Marie Read / Common redpoll (Carduelis flammea), male perched in alder (Alnus rugosa) during a snowstorm in winter, New York, USA, January.

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.

Markus Varesvuo / Lesser Whitethroat (Sylvia curruca) with yellow pollen stain on head from willow catkins. Porvoo, Söderskär, Finland. May

Ammonite / Close-up of a Buff-tailed bumble bee (Bombus terrestris) feeding from Willow (Salix) catkins, before flying out of frame, France, March.

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

Guy Edwardes / 2020VISION / Pussy willow catkins (Salix caprea), Somerset Levels, Somerset, England, UK, April

Colin Varndell / Hazel catkins (Corylus avellana) releasing pollen. Dorset, England, UK February

Alan Williams / Blue tit (Parus caeruleus) perched on twig with catkins, Essex, UK, February

Ross Hoddinott / Close-up of Hazel inflorescence (Corylus avellana) in spring, with both male catkins and female flower visible, near Bradworthy, Devon, UK. March 09.

Ross Hoddinott / Pussy willow / Sallow (Salix caprea) catkins, Cornwall, UK. April .

Andy Sands / Male Greenfinch (Carduelis chloris) amongst Pussy willow catkins, Hertfordshire, England, UK

Ross Hoddinott / Coal tit {Periparus ater} Cornwall. UK