Nick Upton / Eurasian beaver (Castor fiber) adding a branch to its dam, Tayside, Scotland, UK, May. Filmed at night using a remote camera and infra red light.

Chris Mattison / Horned frog (Ceratophrys sp) in shallow water, captive occurs in South America.

Pascal Kobeh / Divers are setting up concrete reef balls to build an artificial reef, Philippines, Sulu Sea. August 2014.

Hanne & Jens Eriksen / Ruppell's weaver (Ploceus galbula) male building nest, Oman, May

Laurie Campbell / Heavy build up of hoar frost on a single stem of dead grass. Berwickshire, Scotland, December 2010

Stephen Dalton / Swallow (Hirundo rustica) feeding chicks on nest build over light bulb, England, UK

Wild Wonders of Europe / della Ferrera / House martin (Delichon urbicum) and a Swallow (Hirundo rustica) collecting mud to build nests, Neretva river delta, Dalmatia region, Croatia, May 2009

Eric Baccega / Hoary marmot (Marmotta caligata) carrying grass to build nest, Banff National Park, Rocky Mountains, Alberta, Canada

Michio Hoshino / American Beaver (Castor canadensis) carrying cut branches used to build its lodge, Alaska

JIM CLARE / Nests of Guanay cormorants, (Phalacrocorax bougainvilliiorum) after breeding has finished, shows build-up of guano around the nest. The colonies are strictly protected and the guano will be harvested...

JIM CLARE / Nest of Guanay cormorants, (Phalacrocorax bougainvilliiorum), after breeding has finished, shows build-up of guano around the nest. The colonies are strictly protected and the guano will be harvested...

JIM CLARE / Nests of Guanay cormorants, (Phalacrocorax bougainvilliiorum), after breeding has finished, shows build-up of guano around the nest. The colonies are strictly protected and the guano will be harvested...