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

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.

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

Ralph Martin/ BIA / Eurasian Reed-Warbler (Acrocephalus scirpaceus), Baden-Wurttemberg, Germany

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