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

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

Matthew Maran / Beaver (Castor fibre) female feeding on willow bark with her two kits, River Otter, Devon, England, UK, July. Highly commended in the Habitat category of the British Wildlife Photography Awards (BWPA)...

Robert Thompson / Sawfly larvae (Nematus pavidus) defensive posture, Peatlands Park, County Armagh, Northern Ireland. September.

Solvin Zankl / Honey bee (Apis mellifera) collecting pollen on Goat willow (Salix caprea) Kiel, Germany, April.

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.

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

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.

Markus Varesvuo / Willow grouse / Ptarmigan (Lagopus lagopus) pecking twig, Utsjoki, Finland, April.

Markus Varesvuo / Female Black grouse (Tetrao / Lyrurus tetrix) perched in Willow feeding, Utajarvi, Finland, May.