Andres M. Dominguez/ BIA / Common Tern (Sterna hirundo) flying with fish prey, Danube Delta, Romania

Guy Edwardes / Marsh Frog (Pelophylax ridibundus) vocalising with bokeh effect in the background, Danube Wetlands, Bulgaria

Guy Edwardes / Marsh Frog (Pelophylax ridibundus) vocalising with bokeh effect in the background, Danube Wetlands, Bulgaria

Remi Masson / Group of Wels catfish (Silurus glanis) gathered in the River Rhone, France, August.

Loic Poidevin / Golden jackal (Canis aureus) portrait. Danube Delta, Romania, May.

Bence Mate / Close up of Dalmatian pelican (Pelecanus crispus) preening, Danube Delta, Romania

Wild Wonders of Europe / Lundgren / European sturgeon (Huso huso) captive at Danube Delta Eco-Tourism Museum Centre aquarium in Tulcea, Danube Delta, Romania, June. Critically endangered.

Wild Wonders of Europe / Lundgren / Pool Frog (Pelophylax lessonae) viewed from below while swimming, underwater around Crisan village, Danube Delta, Romania, June.

Wild Wonders of Europe / Lundgren / Pool frog (Pelophylax lessonae) reflected in waters surface at night, Danube Delta, Romania, June.

Bence Mate / Close up portrait of Eastern white pelican head (Pelecanus onocrotalus) Danube Delta, Romania. Finalist in the Wildlife Photographer of the Year Awards (WPOY) Competition 2016.

Bence Mate / Eastern white pelican (Pelecanus onocrotalus) Danube Delta, Romania

Bence Mate / Dalmatian pelicans (Pelecanus crispus) mobbed by gulls, Danube Delta, Romania