Fred Bavendam / Ring-tailed Cardinalfish (Apogon aureus) male protectively carrying a fertilized egg mass in his mouth while they incubate, Bali, Indonesia

Roger Powell / Common guillemot (Uria aalge) pair at nest, one about to incubate an egg while the other watches, Great Saltee Island, Wexford, Republic of Ireland, June

Roger Powell / Common guillemot (Uria aalge) pair at nest, one about to incubate an egg while the other watches, Great Saltee island, Wexford, Republic of Ireland, June

Kevin Schafer / Maleo (Macrocephalon maleo) pair in nesting territory, Sulawesi, Indonesia, Endangered. Did you know? Maleos don't incubate their eggs, instead they lay them in the sand on beaches where the sun keeps...

LYNN M. STONE / Greater Sandhill Crane (Grus canadensis tabida) settling down to incubate two eggs on mounded nest of reeds in wetland, southern Wisconsin, USA

LYNN M. STONE / Greater Sandhill Crane (Grus canadensis tabida) settling down to incubate two eggs on mounded nest of reeds in wetland, southern Wisconsin, USA

Paul Hobson / Osprey (Pandion haliaetus) on nest, Finland, Europe

Fred Bavendam / Ring-tailed Cardinalfish (Apogon aureus) male protectively carrying a fertilized egg mass in his mouth while they incubate, Bali, Indonesia

Igor Shpilenok / White storks {Ciconia ciconia} place manure in nest to incubate eggs, Russia. Bryanksy

Fred Bavendam / Ring-tailed Cardinalfish (Apogon aureus) male protectively carrying a fertilized egg mass in his mouth while they incubate, Bali, Indonesia