Spinning Tales About Eggs

Various creatures reproduce by laying eggs.  They are oviparous species including birds, reptiles, fish, amphibians, insects, arachnids, mollusks, and a few mammals (monotremes)—the duck-billed platypus and four species of spiny anteaters.

A bird egg is commonplace and often distinguishable by pigmentation, shape, location, markings, gloss, and size.  Composed of calcium carbonate, it may be white, or, if laid by a passerine (perching bird), it is usually colored.  Customarily, an egg is oval and somewhat pinched at one end from compression inside the mother—thus, it safely rolls in a circle when discharged.  Moreover, a cliff-nesting bird produces a highly-conical egg to avoid rolling off.  Interestingly, a bird that lays a spherical egg often builds a deep nest to inhibit the egg from rolling out.  Shells vary:  a duck egg is oily and waterproof; a group nester differentiates its egg by markings; a cavity nester does not need camouflage and usually produces a white egg; color or spotting provides camouflage, and spotting supposedly strengthens a thin, calcium-deficient shell.  Most captivating is the glossy, iridescent, colorful great tinamou egg (Central and South America).  The reflective shell might even protect the embryo from radiation.  One such egg (different species) was found in Darwin’s belongings.  And as for the smallest and the biggest bird egg…the bee hummingbird egg weighs about 0.2 ounces, and the ostrich egg exceeds 3 pounds.

 

Sandhill Crane with egg - photo Charlie Corbeil

Pesticides endanger an egg.  For example, the bald eagle, our national symbol, ingested fish contaminated with DDT which thinned the eggshell and depleted the population.  In her 1961 book, Silent Spring, Rachel Carson exposed this hazard.  Fortunately, the eagle rebounded.

How does a bird embryo survive?  It feeds on the yolk, and pores in the shell allow it to breathe.  Incubation is vital—sitting on the egg to maintain temperature and periodic turning of the egg for crucial development.  To emerge, the chick pecks out of the hard shell with its egg tooth—pipping.  Always a wonder to behold!

Yet, a bird egg might not produce a hatchling.  For instance, an unfertilized chicken egg is generally used for human consumption.  Also, a single pet female parakeet may lay and needlessly brood a clutch of unfertilized eggs (wind eggs). 

Besides birds, other intriguing creatures lay eggs.  The loggerhead turtle, familiar in Brevard County beaches, lays over 100 eggs at a time.  The queen honey bee may lay 1600 eggs daily during active seasons.  Recently, a Burmese python captured in the Florida Everglades carried 87 eggs.  Remarkably, a tenacious octopus spent 4.5 years brooding an estimated 160 eggs!