What bird lays the smallest egg?
Egg
The largest recorded egg is from a whale shark, and was 30cm ×14cm ×9cm (11.8in ×5.5in ×3.5in) in size.[1] Whale shark eggs typically hatch within the mother. At 1.5kg (3.3lb) and up to 17.8cm ×14cm (7.0in ×5.5in), the ostrich egg is the largest egg of any living bird,[2] though the extinct elephant bird and some dinosaurs laid larger eggs. The bee hummingbird produces the smallest known bird egg, which weighs half of a gram (around 0.02oz). Some eggs laid by reptiles and most fish, amphibians, insects and other invertebrates can be even smaller.
House sparrow
Clutches usually comprise four or five eggs, though numbers from one to 10 have been recorded. At least two clutches are usually laid, and up to seven a year may be laid in the tropics or four a year in temperate latitudes. When fewer clutches are laid in a year, especially at higher latitudes, the number of eggs per clutch is greater. Central Asian house sparrows, which migrate and have only one clutch a year, average 6.5 eggs in a clutch. Clutch size is also affected by environmental and seasonal conditions, female age, and breeding density.
Some intraspecific brood parasitism occurs, and instances of unusually large numbers of eggs in a nest may be the result of females laying eggs in the nests of their neighbours. Such foreign eggs are sometimes recognised and ejected by females. The house sparrow is a victim of interspecific brood parasites, but only rarely, since it usually uses nests in holes too small for parasites to enter, and it feeds its young foods unsuitable for young parasites. In turn, the house sparrow has once been recorded as a brood parasite of the American cliff swallow.
The eggs are white, bluish white, or greenish white, spotted with brown or grey. Subelliptical in shape, they range from in length and in width, have an average mass of , and an average surface area of . Eggs from the tropical subspecies are distinctly smaller. Eggs begin to develop with the deposition of yolk in the ovary a few days before ovulation. In the day between ovulation and laying, egg white forms, followed by eggshell. Eggs laid later in a clutch are larger, as are those laid by larger females, and egg size is hereditary. Eggs decrease slightly in size from laying to hatching. The yolk comprises 25% of the egg, the egg white 68%, and the shell 7%. Eggs are watery, being 79% liquid, and otherwise mostly protein.