Nick Upton / Female Eurasian beaver (Castor fiber) and five kits feeding on a Willow (Salix) sapling, River Otter, Devon, England, UK, July. Part of Devon Wildlife Trust's Devon Beaver Trial.

Andres M. Dominguez / Bacteria (Lepthotryx discophora) causing iridescent patterns and White willow tree leaf (Salix alba) in river, Sierra de Grazalema Natural Park, southern Spain, November.

Jussi Murtosaari / Garden warbler (Sylvia borin), catching flies in willow tree, Korpoo, Uto, Finland, May.

Gerrit Vyn / Muskox (Ovibos moschatus) feeding on willows. North Slope, Alaska. September.

Sven Zacek / Misty lake, with trees reflected in the water, and Willow (Salix) trees silhouetted on the shore, Suur Emajogi river, Tartumaa, Estonia, May 2014.

Ernie Janes / Blue tit (Cyanistes caeruleus) hanging on Pussy willow branch, Norfolk, England, UK, April.

Alex Hyde / Peacock butterfly (Inachis io) feeding on Goat Willow catkins (Salix caprea), an important food source for pollinators in early spring. Peak District National Park, UK. April.

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...

Alastair MacEwen / Time-lapse of flowers emerging on a male Willow (Salix) catkin, Somerset, England, UK, April.

Ammonite / Mining bee (Andrena apicata) flying and feeding from Sallow (Salix caprea) catkins, with pollen sacs on hind legs, France, March.

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

Terry Whittaker / 2020VISION / Water vole (Arvicola amphibius / Arvicola terrestris) feeding amongst vegetation, Kent, England, UK, February. 2020VISION Exhibition. 2020VISION Book Plate. Did you know? The character 'Ratty' from Ke...

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

Andy Sands / Blue tit (Parus caeruleus) perched among Pussy willows, West Sussex, England, UK

Paul Harcourt Davies / Swiss willow (Salix helvetica) catkins.Dolomites, Italy. June.

Jenny E. Ross / Polar bear (Ursus maritimus) mother and twin cubs rest in the snow among willows on the shore of Hudson Bay, Manitoba, Canada. November.

Jenny E. Ross / Polar bear (Ursus maritimus) mother and cub rest in willows on the shore of Hudson Bay during a snowstorm, Western Hudson Bay, Manitoba, Canada. November.

Jussi Murtosaari / Honey bee (Apis mellifera) with laden pollen sacs flying towards Pussy willow (Salix caprea) catkins. Jyvaskyla, Central Finland. April.

Linda Pitkin / Weeping willow (Salix sepulcralis), male catkins. South West London, England, UK. April.

Linda Pitkin / Goat willow (Salix caprea), male catkins along the River Thames Path, Richmond , England, UK. April.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Willow (Salix caprea), Vauldalen, Norway, April.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Willow (Salix caprea), Vauldalen, Norway, April.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Willow (Salix caprea), Vauldalen, Norway, April.

Erlend Haarberg / Eurasian elk (Alces alces) feeding on Willow (Salix), Sarek National Park, Sweden, September.

Erlend Haarberg / Eurasian elk (Alces alces) feeding on Willow (Salix), Sarek National Park, Sweden, September.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Goat willow (Salix caprea) at night, Vauldalen, Norway, April.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Goat willow (Salix caprea) at night, Vauldalen, Norway, April.

Erlend Haarberg / Mountain hare (Lepus timidus) feeding on Goat willow (Salix caprea) at night, Vauldalen, Norway, April.

Nick Upton / Pussy willow / Goat willow (Salix caprea) tree flowering, with mass of male catkins, Cornwall, UK, March

Adrian Davies / Pussy / Goat willow (Salix caprea) male catkin shedding pollen. Surrey, England, UK. March.

Brian Bevan / Close-up of a Harvest mouse (Micromys minutus) climbing on Willow (Salix). Captive. Native to Eurasia.

Brian Bevan / Close-up of a Harvest mouse (Micromys minutus) climbing on Willow (Salix). Captive. Native to Eurasia.

Brian Bevan / Close-up of a Harvest mouse (Micromys minutus) climbing on Willow (Salix). Captive. Native to Eurasia.

Marie Read / Weeping Willow (Salix babylonica) newly leafed-out branches against distant flowering red maple (Acer rubrum) in spring, Ithaca, New York, USA. April 2020.

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.

Dave Bevan / Eurasian beaver (Castor fiber) felling and dragging a Willow (Salix) sapling, Ceredigion, Wales, UK, June.

Konrad Wothe / Honey bee (Apis mellifera) on Pussy willow (Salix caprea) Bavaria, Germany. April.

Erlend Haarberg / Dwarf willow (Salix herbacea), Jotunheimen National Park, Norway, July.

Colin Varndell / Portrait of female Goat willow (Salix caprea) catkins. Dorset, England, UK April.

Will Watson / Grey Sallow / Willow (Salix cinerea subspecies oleifolia) female catkins releasing pollen, kettle hole pond, Herefordshire, England, May.

Will Watson / Aerial roots of Crack Willow (Salix fragilis), kettle hole pond, Herefordshire, England, August.

Will Watson / Collapsed and split Crack Willow (Salix fragilis), kettle hole pond, Herefordshire, England, July.

John Shaw / Dwarf willows add color along a small glacial stream before icebergs in Hare Fjord, Scoresby Sund, Greenland, August.

Bernard Castelein / Goat willow (Salix caprea) in mist at dawn, full moon in sky. Klein Schietveld, Brasschaat, Belgium. August 2019.

Bernard Castelein / Goat willow (Salix caprea) tree in mist at dawn. Klein Schietveld, Brasschaat, Belgium. August 2019.

Nigel Cattlin / Goat willow (Salix caprea) male catkins. Kennett and Avon Canal, Berkshire, England, UK. April.

Heather Angel / Common bee fly (Bombylius major) nectaring on Goat willow (Salix caprea) catkin. Surrey, England, UK. March.

Heather Angel / Goat willow (Salix caprea) female catkin in UV light, fine hairs and nectar fluroescing. Surrey, England, UK. Focus stacked.