Steven David Miller / Eclectus parrot (Eclectus roratus) female perched in a tree, The Wildlife Habitat Zoo, Port Douglas, Queensland, Australia. August. Captive.

Alan Murphy / Olive-sided Flycatcher (Contopus cooperi), British Columbia, Canada

Ammonite / Small pod of Atlantic white-sided dolphins (Lagenorhynchus acutus) breaching, Azores, Portugal, July.

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) pod, Nine Mile Bank, San Diego, California

Matthias Breiter / Red-sided Garter Snake (Thamnophis sirtalis parietalis) group mating after hibernation, Narcisse, Manitoba, Canada

Mark Carwardine / Pacific white-sided dolphin / Lag (Lagenorhynchus obliquidens) swimming fast, showing dorsal fin, Johnstone Strait, Vancouver Island, British Columbia, western Canada

Martin Camm / Carwardine / Illustration of Pacific white-sided dolphin / Lag (Lagenorhynchus obliquidens), Delphinidae (Wildlife Art Company).

Shattil & Rozinski / Pacific white-sided dolphin (Lagenorhynchus obliquidens) surfacing off the coast of British Columbia, Canada, September

Steve Gettle / Chestnut-sided Warbler (Setophaga pensylvanica) male, Crane Creek State Park, Ohio

Tim Laman / Rufous-sided sticky frog (Kalophrynus pleurostigma) on the ground in the lowland rainforest, Bako National Park, Sarawak, Borneo, Malaysia

Hiroya Minakuchi / Dusky Dolphin (Lagenorhynchus obscurus) pair, Kaikoura, New Zealand

Doug Allan / Pacific white sided dolphin, CA (Lagenorhynchus obliquidens) USA California

Rolf Nussbaumer / Chestnut sided warbler {Dendroica pennsylvanica} Texas, USA

Michael & Patricia Fogden / Blue-sided Leaf Frog (Agalychnis annae) hanging on leaf, close-up, cloud forest, Costa Rica

Flip Nicklin / Dusky Dolphin (Lagenorhynchus obscurus) jumping, New Zealand

Flip Nicklin / Dusky Dolphin (Lagenorhynchus obscurus) jumping, Kaikoura, New Zealand

Flip Nicklin / Dusky Dolphin (Lagenorhynchus obscurus) trio surfacing, Kaikoura, New Zealand

Flip Nicklin / Dusky Dolphin (Lagenorhynchus obscurus) portrait

Doug Allan / Pacific white sided dolphin, USA off California

Staffan Widstrand / Wild Wonders of China / Grey-sided laughingthrush (Pterorhinus caerulatus) Gaoligong Nature Reserve, Yunnan, China

Staffan Widstrand / Wild Wonders of China / Grey-sided laughingthrush (Pterorhinus caerulatus) Gaoligong Nature Reserve, Yunnan, China

Staffan Widstrand / Wild Wonders of China / Grey-sided laughingthrush (Pterorhinus caerulatus) Gaoligong Nature Reserve, Yunnan, China

Steven David Miller / Zebra Finch (Taeniopygia guttata) group bathing on the shallows of a pond, Alice Springs Desert Park, Northern Territory, Australia. Captive.

Steven David Miller / Eclectus parrot (Eclectus roratus) male perched on a tree vine, The Wildlife Habitat Zoo, Port Douglas, Queensland, Australia. August. Captive.

Steven David Miller / Eclectus parrot (Eclectus roratus) male perched on a tree vine, The Wildlife Habitat Zoo, Port Douglas, Queensland, Australia. August. Captive.

Steven David Miller / Eclectus parrot (Eclectus roratus) female calling, The Wildlife Habitat Zoo, Port Douglas, Queensland, Australia. August. Captive.

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) surfacing, Mission Beach, San Diego, California

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) surfacing, Mission Beach, San Diego, California

Chase Dekker / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) leaping, Monterey Bay, California

David Woodfall / Steeply sided mountains with regenerating Scots Pine and Birch forest in the valley, Alladale Rewilding project, Scottish Highlands, UK, October.

David Woodfall / Steeply sided mountains with regenerating Scots Pine and Birch forest in the valley, Alladale Rewilding project, Scottish Highlands, UK, October.

David Woodfall / Steeply sided mountains with regenerating Scots Pine and Birch forest in the valley, Alladale Rewilding project, Scottish Highlands, UK, October.

David Woodfall / Atlantic white sided dolphins (Lagenorhychus acutus) two animals at the surface. County Cork, Republic of Ireland.

Pal Hermansen / Path through steep-sided Slattdalskravan Gorge, Skuleskogen National Park, High Coast World Heritage Site, Vasternorrland, Sweden. August, 2018.

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) pair hunting Northern Anchovy (Engraulis mordax), Nine Mile Bank, San Diego, California

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) pair hunting Northern Anchovy (Engraulis mordax), Nine Mile Bank, San Diego, California

Karine Aigner / Portrait of a Eastern towhee (Pipilo erythrophthalmus) with white background, Block island, Rhode Island, USA. Bird caught during scientific research.

Felis Images / White-sided bush frog (Raorchestes jayarami) resting, profile, Valparai, Tamil Nadu, India.

Felis Images / White-sided bush frog (Raorchestes jayarami) sitting, front view. Valparai, Tamil Nadu, India.

Robert Thompson / Caranca river flowing through steep-sided gorge. River Gorges de la Caranca / La Vallee de la Caranca. Thues Entre Valls, Pyrenees Orientales, south west France. May 2018.

E.J. Peiker/ BIA / Chestnut-sided Warbler (Setophaga pensylvanica) male, Texas

Alan Murphy/ BIA / Chestnut-sided Warbler (Setophaga pensylvanica) male, Texas

Dave Watts / Eclectus parrot (Eclectus roratus) female on left and male on right, captive. Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) female on left and male on right, captive. Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) female on left and male on right, captive. Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) female, captive Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) male, captive Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) male at nest hole, captive Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) female at nest hollow, captive. Captive.

Dave Watts / Eclectus parrot (Eclectus roratus) female at nest hollow, captive. Captive.

Chien Lee / Black-sided Flowerpecker (Dicaeum monticolum) male, Mount Kinabalu National Park, Sabah, Borneo, Malaysia

Laurie Campbell / Lairig Ghru pass showing a steep sided glacial valley in the Cairngorms Mountains, Speyside, Cairngorms National Park, Scotland, February 1989

Laurie Campbell / Lairig Ghru pass showing a steep sided glacial valley in the Cairngorms Mountains, Speyside, Cairngorms National Park, Scotland, February 1989

Mark Carwardine / Pacific white sided dolphins (Lagenorhynchus obliquidens) porpoising in waves, Baja California, Mexico.

Guy Edwardes / Blue-sided leaf frog (agalychnis annae), Costa Rica.

Nick Hawkins / Researcher measuring the wing length of a Chestnut-sided warbler, (Setophaga pensylvanica) captured in a mist net during a study of migratory birds in Costa Rica, January.

Nick Hawkins / Researcher measuring the wing length of a Chestnut-sided warbler, (Setophaga pensylvanica) captured in a mist net during a study of migratory birds in Costa Rica, January.

Nick Hawkins / Researcher placing a leg band on Chestnut-sided warbler (Setophaga pensylvanica), captured in a mist net during a study of migratory birds in Costa Rica, January.

Nick Hawkins / Chestnut-sided warbler (Setophaga pensylvanica) captured in a mist net during a study of migratory birds in Costa Rica, January.

Nick Hawkins / Chestnut-sided warbler (Setophaga pensylvanica) captured in a mist net during a study of migratory birds in Costa Rica, January.

Tim Laman / Red-sided keelback water snake (Xenochrophis trianguligerus) Gunung Palung National Park, Borneo.

Glenn Bartley/ BIA / White-sided Flower-piercer (Diglossa albilatera), Colombia

Roger Powell / Eclectus parrot pair (Eclectus roratus) inspecting their nest site. North Queensland, Australia.

Roger Powell / Eclectus parrot female (Eclectus roratus) inspecting nest hole entrance. North Queensland, Australia.

Roger Powell / Diamond firetail (Stagonopleura guttata) on a log. Brisbane Ranges, Victoria, Australia.

Loic Poidevin / Grey red-backed vole (Myodes rufocanus) Varenger, Norway, May.

Huw Cordey / Wildlife cameraman, Alastair MacEwen, filming thousands of red-sided garter snakes with a lightweight jib arm, Narcisse snake dens, Manitoba, Canada. These hibernation dens are home to more than 50,00...

Alan Murphy/ BIA / Olive-sided Flycatcher (Contopus cooperi) calling, British Columbia, Canada

Alan Murphy/ BIA / Olive-sided Flycatcher (Contopus cooperi) calling, British Columbia, Canada

Alan Murphy/ BIA / Olive-sided Flycatcher (Contopus cooperi) calling, British Columbia, Canada

Alan Murphy/ BIA / Rufous-sided Towhee (Pipilo erythrophthalmus) male calling, Florida

Richard Herrmann / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) investigating floating Giant Kelp (Macrocystis pyrifera) with school of juvenile fish, open ocean off San Diego, California

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica) male calling, Maine

Chien Lee / Black-sided Flowerpecker (Dicaeum monticolum) female, Mount Kinabalu National Park, Sabah, Borneo, Malaysia

Adrian Davies / Red-sided keelback snake (Xenochrophis trianguligerus) predating foam nest of Wallace's flying tree frog (Rhacophorus nigropalmatus) Danum Valley, Sabah, Borneo.

Alex Hyde / Oaken Bank above the River Derwent. This is an example of clough woodland, steep-sided woodland on the edge of open moorland. Clough woodland has become increasingly fragmented over the years, impacti...

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica), Maine

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica), Maine

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica), Maine

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica), Maine

Scott Leslie / Chestnut-sided Warbler (Setophaga pensylvanica), Maine

Flip Nicklin / Pacific White-sided Dolphin (Lagenorhynchus obliquidens) leaping, Vancouver Island, British Columbia, Canada

Alan Murphy / Chestnut-sided Warbler (Setophaga pensylvanica) male, Texas

Alan Murphy / Chestnut-sided Warbler (Setophaga pensylvanica) male, Texas

Rebecca Robinson / Illustration of the diving and breaching behaviour of a Pacific White-Sided Dolphin (Lagenorhynchus obliquidens).

Marcos Baumann / White-sided Hillstar (Oreotrochilus leucopleurus) hummingbird male, Santiago, Chile

Adrian Davies / Wilson's filmy fern (Hymenophyllum wilsonii) with fallen leaf, Snowdonia, North Wales, October.

Adrian Davies / Wilson's filmy fern (Hymenophyllum wilsonii) Snowdonia, North Wales, October.

Eric Sohn Joo Tan / Dark-sided Flycatcher (Muscicapa sibirica), Singapore

Alan Murphy / Pink-sided Junco (Junco hyemalis mearnsi), New Mexico

Alan Murphy / Pink-sided Junco (Junco hyemalis mearnsi), New Mexico

Adrian Davies / Wilson's Filmy Fern (Hymenophyllum wilsonii) Snowdonia, north Wales, UK, July.

Adrian Davies / Wilson's Filmy Fern (Hymenophyllum wilsonii) Snowdonia, north Wales, UK, July.

Adrian Davies / Wilson's Filmy Fern (Hymenophyllum wilsonii) with sori, Snowdonia, north Wales, UK, July.

Adrian Davies / Wilson's Filmy Fern (Hymenophyllum wilsonii) Snowdonia, north Wales, UK, July.

Chris Mattison / Red sided Garter Snake (Thamnophis sirtalis infernalis) Point Reyes, California, USA, April.