The animal kingdom displays an astonishing variety in egg coloration, ranging from white to speckled brown and vivid blue. Among these natural palettes, the intensely dark-colored egg is a rare phenomenon. This striking coloration often leads to eggs being described as black, though the true hue is a near-black shade of deep green. This unique egg is produced by the largest flightless birds.
Identifying the Primary Species
The animal most famously associated with laying a near-black egg is the Emu (Dromaius novaehollandiae), the second-largest living bird native to Australia. Emu eggs are remarkably large, typically weighing between one and two pounds, with a distinct, rough shell texture.
The color ranges from a deep, glossy dark green to shades so dark they appear charcoal or black. This coloration is an adaptation for survival, as Emus are ground-nesting birds that use a shallow scrape for their nests. The dark, mottled green hue provides camouflage within the low-lying Australian vegetation, concealing the eggs from predators. The female lays a clutch of five to fifteen eggs, which the male Emu incubates for nearly two months.
The Biological Mechanism of Black Eggs
The intense, dark color of the Emu egg results from specialized organic pigments deposited onto the eggshell during its formation within the female’s reproductive tract. The primary pigments involved are biliverdin and protoporphyrin, both derivatives of the breakdown of hemoglobin.
Biliverdin is responsible for blue and green coloration in bird eggs. In the Emu, a very high concentration of this green-blue pigment is deposited in the outermost layers of the shell. Protoporphyrin contributes reddish or brown tones. The combination and layering of these two compounds create the distinctive deep, almost black-green shade characteristic of the Emu egg.
The shell consists of multiple layers, and the darkest green pigment is concentrated in the thick, outermost layer. If the eggshell is scratched, it reveals lighter layers underneath, demonstrating how the pigments are layered onto the calcium carbonate structure.
Other Animals with Dark-Colored Eggs
While the Emu lays the darkest egg, other species produce eggs with notably dark colors sometimes mistaken for black. The Cassowary (Casuarius spp.), a relative of the Emu and another large flightless bird, lays large, distinctively colored eggs. Cassowary eggs are typically bright to dark green or pale blue-green, primarily due to the deposition of biliverdin pigment.
Certain domestic chicken breeds also produce eggs of very dark coloration, though they do not achieve the near-black depth of the Emu egg. Breeds such as the Marans and Welsummer lay deep, rich chocolate brown eggs. This brown coloration comes from a heavy application of protoporphyrin pigment onto the egg’s surface.