Donald M. Jones / Black-capped Chickadee (Poecile atricapillus) in winter, Troy, Montana

Alan Murphy/ BIA / Boreal Chickadee (Poecile hudsonicus) in pine, Alaska

Alan Murphy/ BIA / Boreal Chickadee (Poecile hudsonicus) during snowfall, Alaska

Alan Murphy / Carolina Chickadee (Poecile carolinensis) landing, Texas

Alan Murphy / Black-capped Chickadee (Poecile atricapillus), Texas

Alan Murphy / Black-capped Chickadee (Poecile atricapillus) during snowfall, Alaska

Alan Murphy / Boreal Chickadee (Poecile hudsonicus) feeding on pine cone seeds, Alaska

Alan Murphy / Boreal Chickadee (Poecile hudsonicus), Alaska

Alan Murphy / Boreal Chickadee (Poecile hudsonicus), Alaska

Markus Varesvuo / Siberian Tit (Poecile cinctus) on conifer branch, Finland, January

Markus Varesvuo / Siberian Tit (Poecile cinctus) on lichen-covered branch, Kuusamo, Finland, March

Markus Varesvuo / Willow tit (Poecile montanus) on snow covered branch, Kuusamo, Finland, January