The emu, the second-largest living bird in the world, is an Australian ratite with a specialized reproductive cycle. The emu’s strategy for producing and raising its young involves a distinct seasonal pattern and a unique form of parental responsibility. Its breeding habits are intimately linked to the cooler months, ensuring the chicks hatch during a time when food resources are more readily available.
The Emu Laying Season and Clutch Size
Female emus typically lay a clutch of eggs during the cooler season, which generally falls between April and June in the Southern Hemisphere, though the timing can vary based on local climate conditions. A typical clutch size ranges from five to 15 eggs. However, a female may lay a total of 20 to 40 eggs across the entire season, especially if eggs are removed from the nest, prompting her to lay more. The female lays her large eggs at intervals of approximately two to four days until the clutch is complete. The eggs are laid in a rough nest that the male prepares on the ground, often in a semi-sheltered hollow lined with grass and sticks.
Unique Features of Emu Eggs
Emu eggs are notable for their considerable size and distinctive coloration. They are among the largest eggs laid by any bird, weighing between 450 and 650 grams (roughly one to one-and-a-half pounds) and measuring about 13 centimeters long. The shell is thick, measuring around 1.2 millimeters, which helps provide physical protection for the developing embryo. The most striking feature is the egg’s coloration, which is a deep, dark forest green or blackish-green. This camouflage is highly effective, blending the eggs into the surrounding vegetation of the ground nest.
Paternal Responsibility in Incubation
The incubation of the eggs is solely undertaken by the male emu. Once the female has finished laying the clutch, she leaves the nest, often seeking out other males with whom to mate and lay additional clutches. The male starts the incubation process once the clutch is mostly complete to ensure the eggs hatch closely together. For the entire 56-day period, he will not eat, drink, or defecate, surviving on accumulated body fat and morning dew; he also develops a bare brood patch to efficiently warm the eggs. The male becomes highly aggressive toward all other emus, vigorously protecting the nest, and continues his paternal role after the chicks hatch by guarding and teaching the young how to find food for up to seven months.