Ross Hoddinott / Blue tit {Parus caeruleus} with hazel catkins, Cornwall. UK

Ross Hoddinott / Sallow / Pussy willow {Salix caprea} catkin, Cornwall. UK

David Kjaer / Bullfinch male {Pyrrhula pyrrhula} with Pussy willow catkins (Salix) Yorkshire, UK

Ross Hoddinott / Common alder (Alnus glutinosa) catkins silhouetted. Cornwall. UK

Dave Watts / Two Great tits with willow catkins in snow, France {Parus major}

David Kjaer / Brimstone butterfly on Pussy willow catkins, UK

David Tipling / Willow warbler singing, early spring, New Forest, Hampshire, England,

Hanne & Jens Eriksen / Eurasian blue tit (Cyanistes caeruleus) perched in tree amongst catkins. Denmark, February.

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

Heather Angel / Hazel (Corylus avellana) catkins dispersing pollen with female flower above on branch. Controlled condition.s Surrey, England, UK.

Heather Angel / Cedar (Cedrus sp), male catkins releasing pollen. Surrey England, UK.

Gary K. Smith / Common redpoll (Carduelis flammea) perched on corkscrew hazel with catkins, England, UK. March.