The egg has long been a symbol of rebirth and renewal, which goes a long way toward explaining the connection between eggs and the holiday of Easter. In honor of the upcoming Easter holiday, I thought I’d devote this week’s column to some “egg-citing” egg trivia. I’ll try to avoid any additional “egg-sasperating” puns.
Of course, the familiar Easter egg has traditionally been provided by chickens, although the eggs of other birds, such as ducks, geese and turkeys, are occasionally incorporated into such festivities as egg fights and egg hunts.
Producing eggs encased in a thin calcium shell is one of the ways that the birds are different from other lifeforms. For example, mammals carry their eggs inside the body with the exception of the oddball echidnas and the platypus. Amphibians lay eggs, but their eggs are soft and must usually be deposited in the water to ensure they do not dry out. Insects also lay eggs. It’s only the birds, however, and a few reptiles that have evolved the hard-shelled egg as a more durable means of reproduction.
The shape and size of those eggs varied greatly. Among the world’s 10,000 species of birds, the ostrich lays the largest eggs of any bird. Closer to home, the California condor almost certainly lays the largest eggs of any U.S. bird species. According to the website, All About Birds, eggs of the California Condor eggs are about 4.5 inches long and almost 3 inches wide. These whopper eggs weigh about 11 ounces. By contrast, a large chicken eggs weighs only two ounces.
The eggs produced for one nesting attempt are referred to as a clutch. The number of eggs per clutch varies among different species. Among songbirds, some rather small birds lay large clutches of eggs. For instance, the kinglets, which are tiny birds barely bigger than hummingbirds, are champion egg layers. The ruby-crowned kinglet can lay as many as a dozen eggs in a clutch, while the golden-crowned kinglet may lay as many as 11 eggs per clutch. The house wren, which is also a rather diminutive bird, can lay as many as 10 eggs. Several North American wrens produce large clutches of eggs. The marsh wren and sedge wren are known to lay as many as 10 eggs per clutch. The winter wren is almost their equal with clutch sizes that can include nine eggs. Of course, these same birds may lay more average clutches of between three and six eggs.
The sora, a small, secretive species of rail, lays 10 to 12 eggs in a nest well-concealed in marsh vegetation. The sora has been known to produce exceptional clutches with as many as 18 eggs.
Waterfowl are known to be good egg layers. The mallard hen may lay a clutch of eight to 13 eggs. The redhead hen typically lays only seven to eight eggs, but has parasitic tendencies that include depositing some eggs in the nests of other redheads. On occasion, multiple redhead hens get a little compulsive about slipping their eggs into a communal “dump” nest. These type of nests have been found containing as many as 80 or more eggs, but such clutches are impossible for a single hen to incubate and the eggs are usually lost. The wood duck, which will nest in specially designed bird houses placed near a source of water, can lay as many as 14 eggs in a single clutch.
Other birds concentrate their efforts on laying only a single egg or perhaps a pair of eggs. Many species of albatross lay only a single egg. The parents will dedicate a long period incubating the egg and then tend to the needs of the solitary offspring once the egg hatches.
Hummingbirds typically lay a pair of eggs. The poor female is soon abandoned by her mate and must build a nest, incubate her two eggs, and care and feed her young without any paternal assistance whatsoever. Hummingbirds, having high metabolisms, would find it impossible to feed themselves and any more than two young in a nest.
Penguins lay only a few eggs. Many species lay a pair of eggs, but the king penguin and emperor penguin are single-egg producers. In their harsh environment, these penguins would find meeting the needs of more than one offspring at a time quite impossible.
Let’s talk color. Eggs come in a variety of colors. Some eggshells also feature intricate patterns and splotches.
The killdeer, which usually lays four eggs, produces buff-colored eggs with dark mottling on the shell. These eggs blend remarkably with gravel and other rocks, which helps the ground-nesting killdeer hide their nests from would-be predators.
The American robin is famous for producing a clutch of beautiful blue eggs. The coloration of the eggs have even given rise to the descriptive phrase “robin’s egg blue.” This particular shade of blue is described as a variable one that leans to greenish-blue that is paler than turquoise and more blue than aqua.
The American robin’s blue eggs are not unusual among the thrushes, the group of birds of which the robin can claim kinship. For instance, the Eastern bluebird’s eggs are pale blue or sometimes white. The wood thrush produces eggs that are more to the turquoise shade of blue while the veery’s eggs can vary between green and pale blue.
The blue tint to the eggs of robins and other thrushes is caused by a pigment that gets applied to the shell as the female lays the eggs. It’s like the female robin has an internal egg-dyeing mechanism. In an article published in May of 2012, Science Daily reported that a study conducted by Queen’s University also found that the brighter blue the egg, the more the male robin will apply himself to caring for his offspring.
Among the birds that use my birdhouses for nesting, I’ve always thought the eggs of Carolina chickadees are exquisite. The eggs are pale white with a hint of pinkish coloration. A fine mottling of brown spots dot the shell. The amount of mottling can vary from egg to egg in the same clutch. These tiny eggs produced by a tiny bird are kept safe and sound in a nest of moss and other plant materials with a soft lining of animal hairs. Chickadees lay between three and 10 eggs, but between five and eight eggs per clutch seems more usual.
As mentioned, the ostrich lays the largest egg. Ostrich clutches are also impressive. The wild African ostrich, the largest bird in the world, lays 12 to 18 eggs. The ostrich has been domesticated, however, and hens have been conditioned to produce more eggs than would ever be expected in the wild.
The ostrich belongs to the ratite family, which includes other large birds such as the emu, rhea and cassowary, as well as five species of kiwi, which are considerably smaller than other ratites. The kiwi does have one interesting claim to fame when it comes to eggs. Kiwi are notable for laying eggs that are extremely large in relation to their body size. A kiwi egg may equal 15 to 20 percent of the body mass of a female kiwi. Perhaps not surprisingly, most kiwis lay only a single egg per clutch. The brown kiwi, however, normally lays two eggs per clutch.
Aepyornis, which was a giant, flightless ratite native to Madagascar and now extinct, produced the largest egg of any bird. Also known as the elephant bird, Aepyornis produced an egg with a volume equal to slightly more than 150 chicken eggs. These giant eggs boasted a circumference of 3 feet, 3 inches and reached about 13 inches in length. Research indicates that humans drove these enormous birds into extinction. One theory is that humans feasted so heavily on the giant eggs produced by Aepyornis that the birds were unable to sustain their species.
Humans have long turned to eggs as a source of nourishment, but we do not feed exclusively on eggs. Animals that feed primarily on eggs are classified by experts as ovivores. Some ovivores include fish, snakes, insects and, yes, birds. Some birds have become quite adept at preying on the eggs of other birds. Blue jays and American crows are known for robbing nests for both eggs and nestlings of other birds.
The bird egg has become firmly interwoven into human culture and traditions. According to the website Aghires.com, estimates indicate that about 180 million eggs are purchased each year in the United States specifically for the Easter holiday. Chicken hens must feel really overworked at this time of the year.
Of course, there are also the Easter traditions of chocolate and peanut butter eggs. I suppose that eases the pressure slightly on the overworked hens.
I’m reminding readers that I want to hear from them when they see their first hummingbird of spring. Email me your observations at firstname.lastname@example.org or post them on my Facebook page at http://www.facebook.com/ahoodedwarbler. Please include the date and the approximate time of your sighting.
Observations will be accepted through Sunday, April 18. Winners will be announced in this column on April 28.