Mary McDonald / Hanuman Langur / Northern Plains Grey Langur (Semnopithecus entellus) in leafless tree top. Kanha National Park, Madhya Pradesh, India.

Pete Oxford / Finch specimens at the Charles Darwin Research Station, Puerto Ayora, Santa Cruz Island, Galapagos Islands, L to R Top: Large Ground Finch (Geospiza magnirostris), Woodpecker Finch (Cactospiza pallidu...

Michael D. Kern / Zoo Atlanta / Lemur leaf frog (Hylomantis lemur) mating pair, captive, Critically endangered, from Central America

Lisa Hoffner / Wild Cotton-top tamarins (Saguinus oedipus) climbing up fallen branches in dry tropical forest of Colombia, South America. IUCN List: Critically Endangered

Tim Laman / Lowland dipterocarp rainforest and river in Danum Valley Conservation Area, Sabah, Borneo, Malaysia,

David Woodfall / Drought affected agricultural land, monsoon wind blowing top soil from fields, Madhya Pradesh, India, Asia

Thomas Lazar / Sunlight creating a rainbow in the spray of the Bridalveil Falls, Yosemite National Park, California, USA, June 2008

Andy Rouse / Osprey (Pandion haliaetus) perching on the top of a tree in snowstorm, UK, Europe

Wild Wonders of Europe / López / Leaves of various plants: Lily-of-the-valley, (Convallaria majalis) (top left corner)Wood-sorrel (Oxalis acetosella) with trefoil leaves and Woodruff (Galium odoratum) with leaves in whorls, growing a...

Tim Laman / Red Bird of Paradise (Paradisaea rubra) adult male at lek display site in the top of a canopy tree. Batanta Island, Papua, Indonesia. Near-threatened.

Tim Laman / Red Bird of Paradise (Paradisaea rubra) adult male at lek display site in the top of a canopy tree. Batanta Island, Papua, Indonesia.

Thomas Marent / Cotton-top Tamarin (Saguinus oedipus) in tree, northern Colombia

Igor Shpilenok / Steller's sea eagle {Haliaeetus pelagicus} sunning on tree top, Kuril Lake, Kamchatka, Far East Russia

Claus Meyer / Cotton-top Tamarin (Saguinus oedipus), Colombia

Mike Wilkes / Rookery with nests at top of trees {Corvus frugilegus} Warwickshire, UK

Mike Wilkes / Secretary bird in tree top Masai Mara, Kenya

Gavin Hellier / The view over the Bangkok City skyline from Vertigo, a bar and restaurant on top of the Banyan Tree Hotel, Bangkok, Thailand, 2010

Gavin Hellier / The view over the Bangkok City skyline from Vertigo, a bar and restaurant on top of the Banyan Tree Hotel, Bangkok, Thailand, 2010

Gavin Hellier / The view over the Bangkok City skyline from Vertigo, a bar and restaurant on top of the Banyan Tree Hotel, Bangkok, Thailand, 2010

Nick Upton / Azure winged magpie (Cyanopica cyana) perched at the top of a Mediterranean cypress tree (Cupressus sempervirens), Algarve, Portugal, June.

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) silverback climbing tree, Parc National des Volcans, Rwanda

Sumio Harada / Black Bear (Ursus americanus) female climbing tree to den, Glacier National Park, Montana

Ingo Arndt / Garden Dormouse (Eliomys quercinus) hibernating in old blue tit nest inside hollow tree, Germany

Mark Carwardine / Adult female American kestrel (Falco sparverius) perched on the top of a tree, Bosque del Apache National Wildlife Refuge, New Mexico, USA

Yukihiro Fukuda / Lesser frigatebird (Fregata ariel) adult with chick in tree top nest, Christmas Island, Indian Ocean, July

Christian Ziegler / Red-eyed Tree Frog (Agalychnis callidryas) metamorphose being persued by predatory spider, Soberania National Park, Panama

Christian Ziegler / Red-eyed Tree Frog (Agalychnis callidryas) eggs that have dried up during drought, Soberania National Park, Panama

Christian Ziegler / Red-eyed Tree Frog (Agalychnis callidryas) egg mass with four day old embryos, Soberania National Park, Panama

Donald M. Jones / Ruffed Grouse (Bonasa umbellus) eggs in nest at base of tree, Troy, Montana

Donald M. Jones / Ruffed Grouse (Bonasa umbellus) eggs in nest at base of tree, Troy, Montana

Charlie Summers / Tree Swallow (Tachycineta bicolor) adult seems to land on top of fledged chick as it feeds its offspring on the ground, Colorado, USA, July

Charlie Summers / Palm nut vulture (Gypohierax angolensis) juvenile perched in the top of thorn tree, Lake Manyara National Park, Tanzania

Pete Oxford / Marbled Tree Frog (Hyla marmorata) camouflaged on tree, Yasuni National Park, Amazon Rainforest, Ecuador

Pete Oxford / Banded Tree Snake (Tripanurgos compressus), Yasuni National Park, Amazon Rainforest, Ecuador

Pete Oxford / Banded Tree Snake (Tripanurgos compressus), Yasuni National Park, Amazon Rainforest, Ecuador

Mark Moffett / Green Tree Ant (Oecophylla smaragdina) colony envelops the queen to protect her from harm, Daintree, Queensland, Australia

Mark Moffett / Jumping Spider (Cosmophasis bitaeniata) has infiltrated Green Tree Ant (Oecophylla smaragdina) nest to prey on larvae using chemical mimicry, Daintree, Queensland, Australia

Mark Moffett / Green Tree Ant (Oecophylla smaragdina) holding silk-producing larva in its jaws and weaving the larva's silk to bind leaves for the colony's treetop nest, Daintree, Queensland, Australia

Mark Moffett / Green Tree Ant (Oecophylla smaragdina) trio from two different colonies fighting over territory, Daintree, Queensland, Australia

Mark Moffett / Green Tree Ant (Oecophylla smaragdina) parts in rice dish for human consumption near Angkor Wat, Cambodia

Nick Upton / Adult Grey heron (Ardea cinerea) flying with a twig in its beak for its tree top nest, Regent's Park, London, UK, February.

Markus Varesvuo / Greenshank (Tringa nebularia) perched on top of tree calling, Kuusamo, Finland, June

Diane McAllister / Lappet-faced vulture (Torgos tracheliotus) juvenile preparing for take off from the top of an Umbrella thorn tree, Tanzania

Martin Willis / Red-capped Robin (Petroica goodenovii) nest of spider webs and bark camouflaged in the fork of a tree contains three dark blotched blue eggs, Bourke, New South Wales, Australia

Eric Dragesco / Saker Falcon (Falco cherrug) perched in top of tree, Altai Mountains, Mongolia

Piotr Naskrecki / Tiger-striped Leaf Frog (Phyllomedusa tomopterna) climbing stem, Brownsberg Reserve, Surinam

Chien Lee / Bornean Rainbow Toad (Ansonia latidisca) camouflaged on tree trunk, species was rediscovered in 2011, Sarawak, Borneo, Malaysia

Steve Gettle / Looper Moth (Geometridae) camouflaged on tree trunk, Costa Rica

Steve Gettle / Hawk Moth (Sphingidae) camouflaged on tree trunk, Costa Rica

Steve Gettle / Looper Moth (Geometridae) camouflaged on tree trunk, Costa Rica

Martin Willis / Striped Possum (Dactylopsila trivirgata) in tree trunk burrow, Queensland, Australia

Suzi Eszterhas / Termites on tree trunk, Tanjung Puting National Park, Indonesia

John Cancalosi / Cattle Egret (Bubulcus ibis) perched in tree top. Costa Rican tropical rainforest.

John Cancalosi / Cattle Egret (Bubulcus ibis) with wings spread in tree top. Costa Rican tropical rainforest.

John Cancalosi / Cattle Egret (Bubulcus ibis) taking flight from tree top. Costa Rican tropical rainforest.

Alan Williams / Male Common redstart (Phoenicurus phoenicurus) singing at top of tree, North Wales, UK, June

Alan Williams / Male Common redstart (Phoenicurus phoenicurus) perched at top of tree, North Wales, UK, June

Alan Williams / Male Common redstart (Phoenicurus phoenicurus) singing at top of tree, North Wales, UK, June

Ernie Janes / Male Chaffinch (Fringilla coelebs) on top of Scots pine tree (Pinus sylvestris) singing, Norfolk, UK, May

Kerstin Hinze / Man / tree surgeon climbing up tree to fell the tree top due to vicinity of airport, Braunschweig, Brunswick, Lower Saxony, Germany, February 2011

Philippe Clement / Baumwipfelpfad, a wooden tower construction of the world´s longest tree top walk in the Bavarian Forest National Park. Germany, May 2011.

Kirkendall-Spring / Tree growing on top of seastack on Rialto Beach, with beached timber in the foreground, Oympic National Park, Washington, USA, September 2009

Markus Varesvuo / Hawk Owl (Surnia ulula) perched on top of a snow-covered tree. Kuusamo, Finland, February.

Alan Williams / Female Kestrel (Falco tinnunculus) perched on tree-top lookout. Cheshire, UK, November.

Pete Oxford / Christmas Tree Worm (Spirobranchus giganteus) filter feeding while attached to Brain Coral (Diploria labyrinthiformis), Bonaire, Netherlands Antilles, Caribbean

Kevin Schafer / Banana Slug (Ariolimax columbianus) on trunk of Island Oak (Quercus tomentella), Channel Islands National Park, California

John Cancalosi / Great Egret (Ardea alba) taking flight from tree top. Louisiana, USA, April.

Yva Momatiuk & John Eastcott / Tree Fern (Dicksonia antarctica) in rainforest, Otway National Park, Victoria, Australia

Bernard Castelein / Assamese Macaques (Macaca assamensis) in a tree top. Tawang, Arunachal Pradesh, India, February.

Matthew Maran / Bald Eagle (Haliaeetus leucocephalus) taking flight from a tree top. Clayoquot Sound, Vancouver Island, Canada, September.

Edwin Giesbers / Silhouette of Grey Heron (Ardea cinerea) perched in tree top. The Netherlands, April.

Pete Oxford / Rustic Sphinx Moth (Manduca rustica) camouflaged on tree trunk Puerto Ayora, Santa Cruz Island, Galapagos Islands, Ecuador

Chien Lee / Frilled Treefrog (Rhacophorus appendiculatus) camouflaged on bark, Kubah National Park, Sarawak, Borneo, Malaysia

Chien Lee / Frilled Treefrog (Rhacophorus appendiculatus) male, Bukit Sarang Conservation Area, Bintulu, Borneo, Malaysia

Chien Lee / Java Whipping Frog (Polypedates leucomystax), Kuching, Borneo, Malaysia

Chien Lee / Dusky Gliding Lizard (Draco obscurus) camouflaged on tree trunk, Fairy Cave, Bau, Malaysia

Chien Lee / Mossy Tree Frog (Rhacophorus everetti), Kinabalu National Park, Malaysia

Chien Lee / Collett's Tree Frog (Polypedates colletti) clinging to branch, Bintulu, Borneo, Malaysia

Chien Lee / Giant Crab Spider (Sparassidae) camouflaged on tree trunk, Gunung Mulu National Park, Malaysia

Chien Lee / Old World Tree Frog (Rhacophoridae), Wasur National Park, Wasur National Park, Indonesia

Barry Bland / American bald eagle (Haliaeetus leucocephalus) perched at top of tree, Homer, Alaska, January

Paul Hobson / Merlin (Falco columbarius) portrait of female perched in top of Spruce tree, Captive, UK, October

Jenny E. Ross / Male Wooly spider monkey / Northern muriqui (Brachyteles hypoxanthus) resting high in a tree top. Mata Atlantica, Minas Gerais, Brazil. September

Charlie Summers / Tawny Eagle (Aquila rapax) perched in the top of a dead Palm tree, Amboseli National Park, Kenya, East Africa

Thomas Marent / Asian Horned Frog (Megophrys nasuta) beside a creek, Cameron Highlands, Malaysia

Thomas Marent / Harlequin Flying Tree Frog (Rhacophorus pardalis) hind limb with webbing, Forest Research Institute Malaysia, Malaysia

Thomas Marent / Stick Insect (Diapheromeridae) on tree trunk, Gunung Leuser National Park, northern Sumatra, Indonesia

Konrad Wothe / Green Tree Ant (Oecophylla smaragdina) group guarding their nest, Queensland, Australia

Konrad Wothe / Green Tree Ant (Oecophylla smaragdina) group guarding their nest, Queensland, Australia

Konrad Wothe / Green Tree Ant (Oecophylla smaragdina) trio guarding their nest, Queensland, Australia

Pete Oxford / Golden Palm Tree Frog (Dendropsophus ebraccatus), northwest Ecuador

Pete Oxford / Golden Palm Tree Frog (Dendropsophus ebraccatus), northwest Ecuador

John Cancalosi / Great Egret (Ardea alba) landing in tree top, Louisiana, USA

John Cancalosi / Great Egret (Ardea alba) perched in top of tree, Louisiana, USA

Rod Williams / Eastern Black-and-white Colobus (Colobus guereza) portrait, sitting in tree top. Captive, found in Central and East Africa.

Rod Williams / Eastern Black-and-white Colobus (Colobus guereza) sitting in tree top. Captive, found in Central and East Africa.