Sven Zacek / Eurasian beaver (Castor fiber) with Willow (Salix sp) branch for winter stockpile. Near Suur Emajogi River, Tartumaa, Southern Estonia. January.

Nick Upton / Eurasian beaver (Castor fiber) gnawing the trunk of a Willow tree (Salix sp.) in woodland enclosure at night. Devon Beaver Project, run by Devon Wildlife Trust, Devon, UK, April. Taken by a remote cam...

Theo Bosboom / Reed and Willows (Salix sp) with hoarfrost, Weerribben-Wieden National Park, the Netherlands, December 2007

David Tipling / 2020VISION / Nightingale (Luscina megarhynchos) singing in willow (Salix sp), Norfolk, England, UK, May.

Orsolya Haarberg / Flowering willows (Salix sp.) in midges (Chironomus islandicus) swarming. Mývatn, Iceland. June 2008

Michael Quinton / Snowshoe Hare (Lepus americanus) browsing on a Pussy Willow (Salix discolor) twig in winter, Alaska

Michael Quinton / Snowshoe Hare (Lepus americanus) browsing on a Pussy Willow (Salix discolor) twig in winter, Alaska

Michael Quinton / Snowshoe Hare (Lepus americanus) browsing on a Pussy Willow (Salix discolor) twig in winter, Alaska

Donald M. Jones / American Beaver (Castor canadensis) swimming with willow branch in mouth, western Montana

Michael Quinton / Common Porcupine (Erethizon dorsatum) feeding on Pussy Willow (Salix discolor) in spring, Alaska

Michael Quinton / Common Porcupine (Erethizon dorsatum) feeding on Pussy Willow (Salix discolor) in spring, Alaska

Michael Quinton / Snowshoe Hare (Lepus americanus) feeding on Pussy Willow (Salix discolor) in winter, Alaska

Michael Quinton / Snowshoe Hare (Lepus americanus) feeding on Pussy Willow (Salix discolor) branch in winter, Alaska

Pal Hermansen / Golden oriole (Oriolus oriolus) perched in Willow (Salix sp) tree. Danube delta, Romania. May.

Jussi Murtosaari / Greater white-fronted goose (Anser albifrons) swimming with Bean goose (Anser fabalis) flock, Willow (Salix sp) scrub in background. Vanjarvi, Uusimaa, Finland. April.

Will Watson / River Lugg floodplain featuring Alders (Alnus glutinosa) and Willows (Salix sp.) after Storm Dennis, Bodenham, Herefordshire, UK. Taken during Storm Dennis, 17 February 2020.

Mike Read / Cetti's warbler (Cettia cetti) perched on Willow (Salix sp) branch. Blashford Lakes Nature Reserve, Ellingham, near Ringwood, Hampshire, England, UK. February.

Nick Upton / Blue tit (Parus caeruleus) perched on a Willow (Salix sp.) tree branch, Gloucestershire, UK, February.

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

Sven Zacek / European elk (Alces alces), three standing together near frost covered Willow (Salix sp) bushes with Suur Emajogi River beyond. Alam-Pedja Nature Reserve, Tartumaa, Southern Estonia. January 2011.

Suzi Eszterhas / North American beaver (Castor canadensis) kit eating Willow (Salix sp). Martinez, California, USA. July.

Suzi Eszterhas / North American beaver (Castor canadensis) kit playing with Willow (Salix sp) at water's edge. Martinez, California, USA. June.

Suzi Eszterhas / North American beaver (Castor canadensis) eating Willow (Salix sp). Martinez, California, USA. June.

Suzi Eszterhas / North American beaver (Castor canadensis) eating Willow (Salix sp). Martinez, California, USA. June.

Robert Thompson / Pussy willow (Salix sp), Brackagh Moss Portadown, County Armagh, Republic of Ireland. April.

Ashley Cooper / Pollen from Willow catkins (Salix sp) on black background.

Ashley Cooper / E.ON's biofuel power station in Lockerbie, Scotland with Willow trees (Salix sp,) planted as a biofuel crop. The power station is fuelled 100 by wood sourced from local woodlands and generates enough...

Ashley Cooper / Willow trees (Salix sp) planted as a biofuel crop at E.ON biofuel power station, Lockerbie, Scotland. The power station is fuelled by wood sourced from local woodlands and generates enough electricit...

Michel Roggo / Gallery forest along the channels dominated by mainly Willows (Salix sp.) and Poplars (Populus sp.) Danube Delta Biosphere Reserve, Danube Delta, Romania May 2015. Photographed for The Freshwater Pro...

Michel Roggo / Underwater view of flooded gallery forest of the Danube Delta in spring, with roots of Willows (Salix sp.) Danube Delta Biosphere Reserve, Romania May 2015 . Photographed for The Freshwater Project

Michel Roggo / Split level view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater of in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater of in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Split level view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Split level view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Michel Roggo / Underwater view of meltwater of icefield on the Temnik River with Willows (Salix sp.) The Temnik river enters the Selenga River, Siberia, Russia.

Michel Roggo / Meltwater in icefield on the Temnik River With Willows (Salix sp.) Temnik River, Baikal Nature Reserve, Buryatia, Siberia, Russia, May 2015.

Nick Upton / Willow trees (Salix sp.) fringing the River Avon partly submerged after weeks of heavy rain caused it to burst its banks, Lacock, Wiltshire, UK, February 2014.

Nick Upton / Willow trees (Salix sp.) fringing the River Avon partly submerged after weeks of heavy rain caused it to burst its banks, Lacock, Wiltshire, UK, February 2014.

Nick Upton / Dead Willow trees (Salix sp.), drowned by flooding, Coate water reservoir, Swindon, UK, November.

Nick Upton / Dead Willow trees (Salix sp.), drowned by flooding, Coate water reservoir, Swindon, UK, November.

Nick Upton / Grey squirrel (Sciurus carolinensis) standing on Willow tree (Salix sp) heavily gnawed by Eurasian beavers (Castor fiber) in a large woodland enclosure at night, Devon Beaver Project, run by Devon Wil...

Nick Upton / Willow tree (Salix sp.) felled by Eurasian beavers (Castor fiber) with its bark partially gnawed off by them, lying across a drainage ditch in lowland farmland, Haughs of Cossans, near Forfar, Angus,...

Nick Upton / Young Willow tree (Salix sp.) felled by Eurasian beavers (Castor fiber) lying across a drainage ditch with much of its bark gnawed off by them in partially flooded lowland farmland, Haughs of Cossans,...

Nick Upton / Willow tree (Salix sp.) gnawed by Eurasian beavers (Castor fiber) with a large branch lying across and partially blocking a stream in lowland farmland, Dean Water, near Forfar, Angus, Tayside, Scotlan...