedl, Austria , April.

Ingo Arndt / Sedge warbler (Acrocephalus schoenobaenus) male singing, sitting on reed stem, Lake Neusiedl, Austria , April.

Loic Poidevin / Sedge warbler (Acrocephalus schoenobaenus) in bush. Le Teich , Gironde, France, September

Hanne & Jens Eriksen / Marsh warbler (Acrocephalus palustris) on twig, during migration, Oman, May.

Melvin Grey / Reed warbler (Acrocephalus scirpaceus) adults at nest in reedbed, feeding young, Surrey, England, UK.

Melvin Grey / Great reed warbler (Acrocephalus arundinaceus) adult male singing, Bulgaria

Niall Benvie / Sedge warbler (Acrocephalus schoenobaenus) perched on Bracken singing, Islay, Scotland

Kerstin Hinze / Marsh warbler (Acrocephalus palustris) nest with eggs including one Cuckoo (Cuculus canorus) egg which has been destroyed by the warbler, Germany, June.

Kerstin Hinze / Common cuckoo (Cuculus canorus) fighting with Marsh warbler (Acrocephalus palustris), who is breeding nearby , Braunschweig, Lower Saxony, Germany, May.

Kerstin Hinze / Common cuckoo (Cuculus canorus) fighting with Marsh warbler (Acrocephalus palustris), who is breeding nearby , Braunschweig, Lower Saxony, Germany, May.

Chris Gomersall / Sedge warbler (Acrocephalus schoenobaenus) singing with bokeh effect in background,Norfolk, England, UK, May. Winner of the Birds in Environment Category of the Bird Photographer of the Year 2015.

Sam Hobson / Sedge warbler (Acrocephalus schoenobaenus) caught in bird ringers nets. Severn Estuary, UK. July

Sam Hobson / Sedge warbler (Acrocephalus schoenobaenus) held in bird ringers hand. Severn Estuary, UK. July

Ingo Arndt / Sedge warbler (Acrocephalus schoenobaenus) singing in reedbed at sunset, Lake Neusiedl, Austria , April.

Oliver Richter/ BIA / Eurasian Reed-Warbler (Acrocephalus scirpaceus) feeding parasitic Common Cuckoo (Cuculus canorus) chick in nest, Saxony-Anhalt, Germany

Oliver Richter/ BIA / Eurasian Reed-Warbler (Acrocephalus scirpaceus) feeding parasitic Common Cuckoo (Cuculus canorus) chick in nest, Saxony-Anhalt, Germany

Oliver Richter/ BIA / Eurasian Reed-Warbler (Acrocephalus scirpaceus) feeding parasitic Common Cuckoo (Cuculus canorus) chick in nest, Saxony-Anhalt, Germany

Jussi Murtosaari / Marsh warbler (Acrocephalus palustris) perched, Korpoo, Uto, Finland, May.

Michel Poinsignon / Reed warbler (Acrocephalus scirpaceus) adult perched in reedbed, Remerschen, Luxembourg, May

Michel Poinsignon / Great reed warbler (Acrocephalus arundinaceus) singing amongst reeds, Remerschen, Luxembourg, May

Michel Poinsignon / Great reed warbler (Acrocephalus arundinaceus) singing amongst reeds, Remerschen, Luxembourg, May

Volker Lautenbach/ BIA / Common Cuckoo (Cuculus canorus) chick being fed by Eurasian Reed-Warbler (Acrocephalus scirpaceus), Saxony-Anhalt, Germany

Aflo / Great reed warbler (Acrocephalus arundinaceus) singing, perched in umbellifer, Saitama, Japan, May.

Paul Hobson / Reed warbler (Acrocephalus scirpaceus) among reed bed. South Yorkshire, England, UK, April.

Paul Hobson / Reed warbler (Acrocephalus scirpaceus) among reed bed, South Yorkshire, England, UK, April.

Staffan Widstrand / Sedge warbler (Acrocephalus schoenobaenus) singing in sedge, in its habitat, Nemunas River Delta, Lithuania, May. Vulnerable species.

Staffan Widstrand / Sedge warbler (Acrocephalus schoenobaenus) in grass habitat, Nemunas River Delta, Lithuania, May.

Sven Zacek / Sedge warbler (Acrocephalus schoenobaenus) singing in front of a foggy background colored golden by the rising sun, Valgamaa, Estonia, June.

Robin Chittenden / Reed warbler (Acrocephalus scirpaceus) perched on reed, Norfolk, England, May.

Robin Chittenden / Reed warbler (Acrocephalus scirpaceus) singing, perched on reed, Norfolk, England, May.

Michel Poinsignon / Great reed warbler (Acrocephalus arundinaceus) singing amongst reeds, Remerschen, Luxembourg, May.

Michel Poinsignon / Great reed warbler (Acrocephalus arundinaceus) singing amongst reeds, Remerschen, Luxembourg, May.

David Tipling / 2020VISION / Reed warbler (Acrocephalus scirpaceus) sitting on twelve day old Cuckoo (Cuculus canorus) chick at nest, Norfolk, England, UK, May Sequence 2/2

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

David Tipling / 2020VISION / Reed warbler (Acrocephalus scirpaceus) feeding twelve day old Cuckoo (Cuculus canorus) chick at nest, Norfolk, England, UK, May. Sequene 1/2

David Tipling / Reed warbler (Acrocephalus scirpaceus) perched, Cley, Norfolk, UK, June.

David Tipling / Sedge warbler (Acrocephalus schoenobaenus) in song flight, Cley, Norfolk, UK, May.

David Tipling / Sedge warbler (Acrocephalus schoenobaenus) in song flight, Cley, Norfolk, UK, May.

Thomas Hinsche / Common Cuckoo (Cuculus canorus) chick and Eurasian Reed-Warbler (Acrocephalus scirpaceus), Saxony-Anhalt, Germany

Thomas Hinsche / Eurasian Reed-Warbler (Acrocephalus scirpaceus) feeding Common Cuckoo (Cuculus canorus) chick, Saxony-Anhalt, Germany

Thomas Hinsche / Eurasian Reed-Warbler (Acrocephalus scirpaceus) feeding Common Cuckoo (Cuculus canorus) chick, Saxony-Anhalt, Germany

Mike Read / Great reed warbler (Acrocephalus arundinaceus) perched in Common reed (Phragmites australis) in marshland near Tiszaalpar, Hungary, June.

Pal Hermansen / Reed warbler (Acrocepahlus scirpaceus) singing from reed, Varmland, Sweden, June

David Tipling / Reed Warbler (Acrocephalus scirpaceus) feeding Cuckoo (Cuculus canorus) chick in reedbed nest, Norfolk, May.

Aflo / Great Reed Warbler (Acrocephalus arundinaceus) feeding Cuckoo (Cuculus sp) chick, Japan.

Aflo / Great Reed Warbler (Acrocephalus arundinaceus) feeding Cuckoo (Cuculus sp) chick, Japan.

Robin Chittenden / Sedge warbler (Acrocephalus schoenobaenus) perched on twig, Suffolk, UK, October.

Robin Chittenden / Sedge warbler (Acrocephalus schoenobaenus) perched on twig, Suffolk, UK, October.

Robin Chittenden / Male Sedge warbler (Acrocephalus schoenobaenus) singing, Salthouse, Norfolk, UK, May.

Nature Production / Great Reed Warbler (Acrocephalus arundinaceus) removing cuckoo's egg from nest, Minamimaki village, Nagano Prefecture, Japan

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

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

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

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

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