Dietmar Nill / Tengmalm's Owl (Aegolius funerus) pouncing on mouse, Germany

Wild Wonders of Europe / Lesniewski / Tengmalm's Owl (Aegolius funereus) nesting in an old beech tree. Bieszczady, Carpathian Mountains, Poland, May.

Gerrit Vyn / Two Northern Saw-whet Owls (Aegolius acadicus) fledgling chicks, that have recently left the safety of their nest cavity. Alberta, Canada. June.

Wild Wonders of Europe / Cairns / Tengmalm's owl (Aegolius funereus) peering out of nestbox, Bergslagen, Sweden, June 2009

Konrad Wothe / Boreal Owl (Aegolius funereus) in nest cavity, Sweden

Konrad Wothe / Boreal Owl (Aegolius funereus) in nest cavity, Sweden

Tim Fitzharris / Northern Saw-whet Owl (Aegolius acadicus) perching in a wild rose bush, British Columbia, Canada

Juan Manuel Borrero / Illustration of silhouettes of the Pyrenean animals, Roe deer (Capreolus capreolus), Red deer (Cervus elaphus), Pyrenean chamois (Rupicapra pyrenaica), Red squirrel (Sciurus vulgaris), Red fox (Vulpes...

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) looking out of nest box, Kuusamo, Finland, May

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) perched with eyes shut, Kuusamo, Finland, May

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) perched on branch, Kuusamo, Finland, May

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) perched on branch, Kuusamo, Finland, May

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) perched on branch, Kuusamo, Finland, May

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) looking out of hole in tree, Kuusamo, Finland, June

Markus Varesvuo / Tengmalm's / Boreal owl (Aegolius funereus) looking out of hole in tree, Kuusamo, Finland, June

Markus Varesvuo / Portrait of a Tengmalm's Owl (Aegolius funereus). Kuusamo, Finland, May.

Lassi Rautiainen / Replacing Tengmalm's owl (Aegolius funereus) chick in tree after ringing, Finland, June

Lassi Rautiainen / Tengmalm's owl (Aegolius funereus) chick perched on stump, Finland, June

Diane McAllister / Northern saw-whet owl (Aegolius acadicus) roosting in a juniper tree in a backyard in Reno. Nevada, USA, December

Gerrit Vyn / Two Northern Saw-whet Owls (Aegolius acadicus) fledgling chicks, that have recently left the safety of their nest cavity. Alberta, Canada. June.

Inaki Relanzon / Tengmalm's owl (Aegolius funereus) at nest in tree, Pyrenees, Spain. June

Inaki Relanzon / Tengmalm's owl (Aegolius funereus) at nest in tree, Pyrenees, Spain. June

Wild Wonders of Europe / Cairns / Tengmalms owl (Aegolius funereus) peering out of nestbox, Bergslagen, Sweden, June 2009

Wild Wonders of Europe / Cairns / Tengmalms owl (Aegolius funereus) peering out of nestbox, Bergslagen, Sweden, June 2009

Bengt Lundberg / Young Tengmalm's owls (Aegolius funereus) on apple blossom, Sweden

Seppo Valjakka / Tengmalm's Owl (Aegolius funereus) perched in a tree, June, Finland

Thomas Mangelsen / Boreal Owl (Aegolius funereus) perching in a White Spruce (Picea glauca), northern Minnesota

Gerry Ellis / Boreal Owl (Aegolius funereus) perched in tree, North America

Bengt Lundberg / Tengmalm's owl {Aegolius funereus} face portrait in nest hole, Olsdalen, Sweden

Bengt Lundberg / Tengmalm's owl {Aegolius funereus} in pine tree, Sweden

Bengt Lundberg / Tengmalm's owl {Aegolius funereus} looking out from nest in pine tree, Sweden

Tom Vezo / Northern Saw-whet owl {Aegolius acadius} perching on branch, captive, USA

LYNN M. STONE / Northern saw-whet owl {Aegolius acadicus} captive

David Welling / Northern saw-whet owl {Aegolius acadicus} captive, Colorado, USA

Klaus Echle / Tengmalm's owl {Aegolius funereus} looking out of nest hole in old log, Black Forest, Bavaria, Germany

Juan Manuel Borrero / Three Tengmalm's owl chicks {Aegolius funereus} Pyrennees, Catalonia, Spain

DAVID TIPLING / Tengmalm's Owl {Aegolius funerus} peering out of nest box in coniferous forest, Finland

Philippe Clement / Tengmalm's owl {Aegolius funereus} perching in tree, captive, Bavarian Forest, Germany.

Philippe Clement / Tengmalm's owl {Aegolius funereus} perching in tree, captive, Bavarian Forest, Germany.

Philippe Clement / Tengmalm's owl {Aegolius funereus} perching in tree, captive, Bavarian Forest, Germany.

Seppo Valjakka / Tengmalm's Owl {Aegolius funereus} fledgling with prey, Finland.

Elio Della Ferrera / Tengmalm's owl {Aegolius funereus} looking our ot tree nest hole, Orobie Alps regional park, Central Alps, Italy.

Dietmar Nill / Tengmalm's owl catching a mouse. (Aegolius funereus)

Bengt Lundberg / Juvenile Tengmalm's Owl (Aegolius funereus) perched in flowering tree, Sweden.

Bengt Lundberg / Two Tengmalm's Owl chicks (Aegolius funereus) Sweden.

Bengt Lundberg / Tengmalms owl juveniles {Aegolius funereus} Sweden

Philippe Clement / Tengmalm's owl portrait {Aegolius funereus} captive, Bavarian Forest, Germany.

Philippe Clement / Tengmalm's owl portrait {Aegolius funereus} captive, Bavarian Forest, Germany.

Artur Tabor / Tengmalm's owl chick {Aegolius funereus} in pine tree, Poland.

Artur Tabor / Tengmalm's owl {Aegolius funereus} with mouse prey, Mazovia, Poland

Artur Tabor / Tengmalm's owl {Aegolius funereus} chick perched, Polesie Lubelskie, Poland.

Artur Tabor / Tengmalm's owl {Aegolius funereus} looking out of nest hole, Polesie Lubelskie, Poland.

Artur Tabor / Tengmalm's owl chick {Aegolius funereus} in pine tree, Poland.

Tom Vezo / Northern Saw-whet Owl (Aegolius acadicus) portrait, North America

Thomas Mangelsen / Northern Saw-whet Owl (Aegolius acadicus) in nest cavity in tree, Wyoming

Tom Vezo / Northern Saw-whet Owl (Aegolius acadicus) perched in tree, Long Island, New York

Gerry Ellis / Boreal Owl (Aegolius funereus) peeking out from nest in tree trunk, North America

Konrad Wothe / Boreal Owl (Aegolius funereus) peaking through hole in tree, Sweden

Tim Fitzharris / Northern Saw-whet Owl (Aegolius acadicus) perching on post, British Columbia, Canada

Tim Fitzharris / Northern Saw-whet Owl (Aegolius acadicus) perching in a wild rose bush, British Columbia, Canada

Michio Hoshino / Boreal Owl (Aegolius funereus) in nest cavity, Alaska

Michael Quinton / Boreal Owl (Aegolius funereus) in tree cavity in winter, Alaska

Michael Quinton / Boreal Owl (Aegolius funereus) in tree cavity with captured Bank Vole (Clethrionomys glareolus) in winter, Alaska

John Cancalosi / Tengmalm's / Boreal owl in conifer tree {Aegolius funereus} Spain

LYNN M. STONE / Northern saw-whet owl {Aegolius acadicus} Alaska, US - captive

Asgeir Helgestad / Tengmalm's owl {Aegolius funereus} looking out of hole in tree, Finland

David Welling / Northern saw whet owl {Aegolius acadicus} Colorado, USA

Dietmar Nill / Tengmalm's owl juvenile at nest entrance {Aegolius funereus} Germany

Tom Vezo / Northern saw-whet owl {Aegolius acadicus} at Raptor centre, USA

Dietmar Nill / Tengmalm's owls juveniles (Aegolius funereus). Germany, Europe

Tom Vezo / Northern saw-whet owl in conifer tree, Long Island, New York

Tom Vezo / Northern saw-whet owl (Aegolius acadicas) in conifer LI, New York, USA

Dietmar Nill / Tengmalm's Owl in flight, Germany

Paul Johnson / Six Tengmalm's Owl chicks, France.

Paul Johnson / Tengmalm's owl chicks (Aegolius funereus) among leafs and moss. France, Europe

Seppo Valjakka / Tengmalm's owl (Aegolius funereus) in flight with prey. Finland, Scandinavia, Europe