Gary Bell/ Oceanwide / Lichen (Caloplaca sp) covered coastal rock, Flinders Island, Tasmania, Australia

Gary Bell/ Oceanwide / Granite rocks with lichen and Milky Way, Bicheno, Tasmania, Australia

John Shaw / Great frigatebird (Fregata minor) male at nest site, with gular sac inflated to attract females. Genovesa Island, Galapagos, May.

Guy Edwardes / Marsh Frog (Pelophylax ridibundus) vocalising with bokeh effect in the background, Danube Wetlands, Bulgaria

Guy Edwardes / Marsh Frog (Pelophylax ridibundus) vocalising with bokeh effect in the background, Danube Wetlands, Bulgaria

David Perpinan / Male Mediterranean tree frog (Hyla meridionalis) calling, showing vocal sac inflating, Barcelona, Spain, May. Filmed at night with an infrared camera.

Nick Upton / Running foliage spider / Spiny-legged sac spider (Liocranum rupicola), a nationally scarce species in the UK, hunting at night in an old stone wall, Wiltshire, UK, September.

Dave Bevan / Slow motion clip of a Robin (Erithacus rubecula) flying to nest and feeding chicks, removes faecal sac, Carmarthenshire, Wales, UK, May.

David Fleetham / Blue-spotted Sea Urchin (Astropyga radiata) expelling waste from the sac in the center of it's body. Maui, Hawaii.

Brian Bevan / Wasp spider (Argiope bruennichi) weaving egg sac, Bedfordshire, England, UK, Agust.

Brian Bevan / Pair of Reed warblers (Acrocephalus scirpaceus) feeding young at nest, Bedfordshire, England, UK, July.

Michael Quinton / Northern Flicker (Colaptes auratus) carrying fecal sac from nest cavity in forest, Alaska