Here are some peculiar egg-laying and nesting behaviors of some bird species.
Potoos are unique birds that lay their single egg directly atop a broken stump. They also lay their egg directly into a shallow depression on a branch — typically where an upward-pointing branch died and fell off, leaving a small scar or knot-hole
Cowbirds, Honeyguides and Cuckoos
A young Honeyguide being feed by the host parent, a Lazy Cisticola
These bird species are known for their bizarre nesting behavior. They lay their eggs in the active nest of other species.
A Cowbird juvenile fed by a Rufuos-Collared Sparrow
Cowbirds such as the Shiny Cowbird and Cuckoos like the Common Cuckoo are the two most notable brood parasites.
This Reed Warbler is raising the young of a Common Cuckoo, the best-known cuckoo.
Auk species such as Common Murre, Thick-billed Murre and Razorbill
These birds lay their eggs directly onto the narrow rocky ledges they use as breeding sites. The eggs of these species are dramatically pointed at one end, so that they roll in a circle when disturbed.
This is critical for the survival of the developing eggs, as there are no nests to keep them from rolling off the side of the cliff.
Because of the vulnerability of their unprotected eggs, parent birds of these auk species rarely leave them unattended.
King Penguins and Emperor Penguins
King Penguins and Emperor Penguins, like some Auk species, do not build nest too. These flightless birds tuck their eggs and chicks between their feet and folds of skin on their lower bellies. They are thus able to move about while incubating, though in practice only the Emperor Penguin regularly does so.
Emperor Penguins breed during the harshest months of the Antarctic winter, and their mobility allows them to form huge huddled masses which help them to withstand the extremely high winds and low temperatures of the season.
Ashy Storm-petrel, Pigeon Guillemot, Eurasian Eagle-Owl and Hume’s Tawny Owl
These birds are crevice-nesting species. They lay their eggs in the relative shelter of a crevice in the rocks or a gap between boulders, but provide no additional nest material.
The Eurasian Eagle-Owl is usually found nesting on cliff ledges. It is largely nocturnal.