Eggs are self-contained biological structures that protect and nourish a developing embryo. They vary widely in size, shape, and composition, reflecting diverse reproductive strategies across the animal kingdom.
The World’s Largest Egg
The largest egg in the world belongs to the Ostrich, a flightless bird native to Africa. An average Ostrich egg measures approximately 15 centimeters (6 inches) long and 13 centimeters (5.1 inches) wide. These eggs weigh around 1.4 kilograms (3.1 pounds), though some can exceed 2 kilograms, holding the volume equivalent of about 24 chicken eggs.
Ostrich eggs are notable for their strength and durability. The shell, roughly 2 millimeters thick, is robust and capable of withstanding significant pressure. An Ostrich egg can support a vertical weight of up to 220 kilograms (485 pounds) and a horizontal weight of 120 kilograms (265 pounds) without cracking.
The incubation period for an Ostrich egg ranges from 35 to 46 days. Upon hatching, a chick stands around 25 centimeters (10 inches) tall and weighs between 1 to 1.2 kilograms (2 to 2.6 pounds). Within two to three days, these chicks are capable of walking and running.
Why Size Matters for Eggs
Egg size represents a biological investment from the parent, influencing the offspring’s developmental stage and survival strategy. Producing a large egg, like an ostrich’s, demands substantial energy and nutrient reserves from the female bird, ensuring the embryo receives ample resources to develop before hatching.
The nutrient-rich yolk within a large egg provides the sole source of sustenance for the developing embryo throughout its incubation. This allows for a prolonged developmental phase, resulting in a hatchling that emerges in a more advanced, self-sufficient state, known as precocial development.
Precocial birds, such as ostriches, produce offspring that are mature and mobile soon after hatching. These young are covered in down, have open eyes, and can walk, run, and forage within days. The energy in their large eggs supports this advanced development, allowing them to navigate their environment effectively from an early age. This contrasts with altricial birds, whose smaller eggs yield helpless, underdeveloped chicks requiring extensive parental care.
A larger egg size is linked to higher survival rates for the offspring. Developed hatchlings from larger eggs are more resilient, better equipped to withstand environmental challenges, and more resistant to starvation and predation. They also utilize maternally provided energy more effectively, contributing to their overall fitness and ability to reach nutritional independence.
Other Remarkable Eggs
While the ostrich lays the largest egg in absolute terms, other birds are notable for their egg size relative to their own body dimensions. The kiwi bird of New Zealand, a small flightless bird, lays an egg proportionally the largest of any bird species. A kiwi egg can constitute 15 to 22 percent of the female’s body weight, compared to the ostrich egg, which is only about 2 to 3 percent of the female ostrich’s body mass.
Kiwi eggs weigh between 450 to 500 grams (16 to 17.5 ounces). This investment results in a chick that hatches fully feathered and highly independent, capable of fending for itself shortly after emerging. The rich yolk content, up to 65% of the egg’s volume, provides nourishment to sustain the chick for its first week of life.
Other large living birds, like the emu and cassowary, also produce large eggs. Emu eggs are dark green to black, measuring approximately 13 cm (5.1 inches) long and 9 cm (3.5 inches) wide, and weighing between 450 to 650 grams (1 to 1.4 pounds). Cassowary eggs are distinctively bright green or pale green-blue, around 13 cm (5 inches) long and weighing about 650 grams (23 ounces).
Historically, the largest eggs ever known were laid by the extinct Elephant Bird ( Aepyornis maximus ) from Madagascar. These eggs had a capacity of up to 2 gallons, equivalent to seven ostrich eggs or 180 chicken eggs. Measuring up to 34 cm (13.4 inches) long and 24.5 cm (9.6 inches) wide, these eggs could weigh an estimated 10.5 kilograms (23 pounds), reflecting the size of the bird itself, which stood up to 3 meters (10 feet) tall.