Egg incubation in the context of "Lecithotrophy"

Oviparous animals are animals that reproduce by depositing unfertilized egg cells or fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs (eggs), which nurture the embryo into moving offspring (hatchlings) with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles.

Ovoviviparity is a special form of oviparity where the eggs are retained inside the mother (but still metabolically independent), and are carried internally until they hatch and eventually emerge outside as well-developed juveniles similar to viviparous animals.

An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell – a zygote. Within the vessel, an embryo is incubated until it has become an animal fetus that can survive on its own, at which point the animal hatches. Reproductive structures similar to the egg in other kingdoms are termed "spores", or in spermatophytes "seeds", or in gametophytes "egg cells".

Most arthropods, vertebrates (excluding live-bearing mammals), and mollusks lay eggs, although some, such as scorpions, do not. Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective shell, either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches; i.e., breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering.

The Inaccessible Island rail, or Inaccessible rail (Laterallus rogersi), is a small bird species of the rail family, Rallidae. Endemic to Inaccessible Island in the Tristan Archipelago in the isolated south Atlantic, it is the smallest extant flightless bird in the world. The species was formally described by physician Percy Lowe in 1923 but had first come to the attention of scientists 50 years earlier. The Inaccessible Island rail's taxonomic affinities and origin were a long-standing mystery; in 2018 its closest relative was identified as the South American dot-winged crake, and it was decided that both species are best classified in the genus Laterallus.

The Inaccessible Island rail has brown plumage, black bill and feet, and adults have a red eye. It occupies most habitats on Inaccessible Island, from the beaches to the central plateau, feeding on a variety of small invertebrates and also some plant matter. Pairs are territorial and monogamous, with both parents being responsible for incubating the eggs and raising the chicks. Its adaptations to living on a tiny island at high densities include low base metabolic rates, small clutch sizes, and flightlessness.

The common loon or great northern diver (Gavia immer) is a large member of the loon, or diver, family of birds. Breeding adults have a plumage that includes a broad black head and neck with a greenish, purplish, or bluish sheen, blackish or blackish-grey upperparts, and pure white underparts except some black on the undertail coverts and vent. Non-breeding adults are brownish with a dark neck and head marked with dark grey-brown. Their upperparts are dark brownish-grey with an unclear pattern of squares on the shoulders, and the underparts, lower face, chin, and throat are whitish. The sexes look alike, though males are significantly heavier than females. During the breeding season, loons live on lakes and other waterways in Canada, the northern United States (including Alaska), and southern parts of Greenland and Iceland. Small numbers breed on Svalbard and sporadically elsewhere in Arctic Eurasia. Common loons winter on both coasts of the US as far south as Mexico, and on the Atlantic coast of Europe.

Common loons eat a variety of animal prey including fish, crustaceans, insect larvae, molluscs, and occasionally aquatic plant life. They swallow most of their prey underwater, where it is caught, but some larger items are first brought to the surface. Loons are monogamous; that is, a single female and male often together defend a territory and may breed together for a decade or more. Both members of a pair build a large nest out of dead marsh grasses and other plants formed into a mound along the vegetated shores of lakes. A single brood is raised each year from a clutch of one or two olive-brown oval eggs with dark brown spots which are incubated for about 28 days by both parents. Fed by both parents, the chicks fledge in 70 to 77 days. The chicks are capable of diving underwater when just a few days old, and they fly to their wintering areas before ice forms in the fall.