Sven Zacek / Brimstone butterfly(Gonepteryx rhamni) male and female during mating flight, early spring. Tartumaa county, Southern Estonia. May.

Sven Zacek / Ural Owl (strix uralensis) female with talons ready to attack a ringing ornithologist, Tartumaa county, Southern Estonia. May.

Sven Zacek / Black Grouse (Tetrao tetrix) two males facing off on a lekking site, Varumaa county, Southern Estonia. April.

Sven Zacek / Aerial view of a golden and foggy sunrise over a bog area, Alam-Pedja National Park, Tatrumaa county, Southern Estonia. May.

Sven Zacek / Ural owl (Strix uralensis) female watching fledgling learning to climb and balance on branch. Owlet's first day out of nest. Tartumaa County, Southern Estonia. June.

Sven Zacek / Ural owl (Strix uralensis) hunting, Tartumaa county, Southern Estonia.

Sven Zacek / Ural owl (Strix uralensis) in flight, hunting, Tartumaa county, Southern Estonia. February.

Sven Zacek / Ural owl (Strix uralensis) nestling, Tartumaa county, Southern Estonia. May.

Markus Varesvuo / White-fronted goose (Anser albifrons) and Taiga bean goose (Anser fabalis rossicus) flocks in flight and on water. Latvia. April.

Markus Varesvuo / Citrine wagtail (Motacilla citreola) male perched on Reed. Latvia. April.

Sven Zacek / Eurasian pygmy owl (Glaucidium passerinum) perched on snow covered branch in evening light. Vorumaa, Southern Estonia. November.

Sven Zacek / Wild boar (Sus scrofa) swimming with head above water in Suur Emajogi River. Alam-Pedja Nature Reserve, Tartumaa, Southern Estonia. November.

Sven Zacek / Brown bear (Ursus arctos) in coniferous forest. Ida-Virumaa, Eastern Estonia. September.

Sven Zacek / Sun dog over trees in frosty landscape. Tartumaa, Southern Estonia. December 2015.

Sven Zacek / Bog surrounding river in morning light. Emajoe Suursoo Nature Reserve, Tartumaa, Estonia. October 2015.

Sven Zacek / Sunrise over bog with trees reflected in pool. Endla Nature Reserve, Jogevamaa, Central Estonia. October 2015.

Sven Zacek / White-tailed sea eagle (Haliaeetus albicilla) flying over frost and snow covered forest. Tartumaa, Southern Estonia. January 2011.

Sven Zacek / Ural owl (Strix uralensis) female on nest, male landing with twig in beak. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) male presenting prey to nesting mate. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) female feeding at nest on rodent prey presented by mate. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) female on the nest with nestling hidden under wing. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) female stretching wings whilst perched in Spruce (Picea sp) tree. Tartumaa, Southern Estonia. May.

Sven Zacek / Ural owl (Strix uralensis) female and nestling on nest in tree stump. Tartumaa, Southern Estonia. May.

Sven Zacek / Mist over bog with conifers in pre-dawn light. Endla Nature Reserve, Jogevamaa, Central Estonia. June 2016.

Sven Zacek / Roe deer (Capreolus capreolus) young buck, portrait. Karula National Park, Valgamaa, Southern Estonia. June.

Sven Zacek / Beaver (Castor fiber) felling a Birch (Betula sp) tree for winter supplies. Tartumaa, Southern Estonia. November.

Sven Zacek / Frozen bog pool system, aerial view. Endla Nature Reserve, Jogevamaa, Central Estonia. December 2016.

Sven Zacek / Ural owl (Strix uralensis) female on nest after snowfall. Tartumaa, Southern Estonia. March.

Sven Zacek / Ural owl (Strix uralensis) female on nest in tree stump. Tartumaa, Southern Estonia. April.

Sven Zacek / Black woodpecker (Dryocopus martius) excavating nest hole. Valgamaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) female in flight having taken off from nest, in evening light. Tartumaa, Southern Estonia. May.

Sven Zacek / Ural owl (Strix uralensis) female flying with prey in beak. Flying back to nest in evening light. Tartumaa, Southern Estonia. May.

Sven Zacek / Meandering Loobu River with surrounding meadows and woodlands, aerial view. Lahemaa National Park in Northern Estonia in Laane-Virumaa, Estonia. May 2017.

Sven Zacek / Dandelion (Taraxacum officinale), a field of many seedheads highlighted at sunset. Karula National Park, Valgamaa, Southern Estonia. June 2017.

Sven Zacek / Flooded meanders of Halliste River, aerial view. Soomaa National Park, Parnumaa, Western Estonia. October 2017.

Sven Zacek / Eurasian beaver (Castor fiber) with Willow (Salix sp) branch for winter stockpile. Near Suur Emajogi River, Tartumaa, Southern Estonia. January.

Sven Zacek / Eurasian beaver (Castor fiber) on ice besides reeds in Emajogi River, Tartumaa, Southern Estonia. January.

Sven Zacek / Great bittern (Botaurus stellaris) with fish in beak, caught in stream. Laanemaa, Western Estonia. March.

Sven Zacek / Honey bee (Apis mellifera), two frozen on pond ice after flying out too early. Valgamaa, Southern Estonia. March.

Sven Zacek / Ural owl (Strix uralensis) perched on Alder (Alnus sp) tree at dusk. Tartumaa, Southern Estonia. April.

Sven Zacek / Black woodpecker (Dryocopus martius) feeding chicks at nest in tree trunk viewed from above, Valga County, Estonia. May. Highly commended in the GDT European Wildlife Photographer of the Year Awards...

Neil Aldridge / Two Lady's slipper orchids (Cypripedium calceolus) in flower in spring in woodland near Kuressaare, Saaremaa, Estonia.

Sven Zacek / Great grey owl (Strix nebulosa) perched on dead umbellifer plant, winter, Finland, February.

Sven Zacek / Otter (Lutra lutra) resting in snow, Southern Estonia. January.

Sven Zacek / Ural owl (Strix uralensis) perching on an Apsen tree during the blue hour of dawn, Tartumaa, Estonia, April.

Sven Zacek / Black grouse (Tetrao tetrix) males lekking at sunrise, Southern Estonia, April.

Sven Zacek / Wide angle view of Otter (Lutra lutra) walking on the ice of a river, Southern Estonia, January.

Sven Zacek / Sunrise over a frozen bog pool, Tartumaa, Estonia, November 2014.