Floris van Breugel / Aspen leaves on an early snow, North Fork of Bishop Creek, near Bishop, Eastern Sierra, California, USA, October.

Floris van Breugel / Aspen (Populus tremula) trees in autumn colours, North Fork of Bishop Creek, near Bishop, Eastern Sierra, California, USA

George Sanker / Aspen trees (Populus tremula) in Grand Teton NP, Wyoming, USA, October 2009

Laurie Campbell / Aspen tree (Populus tremula) in autumn, Speyside, Scotland, October

Mark Hamblin / 2020VISION / Aspen trees (Populus tremula) in autumn, Strathspey, Cairngorms NP, Scotland, UK, September 2011

Grzegorz Lesniewski / Peat bog with Eurasian Aspen (Populus tremula) and Bog bilberry (Vaccinium uliginosum). Bieszczady National Park, the Carpathians, Poland, September.

Marie Read / Red-breasted Sapsucker (Sphyrapicus ruber), clinging to Aspen trunk in spring, Mono Lake Basin, California, USA

Marie Read / Northern Flicker (Colaptes auratus) female, red-shafted race, landing at its nest hole in Quaking Aspen (Populus tremuloides) trunk, Mono Lake Basin, California, USA.

Marie Read / Mountain Bluebird (Sialis currucoides), outside its nest hole in Aspen trunk, carrying caterpillar prey in its bill for young, Mono Lake Basin, California, USA

Marie Read / Mountain Bluebird (Sialis currucoides) male looking out of its nest hole in Aspen trunk, Mono Lake Basin, California, USA

MYN / Niall Benvie / Aspen tree (Populus tremula) twig with new leaves, Alam-Pedja nature reserve, Tartumaa, Estonia, May meetyourneighbours.net project

Niall Benvie / Aspen leaves {Populus tremula} in autumn, Scotland, UK, October 2007